Document and Entity Information [Abstract] Document and Entity Information [Abstract] Statement [Table] Statement [Line Items] Document Type Amendment Flag Document Period End Date Document Fiscal Period Focus Document Fiscal Year Focus Entity Registrant Name Trading Symbol Entity Central Index Key Current Fiscal Year End Date Entity Filer Category Entity Common Stock, Shares Outstanding Consolidated Balance Sheets [Abstract] Assets [Abstract] Assets Current assets: Current: Cash and Cash Equivalents, at Carrying Value Cash and cash equivalents at end of period Cash and cash equivalents at beginning of year Cash and cash equivalents Available-for-sale Securities, Current Marketable securities Amount of investments in level 1 mutual funds related to a non-qualified supplemental executive retirement plan and a non-qualified pharmacist deferred compensation plan for certain of its associates. SERP Investment SERP investment Accounts Receivable, Net, Current Accounts receivable, net Inventory, Net Inventories Prepaid Expense, Current Prepaid expenses and other current assets Income Taxes Receivable, Current Income taxes recoverable Assets, Current Total current assets Property, Plant and Equipment, Net Property and equipment, net Goodwill Goodwill Sum of the carrying amounts of all intangible assets and other assets, excluding goodwill, as of the balance sheet date, net of accumulated amortization and impairment charges. Intangible Assets Assets and Other Assets, Net (Excluding Goodwill) Intangible and other assets, net Assets Total assets Liabilities and Stockholders' Equity [Abstract] Liabilities [Abstract] Liabilities Current: Accounts Payable, Current Accounts payable Accrued Liabilities, Current Accrued expenses Self Insurance Reserve, Current Accrued self-insurance Deferred Revenue, Current Deferred revenue, net Liabilities, Current Total current liabilities Long-term Debt, Excluding Current Maturities Long-term debt This represents the noncurrent liability recognized in the balance sheet that is associated with the Company’s postretirement defined benefit plan, the Deferred Compensation Plan, as well as noncurrent liabilities related to the non-qualified supplemental executive retirement plan (SERP) and the non-qualified pharmacist deferred compensation plan as of the balance sheet date. Both the SERP and the pharmacist deferred compensation plan are designed to provide retirement benefits and salary deferral opportunities because of limitations imposed by the Internal Revenue Code and the Regulations implemented by the Internal Revenue Service. All three plans are unfunded and accounted for on an accrual basis. Postretirement benefit obligations Self Insurance Reserve, Noncurrent Accrued self-insurance Deferred Tax Liabilities, Noncurrent Deferred income taxes Other Liabilities, Noncurrent Other Liabilities Total liabilities Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Shareholders' Equity Common Stock, Value, Issued Common stock, no par value, 100,800,000 shares authorized, 33,047,807 shares issued, 26,898,443 shares outstanding Retained Earnings (Accumulated Deficit) Retained earnings Accumulated Other Comprehensive Income (Net of deferred taxes of $3,782 in 2016 and $3,323 in 2015) Accumulated other comprehensive income (Net of deferred taxes of $3,452 in 2017 and $3,382 in 2016) Stockholders' Equity before Treasury Stock Shareholders' equity before treasury stock Treasury Stock, Value Treasury stock at cost, 6,149,364 shares Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Total shareholders' equity Liabilities and Stockholders' Equity Total liabilities and shareholders' equity Common Stock, No Par Value Common stock, par value Common Stock, Shares Authorized Common stock, shares authorized Common Stock, Shares, Issued Common stock, shares issued Common Stock, Shares, Outstanding Common stock, shares outstanding Other Comprehensive Income (Loss), Available-for-sale Securities, Tax Accumulated other comprehensive income, deferred taxes Treasury Stock, Shares Treasury stock, shares Consolidated Statements of Income [Abstract] Sales Revenue, Goods, Net Net sales Cost of sales consists of direct product costs (net of discounts and allowances), warehouse costs, transportation costs and manufacturing facility costs. Also included are vendor allowances recorded as credits in cost of sales. Cost of sales, including warehousing and distribution expenses Gross Profit Gross profit on sales Selling, General and Administrative Expense Operating, general and administrative expenses Operating Income (Loss) Income from operations Amount after accretion (amortization) of discount (premium), and investment expense, of interest income and dividend income on nonoperating securities plus amount of the cost of borrowed funds accounted for as interest expense. Investment income (loss) and interest expense Investment income and interest expense Investment income and interest expense Business Combination, Bargain Purchase, Gain Recognized, Amount Gain on acquisition of business Gain on bargain purchase Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Cumulative Effects of Changes in Accounting Principles, Noncontrolling Interest Income before provision for income taxes Income Tax Expense (Benefit) Provision for income taxes Provision for income taxes Net Income (Loss) Attributable to Parent Net income Net income Weighted-average shares outstanding, basic and diluted Common Stock, Dividends, Per Share, Declared Cash dividends per share Earnings Per Share, Basic and Diluted Basic and diluted earnings per share Consolidated Statements of Comprehensive Income [Abstract] Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax [Abstract] Other comprehensive income (loss) by component, net of tax: Unrealized holding gains arising during period, tax Available-for-sale marketable securities Unrealized holding gains (losses) arising during period (Net of deferred taxes of $194 and $184, respectively for the 13 Weeks Ended and $68 and $738, respectively for the 39 Weeks Ended) Reclassification adjustment for gains included in net income (net of deferred taxes) Reclassification adjustment for (gains) losses included in net income (Net of deferred taxes of $2 and $70, respectively for the 13 Weeks Ended and $2 and $181, respectively for the 39 Weeks Ended Other Comprehensive Income (Loss), Available for Sale Securities Adjustment, Net of Tax Other comprehensive income, net of tax Comprehensive Income (Loss), Net of Tax, Attributable to Parent Comprehensive income, net of tax Other Comprehensive Income (Loss), Available-for-sale Securities, Tax, Portion Attributable to Parent Unrealized holding gains arising during period, deferred taxes Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, Tax Reclassification adjustment for gains included in net income, deferred taxes Consolidated Statements of Cash Flows [Abstract] Cash and Cash Equivalents, Period Increase (Decrease) [Abstract] Net Cash Provided by (Used in) Operating Activities [Abstract] Cash flows from operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net income to net cash provided by operating activities: Depreciation, Depletion and Amortization Depreciation and amortization Gain (Loss) on Sale of Property Plant Equipment (Gain) loss on disposition of fixed assets Gain (Loss) on Sale of Investments (Gain) loss on sale of marketable securities Gain (Loss) on Disposition of Intangible Assets Gain on sale of intangible assets Deferred Income Tax Expense (Benefit) Deferred income taxes Increase (Decrease) in Operating Capital [Abstract] Changes in operating assets and liabilities: Increase (Decrease) in Inventories Inventories The net change during the reporting period of the sum of amounts due within one year (or one business cycle) from customers for the credit sale of goods and services. Also includes the net change during the reporting period in the amount of outstanding money paid in advance for goods or services that bring economic benefits for future periods. Increase (Decrease) in Accounts Receivable and Prepaid Expenses Accounts receivable and prepaid expenses Increase (Decrease) in Accounts Payable and Accrued Liabilities Accounts payable and other liabilities Increase (Decrease) in Income Taxes Payable, Net of Income Taxes Receivable Income taxes Increase (Decrease) in Other Operating Assets and Liabilities, Net Other Net Cash Provided by (Used in) Operating Activities, Continuing Operations Net cash provided by operating activities Net Cash Provided by (Used in) Investing Activities [Abstract] Cash flows from investing activities: Payments to Acquire Property, Plant, and Equipment Purchase of property and equipment Proceeds from Sale of Property, Plant, and Equipment Proceeds from the sale of property and equipment Payments to Acquire Available-for-sale Securities Purchase of marketable securities Proceeds from Maturities, Prepayments and Calls of Held-to-maturity Securities Proceeds from maturities of marketable securities Proceeds from Sale of Held-to-maturity Securities Proceeds from the sale of marketable securities Payments to Acquire Businesses, Net of Cash Acquired Acquisitions Purchase price Payments to Acquire Intangible Assets Purchase of intangible assets Proceeds from Sale of Intangible Assets Proceeds from sale of intangible assets The net cash outflow during the period to acquire investments in level 1 mutual funds related to a non-qualified supplemental executive retirement plan and a non-qualified pharmacist deferred compensation plan for certain of its associates. Payments for SERP Investments Change in SERP investment Net Cash Provided by (Used in) Investing Activities, Continuing Operations Net cash used in investing activities Net Cash Provided by (Used in) Financing Activities [Abstract] Cash flows from financing activities: Proceeds from Issuance of Long-term Debt Proceeds from long-term debt Repayments of Long-term Debt Payments on long-term debt Payments of Dividends, Common Stock Dividends paid Net Cash Provided by (Used in) Financing Activities, Continuing Operations Net cash (used in) provided by financing activities Cash and Cash Equivalents, Period Increase (Decrease) Net increase (decrease) in cash and cash equivalents Income Taxes Paid, Net Income taxes paid Interest Paid, Net Interest paid Significant Accounting Policies [Abstract] Significant Accounting Policies [Text Block] Significant Accounting Policies Current Relevant Accounting Standards [Abstract] New Accounting Pronouncements and Changes in Accounting Principles [Text Block] Current Relevant Accounting Standards Marketable Securities [Abstract] Marketable Securities [Text Block] Marketable Securities Accumulated Other Comprehensive Income [Abstract] Stockholders' Equity Note Disclosure [Text Block] Accumulated Other Comprehensive Income Acquisitions [Abstract] Business Combination Disclosure [Text Block] Acquisitions Long-Term Debt [Abstract] Debt Disclosure [Text Block] Long-Term Debt Basis of Accounting, Policy [Policy Text Block] Basis of Presentation New Accounting Pronouncements, Policy [Policy Text Block] Current Relevant Accounting Standards Schedule of Available-for-sale Securities [Table] Schedule of Available-for-sale Securities [Line Items] Schedule of Available-for-sale Securities Reconciliation [Table Text Block] Schedule Of Marketable securities Investments Classified by Contractual Maturity Date [Table Text Block] Schedule Of Maturities of Marketable Securities Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Schedule of Accumulated Other Comprehensive Income Reclassification out of Accumulated Other Comprehensive Income [Table Text Block] Schedule Of Reclassifications out of Accumulated Other Comprehensive Income Schedule of Business Acquisitions, by Acquisition [Table] Business Acquisition [Line Items] Acquisitions [Line Items] Business Acquisition, Pro Forma Information [Table Text Block] Schedule Of Pro Forma Information Investment Income, Net Investment income Available-for-sale Securities, Amortized Cost Basis Amortized Cost Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax Gross Unrealized Holding Gains Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax Gross Unrealized Holding Losses Available-for-sale Securities Fair Value Available-for-sale Securities, Fair Value, Total Available-for-sale Securities, Debt Maturities, Next Rolling Twelve Months, Amortized Cost Basis Amortized Cost, Due within one year Available-for-sale Securities, Debt Maturities, Next Rolling Twelve Months, Fair Value Fair Value, Due within one year Available-for-sale Securities, Debt Maturities, Rolling Year Two Through Five, Amortized Cost Basis Amortized Cost, Due after one year through five years Available-for-sale Securities, Debt Maturities, Rolling Year Two Through Five, Fair Value Fair Value, Due after one year through five years Available-for-sale Securities, Debt Maturities, Rolling Year Six Through Ten, Amortized Cost Basis Amortized Cost, Due after five years through ten years Available-for-sale Securities, Debt Maturities, Rolling Year Six Through Ten, Fair Value Fair Value, Due after five years through ten years Available-for-sale Equity Securities, Amortized Cost Basis Amortized Cost, Equity securities Available-for-sale Securities, Equity Securities Fair Value, Equity securities Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss), Net of Tax Accumulated other comprehensive income balance, ending balance Accumulated other comprehensive income balance, beginning balance Other Comprehensive Income (Loss), before Reclassifications, Net of Tax Other comprehensive income before reclassifications Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax Amounts reclassified from accumulated other comprehensive income Other Comprehensive Income (Loss), Net of Tax Net current period other comprehensive income Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] Business Acquisition [Axis] Business Acquisition Acquiree [Domain] Business Acquisition, Acquiree [Domain] Mars Super Market [Member] Mars Super Market [Member] Mars Super Market [Member] Food Lion, LLC [Member] Food Lion Llc [Member] Food Lion, LLC [Member] Nell's Family Market [Member] Nell S Family Market [Member] Nell's Family Market [Member] Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual Sales Number of stores acquired. Number of stores acquired Number of owned stores acquired. Number of owned stores acquired Business Combination, Consideration Transferred, Liabilities Incurred Purchase price payable Debt Instrument, Term Purchase price payable, term The number of lease obligations assumed as part of an acquisition. Number of lease obligations assumed Number of new lease agreements entered into due to a business acquisition. Number of new lease agreements due to acquisition Legal Entity [Axis] Entity [Domain] Entity [Domain] Parent Company [Member] Parent Company [Member] Business Acquisition, Pro Forma Revenue Sales Line of Credit Facility [Table] Line of Credit Facility [Line Items] Line of Credit Facility, Maximum Borrowing Capacity Line of Credit Facility, Fair Value of Amount Outstanding Debt Instrument, Maturity Date Debt Instrument, Basis Spread on Variable Rate Debt Instrument, Covenant, Minimum Earnings Before Interest, Tax, Depreciation and Amortization. Debt Instrument, Covenant, Minimum EBITDA Letters of Credit Outstanding, Amount Debt Instrument, Covenant Description Interest Expense, Debt Major Types of Debt and Equity Securities [Axis] Major Types Of Debt And Equity Securities [Domain] Major Types of Debt and Equity Securities [Domain] Equity Securities [Member] Equity Securities [Member] Municipal Bonds [Member] Municipal Bonds [Member] Fair Value, Hierarchy [Axis] Fair Value Measurements Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] Fair Value Inputs Level1 [Member] Fair Value, Inputs, Level 1 [Member] Fair Value Inputs Level2 [Member] Fair Value, Inputs, Level 2 [Member] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Accumulated Net Unrealized Investment Gain Loss [Member] Accumulated Net Investment Gain (Loss) Attributable to Parent [Member] Reclassification out of Accumulated Other Comprehensive Income [Axis] Reclassification Out Of Accumulated Other Comprehensive Income [Domain] Reclassification out of Accumulated Other Comprehensive Income [Domain] Reclassification Out Of Accumulated Other Comprehensive Income [Member] Reclassification out of Accumulated Other Comprehensive Income [Member]