Summary of Significant Accounting Policies (Narrative) (Details) $ / shares in Units, $ in Thousands	3 Months Ended									12 Months Ended
	Dec. 26, 2015 USD ($) $ / shares	Sep. 26, 2015 USD ($) $ / shares	Jun. 27, 2015 USD ($) $ / shares	Mar. 28, 2015 USD ($) $ / shares	Dec. 27, 2014 USD ($) $ / shares	Sep. 27, 2014 USD ($) $ / shares	Jun. 28, 2014 USD ($) $ / shares	Mar. 29, 2014 USD ($) $ / shares	Sep. 28, 2013 USD ($) site	Dec. 26, 2015 USD ($) $ / shares	Dec. 27, 2014 USD ($) $ / shares	Dec. 28, 2013 USD ($) $ / shares	Mar. 01, 2014 USD ($)	Dec. 29, 2012 USD ($)
Cash Equivalents, at Carrying Value	$ 7,700				$ 14,400					$ 7,700	$ 14,400
Allowance for Doubtful Accounts Receivable	1,967				1,578					1,967	1,578
Impairment of Long-Lived Assets Held-for-use									$ 2,088	0	0	$ 2,088
Properties impaired | site									4
Self Insurance, Maximum of Workers Compensation Claims Liability per Associate per Claim										2,000
Stop loss insurance specific deductible													$ 500
Stop loss insurance aggregating deductible													$ 250
Cost of Goods Sold, Vendor Allowances										97,000	89,500	76,400
Vendor Paid Cooperative Advertising Credits										17,100	16,000	16,000
Accounts Receivable, Earned Advertising Credits	842				395					842	395
Accounts Receivable, Earned Promotional Discounts	8,100				5,700					8,100	5,700
Unearned Income for Vendor Programs	823				734					823	734
Advertising Expense										23,100	24,600	23,500
Net income	$ 16,575	$ 12,788	$ 16,644	$ 13,323	$ 13,698	$ 13,511	$ 12,602	$ 14,570		$ 59,330	$ 54,381	$ 73,186
Basic and diluted earnings per share | $ / shares	$ 0.61	$ 0.48	$ 0.62	$ 0.50	$ 0.51	$ 0.50	$ 0.47	$ 0.54		$ 2.21	$ 2.02	$ 2.72
Liabilities	$ 364,212				$ 346,356					$ 364,212	$ 346,356
Retained earnings	$ 1,007,894				980,842					1,007,894	980,842
Accounting Standards Update 2015-17 Member
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Current Deferred Income Taxes											5,800
Prior to March 1, 2013 [Member]
Self Insurance, Annual Maximum of Health Claims Liability per Associate										1,250
Between March 1, 2013 to March 1, 2014 [Member]
Self Insurance, Annual Maximum of Health Claims Liability per Associate										2,000
Maximum [Member]
Property and Casualty Insurance, Deductible										1,000
Minimum [Member]
Property and Casualty Insurance, Deductible										$ 100
Self-Insurance Error Correction [Member]
Net income											$ (786)	$ 1,500
Basic and diluted earnings per share | $ / shares											$ 0.03	$ 0.05
Liabilities					$ 13,100						$ 13,100
Retained earnings														$ 13,700