Summary of Significant Accounting Policies (Narrative) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($) stores states Rate	Dec. 31, 2014 USD ($)		Dec. 31, 2013 USD ($)
Summary of significant accounting policies
Number of stores | stores	4,571
Number of states in which the Company operates | states	44
Accounts receivable due from employees to the Company	$ 1,100	$ 1,000
Allowance for doubtful supplier receivables	0	0
Replacement cost of inventory	2,630,000	2,560,000
LIFO inventory value in excess of replacement cost of inventory	85,900	61,400
Notes receivable from suppliers and other third parties	17,300	17,500
Reserve for uncollectable notes receivables	$ 0	0
Note receivable interest rate | Rate	0.00%
Goodwill impairment	$ 0	0
Impairment of long-lived assets	0	0
Self-insurance reserves, current	72,741	64,882	[1]
Advertising expense, net	79,300	79,000		$ 78,300
Total interest costs capitalized	7,400	11,500		$ 10,600
Deferred debt issuance costs, net of amortization	8,300	9,900
Deferred debt issuance costs, net of amortization, noncurrent	1,200	1,700
Original issuance discounts, net of accretion	2,900	3,400
Valuation allowance for deferred tax assets	0	0
Deferred income tax liabilities	79,772	102,422
Balance Sheet reclassification [Member]
Summary of significant accounting policies
Unamortized debt issuance costs, senior notes	7,100	8,200
Deferred income tax liabilities	7,400	17,300
Line of credit facility [Member] | Balance Sheet reclassification [Member]
Summary of significant accounting policies
Deferred debt issuance costs, net of amortization	500	500
Loyalty program [Member]
Summary of significant accounting policies
Deferred revenue, loyalty program	7,200	4,300
Deferred revenue recognized, loyalty program	$ 11,200	$ 5,600

[1] Certain prior period amounts have been reclassified to conform to current period presentation. See Note 1 "Summary of Significant Accounting Policies" to the Consolidated Financial Statements for more information.