Quarterly Results (Unaudited) (Unaudited Operating Data) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Quarterly Results (Unaudited)
Sales	$ 1,391,307	$ 1,535,453	$ 1,479,318	$ 1,382,738	$ 1,310,330	$ 1,425,887	$ 1,381,241	$ 1,280,067	$ 5,788,816	$ 5,397,525	$ 4,847,062
Gross profit	694,697	754,210	718,661	669,781	636,597	693,415	672,633	618,347	2,837,349	2,620,992	2,326,528
Former CSK officer clawback	(2,798)	0	0	0					(2,798)	0	0
Legacy CSK DOJ investigation charge					0	5,900	15,000	0	0	20,900	0
Operating income	206,911	241,050	222,368	196,437	164,136	199,031	181,164	168,445	866,766	712,776	537,619
Write-off of asset-based revolving credit facility debt issuance costs	0	0	0	(21,626)					(21,626)	0	0
Termination of interest rate swap agreements	0	0	0	(4,237)					(4,237)	0	0
Gain on settlement of note receivable					11,639	0	0	0	0	11,639	0
Net income	$ 122,988	$ 148,439	$ 133,772	$ 102,474	$ 105,760	$ 116,542	$ 99,595	$ 97,476	$ 507,673	$ 419,373	$ 307,498
Earnings per share - basic	$ 0.96	$ 1.12	$ 0.97	$ 0.73	$ 0.76	$ 0.84	$ 0.72	$ 0.71	$ 3.77	$ 3.02	$ 2.26
Earnings per share - assuming dilution	$ 0.94	$ 1.10	$ 0.96	$ 0.72	$ 0.74	$ 0.82	$ 0.71	$ 0.70	$ 3.71	$ 2.95	$ 2.23