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, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Quarterly Results (Unaudited)
Sales	$ 1,488,385	$ 1,601,558	$ 1,562,849	$ 1,529,392	$ 1,391,307	$ 1,535,453	$ 1,479,318	$ 1,382,738	$ 6,182,184	$ 5,788,816	$ 5,397,525
Gross profit	750,384	805,493	779,861	761,680	694,697	754,210	718,661	669,781	3,097,418	2,837,349	2,620,992
Former CSK officer clawback					(2,798)	0	0	0	0	(2,798)	0
Operating income	222,971	263,318	243,603	247,501	206,911	241,050	222,368	196,437	977,393	866,766	712,776
Write-off of asset-based revolving credit facility debt issuance costs					0	0	0	(21,626)	0	(21,626)	0
Termination of interest rate swap agreements					0	0	0	(4,237)	0	(4,237)	0
Gain on settlement of note receivable									0	0	11,639
Net income	$ 132,802	$ 159,332	$ 146,120	$ 147,492	$ 122,988	$ 148,439	$ 133,772	$ 102,474	$ 585,746	$ 507,673	$ 419,373
Earnings per share - basic	$ 1.16	$ 1.34	$ 1.17	$ 1.16	$ 0.96	$ 1.12	$ 0.97	$ 0.73	$ 4.83	$ 3.77	$ 3.02
Earnings per share - assuming dilution	$ 1.14	$ 1.32	$ 1.15	$ 1.14	$ 0.94	$ 1.10	$ 0.96	$ 0.72	$ 4.75	$ 3.71	$ 2.95