Quarterly Financial Data (Unaudited) (Details) (USD $) In Thousands, except 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 Net Sales	$ 648,360	$ 601,114	$ 561,088	$ 498,766	$ 592,765	$ 490,213	$ 468,549	$ 416,651	$ 2,309,328	$ 1,968,178	$ 1,728,853
Gross profit	346,159	314,417	296,191	261,507	316,590	256,055	246,625	217,926	1,218,274	1,037,196	889,337
Net earnings	$ 94,282	$ 68,196	$ 60,188	$ 46,827	$ 80,852	$ 62,081	$ 51,347	$ 37,868	$ 269,493	$ 232,148	$ 172,593
Basic earnings per common share:
Net earnings	$ 2.99	$ 2.15	$ 1.88	$ 1.45	$ 2.48	$ 1.87	$ 1.53	$ 1.12	$ 8.45	$ 6.98	$ 5.12
Weighted average number of common shares	31,542,400	31,760,270	31,997,850	32,290,595	32,657,555	33,171,017	33,536,105	33,757,175	31,897,779	33,280,463	33,716,353
Diluted earnings per common share:
Net earnings	$ 2.91	$ 2.09	$ 1.82	$ 1.41	$ 2.41	$ 1.82	$ 1.49	$ 1.10	$ 8.21	$ 6.80	$ 5.03
Weighted average number of common and common equivalent shares	32,387,459	32,664,482	33,013,887	33,291,632	33,604,641	34,027,191	34,395,487	34,533,067	32,839,365	34,140,097	34,290,771
Market price per share:
Common Stock Value During The Period Maximum	$ 167.13	$ 175.28	$ 191.95	$ 177.07	$ 157.55	$ 124.44	$ 126.70	$ 110.31
Common Stock Value During The Period Mimimum	$ 130.12	$ 131.91	$ 157.13	$ 147.23	$ 123.28	$ 108.42	$ 107.42	$ 94.10