Quarterly Financial Data (Unaudited) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Quarterly Net Sales	$ 684,253	$ 591,686	$ 578,680	$ 524,353	$ 657,292	$ 578,553	$ 570,283	$ 535,400	$ 2,378,972	$ 2,341,528	$ 2,309,328
Gross profit	375,357	318,573	308,843	279,253	356,788	308,157	299,008	277,102	1,282,026	1,241,055	1,218,274
Net earnings	$ 110,162	$ 74,326	$ 69,062	$ 52,544	$ 104,633	$ 72,183	$ 61,704	$ 52,327	$ 306,094	$ 290,847	$ 269,493
Basic earnings per common share:
Net earnings	$ 3.72	$ 2.49	$ 2.29	$ 1.73	$ 3.43	$ 2.34	$ 1.97	$ 1.66	$ 10.22	$ 9.37	$ 8.45
Weighted average number of common shares	29,596,949	29,818,218	30,119,889	30,299,569	30,532,491	30,846,062	31,267,660	31,531,915	29,945,954	31,044,532	31,897,779
Diluted earnings per common share:
Net earnings	$ 3.63	$ 2.43	$ 2.24	$ 1.69	$ 3.35	$ 2.28	$ 1.93	$ 1.62	$ 9.96	$ 9.14	$ 8.21
Weighted average number of common and common equivalent shares	30,366,603	30,579,954	30,849,934	31,101,979	31,271,377	31,599,081	32,038,928	32,386,924	30,728,482	31,824,077	32,839,365
Market price per share:
Common Stock Value During The Period Maximum	$ 253.27	$ 242.56	$ 228.00	$ 221.56	$ 195.00	$ 177.44	$ 185.08	$ 189.67
Common Stock Value During The Period Mimimum	$ 233.71	$ 205.55	$ 197.91	$ 196.72	$ 161.80	$ 148.68	$ 150.57	$ 152.19