Unaudited Quarterly Data (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended			3 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Mar. 31, 2012 First Quarter [Member]	Mar. 31, 2011 First Quarter [Member]	Mar. 31, 2010 First Quarter [Member]	Jun. 30, 2012 Second Quarter [Member]	Jun. 30, 2011 Second Quarter [Member]	Jun. 30, 2010 Second Quarter [Member]	Sep. 30, 2012 Third Quarter [Member]	Sep. 30, 2011 Third Quarter [Member]	Sep. 30, 2010 Third Quarter [Member]	Dec. 31, 2012 Fourth Quarter [Member]	Dec. 31, 2011 Fourth Quarter [Member]	Dec. 31, 2010 Fourth Quarter [Member]
Unaudited Quarterly Data [Line Items]
Revenues	$ 3,082,646	$ 2,882,184	$ 2,731,632	$ 835,254	$ 742,178	$ 718,419	$ 749,698	$ 698,253	$ 671,543	$ 739,314	$ 704,271	$ 664,580	$ 758,380	$ 737,482	$ 677,090
Gross Profit	2,133,917	2,052,516	1,995,672	560,417	523,148	513,000	526,973	506,355	497,665	519,341	505,724	490,013	527,186	517,289	494,994
Operating profit	318,472	293,157	303,769	92,034	80,419	88,703	79,027	73,152	82,831	68,113	57,796	69,393	79,298	81,790	62,842
Net earnings	$ 183,492	$ 164,637	$ 171,642	$ 51,941	$ 44,230	$ 51,461	$ 44,182	$ 39,888	$ 47,830	$ 39,910	$ 31,224	$ 40,497	$ 47,459	$ 49,295	$ 31,854
Basic earnings per common share	$ 3.11	$ 2.69	$ 2.64	$ 0.88	$ 0.70	$ 0.78	$ 0.75	$ 0.64	$ 0.73	$ 0.68	$ 0.52	$ 0.62	$ 0.81	$ 0.84	$ 0.50
Diluted earnings per common share	$ 3.09	$ 2.66	$ 2.60	$ 0.87	$ 0.69	$ 0.77	$ 0.74	$ 0.63	$ 0.72	$ 0.67	$ 0.52	$ 0.62	$ 0.81	$ 0.83	$ 0.49
Cash dividends paid per common share	$ 0.64	$ 0.44	$ 0.12	$ 0.16	$ 0.06		$ 0.16	$ 0.06		$ 0.16	$ 0.16	$ 0.06	$ 0.16	$ 0.16	$ 0.06