Unaudited Quarterly Data (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Unaudited Quarterly Data [Line Items]
Revenues	$ 2,882,184	$ 2,731,632	$ 2,751,956
Net earnings	164,637	171,642	167,855
Basic earnings per common share	$ 2.69	$ 2.64	$ 2.54
Diluted earnings per common share	$ 2.66	$ 2.60	$ 2.52
Cash dividends paid per common share	$ 0.44	$ 0.12
First Quarter [Member]
Unaudited Quarterly Data [Line Items]
Revenues	742,178	718,419	728,183
Gross profit	523,148	513,000	515,212
Operating profit	80,419	88,703	82,092
Net earnings	44,230	51,461	45,376
Basic earnings per common share	$ 0.70	$ 0.78	$ 0.6876
Diluted earnings per common share	$ 0.69	$ 0.77	$ 0.68
Cash dividends paid per common share	$ 0.06
Second Quarter [Member]
Unaudited Quarterly Data [Line Items]
Revenues	698,253	671,543	679,609
Gross profit	506,355	497,665	494,422
Operating profit	73,152	82,831	75,283
Net earnings	39,888	47,830	41,945
Basic earnings per common share	$ 0.64	$ 0.73	$ 0.6353
Diluted earnings per common share	$ 0.63	$ 0.72	$ 0.6294
Cash dividends paid per common share	$ 0.06
Third Quarter [Member]
Unaudited Quarterly Data [Line Items]
Revenues	704,271	664,580	671,251
Gross profit	505,724	490,013	487,239
Operating profit	57,796	69,393	64,367
Net earnings	31,224	40,497	36,840
Basic earnings per common share	$ 0.52	$ 0.62	$ 0.5575
Diluted earnings per common share	$ 0.52	$ 0.62	$ 0.55
Cash dividends paid per common share	$ 0.16	$ 0.06
Fourth Quarter [Member]
Unaudited Quarterly Data [Line Items]
Revenues	737,482	677,090	672,913
Gross profit	517,289	494,994	491,125
Operating profit	81,790	62,842	74,582
Net earnings	$ 49,295	$ 31,854	$ 43,694
Basic earnings per common share	$ 0.84	$ 0.50	$ 0.66
Diluted earnings per common share	$ 0.83	$ 0.49	$ 0.6577
Cash dividends paid per common share	$ 0.16	$ 0.06