Quarterly Financial Data (Unaudited) (Details) (USD $) In Thousands, except Per 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 Financial Data (Unaudited) [Abstract]
Sales	$ 279,300	$ 231,700	$ 226,800	$ 194,400	$ 193,500	$ 172,100	$ 152,900	$ 127,100	$ 932,135	$ 645,643	$ 521,359
Gross profit	69,000	53,900	57,400	46,200	49,200	43,300	37,300	28,600	227,057	158,518	112,544
Net earnings	$ 20,700	$ 14,400	$ 18,500	$ 12,400	$ 14,300	$ 12,600	$ 10,600	$ 6,000	$ 65,971	$ 43,823	$ 22,026
Basic earnings per share	$ 0.68	$ 0.47	$ 0.61	$ 0.41	$ 0.47	$ 0.42	$ 0.35	$ 0.21	$ 2.17	$ 1.46	$ 0.74
Diluted earnings per share	$ 0.67	$ 0.47	$ 0.60	$ 0.40	$ 0.47	$ 0.42	$ 0.35	$ 0.20	$ 2.14	$ 1.45	$ 0.74