Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended													12 Months Ended
	Oct. 27, 2010	Dec. 31, 2015		Sep. 30, 2015		Jun. 30, 2015		Mar. 31, 2015		Dec. 31, 2014		Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Restructuring expenses															$ 1,361	$ 16,383	$ 25,832
Revenue		$ 437,647		$ 381,928		$ 392,975		$ 344,517		$ 434,366		$ 375,366	$ 369,380	$ 351,542	1,557,067	1,530,654	1,496,372
Gross profit		207,310		180,739		189,615		175,897	[1]	214,737	[2]	184,386	182,718	168,532	753,561	750,373	737,010
Net earnings		$ 70,204	[3]	$ 73,072	[3]	$ 50,500	[3]	$ 47,910	[3]	$ 72,752	[4]	$ 52,857	$ 44,758	$ 29,894	$ 241,686	$ 200,261	$ 177,015
Basic earnings per share:
Basic earnings per share		$ 0.51		$ 0.52		$ 0.36		$ 0.34		$ 0.52		$ 0.37	$ 0.32	$ 0.21	$ 1.73	$ 1.42	$ 1.24
Diluted earnings per share:
Diluted earnings per share		$ 0.51		$ 0.52		$ 0.36		$ 0.34		$ 0.51		$ 0.37	$ 0.31	$ 0.21	$ 1.72	$ 1.39	$ 1.22
Litigation settlement payment	$ (3,000)														$ (28,000)
Selling General and Administrative Expense
Restructuring expenses		$ 300		$ 300		$ 500		$ 300		$ 1,000		$ 4,100	$ 3,500		1,361	$ 16,383	$ 25,832
Cost of Goods Sold
Restructuring expenses										600					0	591	1,689
COGS and SGA [Member]
Restructuring expenses										$ 16,974				$ 8,400	$ 1,361	$ 16,974	$ 27,521

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[2] 2014 Gross profit includes restructuring expenses of $0.6 million reported in the fourth quarter.

[3] 2015 Net earnings includes restructuring expenses of $0.3 million reported in the first quarter, $0.5 million reported in the second quarter, $0.3 million reported in the third quarter and $0.3 million reported in the fourth quarter.

[4] 2014 Net earnings includes restructuring expenses