Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended													12 Months Ended
	Dec. 31, 2016		Sep. 30, 2016		Jun. 30, 2016		Mar. 31, 2016		Dec. 31, 2015		Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Condensed Financial Statements, Captions [Line Items]
Restructuring expenses														$ 1,431	$ 1,361	$ 16,383
Revenue	$ 474,738		$ 405,228		$ 402,729		$ 379,472		$ 437,647		$ 381,928	$ 392,975	$ 344,517	1,662,167	1,557,067	1,530,654
Gross profit	214,733		191,376		183,322		177,690	[1]	207,310	[2]	180,739	189,615	175,897	767,121	753,561	750,373
Net earnings	$ 61,500	[3]	$ 58,633	[3]	$ 45,368	[3]	$ 1,125	[3]	$ 70,204	[4]	$ 73,072	$ 50,500	$ 47,910	$ 166,626	$ 241,686	$ 200,261
Basic earnings per share:
Basic earnings per share (in dollars per share)	$ 0.45		$ 0.43		$ 0.33		$ 0.01		$ 0.51		$ 0.52	$ 0.36	$ 0.34	$ 1.22	$ 1.73	$ 1.42
Diluted earnings per share:
Diluted earnings per share (in dollars per share)	$ 0.45		$ 0.43		$ 0.33		$ 0.01		$ 0.51		$ 0.52	$ 0.36	$ 0.34	$ 1.20	$ 1.72	$ 1.39
Selling General and Administrative Expense
Condensed Financial Statements, Captions [Line Items]
Restructuring expenses	$ 200		$ 900		$ 100		$ 200		$ 300		$ 300	$ 500		$ 664	$ 1,361	$ 16,383
Cost of Goods Sold
Condensed Financial Statements, Captions [Line Items]
Restructuring expenses													$ 300	$ 0	$ 0	$ 591

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[3] 2016 Net earnings includes restructuring expenses of $0.2 million reported in the first quarter, $0.1 million reported in the second quarter, $0.9 million reported in the third quarter and $0.2 million reported in the fourth quarter.

[4] 2015 Net earnings includes restructuring expenses