Unaudited Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Net sales	$ 336,963	$ 340,845	$ 294,831	$ 301,951	$ 295,096	$ 287,996	$ 286,850	$ 279,836	$ 1,274,589	$ 1,149,778	$ 1,027,447
Gross profit	151,859	160,817	137,737	138,675	131,939	133,209	127,303	123,232	589,088	515,683	418,831
Selling, general and administrative expense	75,049	75,188	69,423	66,311	71,912	65,493	65,600	59,756	285,849	262,761	226,716
Operating Income (Loss)	76,810	85,629	68,314	72,364	60,027	35,716	61,703	63,476	303,239	220,922	160,115
Net income	$ 53,620	$ 53,137	$ 42,682	$ 44,090	$ 34,802	$ 21,482	$ 36,624	$ 37,333	$ 193,529	$ 130,241	$ 89,388
Basic net income per share (in dollars per share)	$ 0.27	$ 0.27	$ 0.22	$ 0.22	$ 0.18	$ 0.11	$ 0.19	$ 0.19	$ 0.99	$ 0.66	$ 0.46
Diluted net income per share (in dollars per share)	$ 0.27	$ 0.27	$ 0.21	$ 0.22	$ 0.17	$ 0.11	$ 0.18	$ 0.19	$ 0.97	$ 0.65	$ 0.45
Basic weighted average shares (in shares)	195,302,613	196,121,691	196,994,210	196,621,906	196,516,632	196,445,684	196,270,119	196,217,311	196,256,128	196,363,084	195,933,800
Diluted weighted average shares (in shares)	197,889,189	198,659,459	199,618,809	199,524,913	199,446,875	199,452,308	198,441,315	198,160,465	198,918,417	199,348,746	198,047,453