Quarterly Results of Operations (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ 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	$ 585,904	$ 574,490	$ 573,366	$ 553,552	$ 530,419	$ 530,356	$ 549,696	$ 502,572	$ 2,287,312	$ 2,113,043	$ 2,020,668
Gross profit	260,882	257,930	256,925	250,941	232,485	230,889	244,058	223,335	1,026,678	930,767	904,315
Operating income	135,248	126,504	125,133	115,671	85,521	109,708	113,823	103,345	502,556	412,397	436,990
Net income	$ 93,746	$ 83,768	$ 83,844	$ 75,899	$ 57,347	$ 69,873	$ 75,759	$ 68,130	$ 337,257	$ 271,109	$ 282,807
Basic EPS (in dollar per share)	$ 1.23	$ 1.09	$ 1.10	$ 0.99	$ 0.75	$ 0.92	$ 1.00	$ 0.90	$ 4.41	$ 3.57	$ 3.65
Diluted EPS (in dollar per share)	$ 1.21	$ 1.08	$ 1.08	$ 0.99	$ 0.75	$ 0.91	$ 0.99	$ 0.89	$ 4.36	$ 3.53	$ 3.62
Basic weighted average shares outstanding (in shares)	76,283	76,309	76,220	76,115	75,955	75,819	75,690	75,749	76,232	75,803	77,126
Diluted weighted average shares outstanding (in shares)	77,597	77,523	77,320	76,894	76,806	76,880	76,674	76,699	77,333	76,758	77,972