Quarterly Results Of Operations (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
Quarterly Financial Information Disclosure [Abstract]
Net sales	$ 402,899	$ 412,370	$ 440,831	$ 422,798	$ 334,228	$ 345,296	$ 362,085	$ 361,457	$ 1,678,898	$ 1,403,066	$ 1,190,782
Gross profit	98,008	105,550	116,904	108,441	73,414	74,125	82,060	76,403	428,903	306,002	254,923
Income before income taxes	40,203	44,742	58,975	55,252	23,125	26,576	33,019	31,649	199,172	114,369	95,057
Net income	$ 26,299	$ 29,844	$ 37,569	$ 35,959	$ 16,140	$ 17,263	$ 20,869	$ 20,073	$ 129,671	$ 74,345	$ 62,266
Net income per common share, Basic	$ 1.06	$ 1.21	$ 1.52	$ 1.46	$ 0.66	$ 0.71	$ 0.86	$ 0.83	$ 5.26	$ 3.06	$ 2.60
Net income per common share, Diluted	1.05	1.19	1.51	1.45	0.65	0.70	0.85	0.82	5.20	3.02	$ 2.56
Stock market price, High	112.95	102.46	85.09	64.46	61.90	59.42	62.60	64.61	112.95	64.61
Stock market price, Low	84.20	84.61	60.75	52.85	53.55	52.42	55.26	47.63	52.85	47.63
Close (at end of quarter)	$ 107.75	$ 98.02	$ 84.84	$ 64.46	$ 60.89	$ 54.61	$ 58.02	$ 61.54	$ 107.75	$ 60.89