Quarterly Financial Data (Schedule Of Quarterly Financial Information) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended												12 Months Ended
	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, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Data [Abstract]
Sales	$ 625,719	$ 630,191	$ 664,038	$ 620,925	$ 709,547	$ 731,302	$ 716,868	$ 639,344	$ 756,843	$ 599,658	$ 607,522	$ 542,444	$ 2,540,873	$ 2,797,061	$ 2,506,467
Gross profit	56,795	54,284	55,716	51,779	55,689	55,294	57,751	51,123	59,843	45,440	44,367	36,834	218,574	219,857	186,484
Net income	$ 39,421	$ 20,565	$ 21,210	$ 14,205	$ 23,338	$ 16,906	$ 21,558	$ 19,439	$ 67,710	$ 23,648	$ 8,256	$ 11,331	$ 95,401	$ 81,241	$ 110,945
Earnings per common share, Basic	$ 0.78	$ 0.4	$ 0.41	$ 0.27	$ 0.44	$ 0.32	$ 0.4	$ 0.36	$ 1.26	$ 0.44	$ 0.15	$ 0.21	$ 1.85	$ 1.52	$ 2.05
Earnings per common share, Diluted	$ 0.77	$ 0.4	$ 0.4	$ 0.27	$ 0.44	$ 0.31	$ 0.4	$ 0.36	$ 1.25	$ 0.43	$ 0.15	$ 0.21	$ 1.83	$ 1.5	$ 2.03