Quarterly Financial Data (Schedule Of Quarterly Financial Information) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended												12 Months Ended
	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, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Data [Abstract]
Sales	$ 709,547	$ 731,302	$ 716,868	$ 639,344	$ 756,843	$ 599,658	$ 607,522	$ 542,444	$ 633,933	$ 610,769	$ 630,031	$ 593,417	$ 2,797,061	$ 2,506,467	$ 2,468,150
Gross profit	55,689	55,294	57,751	51,123	59,843	45,440	44,367	36,834	45,459	44,780	45,991	40,508	219,857	186,484	176,738
Net income	$ 24,011	$ 17,156	$ 22,150	$ 19,125	$ 67,489	$ 23,726	$ 8,457	$ 11,487	$ 18,115	$ 19,314	$ 13,580	$ 5,598	$ 82,442	$ 111,159	$ 56,607
Earnings per common share, Basic	$ 0.45	$ 0.32	$ 0.41	$ 0.36	$ 1.26	$ 0.44	$ 0.16	$ 0.21	$ 0.33	$ 0.35	$ 0.24	$ 0.10	$ 1.54	$ 2.05	$ 1.01
Earnings per common share, Diluted	$ 0.45	$ 0.32	$ 0.41	$ 0.35	$ 1.24	$ 0.43	$ 0.16	$ 0.21	$ 0.33	$ 0.34	$ 0.24	$ 0.10	$ 1.52	$ 2.03	$ 1.00