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, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Quarterly Financial Data [Abstract]
Sales	$ 756,843	$ 599,658	$ 607,522	$ 542,444	$ 633,933	$ 610,769	$ 630,031	$ 593,417	$ 559,086	$ 570,083	$ 585,549	$ 538,312	$ 2,506,467	$ 2,468,150	$ 2,253,030
Gross profit	59,843	45,440	44,367	36,834	45,459	44,780	45,991	40,508	28,825	34,635	37,751	37,624	186,484	176,738	138,835
Net income	$ 67,489	$ 23,726	$ 8,457	$ 11,487	$ 18,115	$ 19,314	$ 13,580	$ 5,598	$ 2,878	$ 19,867	$ 14,701	$ 14,513	$ 111,159	$ 56,607	$ 51,959
Earnings per common share, Basic	$ 1.26	$ 0.44	$ 0.16	$ 0.21	$ 0.33	$ 0.35	$ 0.24	$ 0.10	$ 0.05	$ 0.34	$ 0.24	$ 0.24	$ 2.05	$ 1.01	$ 0.88
Earnings per common share, Diluted	$ 1.24	$ 0.43	$ 0.16	$ 0.21	$ 0.33	$ 0.34	$ 0.24	$ 0.10	$ 0.05	$ 0.34	$ 0.24	$ 0.24	$ 2.03	$ 1.00	$ 0.87