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, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Quarterly Financial Data [Abstract]
Sales	$ 633,933	$ 610,769	$ 630,031	$ 593,417	$ 559,086	$ 570,083	$ 585,549	$ 538,312	$ 626,925	$ 613,864	$ 589,449	$ 571,905	$ 2,468,150	$ 2,253,030	$ 2,402,143
Gross profit	45,459	44,780	45,991	40,508	28,825	34,635	37,751	37,624	48,732	47,192	46,254	45,237	176,738	138,835	187,415
Net income	$ 18,115	$ 19,314	$ 13,580	$ 5,598	$ 2,878	$ 19,867	$ 14,701	$ 14,513	$ 19,010	$ 22,469	$ 20,137	$ 18,142	$ 56,607	$ 51,959	$ 79,758
Earnings per common share, Basic	$ 0.33	$ 0.35	$ 0.24	$ 0.10	$ 0.05	$ 0.34	$ 0.24	$ 0.24	$ 0.31	$ 0.36	$ 0.32	$ 0.29	$ 1.01	$ 0.88	$ 1.28
Earnings per common share, Diluted	$ 0.33	$ 0.34	$ 0.24	$ 0.10	$ 0.05	$ 0.34	$ 0.24	$ 0.24	$ 0.31	$ 0.36	$ 0.32	$ 0.28	$ 1.00	$ 0.87	$ 1.27