Condensed Consolidated Statements of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Revenues	$ 495,887	$ 540,238	$ 978,409	$ 1,058,823
Costs and expenses:
Cost of sales	364,543	403,727	725,311	792,621
Selling, general and administrative	77,723	83,523	154,055	161,140
Amortization expense	3,729	3,156	7,458	6,312
Goodwill impairment (Note 10)	0	7,585	0	7,585
Total costs and expenses	445,995	497,991	886,824	967,658
Earnings (loss) from operations	49,892	42,247	91,585	91,165
Other expenses and income:
Interest expense	7,498	6,755	15,177	13,809
Interest income	(46)	(70)	(108)	(128)
Other income, net	(621)	(77)	(923)	(774)
Total other expenses (income), net	6,831	6,608	14,146	12,907
Earnings (loss) before income taxes	43,061	35,639	77,439	78,258
Income tax expense (Note 1)	16,275	13,932	28,984	30,130
Net earnings	$ 26,786	$ 21,707	$ 48,455	$ 48,128
Net earnings per common share, basic (Note 6)	$ 0.70	$ 0.53	$ 1.25	$ 1.16
Net earnings per common share, diluted (Note 6)	$ 0.68	$ 0.51	$ 1.21	$ 1.11
Weighted-average common shares outstanding, basic (Note 6)	37,687	41,170	37,998	41,642
Weighted-average common shares outstanding, diluted (Note 6)	38,951	42,719	39,379	43,382
Common Stock, Dividends, Per Share, Declared	$ 0.31	$ 0	$ 0.62	$ 0