Condensed Consolidated Statements of Equity (Unaudited) (USD $) In Thousands, unless otherwise specified	Total		Common Shares	Additional Paid-in Capital	Treasury Shares	Accumulated Other Comprehensive Loss	Retained Earnings	Noncontrolling Interests
Beginning Balance at Dec. 31, 2011	$ 538,842		$ 96	$ 179,463	$ (14,997)	$ (43,090)	$ 402,523	$ 14,847
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	46,199						47,606	(1,407)
Other comprehensive income	92					92
Proceeds received from minority investor	6,100							6,100
Stock awards, stock option exercises and other shares issued to employees and directors, net of income tax of $1,099 (85 shares) and $675 (140 shares) for the period June 30, 2013 and 2012, respectively	3,550			1,072	2,478
Dividends declared ($0.32 and $0.30 per common share for the year June 30, 2013 and 2012, respectively)	(5,590)						(5,590)
Ending Balance at Jun. 30, 2012	589,193		96	180,535	(12,519)	(42,998)	444,539	19,540
Beginning Balance at Dec. 31, 2012	611,445		96	181,627	(12,559)	(45,379)	470,628	17,032
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	43,044						42,117	927
Other comprehensive income	3,354	[1]				3,354
Proceeds received from minority investor	152							152
Stock awards, stock option exercises and other shares issued to employees and directors, net of income tax of $1,099 (85 shares) and $675 (140 shares) for the period June 30, 2013 and 2012, respectively	1,884			773	1,111
Dividends declared ($0.32 and $0.30 per common share for the year June 30, 2013 and 2012, respectively)	(5,999)						(5,999)
Performance share unit dividend equivalents	0			55			(55)
Ending Balance at Jun. 30, 2013	$ 653,880		$ 96	$ 182,455	$ (11,448)	$ (42,025)	$ 506,691	$ 18,111

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