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 Interest
Beginning Balance at Dec. 31, 2010	$ 464,559	$ 96	$ 177,875	$ (14,058)	$ (28,799)	$ 316,317	$ 13,128
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	74,654					73,409	1,245
Other comprehensive income	(566)				(566)
Purchase of treasury shares (76 shares)	(2,747)			(2,747)
Stock awards, stock option exercises and other shares issued to employees and directors, net of income tax of $678 (139 shares) and $1,199 (137 shares) for the year September 30, 2012 and 2011, respectively	2,289		298	1,991
Dividends declared ($0.45 and $0.33 per common share for the year September 30, 2012 and 2011, respectively)	(6,120)					(6,120)
Ending Balance at Sep. 30, 2011	532,069	96	178,173	(14,814)	(29,365)	383,606	14,373
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	61,390					64,490	(3,100)
Other comprehensive income	483				483
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 $678 (139 shares) and $1,199 (137 shares) for the year September 30, 2012 and 2011, respectively	3,991		1,535	2,456
Dividends declared ($0.45 and $0.33 per common share for the year September 30, 2012 and 2011, respectively)	(8,386)					(8,386)
Ending Balance at Sep. 30, 2012	$ 602,420	$ 96	$ 180,998	$ (12,541)	$ (42,607)	$ 458,627	$ 17,847