Condensed Consolidated Statements of Equity (Unaudited) - USD ($) $ in Thousands	Total		Common Shares	Additional Paid-in Capital	Treasury Shares	Accumulated Other Comprehensive Loss	Retained Earnings	Noncontrolling Interests
Beginning Balance at Dec. 31, 2013	$ 724,421		$ 96	$ 184,380	$ (10,222)	$ (21,181)	$ 548,401	$ 22,947
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	75,399						67,009	8,390
Other comprehensive (loss)	(5,842)	[1]				(5,842)
Cash distributions to noncontrolling interest	(2,451)							(2,451)
Stock awards, stock option exercises and other shares issued to employees and directors, net of income tax of $819 (163 shares) and $1,522 (215 shares) for the period June 30, 2015 and 2014, respectively	6,063			4,642	1,421
Payment of cash in lieu for stock split (187 shares)	(58)			(58)
Dividends declared ($0.28 and $0.22 per common share for the year March 30, 2015 and 2014, respectively)	(6,252)						(6,252)
Performance share unit dividend equivalents	0			134			(134)
Ending Balance at Jun. 30, 2014	791,280		96	189,098	(8,801)	(27,023)	609,024	28,886
Beginning Balance at Dec. 31, 2014	824,049		96	222,789	(9,743)	(54,595)	644,556	20,946
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	36,344						35,189	1,155
Other comprehensive (loss)	(564)	[1]				(564)
Cash distributions to noncontrolling interest	(1,700)							(1,700)
Stock awards, stock option exercises and other shares issued to employees and directors, net of income tax of $819 (163 shares) and $1,522 (215 shares) for the period June 30, 2015 and 2014, respectively	1,595			(3,428)	5,023
Purchase of treasury shares (786 shares)	(34,160)				(34,160)
Dividends declared ($0.28 and $0.22 per common share for the year March 30, 2015 and 2014, respectively)	(7,952)						(7,952)
Shares issued for acquisitions (77 shares)	4,303			4,303
Performance share unit dividend equivalents	0			138			(138)
Ending Balance at Jun. 30, 2015	$ 821,915		$ 96	$ 223,802	$ (38,880)	$ (55,159)	$ 671,655	$ 20,401

[1] All amounts are net of tax. Amounts in parentheses indicate debits