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	94,678						83,834	10,844
Other comprehensive (loss)	(6,790)	[1]				(6,790)
Cash distributions to noncontrolling interest	(8,916)							(8,916)
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	7,621			6,161	1,460
Payment of cash in lieu for stock split (187 shares)	(58)			(58)
Dividends declared ($0.42 and $0.33 per common share for the year September 30, 2015 and 2014, respectively)	(9,379)						(9,379)
Performance share unit dividend equivalents	0			134			(134)
Ending Balance at Sep. 30, 2014	801,577		96	190,617	(8,762)	(27,971)	622,722	24,875
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	35,394						33,961	1,433
Other comprehensive (loss)	(2,864)	[1]				(2,864)
Cash distributions to noncontrolling interest	(2,453)							(2,453)
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	2,226			(2,635)	4,861
Purchase of treasury shares (1,193 shares)	(49,089)				(49,089)
Dividends declared ($0.42 and $0.33 per common share for the year September 30, 2015 and 2014, respectively)	(11,872)						(11,872)
Shares issued for acquisitions (77 shares)	4,303			4,303
Performance share unit dividend equivalents	0			138			(138)
Ending Balance at Sep. 30, 2015	$ 799,694		$ 96	$ 224,595	$ (53,971)	$ (57,459)	$ 666,507	$ 19,926

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