Condensed, Consolidated Statements of Equity (Unaudited) (USD $) In Thousands	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss (Income)	Noncontrolling Interests	Noncontrolling Interest [Member]
Beginning Balances at Dec. 31, 2011	$ 1,117,952	$ 87	$ 361,715	$ 745,658	$ 418	$ 10,074
Beginning Balances, shares at Dec. 31, 2011		86,796
Net income	35,811	0	0	35,245	0	566
Foreign currency translation adjustment	1,064
Other Comprehensive Income (Loss), Net of Tax	1,064	0	0	0	1,064	0
Distribution to noncontrolling interests	(103)	0	0	0	0	(426)	(426)
Share-based compensation	4,183	0	4,183	0	0	0
Issuance of common stock under stock incentive plans	2,621	0	2,621	0	0	0
Stock Repurchased During Period, Shares		(27)
Stock Issued During Period, Shares, Acquisitions		473
Stock Issued During Period, Value, Acquisitions	10,500	0	10,500	0	0	0
Issuance of common stock under stock incentive plans, shares		256
Stock repurchases	(614)	0	(614)	0	0	0
Excess tax benefit from stock options	187	0	187	0	0	0
Tax shortfall and other from stock options and awards	17	0	17	0	0	0
Ending Balances at Mar. 31, 2012	1,171,295	87	378,609	780,903	1,482	10,214
Ending Balances, shares at Mar. 31, 2012		87,498
Beginning Balances at Dec. 31, 2012	1,194,393	88	390,359	791,209	1,847	10,890
Beginning Balances, shares at Dec. 31, 2012		88,372
Net income	31,112	0	0	30,485	0	627
Foreign currency translation adjustment	(2,744)
Other Comprehensive Income (Loss), Net of Tax	(2,744)	0	0	0	(2,744)	0
Distribution to noncontrolling interests	(559)	0	0	0	0	(452)	(452)
Adjustments to Additional Paid in Capital, Purchase of Noncontrolling Interest						(470)
Purchase of noncontrolling interests	658					4,082	4,552
Share-based compensation	3,770	0	3,770	0	0	0
Issuance of common stock under stock incentive plans	1,876	0	1,876	0	0	0
Stock Repurchased During Period, Shares		(6)
Stock Issued During Period, Value, Acquisitions	0
Issuance of common stock under stock incentive plans, shares		128
Stock repurchases	(59)	0	(59)	0	0	0
Excess tax benefit from stock options	62	0	62	0	0	0
Tax shortfall and other from stock options and awards	26	0	26	0	0	0
Ending Balances at Mar. 31, 2013	$ 1,223,432	$ 88	$ 395,564	$ 821,694	$ (897)	$ 6,983
Ending Balances, shares at Mar. 31, 2013		88,494