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	105,680	0	0	103,602	0	2,078
Foreign currency translation adjustment	2,465
Other Comprehensive Income (Loss), Net of Tax	2,465	0	0	0	2,465	0
Noncontrolling Interest, Increase from Business Combination	(8,161)
Distribution to noncontrolling interests	(1,009)	0	0	0	0	(1,102)	(1,102)
Share-based compensation	10,466	0	10,466	0	0	0
Issuance of common stock under stock incentive plans	3,322	1	3,321	0	0	0
Stock Repurchased During Period, Shares		(185)
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		745
Stock repurchases	(3,933)	0	(3,933)	0	0	0
Excess tax benefit from stock options	358	0	358	0	0	0
Tax shortfall and other from stock options and awards	52	0	52	0	0	0
Ending Balances at Sep. 30, 2012	1,245,760	88	382,479	849,260	2,883	11,050
Ending Balances, shares at Sep. 30, 2012		87,829
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	114,567	0	0	112,794	0	1,773
Foreign currency translation adjustment	(3,708)
Other Comprehensive Income (Loss), Net of Tax	(3,708)	0	0	0	(3,708)	0
Noncontrolling Interest, Increase from Business Combination	5,406	0	0	0	0	1,806	1,806
Distribution to noncontrolling interests	(1,437)	0	0	0	0	(1,175)	(1,175)
Adjustments to Additional Paid in Capital, Purchase of Noncontrolling Interest		0		0	0	(976)
Purchase of noncontrolling interests	658					4,309	5,285
Share-based compensation	10,340	0	10,340	0	0	0
Issuance of common stock under stock incentive plans	15,111	1	15,110	0	0	0
Stock Repurchased and Retired During Period, Shares		737
Stock Repurchased and Retired During Period, Value	19,384	0	19,384	0	0	0
Issuance of common stock under stock incentive plans, shares		1,313
Excess tax benefit from stock options	2,654	0	2,654	0	0	0
Tax shortfall and other from stock options and awards	(4)	0	4	0	0	0
Stockholders' Equity, Other Shares		0
Stockholders' Equity, Other	163	0	0	0	0	163
Ending Balances at Sep. 30, 2013	$ 1,309,478	$ 89	$ 398,099	$ 904,003	$ (1,861)	$ 9,148
Ending Balances, shares at Sep. 30, 2013		88,948