Consolidated Statements of Stockholders' Equity (USD $) In Thousands	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interests
Beginning Balances at Dec. 31, 2009	$ 886,476	$ 86	$ 335,114	$ 540,010	$ (163)	$ 11,429
Beginning Balances, shares at Dec. 31, 2009		85,584
Net income (excludes $632 and $485 in 2009, $757 and $419 in 2010 and $1555 and $450 in 2011 related to redeemable and mandatorily redeemable noncontrolling interests, respectively)	112,982			110,243		2,739
Foreign currency translation adjustment	668
Distribution to noncontrolling interests	3,123					3,123
Purchase of noncontrolling interests	484					484
Share-based compensation	9,340		9,340
Stock Issued During Period, Value, Acquisitions	0
Shares Paid for Tax Withholding for Share Based Compensation		(92)
Issuance of common stock under stock incentive plans	5,510		5,510
Issuance of common stock under stock incentive plans, shares		687
Stock repurchases	2,310		2,310
Excess tax benefit from stock options	378		378
Tax shortfall and other from stock options and awards	184		184
Other Comprehensive Income (Loss), Net of Tax	900				900
Ending Balances at Dec. 31, 2010	1,009,485	86	347,848	650,253	737	10,561
Ending Balances, shares at Dec. 31, 2010		86,179
Net income (excludes $632 and $485 in 2009, $757 and $419 in 2010 and $1555 and $450 in 2011 related to redeemable and mandatorily redeemable noncontrolling interests, respectively)	97,855			95,405		2,450
Foreign currency translation adjustment	(319)
Distribution to noncontrolling interests	1,952					1,952
Purchase of noncontrolling interests	722		(263)			985
Share-based compensation	10,773		10,773
Stock Issued During Period, Value, Acquisitions	0
Shares Paid for Tax Withholding for Share Based Compensation		(114)
Issuance of common stock under stock incentive plans	3,999	1	3,998
Issuance of common stock under stock incentive plans, shares		731
Stock repurchases	2,673		2,673
Excess tax benefit from stock options	1,708		1,708
Tax shortfall and other from stock options and awards	202		202
Other Comprehensive Income (Loss), Net of Tax	(319)				(319)
Ending Balances at Dec. 31, 2011	1,117,952	87	361,715	745,658	418	10,074
Ending Balances, shares at Dec. 31, 2011		86,796
Net income (excludes $632 and $485 in 2009, $757 and $419 in 2010 and $1555 and $450 in 2011 related to redeemable and mandatorily redeemable noncontrolling interests, respectively)	48,199			45,551		2,648
Foreign currency translation adjustment	1,429
Distribution to noncontrolling interests	1,832					1,832
Share-based compensation	14,087		14,087
Stock Issued During Period, Shares, Acquisitions		473
Stock Issued During Period, Value, Acquisitions	10,500		10,500
Shares Paid for Tax Withholding for Share Based Compensation		(403)
Issuance of common stock under stock incentive plans	9,533	1	9,532
Issuance of common stock under stock incentive plans, shares		1,506
Stock repurchases	8,216		8,216
Excess tax benefit from stock options	2,868		2,868
Tax shortfall and other from stock options and awards	127		127
Other Comprehensive Income (Loss), Net of Tax	1,429				1,429
Ending Balances at Dec. 31, 2012	$ 1,194,393	$ 88	$ 390,359	$ 791,209	$ 1,847	$ 10,890
Ending Balances, shares at Dec. 31, 2012		88,372