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, 2008	$ 719,307	$ 85	$ 308,674	$ 408,582	$ (6,352)	$ 8,318
Beginning Balances, shares at Dec. 31, 2008		84,633
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)	134,469			131,428		3,041
Foreign currency translation adjustment	684				684
Unrealized gain (loss) on foreign currency, net of tax	344				344
Unrealized loss on hedging instruments, net of tax	(815)				(815)
Losses on hedging instruments reclassified to income, net of tax	5,976				5,976
Formation of noncontrolling interests	3,106					3,106
Distribution to noncontrolling interests	(3,036)					(3,036)
Restricted stock unit grant	1,941		1,941
Share-based compensation	7,951		7,951
Issuance of common stock under stock incentive plans	15,297	1	15,296
Issuance of common stock under stock incentive plans, shares		951
Stock repurchases	(561)		(561)
Excess tax benefit from stock options	866		866
Tax benefit and other from stock options and awards	947		947
Ending Balances at Dec. 31, 2009	886,476	86	335,114	540,010	(163)	11,429
Ending 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	482				482
Unrealized gain (loss) on foreign currency, net of tax	186				186
Unrealized loss on hedging instruments, net of tax	(1)				(1)
Losses on hedging instruments reclassified to income, net of tax	233				233
Distribution to noncontrolling interests	(3,123)					(3,123)
Purchase of noncontrolling interests	(484)					(484)
Share-based compensation	9,340		9,340
Issuance of common stock under stock incentive plans	5,510		5,510
Issuance of common stock under stock incentive plans, shares		595
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)
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	(160)				(160)
Unrealized gain (loss) on foreign currency, net of tax	(159)				(159)
Distribution to noncontrolling interests	(1,952)					(1,952)
Purchase of noncontrolling interests	(722)		263			(985)
Share-based compensation	10,773		10,773
Issuance of common stock under stock incentive plans	3,999	1	3,998
Issuance of common stock under stock incentive plans, shares		617
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)
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