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
Beginning Balances at Dec. 31, 2010	$ 1,009,485	$ 86	$ 347,848	$ 650,253	$ 737	$ 10,561
Beginning Balances, shares at Dec. 31, 2010		86,179
Net income	69,504	0	0	68,451	0	1,053
Foreign currency translation adjustment	296
Other Comprehensive Income (Loss), Net of Tax	441	0	0	0	441	0
Distribution to noncontrolling interests	(607)	0	0	0	0	(607)
Purchase of noncontrolling interests	(611)	0	263	0	0	(874)
Share-based compensation	2,531	0	2,531	0	0	0
Issuance of common stock under stock incentive plans	2,456	1	2,455	0	0	0
Stock Issued During Period, Value, Acquisitions	0
Issuance of common stock under stock incentive plans, shares		416
Stock repurchases	(2,337)	0	(2,337)	0	0	0
Excess tax benefit from stock options	906	0	906	0	0	0
Tax shortfall and other from stock options and awards	(460)	0	(460)	0	0	0
Ending Balances at Jun. 30, 2011	1,081,308	87	351,206	718,704	1,178	10,133
Ending Balances, shares at Jun. 30, 2011		86,595
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	70,797	0	0	69,565	0	1,232
Foreign currency translation adjustment	(442)
Other Comprehensive Income (Loss), Net of Tax	(413)	0	0	0	(413)	0
Distribution to noncontrolling interests	(635)	0	0	0	0	(635)
Share-based compensation	7,767	0	7,767	0	0	0
Issuance of common stock under stock incentive plans	2,191	1	2,190	0	0	0
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		472
Stock repurchases	(2,805)	0	(2,805)	0	0	0
Excess tax benefit from stock options	248	0	248	0	0	0
Tax shortfall and other from stock options and awards	9	0	9	0	0	0
Ending Balances at Jun. 30, 2012	$ 1,205,611	$ 88	$ 379,624	$ 815,223	$ 5	$ 10,671
Ending Balances, shares at Jun. 30, 2012		87,741