Stockholders' Equity (Schedule of Stockholders' Equity) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended							9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 Redeemable Noncontrolling Interests (Non- Equity) [Member]	Sep. 30, 2012 Common Stock [Member]	Sep. 30, 2012 Additional Paid-in Capital [Member]	Sep. 30, 2012 Treasury Stock [Member]	Dec. 31, 2011 Treasury Stock [Member]	Sep. 30, 2012 Accumulated Other Comprehensive Income (Loss) [Member]	Sep. 30, 2012 Retained Earnings	Sep. 30, 2012 Noncontrolling Interest
Beginning Balance			$ 2,464,445		$ 395,743	$ 915	$ 1,086,008	$ (6,678)	$ (6,678)	$ (184,479)	$ 1,501,330	$ 67,349
Comprehensive income	69,584	92,114	295,935	254,379	40,636					35,758	203,066	16,475
Distributions to noncontrolling interests, net of contributions			(23,803)		(36,338)							(23,803)
Purchase of subsidiary shares from noncontrolling interests			(21,106)		(18,603)		(19,963)					(1,143)
Other reclassifications of noncontrolling interests			(623)		1,626							(623)
Adjustment to redemption value of redeemable noncontrolling interests			12,550		(12,550)		12,550
Issuance of common stock in connection with the exercise of stock options			5,753			3	5,750
Cancellation of restricted stock for tax withholdings on vested shares			(9,168)			(3)	(9,165)
Excess tax benefit from exercise of stock options			(1,318)				(1,318)
Share-based compensation			30,715			7	30,708
Ending Balance	$ 2,712,744		$ 2,712,744		$ 370,514	$ 922	$ 1,104,570	$ (6,678)	$ (6,678)	$ (148,721)	$ 1,704,396	$ 58,255