Stockholders' Equity (Schedule of Stockholders' Equity) (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended						6 Months Ended
	Jun. 30, 2013	Jun. 30, 2013 Redeemable Noncontrolling Interests [Member]	Jun. 30, 2013 Common Stock [Member]	Jun. 30, 2013 Additional Paid In Capital [Member]	Jun. 30, 2013 Treasury Stock [Member]	Dec. 31, 2012 Treasury Stock [Member]	Jun. 30, 2013 Accumulated Other Comprehensive Income [Member]	Jun. 30, 2013 Retained Earnings [Member]	Jun. 30, 2013 Noncontrolling Interest [Member]
Equity, beginning balance	$ 2,796,521	$ 367,666	$ 929	$ 1,138,274	$ (6,678)	$ (6,678)	$ (145,310)	$ 1,743,992	$ 65,314
Comprehensive income (loss) attributable to redeemable noncontrolling interest		23,646
Comprehensive Income (Loss) Including Portion Attributable to Nonredeemable Noncontrolling Interests	159,805						40,043	108,927	10,835
Distributions to noncontrolling interests, net of contributions	(13,929)	(23,944)							(13,929)
Purchase of subsidiary shares from noncontrolling interests	(210)	(490)		(211)					1
Other reclassifications of noncontrolling interests	(2,317)	2,317							(2,317)
Adjustment to redemption value of redeemable noncontrolling interests	(2,218)	2,218		(2,218)
Repurchases of Common Stock	(27,140)		(7)	(27,133)
Issuance of common stock in connection with the exercise of stock options	103,657		31	103,626
Cancellation of restricted stock for tax withholdings on vested shares	(14,572)		(3)	(14,569)
Excess tax benefit from exercise of stock options	3,325			3,325
Share-based compensation	19,437		8	19,429
Equity, ending balance	$ 3,022,359	$ 371,413	$ 958	$ 1,220,523	$ (6,678)	$ (6,678)	$ (105,267)	$ 1,852,919	$ 59,904