Stockholders' Equity (Schedule of Stockholders' Equity) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended						3 Months Ended
	Mar. 31, 2013	Mar. 31, 2013 Redeemable Noncontrolling Interests [Member]	Mar. 31, 2013 Common Stock [Member]	Mar. 31, 2013 Additional Paid In Capital [Member]	Mar. 31, 2013 Treasury Stock [Member]	Dec. 31, 2012 Treasury Stock [Member]	Mar. 31, 2013 Accumulated Other Comprehensive Income [Member]	Mar. 31, 2013 Retained Earnings [Member]	Mar. 31, 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		11,746
Comprehensive Income (Loss) Including Portion Attributable to Nonredeemable Noncontrolling Interests	102,889						18,312	79,174	5,403
Distributions to noncontrolling interests, net of contributions	(5,837)	(9,455)							(5,837)
Purchase of subsidiary shares from noncontrolling interests	(145)	(291)		(146)					1
Other reclassifications of noncontrolling interests	(2,317)	2,317							(2,317)
Adjustment to redemption value of redeemable noncontrolling interests	(3,523)	3,523		(3,523)
Repurchases of Common Stock	(18,731)		(5)	(18,726)
Issuance of common stock in connection with the exercise of stock options	73,451		22	73,429
Cancellation of restricted stock for tax withholdings on vested shares	(14,482)		(4)	(14,478)
Excess tax benefit from exercise of stock options	2,747			2,747
Share-based compensation	9,966		8	9,958
Equity, ending balance	$ 2,940,539	$ 375,506	$ 950	$ 1,187,535	$ (6,678)	$ (6,678)	$ (126,998)	$ 1,823,166	$ 62,564