Equity (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Changes in equity
Beginning Balance	$ 9,046,405
Net income attributable to common stockholders	208,144	141,739
Cash flow hedge loss reclassified to earnings	1,565	1,573
Change in redemption value of redeemable noncontrolling interest	2,065
Dividends declared to common stockholders	165,215
Issuance of common stock, net of withholdings	(3,505)
Amortization of deferred compensation	8,053
Ending Balance	9,097,512
Common stock
Changes in equity
Beginning Balance	1,320
Issuance of common stock, net of withholdings	2
Ending Balance	1,322
Additional paid-in capital
Changes in equity
Beginning Balance	9,354,685
Issuance of common stock, net of withholdings	(2,268)
Amortization of deferred compensation	8,053
Ending Balance	9,360,470
Accumulated earnings less dividends
Changes in equity
Beginning Balance	(267,085)
Net income attributable to common stockholders	208,144
Change in redemption value of redeemable noncontrolling interest	2,065
Dividends declared to common stockholders	(165,215)
Issuance of common stock, net of withholdings	(1,239)
Ending Balance	(223,330)
Accumulated other comprehensive loss
Changes in equity
Beginning Balance	(42,515)
Cash flow hedge loss reclassified to earnings	1,565
Ending Balance	$ (40,950)