Equity (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013
Changes in equity
Balance	$ 6,840,793
Net income attributable to common stockholders	75,427
Cash flow hedge loss reclassified to earnings	1,391
Change in redemption value of redeemable noncontrolling interest	(526)
Noncontrolling interests income allocation	1
Dividends declared to common stockholders	(138,438)
Issuance of common stock, net of withholdings	1,871,167
Amortization of deferred compensation	9,073
Balance	8,658,888
Common stock
Changes in equity
Balance	1,144
Issuance of common stock, net of withholdings	150
Balance	1,294
Additional paid-in capital
Changes in equity
Balance	7,086,407
Issuance of common stock, net of withholdings	1,871,818
Amortization of deferred compensation	9,073
Balance	8,967,298
Accumulated earnings less dividends
Changes in equity
Balance	(142,329)
Net income attributable to common stockholders	75,427
Change in redemption value of redeemable noncontrolling interest	(526)
Dividends declared to common stockholders	(138,438)
Issuance of common stock, net of withholdings	(801)
Balance	(206,667)
Accumulated other comprehensive gain (loss)
Changes in equity
Balance	(108,007)
Cash flow hedge loss reclassified to earnings	1,391
Balance	(106,616)
Total stockholders' equity
Changes in equity
Balance	6,837,215
Net income attributable to common stockholders	75,427
Cash flow hedge loss reclassified to earnings	1,391
Change in redemption value of redeemable noncontrolling interest	(526)
Dividends declared to common stockholders	(138,438)
Issuance of common stock, net of withholdings	1,871,167
Amortization of deferred compensation	9,073
Balance	8,655,309
Noncontrolling interests
Changes in equity
Balance	3,578
Noncontrolling interests income allocation	1
Balance	$ 3,579