Disclosures About Fair Value of Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Summary of financial instruments
Senior unsecured notes	$ 6,912,812	$ 6,963,375
Mortgage debt	1,235,169	1,396,485
Other debt	74,097	74,909
Carrying Value
Summary of financial instruments
Loans receivable, net	371,172	366,001
Marketable debt securities	245,649	244,089
Marketable equity securities	35
Term loan	228,269	226,858
Senior unsecured notes	6,912,812	6,963,375
Mortgage debt	1,235,169	1,396,485
Other debt	74,097	74,909
Carrying Value \| Warrants
Summary of financial instruments
Derivative assets	167	114
Carrying Value \| Interest-rate swap contracts
Summary of financial instruments
Derivative assets	2,035	2,325
Derivative liabilities	(8,292)	8,384
Carrying Value \| Currency swap contracts
Summary of financial instruments
Derivative liabilities	(3,254)	2,756
Fair Value \| Level 1
Summary of financial instruments
Marketable debt securities	283,335	280,850
Marketable equity securities	35
Senior unsecured notes	7,475,065	7,405,817
Fair Value \| Level 2
Summary of financial instruments
Loans receivable, net	378,380	373,441
Term loan	228,269	226,858
Mortgage debt	1,259,067	1,421,214
Other debt	74,097	74,909
Fair Value \| Warrants \| Level 3
Summary of financial instruments
Derivative assets	167	114
Fair Value \| Interest-rate swap contracts \| Level 2
Summary of financial instruments
Derivative assets	2,035	2,325
Derivative liabilities	(8,292)	8,384
Fair Value \| Currency swap contracts \| Level 2
Summary of financial instruments
Derivative liabilities	$ (3,254)	$ 2,756

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Fair value of investments in debt securities classified as held-to-maturity.

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Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

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Carrying value as of the balance sheet date of loans from a bank with maturities initially due after one year or beyond the operating cycle if longer, excluding current portion.

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The carrying amount as of the balance sheet date for the aggregate of other miscellaneous borrowings owed by the reporting entity.

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Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of uncollateralized debt obligations (with maturities initially due after one year or beyond the operating cycle if longer).

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