Disclosures About Fair Value of Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Summary of financial instruments
Bank line of credit	$ 838,516us-gaap_LineOfCredit
Senior unsecured notes	7,626,194us-gaap_UnsecuredDebt	6,963,375us-gaap_UnsecuredDebt
Mortgage debt	984,431us-gaap_SecuredDebt	1,396,485us-gaap_SecuredDebt
Other debt	97,022us-gaap_OtherBorrowings	74,909us-gaap_OtherBorrowings
Carrying Value
Summary of financial instruments
Loans receivable, net	906,961	366,001
Marketable debt securities	231,442	244,089
Marketable equity securities	43
Bank line of credit	838,516
Term loan	213,610	226,858
Senior unsecured notes	7,626,194	6,963,375
Mortgage debt	984,431	1,396,485
Other debt	97,022	74,909
Carrying Value \| Warrants
Summary of financial instruments
Derivative assets	2,220	114
Carrying Value \| Interest-rate swap contracts
Summary of financial instruments
Derivative assets	178	2,325
Derivative liabilities	7,663	8,384
Carrying Value \| Currency Swap
Summary of financial instruments
Derivative liabilities	929	2,756
Fair Value
Summary of financial instruments
Loans receivable, net	898,522	373,441
Marketable debt securities	252,125	280,850
Marketable equity securities	43
Bank line of credit	838,516
Term loan	213,610	226,858
Senior unsecured notes	8,187,458	7,405,817
Mortgage debt	1,025,091	1,421,214
Other debt	97,022	74,909
Fair Value \| Warrants
Summary of financial instruments
Derivative assets	2,220	114
Fair Value \| Interest-rate swap contracts
Summary of financial instruments
Derivative assets	178	2,325
Derivative liabilities	7,663	8,384
Fair Value \| Currency Swap
Summary of financial instruments
Derivative liabilities	$ 929	$ 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, after the effects of master netting arrangements, of a financial liability or 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 liabilities 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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The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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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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