Fair Value Measurements (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Summary of financial instruments
Bank line of credit	$ 276,500	$ 80,103
Senior unsecured notes	5,260,622	5,258,550
Mortgage debt	137,525	138,470
Other debt	89,223	90,785
Carrying Value
Summary of financial instruments
Loans receivable, net	86,139	62,998
Marketable debt securities	19,337	19,202
Bank line of credit	276,500	80,103
Senior unsecured notes	5,260,622	5,258,550
Mortgage debt	137,525	138,470
Other debt	89,223	90,785
Derivative liabilities	1,217	1,310
Fair Value \| Level 1
Summary of financial instruments
Senior unsecured notes	5,484,915	5,302,485
Fair Value \| Level 2
Summary of financial instruments
Loans receivable, net	86,139	62,998
Marketable debt securities	19,337	19,202
Bank line of credit	276,500	80,103
Mortgage debt	133,652	136,161
Other debt	89,223	90,785
Derivative liabilities	$ 1,217	$ 1,310

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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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Fair value of investment in debt security measured at amortized cost (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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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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