Debt Structure (Details) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018 USD ($)	Sep. 30, 2018 USD ($)
Debt Instrument [Line Items]
Total Outstanding Debt	$ 4,504,023	$ 4,504,023
Debt Instrument, Interest Rate, Effective Percentage	3.70%	3.70%
Secured Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage	3.90%	3.90%
Secured Debt [Member] \| Fair Market Value Adjustment and Debt Issuance Cost [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding	$ 4,886	$ 4,886
Secured Debt [Member] \| Mortgages [Member] \| Fixed Rate Debt
Debt Instrument [Line Items]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate	$ 836,513	$ 836,513
Debt Instrument, Interest Rate, Effective Percentage	4.00%	4.00%
Contract Maturity		Nov. 01, 2019
Secured Debt [Member] \| Federal National Mortgage Association Certificates and Obligations (FNMA) [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding	$ 80,000	$ 80,000
Secured Debt [Member] \| Federal National Mortgage Association Certificates and Obligations (FNMA) [Member] \| Variable Rate Credit Facility [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage	2.70%	2.70%
Contract Maturity		Dec. 01, 2018
Line of Credit Facility, Amount Outstanding	$ 80,000	$ 80,000
Secured Debt [Member] \| Federal National Mortgage Association Certificates and Obligations (FNMA) [Member] \| Variable Rate Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage	2.70%	2.70%
Secured Debt [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Total Outstanding Debt	$ 921,399	$ 921,399
Unsecured Debt [Member]
Debt Instrument [Line Items]
Total Outstanding Debt	$ 3,582,624	$ 3,582,624
Debt Instrument, Interest Rate, Effective Percentage	3.70%	3.70%
Unsecured Debt [Member] \| Wells Fargo Term Loan 2018 [Domain]
Debt Instrument [Line Items]
Repayments of Unsecured Debt	$ 250,000
Unsecured Debt [Member] \| Wells Fargo Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 300,000	$ 300,000
Unsecured Debt [Member] \| Variable Rate Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage	3.10%	3.10%
Contract Maturity		Aug. 29, 2020
Unsecured Debt	$ 300,000	$ 300,000
Unsecured Debt [Member] \| Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage	2.30%	2.30%
Contract Maturity		Mar. 01, 2022
Debt Instrument, Face Amount	$ 300,000	$ 300,000
Unsecured Debt [Member] \| Senior Notes [Member] \| Fixed Rate Debt
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage	4.00%	4.00%
Contract Maturity		Jul. 12, 2025
Debt Instrument, Face Amount	$ 2,642,000	$ 2,642,000
Unsecured Debt [Member] \| $1 billion unsecured revolving credit facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding	370,000	370,000
Unsecured Debt [Member] \| $1 billion unsecured revolving credit facility [Member] \| Fair Market Value Adjustment and Debt Issuance Cost [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ (29,376)	$ (29,376)
Maximum [Member] \| Unsecured Debt [Member] \| Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.75%
Maximum [Member] \| Unsecured Debt [Member] \| $1 billion unsecured revolving credit facility [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.55%
Minimum [Member] \| Unsecured Debt [Member] \| Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		0.90%
Minimum [Member] \| Unsecured Debt [Member] \| $1 billion unsecured revolving credit facility [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		0.85%

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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Face (par) amount of debt instrument at time of issuance.

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Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

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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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Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

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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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- Definition

Amount of investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate.

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Including the current and noncurrent portions, aggregate carrying amount of all types of notes payable, as of the balance sheet date, with initial maturities beyond one year or beyond the normal operating cycle, if longer.

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The cash outflow to repay long-term debt that is not secured by collateral. Excludes repayments of tax exempt unsecured debt.

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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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