Borrowings - Summary of Outstanding Debt (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Total Outstanding Debt	$ 4,562,712	$ 4,454,598
Debt Instrument, Interest Rate, Effective Percentage	3.60%
Fixed Rate Property Mortgages [Member]
Debt Instrument [Line Items]
Contract Maturity	Jan. 12, 2042
Unsecured Debt [Member]
Debt Instrument [Line Items]
Total Outstanding Debt	$ 4,077,373	3,828,201
Debt Instrument, Interest Rate, Effective Percentage	3.50%
Unsecured Debt [Member] \| Fixed Rate Debt Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 3,922,000	3,472,000
Debt Instrument, Interest Rate, Effective Percentage	3.60%
Contract Maturity	Jan. 27, 2027
Unsecured Debt [Member] \| Commercial Paper Notes [Member] \| Variable Rate Commercial Paper Program [Member]
Debt Instrument [Line Items]
Unsecured Debt	$ 172,000	70,000
Debt Instrument, Interest Rate, Effective Percentage	0.30%
Contract Maturity	Jan. 07, 2021
Unsecured Debt [Member] \| Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		300,000
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	$ (16,627)	(13,799)
Secured Debt [Member]
Debt Instrument [Line Items]
Total Outstanding Debt	$ 485,339	626,397
Debt Instrument, Interest Rate, Effective Percentage	4.60%
Secured Debt [Member] \| Fair Market Value Adjustment and Debt Issuance Cost [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding	$ (3,370)	(3,420)
Secured Debt [Member] \| Fixed Rate Property Mortgages [Member]
Debt Instrument [Line Items]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate	$ 488,709	$ 629,817
Debt Instrument, Interest Rate, Effective Percentage	4.60%

Carrying value as of the balance sheet date of short-term borrowings using unsecured obligations issued by banks, corporations and other borrowers to investors. The maturities of these money market securities generally do not exceed 270 days.

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

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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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