Mortgage Notes Payable, Credit Facilities and Senior Notes Mortgage Notes Payable, Credit Facility and Senior Notes - Principal Repayments of Unsecured Senior Notes (Details) - Senior Notes	Dec. 31, 2018 USD ($)
Debt Instrument [Line Items]
2019	$ 0
2020	0
2021	0
2022	0
2023	250,000,000
Thereafter	700,000,000
Principal amount	$ 950,000,000

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-Topic 835
-SubTopic 30
-Section 45
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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-04.(a))
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