Basis of Presentation (Details) $ in Thousands	3 Months Ended
Mar. 31, 2020 USD ($) property	Dec. 31, 2019 USD ($)
Basis Of Presentation [Line Items]
Assets	$ 6,703,723	$ 6,653,826
Liabilities	(3,916,554)	(3,776,776)
VIE, Primary Beneficiary
Basis Of Presentation [Line Items]
Assets	1,004,119	1,015,661
Liabilities	$ (702,544)	$ (704,344)
Joint Venture
Basis Of Presentation [Line Items]
Noncontrolling interest, ownership percentage by parent	45.00%
Ownership percentage	55.00%
Boston, MA \| Joint Venture \| Life Science Building
Basis Of Presentation [Line Items]
Number of properties included in joint venture agreement \| property	1

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