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Fair Value of Assets and Liabilities - Assets and Liabilities (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2022 USD ($) property shares	Mar. 31, 2021 USD ($)	Dec. 31, 2021 USD ($)	Mar. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Losses on equity securities, net	$ (8,553)	$ (8,339)
Corporate Joint Venture | Seaport Innovation LLC
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Equity method investment ownership percentage	20.00%		20.00%	55.00%
Holding period	10 years
Corporate Joint Venture | Seaport Innovation LLC | Measurement Input, Discount Rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Measurement input	0.0558
Corporate Joint Venture | Seaport Innovation LLC | Measurement Input, Market Capitalization Rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Measurement input	0.0525
Corporate Joint Venture | Medical Office and Life Science Properties
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Equity method investment ownership percentage	20.00%
Holding period	10 years
Number Of owned properties | property	10
Corporate Joint Venture | Medical Office and Life Science Properties | Measurement Input, Discount Rate | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Measurement input	0.0567
Corporate Joint Venture | Medical Office and Life Science Properties | Measurement Input, Discount Rate | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Measurement input	0.0893
Corporate Joint Venture | Medical Office and Life Science Properties | Measurement Input, Market Capitalization Rate | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Measurement input	0.0475
Corporate Joint Venture | Medical Office and Life Science Properties | Measurement Input, Market Capitalization Rate | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Measurement input	0.0600
Recurring | Carrying Amount | AlerisLife Inc
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Investments in affiliates, fair value	$ 22,987
Recurring | Level 1 | Carrying Amount | AlerisLife Inc
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Investments in affiliates, fair value	$ 22,987		$ 31,540
Equity securities investment (in shares) | shares	10,691,658
Recurring | Level 1 | Estimated Fair Value | AlerisLife Inc
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Investments in affiliates, fair value	$ 22,987		31,540
Recurring | Level 3 | Joint Venture | Carrying Amount | Life Science Property
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Investments in affiliates, fair value			215,127
Recurring | Level 3 | Joint Venture | Carrying Amount | Medical Office and Life Science Properties
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Investments in affiliates, fair value			0
Recurring | Level 3 | Joint Venture | Estimated Fair Value | Life Science Property
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Investments in affiliates, fair value	216,416		215,127
Recurring | Level 3 | Joint Venture | Estimated Fair Value | Medical Office and Life Science Properties
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Investments in affiliates, fair value	$ 50,325		$ 0

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