Dispositions of Real Estate and Discontinued Operations - Assets and Liabilities for Discontinued Operations (Details) $ in Thousands	Mar. 31, 2022 USD ($) property	Dec. 31, 2021 USD ($) property	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
ASSETS
Cash and cash equivalents	$ 7,989	$ 7,707	$ 40,161	$ 53,085
Total assets of discontinued operations, net	33,812	37,190
LIABILITIES
Total liabilities of discontinued operations, net	14,318	15,056
Allowance for doubtful accounts receivable	4,146	4,138
Right-of-use asset	232,457	233,942
Deferred revenue	817,022	789,207
Held-for-sale
ASSETS
Accounts receivable, net of allowance of $4,146 and $4,138	2,764	2,446
Cash and cash equivalents	7,989	7,707
Right-of-use asset, net	23	26
Other assets, net	1,976	3,237
Total assets of discontinued operations, net	12,752	13,416
Assets held for sale, net	21,060	23,774
Assets held for sale and discontinued operations, net	33,812	37,190
LIABILITIES
Lease liability	23	26
Accounts payable, accrued liabilities, and other liabilities	14,072	14,843
Deferred revenue	139	92
Total liabilities of discontinued operations, net	14,234	14,961
Liabilities related to assets held for sale, net	84	95
Liabilities related to assets held for sale and discontinued operations, net	14,318	15,056
Net real estate assets	20,000	23,000
Right-of-use asset	$ 1,000	$ 1,000
Held-for-sale | Medical Office Buildings
LIABILITIES
Number of properties classified as held for sale | property	5	4
Held-for-sale | Life Science
LIABILITIES
Number of properties classified as held for sale | property		1