Master Transactions and Cooperation Agreement with Brookdale (Details)		1 Months Ended		3 Months Ended		12 Months Ended
	Jan. 31, 2020 USD ($) property lease	Dec. 31, 2020 USD ($) property	Oct. 31, 2019 USD ($) property	Mar. 31, 2021 USD ($) property	Mar. 31, 2020 USD ($) property	Dec. 31, 2020 USD ($) property	Jan. 31, 2021 property
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Property count | property	15
Number of properties disposed | property					18
Capital investment		$ 5,000,000				$ 5,000,000
Gain upon change of control, net				$ 1,042,000	$ 167,434,000
Long-term debt				6,041,221,000
Gain on sales of real estate, net				$ 0	$ 2,069,000
Measurement Input, Discount Rate | Minimum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Measurement input	0.10
Measurement Input, Discount Rate | Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Measurement input	0.12
Measurement Input, Annual Rent Escalators | Minimum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Measurement input	0.02
Measurement Input, Annual Rent Escalators | Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Measurement input	0.03
Measurement Input, Cap Rate | Minimum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Measurement input	0.07
Measurement Input, Cap Rate | Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Measurement input	0.09
Brookedale MTCA
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of properties disposed | property	18					18
Cash proceeds	$ 385,000,000
Gain on sales of real estate, net	$ 164,000,000
CCRC JV
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Property count | property				2
Investment ownership percentage	49.00%			49.00%
Equity method investments		$ 1,581,000		$ 6,481,000		$ 1,581,000
CCRC JV | Brookedale MTCA
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Interest acquired	51.00%
Purchase cost	$ 1,060,000,000.00
Management termination fee	$ 100,000,000
Number of assets to be sold | property			2
CCRC JV | Brookedale MTCA
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Property count | property	15
Number of properties acquired | property	13				13
Equity method investments	$ 323,000,000
Real estate and intangible assets					$ 1,800,000,000
Refundable entrance fee liabilities					308,000,000
Non-refundable entrance fee liabilities					436,000,000
Long-term debt					215,000,000
Working capital					48,000,000
Cash paid					$ 396,000,000
CCRC JV | Brookedale MTCA | Government grant income recorded in other income (expense), net
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Gain upon change of control, net	$ 170,000,000
Senior Housing Triple-Net
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of assets to be sold | property						21
2019 Amended Master Lease | Brookedale MTCA
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Annual rent escalator	2.40%
Assets Leased to Others | 2019 Amended Master Lease | Brookedale MTCA
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of properties to be restructured | property	24						24
Number of leases to be terminated	1	1
Percent of sales proceeds	6.50%
Number of properties to be reallocated | property	14
Future rent	$ 20,000,000
Capital investment			$ 35,000,000
Capital investment term			5 years
Annual percent increase			7.00%
Other Non-reportable Segments
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of assets to be sold | property						1
Other Non-reportable Segments | Assets Leased to Others
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Property count | property		1				1
Other Non-reportable Segments | Assets Leased to Others | Brookedale MTCA
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Property count | property	13
Other Non-reportable Segments | Assets Leased to Others | CCRC JV
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Property count | property			15
Other Non-reportable Segments | Assets Leased to Others | CCRC JV | Brookedale MTCA
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Property count | property	13
Senior Housing Triple-Net
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of assets to be sold | property					18
Senior Housing Triple-Net | Assets Leased to Others
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Property count | property			43