Master Transactions and Cooperation Agreement with Brookdale (Details)		1 Months Ended				3 Months Ended			6 Months Ended		12 Months Ended
	Jan. 31, 2020 USD ($) lease property	May 31, 2021 USD ($) property	Jan. 31, 2021 USD ($) property	Dec. 31, 2020 USD ($) property	Oct. 31, 2019 USD ($) property	Jun. 30, 2021 USD ($) property	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($) property	Jun. 30, 2021 USD ($) asset property	Jun. 30, 2020 USD ($) property	Dec. 31, 2020 USD ($) property
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Property count | property	15
Number of properties acquired | asset									0
Number of properties disposed | property										18
Capital investment				$ 5,000,000							$ 5,000,000
Gain upon change of control, net									$ 1,042,000	$ 169,962,000
Long-term debt						$ 5,075,445,000			5,075,445,000
Gain on sales of real estate, net						$ 175,238,000	$ 81,284,000		$ 175,238,000	83,353,000
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						0			0
Investment ownership percentage	49.00%	49.00%		49.00%		0.00%			0.00%		49.00%
Equity method investments				$ 1,581,000		$ 2,041,000			$ 2,041,000		$ 1,581,000
Proceeds from sale of buildings		$ 19,000,000
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
Proceeds from sale of buildings		$ 38,000,000
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
Proceeds from sale of buildings						$ 12,000,000				$ 385,000,000	$ 428,000,000
2019 Amended Master Lease | Brookedale MTCA
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Annual rent escalator	2.40%
Lessor Asset Under Operating Lease | 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
Proceeds from sale of buildings											$ 1,000,000
Other Non-reportable Segments | Lessor Asset Under Operating Lease
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Property count | property				1							1
Other Non-reportable Segments | Lessor Asset Under Operating Lease | Brookedale MTCA
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Property count | property	13
Other Non-reportable Segments | Lessor Asset Under Operating Lease | CCRC JV
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Property count | property					15
Other Non-reportable Segments | Lessor Asset Under Operating Lease | 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						3				18
Senior Housing Triple-Net | Lessor Asset Under Operating Lease
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Property count | property					43