Master Transactions and Cooperation Agreement with Brookdale (Details) $ in Thousands		1 Months Ended				3 Months Ended			6 Months Ended		12 Months Ended
	Jan. 31, 2020 USD ($) property lease	Jan. 31, 2020	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Nov. 30, 2017 USD ($) property facility	Jun. 30, 2020 USD ($) property	Mar. 31, 2020 USD ($) property	Jun. 30, 2019 USD ($) property	Jun. 30, 2020 USD ($) property	Jun. 30, 2019 USD ($) property	Dec. 31, 2020 USD ($) property	Dec. 31, 2019 USD ($) property	Dec. 31, 2018 property	Jan. 31, 2020 property	Jan. 31, 2020 facility	Jan. 31, 2020 USD ($)	Oct. 31, 2019 property	Jan. 01, 2018 USD ($) property
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Capital investment						$ 3,000			$ 3,000
Loss (gain) upon change of control, net									169,962	$ 11,501
Long-term debt						6,756,432			6,756,432
Gain (loss) on sales of real estate, net						$ 82,863		$ 11,448	$ 247,732	$ 19,492
Payment to acquired noncontrolling interest			$ 63,000	$ 32,000
RIDEA Facilities
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Ownership percentage (as a percent)					90.00%
Assets Leased to Others
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of assets transitioned | property													37
Assets Leased to Others | RIDEA Facilities
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Property count | facility					58
Other non-reportable segments | Assets Leased to Others | CCRC JV
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Property count														15	15		15
Senior housing triple-net
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of assets to be sold | property							18			2
Senior housing triple-net | Assets Leased to Others
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Property count | property					78												43
Disposition of properties, available for sale | property					32
Reduction in rent																		$ 5,000
Number of properties with rent concessions | property																		3
Total consideration for disposition of real estate					$ 35,000
Number of assets transitioned | property													17
Senior housing triple-net | Assets Leased to Others | Brookedale MTCA
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of properties disposed | property					2
SHOP
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of assets to be sold | property						2	7	1		10
SHOP | Assets Leased to Others
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of assets transitioned | property													20
SHOP | Assets Leased to Others | RIDEA Facilities
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Property count | property					36
Total consideration for disposition of real estate					$ 240,000
SHOP | Assets Leased to Others | Brookedale MTCA
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of assets to be sold | property					4
CCRC JV
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Percentage of interest acquired					10.00%
CCRC JV
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Property count | property						2			2
Investment ownership percentage	49.00%	49.00%				49.00%			49.00%			49.00%
Equity method investments						$ 179			$ 179			$ 325,830
Brookedale MTCA
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of properties disposed | property	18						18					18
Cash proceeds	$ 385,000
Gain (loss) on sales of real estate, net	$ 164,000						$ 165,000
Brookedale MTCA | 2019 Amended Master Lease
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Annual rent escalator	2.40%
Brookedale MTCA | CCRC JV
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Property count | property														15
Number of properties acquired | property	13
Equity method investments																$ 323,000
Real estate and intangible assets																1,800,000
Refundable entrance fee liabilities																308,000
Non-refundable entrance fee liabilities																436,000
Long-term debt																215,000
Working capital																48,000
Cash paid	$ 396,000
Brookedale MTCA | Assets Leased to Others | 2019 Amended Master Lease
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of properties to be restructured | property														24
Number of leases to be terminated | lease	1
Percent of sales proceeds	6.50%
Number of properties to be reallocated | property														14
Future rent																20,000
Capital investment term	5 years
Brookedale MTCA | Other non-reportable segments | Assets Leased to Others | CCRC JV
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Property count														13	13
Interest acquired		51.00%
Brookedale MTCA | CCRC JV
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Interest acquired	51.00%
Purchase cost																$ 1,060,000
Management termination fee	$ 100,000
Other Income (Expense) | Brookedale MTCA | CCRC JV
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Loss (gain) upon change of control, net	$ 170,000
Measurement Input, Discount Rate | Minimum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Measurement input	0.10	0.10
Measurement Input, Discount Rate | Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Measurement input	0.12	0.12
Measurement Input, Annual Rent Escalators | Minimum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Measurement input	0.02	0.02
Measurement Input, Annual Rent Escalators | Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Measurement input	0.03	0.03
Measurement Input, Cap Rate | Minimum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Measurement input	0.07	0.07
Measurement Input, Cap Rate | Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Measurement input	0.09	0.09
Subsequent Event | Brookedale MTCA | Assets Leased to Others | 2019 Amended Master Lease
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of leases to be terminated | property											1
Capital investment											$ 35,000
Annual percent increase											7.00%
Subsequent Event | Brookedale MTCA | CCRC JV
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of assets to be sold | property											2