Master Transactions and Cooperation Agreement with Brookdale (Details) $ in Thousands		1 Months Ended					3 Months Ended		12 Months Ended
	Jan. 31, 2020 USD ($) property lease	Jan. 31, 2020 USD ($) property	Oct. 31, 2019 property	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Nov. 30, 2017 USD ($) property facility	Mar. 31, 2020 USD ($) property	Mar. 31, 2019 USD ($) property	Dec. 31, 2020 USD ($) property	Dec. 31, 2019 USD ($) property	Apr. 30, 2020 property	Jan. 01, 2018 USD ($) property
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Long-term debt | $							$ 6,416,941
Payment to acquired noncontrolling interest | $				$ 63,000	$ 32,000
Loss (gain) upon change of control, net | $							167,434	$ 0
Gain (loss) on sales of real estate, net | $							$ 164,869	$ 8,044
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								37
Assets Leased to Others | RIDEA Facilities
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Property count | facility						58
Other non-reportable segments
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of assets to be sold										2
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							18	2		2
Senior housing triple-net | Assets Leased to Others
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Property count			43			78
Disposition of properties, available for sale						32
Reduction in rent | $												$ 5,000
Number of properties with rent concessions												3
Total consideration for disposition of real estate | $						$ 35,000
Number of assets transitioned								17
Senior housing triple-net | Assets Leased to Others | Brookedale MTCA
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of properties disposed						2
SHOP
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of assets to be sold							7	9		18
SHOP | Assets Leased to Others
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of assets transitioned								20
SHOP | Assets Leased to Others | RIDEA Facilities
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Property count						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						4
CCRC JV [Member]
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							2
Investment ownership percentage	49.00%	49.00%					49.00%			49.00%
Equity method investments | $							$ 0			$ 325,830
Brookedale MTCA
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of properties disposed	18						18			18
Cash proceeds | $	$ 385,000
Gain (loss) on sales of real estate, net | $	$ 164,000
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	15	15
Number of properties acquired	13
Real estate and intangible assets | $	$ 1,800,000	$ 1,800,000
Working capital | $	48,000	48,000
Refundable entrance fee liabilities | $	308,000	308,000
Non-refundable entrance fee liabilities | $	436,000	436,000
Long-term debt | $	215,000	215,000
Cash paid | $	396,000
Equity method investments | $	$ 323,000	$ 323,000
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	24	24
Percent of sales proceeds	6.50%
Number of properties to be reallocated	14	14
Future rent | $	$ 20,000	$ 20,000
Number of leases to be terminated | lease	1
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	$ 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 [Member] | Minimum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Measurement input	0.02	0.02
Measurement Input, Annual Rent Escalators [Member] | 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 | SHOP
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of assets to be sold											1
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									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									2