Accounting Policies and Related Matters - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Mar. 12, 2021
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Agreements with residents, cancelable period	30 days
Redeemable noncontrolling interests, carrying value	$ 401,294
Current redemption value of redeemable noncontrolling interest that exceeded the carrying value	40,212
Property operating expenses	$ 2,774,562	$ 2,597,823	$ 2,690,042
United States
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Basis points	4.90%
UNITED KINGDOM
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Basis points	0.80%
CANADA
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Basis points	2.90%
COVID-19
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property operating expenses	$ 97,933	31,927
Rent collected percentage	94.00%
COVID-19 | Grant
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue from contract with customer	$ 4,642	$ 3,014
COVID-19 | Seniors Housing Operating
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Spot occupancy	77.70%	74.90%		76.90%	74.80%	72.90%	72.60%
Basis points	5.10%
Property operating expenses	$ 63,681	$ 110,719
Buildings | Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Properties, estimated useful life	15 years
Buildings | Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Properties, estimated useful life	40 years
Improvements | Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Properties, estimated useful life	5 years
Improvements | Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Properties, estimated useful life	15 years