Accounting Policies and Related Matters - Spot Occupancy (Details) - property	Sep. 30, 2021	Aug. 31, 2021	Jul. 31, 2021	Jun. 30, 2021	May 31, 2021	Apr. 30, 2021	Mar. 31, 2021	Mar. 12, 2021	Feb. 28, 2021	Jan. 30, 2021	Dec. 31, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in occupancy basis	4.40%
Spot occupancy properties											591
United States
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in occupancy basis	2.60%
United Kingdom
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in occupancy basis	3.00%
Canada
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in occupancy basis	0.70%
Seniors Housing Operating
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Spot occupancy	96.00%
Seniors Housing Operating | COVID-19
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Spot occupancy	76.70%	75.90%	75.20%	74.60%	73.70%	73.20%	72.70%	72.30%	72.50%	73.40%	74.80%
Sequential occupancy change	0.80%	0.80%	0.60%	0.90%	0.50%	0.50%	0.10%		(0.80%)	(1.40%)