Segment Reporting - Properties and Other Investments by Geographic Location (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenues:
Amount	$ 4,742,115	$ 4,605,967	$ 5,121,306
Assets:
Amount	34,910,325	32,483,642
United States
Revenues:
Amount	3,766,707	3,720,155	4,205,492
Assets:
Amount	28,595,703	26,658,659
United Kingdom
Revenues:
Amount	552,650	451,399	452,698
Assets:
Amount	3,938,258	3,352,549
Canada
Revenues:
Amount	422,758	434,413	$ 463,116
Assets:
Amount	$ 2,376,364	$ 2,472,434
Revenue | Geographic Concentration Risk
Assets:
Percentage	100.00%	100.00%	100.00%
Revenue | United States | Geographic Concentration Risk
Assets:
Percentage	79.40%	80.80%	82.10%
Revenue | United States | Resident fees and services | Geographic Concentration Risk
Assets:
Percentage	75.00%
Revenue | United Kingdom | Geographic Concentration Risk
Assets:
Percentage	11.70%	9.80%	8.80%
Revenue | United Kingdom | Resident fees and services | Geographic Concentration Risk
Assets:
Percentage	12.00%
Revenue | Canada | Geographic Concentration Risk
Assets:
Percentage	8.90%	9.40%	9.10%
Revenue | Canada | Resident fees and services | Geographic Concentration Risk
Assets:
Percentage	13.00%
Assets | Geographic Concentration Risk
Assets:
Percentage	100.00%	100.00%
Assets | United States | Geographic Concentration Risk
Assets:
Percentage	81.90%	82.10%
Assets | United Kingdom | Geographic Concentration Risk
Assets:
Percentage	11.30%	10.30%
Assets | Canada | Geographic Concentration Risk
Assets:
Percentage	6.80%	7.60%