Segment Reporting - Summary of Geographic Information (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 1,239,797		$ 1,036,874	$ 3,432,851	$ 3,483,951
Total assets	33,480,025			33,480,025		$ 32,483,642
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	990,034		819,057	2,709,354	2,820,609
Total assets	27,132,959			27,132,959		26,658,659
United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	146,308		110,281	405,938	337,601
Total assets	3,978,661			3,978,661		3,352,549
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	103,455		$ 107,536	317,559	$ 325,741
Total assets	$ 2,368,405			$ 2,368,405		$ 2,472,434
Revenue | Geographic Concentration Risk
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage	100.00%		100.00%	100.00%	100.00%
Revenue | United States | Geographic Concentration Risk
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage	79.90%		79.00%	78.90%	81.00%
Revenue | United Kingdom | Geographic Concentration Risk
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage	11.80%		10.60%	11.80%	9.70%
Revenue | Canada | Geographic Concentration Risk
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage	8.30%		10.40%	9.30%	9.30%
Assets | Geographic Concentration Risk
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage		100.00%		100.00%
Assets | United States | Geographic Concentration Risk
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage		82.10%		81.00%
Assets | United Kingdom | Geographic Concentration Risk
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage		10.30%		11.90%
Assets | Canada | Geographic Concentration Risk
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage		7.60%		7.10%
Resident fees and services | Revenue | United States | Geographic Concentration Risk
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage	74.00%			74.00%
Resident fees and services | Revenue | United Kingdom | Geographic Concentration Risk
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage	13.00%			13.00%
Resident fees and services | Revenue | Canada | Geographic Concentration Risk
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage	13.00%			13.00%