Segment Reporting - Summary of Geographic Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 1,140,992	$ 1,188,475	$ 2,193,054	$ 2,447,077
Total assets	32,176,116		32,176,116		$ 32,483,642	[1]
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	893,672	973,772	1,719,320	2,001,553
Total assets	25,673,854		25,673,854		26,658,659
United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	140,756	109,437	259,630	227,319
Total assets	4,075,693		4,075,693		3,352,549
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	106,564	$ 105,266	214,104	$ 218,205
Total assets	$ 2,426,569		$ 2,426,569		$ 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	78.40%	81.90%	78.40%	81.80%
Revenue | United Kingdom | Geographic Concentration Risk
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage	12.30%	9.20%	11.80%	9.30%
Revenue | Canada | Geographic Concentration Risk
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage	9.30%	8.90%	9.80%	8.90%
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			79.80%		82.10%
Assets | United Kingdom | Geographic Concentration Risk
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage			12.70%		10.30%
Assets | Canada | Geographic Concentration Risk
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage			7.50%		7.60%
Resident fees and services | Revenue | United States | Geographic Concentration Risk
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage	73.00%		73.00%
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	14.00%		14.00%

[1] Note: The consolidated balance sheet at December 31, 2020 has been derived from the audited financial statements at that date but does not include all of the information and footnotes required by U.S. generally accepted accounting principles for complete financial statements.