Segment Reporting - Summary of Geographic Information (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 1,052,062	$ 1,258,602
Total assets	32,992,251		$ 32,483,642
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	825,648	1,027,781
Total assets	27,112,760		26,658,659
United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	118,874	117,882
Total assets	3,415,851		3,352,549
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	107,540	$ 112,939
Total assets	$ 2,463,640		$ 2,472,434
Revenue
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage	100.00%	100.00%
Revenue | United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage	78.50%	81.60%
Revenue | United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage	11.30%	9.40%
Revenue | Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage	10.20%	9.00%
Assets
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage	100.00%		100.00%
Assets | United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage	82.10%		82.10%
Assets | United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage	10.40%		10.30%
Assets | Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage	7.50%		7.60%
Resident fees and services | Revenue | United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage	72.00%
Resident fees and services | Revenue | United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage	14.00%
Resident fees and services | Revenue | Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage	14.00%