Segment Reporting - Summary of Geographic Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 1,258,602	$ 1,272,245
Total assets	32,923,028		$ 33,380,751	[1]
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	1,027,781	1,043,667
Total assets	27,431,135		27,513,911
United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	117,882	112,418
Total assets	3,216,727		3,405,388
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	112,939	$ 116,160
Total assets	$ 2,275,166		$ 2,461,452
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	81.60%	82.10%
Revenue | United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage	9.40%	8.80%
Revenue | Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage	9.00%	9.10%
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	83.30%	82.40%
Assets | United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage	9.80%	10.20%
Assets | Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage	6.90%	7.40%
Resident fees and services | Revenue | United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage	77.00%
Resident fees and services | Revenue | United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage	10.00%
Resident fees and services | Revenue | Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage	13.00%

[1] The consolidated balance sheet at December 31, 2019 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.