Segment Reporting - Summary of Geographic Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 1,188,475	$ 1,320,106	$ 2,447,077	$ 2,592,351
Total assets	33,162,652		33,162,652		$ 33,380,751	[1]
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	973,772	1,092,376	2,001,553	2,136,042
Total assets	27,655,745		27,655,745		27,513,911
United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	109,437	112,647	227,319	225,065
Total assets	3,175,033		3,175,033		3,405,388
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	105,266	$ 115,083	218,205	$ 231,244
Total assets	$ 2,331,874		$ 2,331,874		$ 2,461,452
Revenue
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage	100.00%	100.00%	100.00%	100.00%
Revenue | United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage	81.90%	82.80%	81.80%	82.40%
Revenue | United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage	9.20%	8.50%	9.30%	8.70%
Revenue | Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage	8.90%	8.70%	8.90%	8.90%
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			83.40%		82.40%
Assets | United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage			9.60%		10.20%
Assets | Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage			7.00%		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.