Segment Reporting - Summary of Geographic Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Assets:
Amount	$ 59,504,802		$ 59,504,802		$ 51,044,308	[1]
Revenues:
Amount	2,685,692	$ 2,055,663	7,657,023	$ 5,740,288
Resident fees and services	2,061,370	1,511,524	5,896,944	4,265,271
Operating Segments | Seniors Housing Operating
Assets:
Amount	33,567,442		33,567,442		30,094,016
Revenues:
Amount	2,070,115	1,514,022	5,913,718	4,271,132
Resident fees and services	2,061,370	1,511,524	5,896,944	4,265,271
Operating Segments | Triple-net
Assets:
Amount	9,434,879		9,434,879		7,934,415
Revenues:
Amount	286,637	228,649	815,421	593,674
Resident fees and services	0	0	0	0
Operating Segments | Outpatient Medical
Assets:
Amount	7,496,841		7,496,841		7,530,815
Revenues:
Amount	215,172	204,995	637,999	600,542
Resident fees and services	0	0	0	0
Non-segment/Corporate
Assets:
Amount	9,005,640		9,005,640		5,485,062
Revenues:
Amount	113,768	107,997	289,885	274,940
Resident fees and services	0	0	0	0
Resident fees and services
Revenues:
Resident fees and services	2,061,370	1,511,524	5,896,944	4,265,271
United States
Assets:
Amount	46,803,623		46,803,623		41,966,871
Revenues:
Amount	2,044,666	1,745,893	5,878,406	4,822,963
United States | Resident fees and services
Revenues:
Resident fees and services	1,499,789	1,255,020	4,340,445	3,501,168
United Kingdom
Assets:
Amount	7,214,380		7,214,380		5,892,598
Revenues:
Amount	448,018	174,337	1,240,334	499,109
United Kingdom | Resident fees and services
Revenues:
Resident fees and services	388,021	125,581	1,066,789	360,254
Canada
Assets:
Amount	5,486,799		5,486,799		$ 3,184,839
Revenues:
Amount	193,008	135,433	538,283	418,216
Canada | Resident fees and services
Revenues:
Resident fees and services	$ 173,560	$ 130,923	$ 489,710	$ 403,849
Revenue | Geographic Concentration Risk
Assets:
Percentage	100.00%	100.00%	100.00%	100.00%
Revenue | Resident fees and services | Geographic Concentration Risk
Assets:
Percentage	100.00%	100.00%	100.00%	100.00%
Revenue | United States | Geographic Concentration Risk
Assets:
Percentage	76.10%	84.90%	76.80%	84.00%
Revenue | United States | Resident fees and services | Geographic Concentration Risk
Assets:
Percentage	72.80%	83.00%	73.60%	82.10%
Revenue | United Kingdom | Geographic Concentration Risk
Assets:
Percentage	16.70%	8.50%	16.20%	8.70%
Revenue | United Kingdom | Resident fees and services | Geographic Concentration Risk
Assets:
Percentage	18.80%	8.30%	18.10%	8.40%
Revenue | Canada | Geographic Concentration Risk
Assets:
Percentage	7.20%	6.60%	7.00%	7.30%
Revenue | Canada | Resident fees and services | Geographic Concentration Risk
Assets:
Percentage	8.40%	8.70%	8.30%	9.50%
Assets | Geographic Concentration Risk
Assets:
Percentage			100.00%		100.00%
Assets | Segment Concentration Risk
Assets:
Percentage			100.00%		100.00%
Assets | Segment Concentration Risk | Operating Segments | Seniors Housing Operating
Assets:
Percentage			56.40%		59.00%
Assets | Segment Concentration Risk | Operating Segments | Triple-net
Assets:
Percentage			15.90%		15.50%
Assets | Segment Concentration Risk | Operating Segments | Outpatient Medical
Assets:
Percentage			12.60%		14.80%
Assets | Segment Concentration Risk | Non-segment/Corporate
Assets:
Percentage			15.10%		10.70%
Assets | United States | Geographic Concentration Risk
Assets:
Percentage			78.70%		82.20%
Assets | United Kingdom | Geographic Concentration Risk
Assets:
Percentage			12.10%		11.50%
Assets | Canada | Geographic Concentration Risk
Assets:
Percentage			9.20%		6.30%

[1] The consolidated balance sheet at December 31, 2024 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.