Segment Reporting - Summary of Geographic Information (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Dec. 31, 2024
Assets:
Amount	$ 53,293,614		$ 51,044,308	[1]
Revenues:
Amount	2,423,087	$ 1,859,741
Resident fees and services	1,864,530	1,360,274
Operating Segments | Seniors Housing Operating
Assets:
Amount	31,598,061		30,094,016
Revenues:
Amount	1,867,871	1,361,737
Resident fees and services	1,864,530	1,360,274
Operating Segments | Triple-net
Assets:
Amount	8,757,037		7,934,415
Revenues:
Amount	255,030	222,943
Resident fees and services	0	0
Operating Segments | Outpatient Medical
Assets:
Amount	7,538,246		7,530,815
Revenues:
Amount	211,016	198,310
Resident fees and services	0	0
Non-segment/Corporate
Assets:
Amount	5,400,270		5,485,062
Revenues:
Amount	89,170	76,751
Resident fees and services	0	0
Resident fees and services
Revenues:
Resident fees and services	1,864,530	1,360,274
United States
Assets:
Amount	41,525,349		41,966,871
Revenues:
Amount	1,889,335	1,546,896
United States | Resident fees and services
Revenues:
Resident fees and services	1,394,008	1,097,339
United Kingdom
Assets:
Amount	6,412,025		5,892,598
Revenues:
Amount	375,507	161,508
United Kingdom | Resident fees and services
Revenues:
Resident fees and services	321,829	116,879
Canada
Assets:
Amount	5,356,240		$ 3,184,839
Revenues:
Amount	158,245	151,337
Canada | Resident fees and services
Revenues:
Resident fees and services	$ 148,693	$ 146,056
Revenue | Geographic Concentration Risk
Assets:
Percentage	100.00%	100.00%
Revenue | Resident fees and services | Geographic Concentration Risk
Assets:
Percentage	100.00%	100.00%
Revenue | United States | Geographic Concentration Risk
Assets:
Percentage	78.00%	83.20%
Revenue | United States | Resident fees and services | Geographic Concentration Risk
Assets:
Percentage	74.70%	80.70%
Revenue | United Kingdom | Geographic Concentration Risk
Assets:
Percentage	15.50%	8.70%
Revenue | United Kingdom | Resident fees and services | Geographic Concentration Risk
Assets:
Percentage	17.30%	8.60%
Revenue | Canada | Geographic Concentration Risk
Assets:
Percentage	6.50%	8.10%
Revenue | Canada | Resident fees and services | Geographic Concentration Risk
Assets:
Percentage	8.00%	10.70%
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	59.30%		59.00%
Assets | Segment Concentration Risk | Operating Segments | Triple-net
Assets:
Percentage	16.40%		15.50%
Assets | Segment Concentration Risk | Operating Segments | Outpatient Medical
Assets:
Percentage	14.10%		14.80%
Assets | Segment Concentration Risk | Non-segment/Corporate
Assets:
Percentage	10.10%		10.70%
Assets | United States | Geographic Concentration Risk
Assets:
Percentage	77.90%		82.20%
Assets | United Kingdom | Geographic Concentration Risk
Assets:
Percentage	12.00%		11.50%
Assets | Canada | Geographic Concentration Risk
Assets:
Percentage	10.10%		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.