Segment Reporting - Summary of Geographic Information (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Dec. 31, 2025
Revenues:
Amount	$ 3,351,926	$ 2,423,087
Resident fees and services	2,780,931	1,864,530
Assets:
Amount	67,220,556		$ 67,303,047	[1]
Operating Segments | Seniors Housing Operating
Revenues:
Amount	2,790,374	1,867,871
Resident fees and services	2,780,931	1,864,530
Assets:
Amount	42,769,806		42,014,932
Operating Segments | Triple-net
Revenues:
Amount	392,112	255,030
Resident fees and services	0	0
Assets:
Amount	12,871,092		13,448,058
Operating Segments | Outpatient Medical
Revenues:
Amount	71,132	211,016
Resident fees and services	0	0
Assets:
Amount	2,404,025		3,322,225
Non-segment/Corporate
Revenues:
Amount	98,308	89,170
Resident fees and services	0	0
Assets:
Amount	9,175,633		8,517,832
Resident fees and services
Revenues:
Resident fees and services	2,780,931	1,864,530
United States
Revenues:
Amount	2,067,124	1,889,335
Assets:
Amount	43,212,714		43,536,068
United States | Resident fees and services
Revenues:
Resident fees and services	1,634,557	1,394,008
United Kingdom
Revenues:
Amount	1,083,186	375,507
Assets:
Amount	17,803,264		18,056,095
United Kingdom | Resident fees and services
Revenues:
Resident fees and services	961,814	321,829
Canada
Revenues:
Amount	201,616	158,245
Assets:
Amount	6,204,578		$ 5,710,884
Canada | Resident fees and services
Revenues:
Resident fees and services	$ 184,560	$ 148,693
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	61.70%	78.00%
Revenue | United States | Resident fees and services | Geographic Concentration Risk
Assets:
Percentage	58.80%	74.70%
Revenue | United Kingdom | Geographic Concentration Risk
Assets:
Percentage	32.30%	15.50%
Revenue | United Kingdom | Resident fees and services | Geographic Concentration Risk
Assets:
Percentage	34.60%	17.30%
Revenue | Canada | Geographic Concentration Risk
Assets:
Percentage	6.00%	6.50%
Revenue | Canada | Resident fees and services | Geographic Concentration Risk
Assets:
Percentage	6.60%	8.00%
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	63.60%		62.40%
Assets | Segment Concentration Risk | Operating Segments | Triple-net
Assets:
Percentage	19.10%		20.00%
Assets | Segment Concentration Risk | Operating Segments | Outpatient Medical
Assets:
Percentage	3.60%		4.90%
Assets | Segment Concentration Risk | Non-segment/Corporate
Assets:
Percentage	13.70%		12.70%
Assets | United States | Geographic Concentration Risk
Assets:
Percentage	64.30%		64.70%
Assets | United Kingdom | Geographic Concentration Risk
Assets:
Percentage	26.50%		26.80%
Assets | Canada | Geographic Concentration Risk
Assets:
Percentage	9.20%		8.50%

[1] The consolidated balance sheet at December 31, 2025 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.