Segment Reporting - Summary of Geographic Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	Dec. 31, 2024
Assets:
Amount	$ 55,833,495		$ 55,833,495		$ 51,044,308	[1]
Revenues:
Amount	2,548,244	$ 1,824,884	4,971,331	$ 3,684,625
Resident fees and services	1,971,044	1,393,473	3,835,574	2,753,747
Operating Segments | Seniors Housing Operating
Assets:
Amount	33,037,597		33,037,597		30,094,016
Revenues:
Amount	1,975,732	1,395,373	3,843,603	2,757,110
Resident fees and services	1,971,044	1,393,473	3,835,574	2,753,747
Operating Segments | Triple-net
Assets:
Amount	8,880,142		8,880,142		7,934,415
Revenues:
Amount	273,754	142,082	528,784	365,025
Resident fees and services	0	0	0	0
Operating Segments | Outpatient Medical
Assets:
Amount	7,495,922		7,495,922		7,530,815
Revenues:
Amount	211,811	197,237	422,827	395,547
Resident fees and services	0	0	0	0
Non-segment/Corporate
Assets:
Amount	6,419,834		6,419,834		5,485,062
Revenues:
Amount	86,947	90,192	176,117	166,943
Resident fees and services	0	0	0	0
Resident fees and services
Revenues:
Resident fees and services	1,971,044	1,393,473	3,835,574	2,753,747
United States
Assets:
Amount	43,370,689		43,370,689		41,966,871
Revenues:
Amount	1,944,405	1,530,174	3,833,740	3,077,070
United States | Resident fees and services
Revenues:
Resident fees and services	1,446,648	1,148,809	2,840,656	2,246,148
United Kingdom
Assets:
Amount	6,826,892		6,826,892		5,892,598
Revenues:
Amount	416,809	163,264	792,316	324,772
United Kingdom | Resident fees and services
Revenues:
Resident fees and services	356,939	117,794	678,768	234,673
Canada
Assets:
Amount	5,635,914		5,635,914		$ 3,184,839
Revenues:
Amount	187,030	131,446	345,275	282,783
Canada | Resident fees and services
Revenues:
Resident fees and services	$ 167,457	$ 126,870	$ 316,150	$ 272,926
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	76.30%	83.90%	77.20%	83.50%
Revenue | United States | Resident fees and services | Geographic Concentration Risk
Assets:
Percentage	73.40%	82.40%	74.10%	81.60%
Revenue | United Kingdom | Geographic Concentration Risk
Assets:
Percentage	16.40%	8.90%	15.90%	8.80%
Revenue | United Kingdom | Resident fees and services | Geographic Concentration Risk
Assets:
Percentage	18.10%	8.50%	17.70%	8.50%
Revenue | Canada | Geographic Concentration Risk
Assets:
Percentage	7.30%	7.20%	6.90%	7.70%
Revenue | Canada | Resident fees and services | Geographic Concentration Risk
Assets:
Percentage	8.50%	9.10%	8.20%	9.90%
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			59.20%		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			13.40%		14.80%
Assets | Segment Concentration Risk | Non-segment/Corporate
Assets:
Percentage			11.50%		10.70%
Assets | United States | Geographic Concentration Risk
Assets:
Percentage			77.70%		82.20%
Assets | United Kingdom | Geographic Concentration Risk
Assets:
Percentage			12.20%		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.