Segment Reporting - Summary of Geographic Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Revenues [Abstract]
Amount	$ 2,055,663	$ 1,662,013	$ 5,740,288	$ 4,888,220
Resident fees and services	1,511,524	1,199,808	4,265,271	3,490,942
Assets:
Amount	48,953,698		48,953,698		$ 44,012,166	[1]
Resident fees and services
Revenues [Abstract]
Resident fees and services	1,511,524	1,199,808	4,265,271	3,490,942
United States
Revenues [Abstract]
Amount	1,745,893	1,384,381	4,822,963	4,072,915
Assets:
Amount	40,861,259		40,861,259		36,929,186
United States | Resident fees and services
Revenues [Abstract]
Resident fees and services	1,255,020	967,360	3,501,168	2,806,301
United Kingdom
Revenues [Abstract]
Amount	174,337	153,765	499,109	455,669
Assets:
Amount	4,930,587		4,930,587		3,587,230
United Kingdom | Resident fees and services
Revenues [Abstract]
Resident fees and services	125,581	111,947	360,254	334,544
Canada
Revenues [Abstract]
Amount	135,433	123,867	418,216	359,636
Assets:
Amount	3,161,852		3,161,852		$ 3,495,750
Canada | Resident fees and services
Revenues [Abstract]
Resident fees and services	$ 130,923	$ 120,501	$ 403,849	$ 350,097
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	84.90%	83.20%	84.00%	83.30%
Revenue | United States | Resident fees and services | Geographic Concentration Risk
Assets:
Percentage	83.00%	80.70%	82.10%	80.40%
Revenue | United Kingdom | Geographic Concentration Risk
Assets:
Percentage	8.50%	9.30%	8.70%	9.30%
Revenue | United Kingdom | Resident fees and services | Geographic Concentration Risk
Assets:
Percentage	8.30%	9.30%	8.40%	9.60%
Revenue | Canada | Geographic Concentration Risk
Assets:
Percentage	6.60%	7.50%	7.30%	7.40%
Revenue | Canada | Resident fees and services | Geographic Concentration Risk
Assets:
Percentage	8.70%	10.00%	9.50%	10.00%
Assets | Geographic Concentration Risk
Assets:
Percentage			100.00%		100.00%
Assets | United States | Geographic Concentration Risk
Assets:
Percentage			83.40%		83.90%
Assets | United Kingdom | Geographic Concentration Risk
Assets:
Percentage			10.10%		8.20%
Assets | Canada | Geographic Concentration Risk
Assets:
Percentage			6.50%		7.90%

[1] The consolidated balance sheet at December 31, 2023 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.