Segment Reporting - Summary Information for Reportable Segments (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($) segment	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)	[1]
Segment Reporting [Abstract]
Number of operating segments | segment			3
Segment Reporting Information [Line Items]
Rental income	$ 361,983	$ 357,984	$ 1,079,784	$ 1,015,550
Total revenues	1,473,844	1,239,797	4,342,084	3,432,851
Property operating expenses	912,180	729,400	2,619,932	1,989,383
Consolidated net operating income (loss)	561,664	510,397	1,722,152	1,443,468
Depreciation and amortization	353,699	267,754	968,082	753,065
Interest expense	139,682	122,522	389,128	368,005
General and administrative expenses	34,811	32,256	109,071	93,618
Loss (gain) on derivatives and financial instruments, net	6,905	(8,078)	8,076	(6,503)
Loss (gain) on extinguishment of debt, net	2	(5)	593	50,964
Provision for loan losses, net	490	(271)	(149)	7,309
Impairment of assets	4,356	1,490	4,356	48,750
Other expenses	15,481	3,575	76,716	26,256
Income (loss) from continuing operations before income taxes and other items	6,238	91,154	166,279	102,004
Income tax (expense) benefit	(3,257)	(4,940)	(11,335)	(6,662)
Income (loss) from unconsolidated entities	(6,698)	(15,832)	(16,640)	(10,759)
Gain (loss) on real estate dispositions, net	1,064	119,954	20,466	223,702
Income (loss) from continuing operations	(2,653)	190,336	158,770	308,285
Net income (loss)	(2,653)	190,336	158,770	308,285
Total assets	37,414,488		37,414,488		$ 34,910,325
Resident fees and services
Segment Reporting Information [Line Items]
Revenue from contract with customer	1,068,706	835,617	3,073,040	2,299,972
Interest income
Segment Reporting Information [Line Items]
Revenue from contract with customer	37,791	39,864	113,925	97,891
Other income
Segment Reporting Information [Line Items]
Revenue from contract with customer	5,364	6,332	75,335	19,438
Seniors Housing Operating
Segment Reporting Information [Line Items]
Rental income			304,338	100,328
Operating Segments | Seniors Housing Operating
Segment Reporting Information [Line Items]
Rental income	0	0	0	0
Total revenues	1,072,600	839,519	3,140,422	2,308,470
Property operating expenses	841,914	666,610	2,421,141	1,804,939
Consolidated net operating income (loss)	230,686	172,909	719,281	503,531
Depreciation and amortization	235,984	157,176	629,955	420,797
Interest expense	9,022	9,360	24,153	31,331
General and administrative expenses	0	0	0	0
Loss (gain) on derivatives and financial instruments, net	0	0	0	0
Loss (gain) on extinguishment of debt, net	0	0	385	(1,537)
Provision for loan losses, net	198	152	807	222
Impairment of assets	0	0	0	22,317
Other expenses	8,341	5,449	45,781	12,617
Income (loss) from continuing operations before income taxes and other items	(22,859)	772	18,200	17,784
Income tax (expense) benefit	0	0	0	0
Income (loss) from unconsolidated entities	(8,788)	(15,810)	(39,239)	(23,514)
Gain (loss) on real estate dispositions, net	1,146	(615)	2,623	4,552
Income (loss) from continuing operations	(30,501)	(15,653)	(18,416)	(1,178)
Net income (loss)	(30,501)	(15,653)	(18,416)	(1,178)
Total assets	21,560,096		21,560,096
Operating Segments | Seniors Housing Operating | Resident fees and services
Segment Reporting Information [Line Items]
Revenue from contract with customer	1,068,706	835,617	3,073,040	2,299,972
Operating Segments | Seniors Housing Operating | Interest income
Segment Reporting Information [Line Items]
Revenue from contract with customer	2,155	1,135	5,255	3,110
Operating Segments | Seniors Housing Operating | Other income
Segment Reporting Information [Line Items]
Revenue from contract with customer	1,739	2,767	62,127	5,388
Operating Segments | Triple-net
Segment Reporting Information [Line Items]
Rental income	191,443	200,641	584,626	557,829
Total revenues	228,819	239,985	698,342	647,408
Property operating expenses	11,495	11,664	34,197	37,132
Consolidated net operating income (loss)	217,324	228,321	664,145	610,276
Depreciation and amortization	57,338	54,226	160,403	165,299
Interest expense	196	1,548	830	5,134
General and administrative expenses	0	0	0	0
Loss (gain) on derivatives and financial instruments, net	6,905	(8,078)	8,076	(6,503)
Loss (gain) on extinguishment of debt, net	0	0	0	0
Provision for loan losses, net	290	(323)	(951)	10,549
Impairment of assets	3,595	1,490	3,595	24,222
Other expenses	820	(4,248)	12,327	4,845
Income (loss) from continuing operations before income taxes and other items	148,180	183,706	479,865	406,730
Income tax (expense) benefit	0	0	0	0
Income (loss) from unconsolidated entities	3,167	5,038	24,584	14,822
Gain (loss) on real estate dispositions, net	674	81,712	18,994	126,463
Income (loss) from continuing operations	152,021	270,456	523,443	548,015
Net income (loss)	152,021	270,456	523,443	548,015
Total assets	8,700,199		8,700,199
Operating Segments | Triple-net | Resident fees and services
Segment Reporting Information [Line Items]
Revenue from contract with customer	0	0	0	0
Operating Segments | Triple-net | Interest income
Segment Reporting Information [Line Items]
Revenue from contract with customer	35,556	38,257	108,454	86,040
Operating Segments | Triple-net | Other income
Segment Reporting Information [Line Items]
Revenue from contract with customer	1,820	1,087	5,262	3,539
Operating Segments | Outpatient Medical
Segment Reporting Information [Line Items]
Rental income	170,540	157,343	495,158	457,721
Total revenues	172,178	159,503	501,823	474,798
Property operating expenses	52,921	48,072	153,484	140,430
Consolidated net operating income (loss)	119,257	111,431	348,339	334,368
Depreciation and amortization	60,377	56,352	177,724	166,969
Interest expense	4,343	4,811	13,441	12,733
General and administrative expenses	0	0	0	0
Loss (gain) on derivatives and financial instruments, net	0	0	0	0
Loss (gain) on extinguishment of debt, net	2	(5)	9	(5)
Provision for loan losses, net	2	(100)	(5)	(3,462)
Impairment of assets	761	0	761	2,211
Other expenses	366	640	1,362	2,450
Income (loss) from continuing operations before income taxes and other items	53,406	49,733	155,047	153,472
Income tax (expense) benefit	0	0	0	0
Income (loss) from unconsolidated entities	(1,077)	(5,060)	(1,985)	(2,067)
Gain (loss) on real estate dispositions, net	(606)	38,857	(1,001)	92,687
Income (loss) from continuing operations	51,723	83,530	152,061	244,092
Net income (loss)	51,723	83,530	152,061	244,092
Total assets	6,569,005		6,569,005
Operating Segments | Outpatient Medical | Resident fees and services
Segment Reporting Information [Line Items]
Revenue from contract with customer	0	0	0	0
Operating Segments | Outpatient Medical | Interest income
Segment Reporting Information [Line Items]
Revenue from contract with customer	80	472	216	8,741
Operating Segments | Outpatient Medical | Other income
Segment Reporting Information [Line Items]
Revenue from contract with customer	1,558	1,688	6,449	8,336
Non-segment / Corporate
Segment Reporting Information [Line Items]
Rental income	0	0	0	0
Total revenues	247	790	1,497	2,175
Property operating expenses	5,850	3,054	11,110	6,882
Consolidated net operating income (loss)	(5,603)	(2,264)	(9,613)	(4,707)
Depreciation and amortization	0	0	0	0
Interest expense	126,121	106,803	350,704	318,807
General and administrative expenses	34,811	32,256	109,071	93,618
Loss (gain) on derivatives and financial instruments, net	0	0	0	0
Loss (gain) on extinguishment of debt, net	0	0	199	52,506
Provision for loan losses, net	0	0	0	0
Impairment of assets	0	0	0	0
Other expenses	5,954	1,734	17,246	6,344
Income (loss) from continuing operations before income taxes and other items	(172,489)	(143,057)	(486,833)	(475,982)
Income tax (expense) benefit	(3,257)	(4,940)	(11,335)	(6,662)
Income (loss) from unconsolidated entities	0	0	0	0
Gain (loss) on real estate dispositions, net	(150)	0	(150)	0
Income (loss) from continuing operations	(175,896)	(147,997)	(498,318)	(482,644)
Net income (loss)	(175,896)	(147,997)	(498,318)	(482,644)
Total assets	585,188		585,188
Non-segment / Corporate | Resident fees and services
Segment Reporting Information [Line Items]
Revenue from contract with customer	0	0	0	0
Non-segment / Corporate | Interest income
Segment Reporting Information [Line Items]
Revenue from contract with customer	0	0	0	0
Non-segment / Corporate | Other income
Segment Reporting Information [Line Items]
Revenue from contract with customer	$ 247	$ 790	$ 1,497	$ 2,175

[1] The consolidated balance sheet at December 31, 2021 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.