Segment Reporting - Summary Information for Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022	[1]
Segment Reporting Information [Line Items]
Rental income	$ 384,507	$ 361,983	$ 1,152,005	$ 1,079,784
Total revenues	1,662,013	1,473,844	4,888,220	4,342,084
Property operating expenses	995,273	912,180	2,911,698	2,619,932
Consolidated net operating income (loss)	666,740	561,664	1,976,522	1,722,152
Depreciation and amortization	339,314	353,699	1,020,371	968,082
Interest expense	156,532	139,682	453,272	389,128
General and administrative expenses	46,106	34,811	134,764	109,071
Loss (gain) on derivatives and financial instruments, net	2,885	6,905	5,095	8,076
Loss (gain) on extinguishment of debt, net	1	2	7	593
Provision for loan losses, net	4,059	490	7,292	(149)
Impairment of assets	7,388	4,356	21,103	4,356
Other expenses	38,220	15,481	72,034	76,716
Income (loss) from continuing operations before income taxes and other items	72,235	6,238	262,584	166,279
Income tax (expense) benefit	(4,584)	(3,257)	(11,132)	(11,335)
Income (loss) from unconsolidated entities	(4,031)	(6,698)	(51,434)	(16,640)
Gain (loss) on real estate dispositions, net	71,102	1,064	69,681	20,466
Income (loss) from continuing operations	134,722	(2,653)	269,699	158,770
Net income (loss)	134,722	(2,653)	269,699	158,770
Total assets	41,654,702		41,654,702		$ 37,893,233
Resident fees and services
Segment Reporting Information [Line Items]
Non-cash consideration	1,199,808	1,068,706	3,490,942	3,073,040
Interest income
Segment Reporting Information [Line Items]
Non-cash consideration	42,220	37,791	117,335	113,925
Other income
Segment Reporting Information [Line Items]
Non-cash consideration	35,478	5,364	127,938	75,335
Seniors Housing Operating
Segment Reporting Information [Line Items]
Rental income			341,172	304,338
Operating Segments | Seniors Housing Operating
Segment Reporting Information [Line Items]
Rental income	0	0	0	0
Total revenues	1,203,899	1,072,600	3,505,019	3,140,422
Property operating expenses	918,990	841,914	2,687,961	2,421,141
Consolidated net operating income (loss)	284,909	230,686	817,058	719,281
Depreciation and amortization	215,195	235,984	656,030	629,955
Interest expense	14,358	9,022	41,981	24,153
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	0	385
Provision for loan losses, net	384	198	2,178	807
Impairment of assets	2,400	0	15,029	0
Other expenses	34,865	8,341	60,504	45,781
Income (loss) from continuing operations before income taxes and other items	17,707	(22,859)	41,336	18,200
Income tax (expense) benefit	0	0	0	0
Income (loss) from unconsolidated entities	(6,021)	(8,788)	(61,055)	(39,239)
Gain (loss) on real estate dispositions, net	71,173	1,146	69,910	2,623
Income (loss) from continuing operations	82,859	(30,501)	50,191	(18,416)
Net income (loss)	82,859	(30,501)	50,191	(18,416)
Total assets	22,568,523		22,568,523
Operating Segments | Seniors Housing Operating | Resident fees and services
Segment Reporting Information [Line Items]
Non-cash consideration	1,199,808	1,068,706	3,490,942	3,073,040
Operating Segments | Seniors Housing Operating | Interest income
Segment Reporting Information [Line Items]
Non-cash consideration	2,194	2,155	6,840	5,255
Operating Segments | Seniors Housing Operating | Other income
Segment Reporting Information [Line Items]
Non-cash consideration	1,897	1,739	7,237	62,127
Operating Segments | Triple-net
Segment Reporting Information [Line Items]
Rental income	194,912	191,443	596,247	584,626
Total revenues	236,322	228,819	776,515	698,342
Property operating expenses	10,044	11,495	32,365	34,197
Consolidated net operating income (loss)	226,278	217,324	744,150	664,145
Depreciation and amortization	58,196	57,338	167,958	160,403
Interest expense	374	196	(436)	830
General and administrative expenses	0	0	0	0
Loss (gain) on derivatives and financial instruments, net	2,885	6,905	5,095	8,076
Loss (gain) on extinguishment of debt, net	0	0	0	0
Provision for loan losses, net	3,675	290	5,116	(951)
Impairment of assets	4,988	3,595	6,074	3,595
Other expenses	1,627	820	4,912	12,327
Income (loss) from continuing operations before income taxes and other items	154,533	148,180	555,431	479,865
Income tax (expense) benefit	0	0	0	0
Income (loss) from unconsolidated entities	2,056	3,167	9,858	24,584
Gain (loss) on real estate dispositions, net	(12)	674	436	18,994
Income (loss) from continuing operations	156,577	152,021	565,725	523,443
Net income (loss)	156,577	152,021	565,725	523,443
Total assets	9,891,968		9,891,968
Operating Segments | Triple-net | Resident fees and services
Segment Reporting Information [Line Items]
Non-cash consideration	0	0	0	0
Operating Segments | Triple-net | Interest income
Segment Reporting Information [Line Items]
Non-cash consideration	39,928	35,556	110,211	108,454
Operating Segments | Triple-net | Other income
Segment Reporting Information [Line Items]
Non-cash consideration	1,482	1,820	70,057	5,262
Operating Segments | Outpatient Medical
Segment Reporting Information [Line Items]
Rental income	189,595	170,540	555,758	495,158
Total revenues	191,958	172,178	562,981	501,823
Property operating expenses	62,204	52,921	179,266	153,484
Consolidated net operating income (loss)	129,754	119,257	383,715	348,339
Depreciation and amortization	65,923	60,377	196,383	177,724
Interest expense	2,313	4,343	9,569	13,441
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	1	2	7	9
Provision for loan losses, net	0	2	(2)	(5)
Impairment of assets	0	761	0	761
Other expenses	1,117	366	2,311	1,362
Income (loss) from continuing operations before income taxes and other items	60,400	53,406	175,447	155,047
Income tax (expense) benefit	0	0	0	0
Income (loss) from unconsolidated entities	(66)	(1,077)	(237)	(1,985)
Gain (loss) on real estate dispositions, net	(59)	(606)	(665)	(1,001)
Income (loss) from continuing operations	60,275	51,723	174,545	152,061
Net income (loss)	60,275	51,723	174,545	152,061
Total assets	7,204,561		7,204,561
Operating Segments | Outpatient Medical | Resident fees and services
Segment Reporting Information [Line Items]
Non-cash consideration	0	0	0	0
Operating Segments | Outpatient Medical | Interest income
Segment Reporting Information [Line Items]
Non-cash consideration	98	80	284	216
Operating Segments | Outpatient Medical | Other income
Segment Reporting Information [Line Items]
Non-cash consideration	2,265	1,558	6,939	6,449
Non-segment / Corporate
Segment Reporting Information [Line Items]
Rental income	0	0	0	0
Total revenues	29,834	247	43,705	1,497
Property operating expenses	4,035	5,850	12,106	11,110
Consolidated net operating income (loss)	25,799	(5,603)	31,599	(9,613)
Depreciation and amortization	0	0	0	0
Interest expense	139,487	126,121	402,158	350,704
General and administrative expenses	46,106	34,811	134,764	109,071
Loss (gain) on derivatives and financial instruments, net	0	0	0	0
Loss (gain) on extinguishment of debt, net	0	0	0	199
Provision for loan losses, net	0	0	0	0
Impairment of assets	0	0	0	0
Other expenses	611	5,954	4,307	17,246
Income (loss) from continuing operations before income taxes and other items	(160,405)	(172,489)	(509,630)	(486,833)
Income tax (expense) benefit	(4,584)	(3,257)	(11,132)	(11,335)
Income (loss) from unconsolidated entities	0	0	0	0
Gain (loss) on real estate dispositions, net	0	(150)	0	(150)
Income (loss) from continuing operations	(164,989)	(175,896)	(520,762)	(498,318)
Net income (loss)	(164,989)	(175,896)	(520,762)	(498,318)
Total assets	1,989,650		1,989,650
Non-segment / Corporate | Resident fees and services
Segment Reporting Information [Line Items]
Non-cash consideration	0	0	0	0
Non-segment / Corporate | Interest income
Segment Reporting Information [Line Items]
Non-cash consideration	0	0	0	0
Non-segment / Corporate | Other income
Segment Reporting Information [Line Items]
Non-cash consideration	$ 29,834	$ 247	$ 43,705	$ 1,497

[1] The consolidated balance sheet at December 31, 2022 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.