Segment Reporting - Segment Information for Reportable Segments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Rental income	$ 1,451,786	$ 1,374,695	$ 1,443,360
Total revenues	5,860,615	4,742,115	4,605,967
Property operating expenses	3,558,770	2,774,562	2,597,823
Consolidated net operating income (loss)	2,301,845	1,967,553	2,008,144
Depreciation and amortization	1,310,368	1,037,566	1,038,437
Interest expense	529,519	489,853	514,388
General and administrative expenses	150,390	126,727	128,394
Loss (gain) on derivatives and financial instruments, net	8,334	(7,333)	11,049
Loss (gain) on extinguishment of debt, net	680	49,874	47,049
Provision for loan losses, net	10,320	7,270	94,436
Impairment of assets	17,502	51,107	135,608
Other expenses	101,670	41,739	70,335
Income (loss) from continuing operations before income taxes and other items	173,062	170,750	(31,552)
Income tax (expense) benefit	(7,247)	(8,713)	(9,968)
Income (loss) from unconsolidated entities	(21,290)	(22,933)	(8,083)
Gain (loss) on real estate dispositions, net	16,043	235,375	1,088,455
Income (loss) from continuing operations	160,568	374,479	1,038,852
Net income (loss)	160,568	374,479	1,038,852
Total assets	37,893,233	34,910,325
Non-segment / Corporate
Segment Reporting Information [Line Items]
Rental income	0	0	0
Total revenues	4,934	2,992	2,781
Property operating expenses	16,245	8,817	3,381
Consolidated net operating income (loss)	(11,311)	(5,825)	(600)
Depreciation and amortization	0	0	0
Interest expense	475,645	426,644	432,431
General and administrative expenses	150,390	126,727	128,394
Loss (gain) on derivatives and financial instruments, net	0	0	0
Loss (gain) on extinguishment of debt, net	199	52,506	33,344
Provision for loan losses, net	0	0	0
Impairment of assets	0	0	0
Other expenses	20,064	7,895	24,929
Income (loss) from continuing operations before income taxes and other items	(657,609)	(619,597)	(619,698)
Income tax (expense) benefit	(7,247)	(8,713)	(9,968)
Income (loss) from unconsolidated entities	0	0	0
Gain (loss) on real estate dispositions, net	0	0	0
Income (loss) from continuing operations	(664,856)	(628,310)	(629,666)
Net income (loss)	(664,856)	(628,310)	(629,666)
Total assets	658,300	144,068
Seniors Housing Operating
Segment Reporting Information [Line Items]
Rental income	410,749	194,078	58,053
Seniors Housing Operating | Operating Segments
Segment Reporting Information [Line Items]
Rental income	0	0	0
Total revenues	4,245,417	3,213,250	3,081,863
Property operating expenses	3,292,045	2,529,344	2,326,311
Consolidated net operating income (loss)	953,372	683,906	755,552
Depreciation and amortization	854,800	593,565	544,462
Interest expense	34,833	39,327	54,901
General and administrative expenses	0	0	0
Loss (gain) on derivatives and financial instruments, net	0	0	0
Loss (gain) on extinguishment of debt, net	386	(2,628)	12,659
Provision for loan losses, net	1,039	394	671
Impairment of assets	13,146	22,317	100,741
Other expenses	66,026	27,132	14,265
Income (loss) from continuing operations before income taxes and other items	(16,858)	3,799	27,853
Income tax (expense) benefit	0	0	0
Income (loss) from unconsolidated entities	(53,318)	(39,225)	(33,857)
Gain (loss) on real estate dispositions, net	5,794	6,146	328,249
Income (loss) from continuing operations	(64,382)	(29,280)	322,245
Net income (loss)	(64,382)	(29,280)	322,245
Total assets	22,000,732	18,851,999
Triple-net | Operating Segments
Segment Reporting Information [Line Items]
Rental income	782,329	761,441	733,776
Total revenues	931,507	890,584	801,304
Property operating expenses	44,483	49,462	53,183
Consolidated net operating income (loss)	887,024	841,122	748,121
Depreciation and amortization	215,887	220,699	232,604
Interest expense	963	6,376	9,477
General and administrative expenses	0	0	0
Loss (gain) on derivatives and financial instruments, net	8,334	(7,333)	11,049
Loss (gain) on extinguishment of debt, net	80	0	0
Provision for loan losses, net	9,289	10,339	90,563
Impairment of assets	3,595	26,579	34,867
Other expenses	13,043	4,189	22,923
Income (loss) from continuing operations before income taxes and other items	635,833	580,273	346,638
Income tax (expense) benefit	0	0	0
Income (loss) from unconsolidated entities	34,495	20,687	18,462
Gain (loss) on real estate dispositions, net	16,648	135,881	64,288
Income (loss) from continuing operations	686,976	736,841	429,388
Net income (loss)	686,976	736,841	429,388
Total assets	8,619,314	9,710,194
Outpatient Medical | Operating Segments
Segment Reporting Information [Line Items]
Rental income	669,457	613,254	709,584
Total revenues	678,757	635,289	720,019
Property operating expenses	205,997	186,939	214,948
Consolidated net operating income (loss)	472,760	448,350	505,071
Depreciation and amortization	239,681	223,302	261,371
Interest expense	18,078	17,506	17,579
General and administrative expenses	0	0	0
Loss (gain) on derivatives and financial instruments, net	0	0	0
Loss (gain) on extinguishment of debt, net	15	(4)	1,046
Provision for loan losses, net	(8)	(3,463)	3,202
Impairment of assets	761	2,211	0
Other expenses	2,537	2,523	8,218
Income (loss) from continuing operations before income taxes and other items	211,696	206,275	213,655
Income tax (expense) benefit	0	0	0
Income (loss) from unconsolidated entities	(2,467)	(4,395)	7,312
Gain (loss) on real estate dispositions, net	(6,399)	93,348	695,918
Income (loss) from continuing operations	202,830	295,228	916,885
Net income (loss)	202,830	295,228	916,885
Total assets	6,614,887	6,204,064
Resident fees and services
Segment Reporting Information [Line Items]
Revenue from contract with customer	4,173,711	3,197,223	3,074,022
Resident fees and services | Non-segment / Corporate
Segment Reporting Information [Line Items]
Revenue from contract with customer	0	0	0
Resident fees and services | Seniors Housing Operating | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer	4,173,711	3,197,223	3,074,022
Resident fees and services | Triple-net | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer	0	0	0
Resident fees and services | Outpatient Medical | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer	0	0	0
Interest income
Segment Reporting Information [Line Items]
Revenue from contract with customer	150,571	137,563	69,156
Interest income | Non-segment / Corporate
Segment Reporting Information [Line Items]
Revenue from contract with customer	0	0	0
Interest income | Seniors Housing Operating | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer	7,867	4,231	618
Interest income | Triple-net | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer	142,402	124,540	62,625
Interest income | Outpatient Medical | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer	302	8,792	5,913
Other income
Segment Reporting Information [Line Items]
Revenue from contract with customer	84,547	32,634	19,429
Other income | Non-segment / Corporate
Segment Reporting Information [Line Items]
Revenue from contract with customer	4,934	2,992	2,781
Other income | Seniors Housing Operating | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer	63,839	11,796	7,223
Other income | Triple-net | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer	6,776	4,603	4,903
Other income | Outpatient Medical | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer	$ 8,998	$ 13,243	$ 4,522