Segment Reporting - Summary Information for Reportable Segments (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2022 USD ($) segment	Jun. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)	[1]
Segment Reporting [Abstract]
Number of operating segments | segment			3
Segment Reporting Information [Line Items]
Rental income	$ 361,411	$ 354,723	$ 717,801	$ 657,566
Total revenues	1,472,536	1,140,992	2,868,240	2,193,054
Property operating expenses	854,083	642,657	1,707,752	1,259,983
Consolidated net operating income (loss)	618,453	498,335	1,160,488	933,071
Depreciation and amortization	310,295	240,885	614,383	485,311
Interest expense	127,750	122,341	249,446	245,483
General and administrative expenses	36,554	31,436	74,260	61,362
Loss (gain) on derivatives and financial instruments, net	(1,407)	(359)	1,171	1,575
Loss (gain) on extinguishment of debt, net	603	55,612	591	50,969
Provision for loan losses	165	6,197	(639)	7,580
Impairment of assets	0	23,692	0	47,260
Other expenses	35,166	11,687	61,235	22,681
Income (loss) from continuing operations before income taxes and other items	109,327	6,844	160,041	10,850
Income tax (expense) benefit	(3,065)	2,221	(8,078)	(1,722)
Income (loss) from unconsolidated entities	(7,058)	(7,976)	(9,942)	5,073
Gain (loss) on real estate dispositions, net	(3,532)	44,668	19,402	103,748
Income (loss) from continuing operations	95,672	45,757	161,423	117,949
Net income (loss)	95,672	45,757	161,423	117,949
Total assets	36,573,671		36,573,671		$ 34,910,325
Resident fees and services
Segment Reporting Information [Line Items]
Revenue from contract with customer	1,009,999	740,891	2,004,334	1,464,355
Interest income
Segment Reporting Information [Line Items]
Revenue from contract with customer	37,140	38,448	76,134	58,027
Other income
Segment Reporting Information [Line Items]
Revenue from contract with customer	63,986	6,930	69,971	13,106
Seniors Housing Operating | Resident fees and services
Segment Reporting Information [Line Items]
Revenue from contract with customer			198,052	31,918
Operating Segments | Seniors Housing Operating
Segment Reporting Information [Line Items]
Rental income	0	0	0	0
Total revenues	1,071,210	742,549	2,067,822	1,468,951
Property operating expenses	789,299	582,361	1,579,227	1,138,329
Consolidated net operating income (loss)	281,911	160,188	488,595	330,622
Depreciation and amortization	201,178	131,035	393,971	263,621
Interest expense	7,481	10,553	15,131	21,971
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	400	3,106	385	(1,537)
Provision for loan losses	342	(181)	609	70
Impairment of assets		17,713		22,317
Other expenses	29,249	3,709	37,440	7,168
Income (loss) from continuing operations before income taxes and other items	43,261	(5,747)	41,059	17,012
Income tax (expense) benefit	0	0	0	0
Income (loss) from unconsolidated entities	(12,669)	(12,938)	(30,451)	(7,704)
Gain (loss) on real estate dispositions, net	(1,224)	(28)	1,477	5,167
Income (loss) from continuing operations	29,368	(18,713)	12,085	14,475
Net income (loss)	29,368	(18,713)	12,085	14,475
Total assets	20,972,302		20,972,302
Operating Segments | Seniors Housing Operating | Resident fees and services
Segment Reporting Information [Line Items]
Revenue from contract with customer	1,009,999	740,891	2,004,334	1,464,355
Operating Segments | Seniors Housing Operating | Interest income
Segment Reporting Information [Line Items]
Revenue from contract with customer	1,683	856	3,100	1,975
Operating Segments | Seniors Housing Operating | Other income
Segment Reporting Information [Line Items]
Revenue from contract with customer	59,528	802	60,388	2,621
Operating Segments | Triple-net
Segment Reporting Information [Line Items]
Rental income	197,182	204,725	393,183	357,188
Total revenues	234,360	238,941	469,523	407,423
Property operating expenses	11,491	12,627	22,702	25,468
Consolidated net operating income (loss)	222,869	226,314	446,821	381,955
Depreciation and amortization	49,561	54,406	103,065	111,073
Interest expense	320	1,704	634	3,586
General and administrative expenses	0	0	0	0
Loss (gain) on derivatives and financial instruments, net	(1,407)	(359)	1,171	1,575
Loss (gain) on extinguishment of debt, net	0	0	0	0
Provision for loan losses	(176)	10,019	(1,241)	10,872
Impairment of assets		3,768		22,732
Other expenses	463	4,110	11,507	9,093
Income (loss) from continuing operations before income taxes and other items	174,108	152,666	331,685	223,024
Income tax (expense) benefit	0	0	0	0
Income (loss) from unconsolidated entities	5,874	4,877	21,417	9,784
Gain (loss) on real estate dispositions, net	(2,129)	42,709	18,320	44,751
Income (loss) from continuing operations	177,853	200,252	371,422	277,559
Net income (loss)	177,853	200,252	371,422	277,559
Total assets	8,851,738		8,851,738
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	35,392	32,861	72,898	47,783
Operating Segments | Triple-net | Other income
Segment Reporting Information [Line Items]
Revenue from contract with customer	1,786	1,355	3,442	2,452
Operating Segments | Outpatient Medical
Segment Reporting Information [Line Items]
Rental income	164,229	149,998	324,618	300,378
Total revenues	166,322	159,072	329,645	315,295
Property operating expenses	50,648	45,495	100,563	92,358
Consolidated net operating income (loss)	115,674	113,577	229,082	222,937
Depreciation and amortization	59,556	55,444	117,347	110,617
Interest expense	4,531	3,907	9,098	7,922
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	4	0	7	0
Provision for loan losses	(1)	(3,641)	(7)	(3,362)
Impairment of assets		2,211		2,211
Other expenses	207	1,098	996	1,810
Income (loss) from continuing operations before income taxes and other items	51,377	54,558	101,641	103,739
Income tax (expense) benefit	0	0	0	0
Income (loss) from unconsolidated entities	(263)	85	(908)	2,993
Gain (loss) on real estate dispositions, net	(179)	1,987	(395)	53,830
Income (loss) from continuing operations	50,935	56,630	100,338	160,562
Net income (loss)	50,935	56,630	100,338	160,562
Total assets	6,451,415		6,451,415
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	65	4,731	136	8,269
Operating Segments | Outpatient Medical | Other income
Segment Reporting Information [Line Items]
Revenue from contract with customer	2,028	4,343	4,891	6,648
Non-segment / Corporate
Segment Reporting Information [Line Items]
Rental income	0	0	0	0
Total revenues	644	430	1,250	1,385
Property operating expenses	2,645	2,174	5,260	3,828
Consolidated net operating income (loss)	(2,001)	(1,744)	(4,010)	(2,443)
Depreciation and amortization	0	0	0	0
Interest expense	115,418	106,177	224,583	212,004
General and administrative expenses	36,554	31,436	74,260	61,362
Loss (gain) on derivatives and financial instruments, net	0	0	0	0
Loss (gain) on extinguishment of debt, net	199	52,506	199	52,506
Provision for loan losses	0	0	0	0
Impairment of assets		0		0
Other expenses	5,247	2,770	11,292	4,610
Income (loss) from continuing operations before income taxes and other items	(159,419)	(194,633)	(314,344)	(332,925)
Income tax (expense) benefit	(3,065)	2,221	(8,078)	(1,722)
Income (loss) from unconsolidated entities	0	0	0	0
Gain (loss) on real estate dispositions, net	0	0	0	0
Income (loss) from continuing operations	(162,484)	(192,412)	(322,422)	(334,647)
Net income (loss)	(162,484)	(192,412)	(322,422)	(334,647)
Total assets	298,216		298,216
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	$ 644	$ 430	$ 1,250	$ 1,385

[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.