Segment Reporting - Summary Information for Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022	[1]
Segment Reporting Information [Line Items]
Rental income	$ 384,059	$ 356,390
Total revenues	1,560,729	1,395,704
Property operating expenses	957,753	853,669
Consolidated net operating income (loss)	602,976	542,035
Depreciation and amortization	339,112	304,088
Interest expense	144,403	121,696
General and administrative expenses	44,371	37,706
Loss (gain) on derivatives and financial instruments, net	930	2,578
Loss (gain) on extinguishment of debt, net	5	(12)
Provision for loan losses, net	777	(804)
Impairment of assets	12,629	0
Other expenses	22,745	26,069
Income (loss) from continuing operations before income taxes and other items	38,004	50,714
Income tax (expense) benefit	(3,045)	(5,013)
Income (loss) from unconsolidated entities	(7,071)	(2,884)
Gain (loss) on real estate dispositions, net	747	22,934
Income (loss) from continuing operations	28,635	65,751
Net income (loss)	28,635	65,751
Total assets	38,493,889		$ 37,893,233
Resident fees and services
Segment Reporting Information [Line Items]
Revenue from contract with customer	1,131,685	994,335
Interest income
Segment Reporting Information [Line Items]
Revenue from contract with customer	36,405	38,994
Other income
Segment Reporting Information [Line Items]
Revenue from contract with customer	8,580	5,985
Seniors Housing Operating
Segment Reporting Information [Line Items]
Rental income	108,915	94,827
Operating Segments | Seniors Housing Operating
Segment Reporting Information [Line Items]
Rental income	0	0
Total revenues	1,136,681	996,612
Property operating expenses	883,784	789,928
Consolidated net operating income (loss)	252,897	206,684
Depreciation and amortization	220,407	192,793
Interest expense	11,487	7,650
General and administrative expenses	0	0
Loss (gain) on derivatives and financial instruments, net	0	0
Loss (gain) on extinguishment of debt, net	0	(15)
Provision for loan losses, net	(73)	267
Impairment of assets	12,629
Other expenses	17,579	8,191
Income (loss) from continuing operations before income taxes and other items	(9,132)	(2,202)
Income tax (expense) benefit	0	0
Income (loss) from unconsolidated entities	(15,589)	(17,782)
Gain (loss) on real estate dispositions, net	833	2,701
Income (loss) from continuing operations	(23,888)	(17,283)
Net income (loss)	(23,888)	(17,283)
Total assets	22,201,219
Operating Segments | Seniors Housing Operating | Resident fees and services
Segment Reporting Information [Line Items]
Revenue from contract with customer	1,131,685	994,335
Operating Segments | Seniors Housing Operating | Interest income
Segment Reporting Information [Line Items]
Revenue from contract with customer	2,551	1,417
Operating Segments | Seniors Housing Operating | Other income
Segment Reporting Information [Line Items]
Revenue from contract with customer	2,445	860
Operating Segments | Triple-net
Segment Reporting Information [Line Items]
Rental income	202,419	196,001
Total revenues	238,065	235,163
Property operating expenses	11,723	11,211
Consolidated net operating income (loss)	226,342	223,952
Depreciation and amortization	54,528	53,504
Interest expense	(15)	314
General and administrative expenses	0	0
Loss (gain) on derivatives and financial instruments, net	930	2,578
Loss (gain) on extinguishment of debt, net	0	0
Provision for loan losses, net	850	(1,065)
Impairment of assets	0
Other expenses	2,467	11,044
Income (loss) from continuing operations before income taxes and other items	167,582	157,577
Income tax (expense) benefit	0	0
Income (loss) from unconsolidated entities	8,432	15,543
Gain (loss) on real estate dispositions, net	520	20,449
Income (loss) from continuing operations	176,534	193,569
Net income (loss)	176,534	193,569
Total assets	8,776,956
Operating Segments | Triple-net | Resident fees and services
Segment Reporting Information [Line Items]
Revenue from contract with customer	0	0
Operating Segments | Triple-net | Interest income
Segment Reporting Information [Line Items]
Revenue from contract with customer	33,763	37,506
Operating Segments | Triple-net | Other income
Segment Reporting Information [Line Items]
Revenue from contract with customer	1,883	1,656
Operating Segments | Outpatient Medical
Segment Reporting Information [Line Items]
Rental income	181,640	160,389
Total revenues	184,831	163,323
Property operating expenses	58,365	49,915
Consolidated net operating income (loss)	126,466	113,408
Depreciation and amortization	64,177	57,791
Interest expense	4,104	4,567
General and administrative expenses	0	0
Loss (gain) on derivatives and financial instruments, net	0	0
Loss (gain) on extinguishment of debt, net	5	3
Provision for loan losses, net	0	(6)
Impairment of assets	0
Other expenses	547	789
Income (loss) from continuing operations before income taxes and other items	57,633	50,264
Income tax (expense) benefit	0	0
Income (loss) from unconsolidated entities	86	(645)
Gain (loss) on real estate dispositions, net	(606)	(216)
Income (loss) from continuing operations	57,113	49,403
Net income (loss)	57,113	49,403
Total assets	7,007,092
Operating Segments | Outpatient Medical | Resident fees and services
Segment Reporting Information [Line Items]
Revenue from contract with customer	0	0
Operating Segments | Outpatient Medical | Interest income
Segment Reporting Information [Line Items]
Revenue from contract with customer	91	71
Operating Segments | Outpatient Medical | Other income
Segment Reporting Information [Line Items]
Revenue from contract with customer	3,100	2,863
Non-segment / Corporate
Segment Reporting Information [Line Items]
Rental income	0	0
Total revenues	1,152	606
Property operating expenses	3,881	2,615
Consolidated net operating income (loss)	(2,729)	(2,009)
Depreciation and amortization	0	0
Interest expense	128,827	109,165
General and administrative expenses	44,371	37,706
Loss (gain) on derivatives and financial instruments, net	0	0
Loss (gain) on extinguishment of debt, net	0	0
Provision for loan losses, net	0	0
Impairment of assets	0
Other expenses	2,152	6,045
Income (loss) from continuing operations before income taxes and other items	(178,079)	(154,925)
Income tax (expense) benefit	(3,045)	(5,013)
Income (loss) from unconsolidated entities	0	0
Gain (loss) on real estate dispositions, net	0	0
Income (loss) from continuing operations	(181,124)	(159,938)
Net income (loss)	(181,124)	(159,938)
Total assets	508,622
Non-segment / Corporate | Resident fees and services
Segment Reporting Information [Line Items]
Revenue from contract with customer	0	0
Non-segment / Corporate | Interest income
Segment Reporting Information [Line Items]
Revenue from contract with customer	0	0
Non-segment / Corporate | Other income
Segment Reporting Information [Line Items]
Revenue from contract with customer	$ 1,152	$ 606

[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.