Segment Reporting - Summary Information for Reportable Segments (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2022 USD ($) segment	Mar. 31, 2021 USD ($)	Dec. 31, 2021 USD ($)
Segment Reporting [Abstract]
Number of operating segments | segment	3
Segment Reporting Information [Line Items]
Rental income	$ 356,390	$ 302,843
Total revenues	1,395,704	1,052,062
Property operating expenses	853,669	617,326
Consolidated net operating income (loss)	542,035	434,736
Depreciation and amortization	304,088	244,426
Interest expense	121,696	123,142
General and administrative expenses	37,706	29,926
Loss (gain) on derivatives and financial instruments, net	2,578	1,934
Loss (gain) on extinguishment of debt, net	(12)	(4,643)
Provision for loan losses, net	(804)	1,383
Impairment of assets	0	23,568
Other expenses	26,069	10,994
Income (loss) from continuing operations before income taxes and other items	50,714	4,006
Income tax (expense) benefit	(5,013)	(3,943)
Income (loss) from unconsolidated entities	(2,884)	13,049
Gain (loss) on real estate dispositions, net	22,934	59,080
Income (loss) from continuing operations	65,751	72,192
Net income (loss)	65,751	72,192
Total assets	35,472,453		$ 34,910,325
Resident fees and services
Segment Reporting Information [Line Items]
Revenue from contract with customer	994,335	723,464
Interest income
Segment Reporting Information [Line Items]
Revenue from contract with customer	38,994	19,579
Other income
Segment Reporting Information [Line Items]
Revenue from contract with customer	5,985	6,176
Seniors Housing Operating | Resident fees and services
Segment Reporting Information [Line Items]
Revenue from contract with customer	94,827	15,771
Operating Segments | Seniors Housing Operating
Segment Reporting Information [Line Items]
Rental income	0	0
Total revenues	996,612	726,402
Property operating expenses	789,928	555,968
Consolidated net operating income (loss)	206,684	170,434
Depreciation and amortization	192,793	132,586
Interest expense	7,650	11,418
General and administrative expenses	0	0
Loss (gain) on derivatives and financial instruments, net	0	0
Loss (gain) on extinguishment of debt, net	(15)	(4,643)
Provision for loan losses, net	267	251
Impairment of assets		4,604
Other expenses	8,191	3,459
Income (loss) from continuing operations before income taxes and other items	(2,202)	22,759
Income tax (expense) benefit	0	0
Income (loss) from unconsolidated entities	(17,782)	5,234
Gain (loss) on real estate dispositions, net	2,701	5,195
Income (loss) from continuing operations	(17,283)	33,188
Net income (loss)	(17,283)	33,188
Total assets	19,986,904
Operating Segments | Seniors Housing Operating | Resident fees and services
Segment Reporting Information [Line Items]
Revenue from contract with customer	994,335	723,464
Operating Segments | Seniors Housing Operating | Interest income
Segment Reporting Information [Line Items]
Revenue from contract with customer	1,417	1,119
Operating Segments | Seniors Housing Operating | Other income
Segment Reporting Information [Line Items]
Revenue from contract with customer	860	1,819
Operating Segments | Triple-net
Segment Reporting Information [Line Items]
Rental income	196,001	152,463
Total revenues	235,163	168,482
Property operating expenses	11,211	12,841
Consolidated net operating income (loss)	223,952	155,641
Depreciation and amortization	53,504	56,667
Interest expense	314	1,882
General and administrative expenses	0	0
Loss (gain) on derivatives and financial instruments, net	2,578	1,934
Loss (gain) on extinguishment of debt, net	0	0
Provision for loan losses, net	(1,065)	853
Impairment of assets		18,964
Other expenses	11,044	4,983
Income (loss) from continuing operations before income taxes and other items	157,577	70,358
Income tax (expense) benefit	0	0
Income (loss) from unconsolidated entities	15,543	4,907
Gain (loss) on real estate dispositions, net	20,449	2,042
Income (loss) from continuing operations	193,569	77,307
Net income (loss)	193,569	77,307
Total assets	8,986,422
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	37,506	14,922
Operating Segments | Triple-net | Other income
Segment Reporting Information [Line Items]
Revenue from contract with customer	1,656	1,097
Operating Segments | Outpatient Medical
Segment Reporting Information [Line Items]
Rental income	160,389	150,380
Total revenues	163,323	156,223
Property operating expenses	49,915	46,863
Consolidated net operating income (loss)	113,408	109,360
Depreciation and amortization	57,791	55,173
Interest expense	4,567	4,015
General and administrative expenses	0	0
Loss (gain) on derivatives and financial instruments, net	0	0
Loss (gain) on extinguishment of debt, net	3	0
Provision for loan losses, net	(6)	279
Impairment of assets		0
Other expenses	789	712
Income (loss) from continuing operations before income taxes and other items	50,264	49,181
Income tax (expense) benefit	0	0
Income (loss) from unconsolidated entities	(645)	2,908
Gain (loss) on real estate dispositions, net	(216)	51,843
Income (loss) from continuing operations	49,403	103,932
Net income (loss)	49,403	103,932
Total assets	6,333,821
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	71	3,538
Operating Segments | Outpatient Medical | Other income
Segment Reporting Information [Line Items]
Revenue from contract with customer	2,863	2,305
Non-segment / Corporate
Segment Reporting Information [Line Items]
Rental income	0	0
Total revenues	606	955
Property operating expenses	2,615	1,654
Consolidated net operating income (loss)	(2,009)	(699)
Depreciation and amortization	0	0
Interest expense	109,165	105,827
General and administrative expenses	37,706	29,926
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	6,045	1,840
Income (loss) from continuing operations before income taxes and other items	(154,925)	(138,292)
Income tax (expense) benefit	(5,013)	(3,943)
Income (loss) from unconsolidated entities	0	0
Gain (loss) on real estate dispositions, net	0	0
Income (loss) from continuing operations	(159,938)	(142,235)
Net income (loss)	(159,938)	(142,235)
Total assets	165,306
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	$ 606	$ 955