Segment Reporting - Summary Information for Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022	[1]
Segment Reporting Information [Line Items]
Rental income	$ 383,439	$ 361,411	$ 767,498	$ 717,801
Total revenues	1,665,478	1,472,536	3,226,207	2,868,240
Property operating expenses	958,672	854,083	1,916,425	1,707,752
Consolidated net operating income (loss)	706,806	618,453	1,309,782	1,160,488
Depreciation and amortization	341,945	310,295	681,057	614,383
Interest expense	152,337	127,750	296,740	249,446
General and administrative expenses	44,287	36,554	88,658	74,260
Loss (gain) on derivatives and financial instruments, net	1,280	(1,407)	2,210	1,171
Loss (gain) on extinguishment of debt, net	1	603	6	591
Provision for loan losses, net	2,456	165	3,233	(639)
Impairment of assets	1,086	0	13,715	0
Other expenses	11,069	35,166	33,814	61,235
Income (loss) from continuing operations before income taxes and other items	152,345	109,327	190,349	160,041
Income tax (expense) benefit	(3,503)	(3,065)	(6,548)	(8,078)
Income (loss) from unconsolidated entities	(40,332)	(7,058)	(47,403)	(9,942)
Gain (loss) on real estate dispositions, net	(2,168)	(3,532)	(1,421)	19,402
Income (loss) from continuing operations	106,342	95,672	134,977	161,423
Net income (loss)	106,342	95,672	134,977	161,423
Total assets	40,064,135		40,064,135		$ 37,893,233
Resident fees and services
Segment Reporting Information [Line Items]
Non-cash consideration	1,159,449	1,009,999	2,291,134	2,004,334
Interest income
Segment Reporting Information [Line Items]
Non-cash consideration	38,710	37,140	75,115	76,134
Other income
Segment Reporting Information [Line Items]
Non-cash consideration	83,880	63,986	92,460	69,971
Seniors Housing Operating
Segment Reporting Information [Line Items]
Rental income			222,452	198,052
Operating Segments | Seniors Housing Operating
Segment Reporting Information [Line Items]
Rental income	0	0	0	0
Total revenues	1,164,439	1,071,210	2,301,120	2,067,822
Property operating expenses	885,187	789,299	1,768,971	1,579,227
Consolidated net operating income (loss)	279,252	281,911	532,149	488,595
Depreciation and amortization	220,428	201,178	440,835	393,971
Interest expense	16,136	7,481	27,623	15,131
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	400	0	385
Provision for loan losses, net	1,867	342	1,794	609
Impairment of assets	0		12,629
Other expenses	8,060	29,249	25,639	37,440
Income (loss) from continuing operations before income taxes and other items	32,761	43,261	23,629	41,059
Income tax (expense) benefit	0	0	0	0
Income (loss) from unconsolidated entities	(39,445)	(12,669)	(55,034)	(30,451)
Gain (loss) on real estate dispositions, net	(2,096)	(1,224)	(1,263)	1,477
Income (loss) from continuing operations	(8,780)	29,368	(32,668)	12,085
Net income (loss)	(8,780)	29,368	(32,668)	12,085
Total assets	22,074,247		22,074,247
Operating Segments | Seniors Housing Operating | Resident fees and services
Segment Reporting Information [Line Items]
Non-cash consideration	1,159,449	1,009,999	2,291,134	2,004,334
Operating Segments | Seniors Housing Operating | Interest income
Segment Reporting Information [Line Items]
Non-cash consideration	2,095	1,683	4,646	3,100
Operating Segments | Seniors Housing Operating | Other income
Segment Reporting Information [Line Items]
Non-cash consideration	2,895	59,528	5,340	60,388
Operating Segments | Triple-net
Segment Reporting Information [Line Items]
Rental income	198,916	197,182	401,335	393,183
Total revenues	302,128	234,360	540,193	469,523
Property operating expenses	10,598	11,491	22,321	22,702
Consolidated net operating income (loss)	291,530	222,869	517,872	446,821
Depreciation and amortization	55,234	49,561	109,762	103,065
Interest expense	(795)	320	(810)	634
General and administrative expenses	0	0	0	0
Loss (gain) on derivatives and financial instruments, net	1,280	(1,407)	2,210	1,171
Loss (gain) on extinguishment of debt, net	0	0	0	0
Provision for loan losses, net	591	(176)	1,441	(1,241)
Impairment of assets	1,086		1,086
Other expenses	818	463	3,285	11,507
Income (loss) from continuing operations before income taxes and other items	233,316	174,108	400,898	331,685
Income tax (expense) benefit	0	0	0	0
Income (loss) from unconsolidated entities	(630)	5,874	7,802	21,417
Gain (loss) on real estate dispositions, net	(72)	(2,129)	448	18,320
Income (loss) from continuing operations	232,614	177,853	409,148	371,422
Net income (loss)	232,614	177,853	409,148	371,422
Total assets	8,754,820		8,754,820
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	36,520	35,392	70,283	72,898
Operating Segments | Triple-net | Other income
Segment Reporting Information [Line Items]
Non-cash consideration	66,692	1,786	68,575	3,442
Operating Segments | Outpatient Medical
Segment Reporting Information [Line Items]
Rental income	184,523	164,229	366,163	324,618
Total revenues	186,192	166,322	371,023	329,645
Property operating expenses	58,697	50,648	117,062	100,563
Consolidated net operating income (loss)	127,495	115,674	253,961	229,082
Depreciation and amortization	66,283	59,556	130,460	117,347
Interest expense	3,152	4,531	7,256	9,098
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	4	6	7
Provision for loan losses, net	(2)	(1)	(2)	(7)
Impairment of assets	0		0
Other expenses	647	207	1,194	996
Income (loss) from continuing operations before income taxes and other items	57,414	51,377	115,047	101,641
Income tax (expense) benefit	0	0	0	0
Income (loss) from unconsolidated entities	(257)	(263)	(171)	(908)
Gain (loss) on real estate dispositions, net	0	(179)	(606)	(395)
Income (loss) from continuing operations	57,157	50,935	114,270	100,338
Net income (loss)	57,157	50,935	114,270	100,338
Total assets	7,049,214		7,049,214
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	95	65	186	136
Operating Segments | Outpatient Medical | Other income
Segment Reporting Information [Line Items]
Non-cash consideration	1,574	2,028	4,674	4,891
Non-segment / Corporate
Segment Reporting Information [Line Items]
Rental income	0	0	0	0
Total revenues	12,719	644	13,871	1,250
Property operating expenses	4,190	2,645	8,071	5,260
Consolidated net operating income (loss)	8,529	(2,001)	5,800	(4,010)
Depreciation and amortization	0	0	0	0
Interest expense	133,844	115,418	262,671	224,583
General and administrative expenses	44,287	36,554	88,658	74,260
Loss (gain) on derivatives and financial instruments, net	0	0	0	0
Loss (gain) on extinguishment of debt, net	0	199	0	199
Provision for loan losses, net	0	0	0	0
Impairment of assets	0		0
Other expenses	1,544	5,247	3,696	11,292
Income (loss) from continuing operations before income taxes and other items	(171,146)	(159,419)	(349,225)	(314,344)
Income tax (expense) benefit	(3,503)	(3,065)	(6,548)	(8,078)
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	(174,649)	(162,484)	(355,773)	(322,422)
Net income (loss)	(174,649)	(162,484)	(355,773)	(322,422)
Total assets	2,185,854		2,185,854
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	$ 12,719	$ 644	$ 13,871	$ 1,250

[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.