SEGMENT INFORMATION - Income Statement (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Revenues:
Rental income	$ 348,638	$ 359,611	$ 700,739	$ 716,951
Income from loans and investments	10,752	17,665	20,599	36,675
Interest and other income	1,166	585	1,702	926
Total revenues	1,022,938	919,194	2,040,492	1,829,485
Less:
Interest and other income	1,166	585	1,702	926
Property-level operating expenses	574,359	494,195	1,117,080	980,795
Office building and other services costs	1,410	658	2,723	1,276
NOI	446,003	423,756	918,987	846,488
Interest and other income	1,166	585	1,702	926
Interest expense	(113,951)	(110,051)	(224,745)	(220,818)
Depreciation and amortization	(283,075)	(250,700)	(572,139)	(564,848)
General, administrative and professional fees	(32,915)	(30,588)	(75,913)	(70,897)
Loss on extinguishment of debt, net	(7)	74	(7)	(27,016)
Transaction expenses and deal costs	(13,078)	(721)	(33,070)	(5,338)
Allowance on loans receivable and investments	62	59	116	8,961
Other	(48,116)	13,490	(20,926)	22,918
(Loss) income from unconsolidated entities	(1,047)	4,767	(5,316)	4,517
Loss on real estate dispositions	(34)	41,258	2,421	43,791
Income tax benefit (expense)	3,790	(3,641)	8,280	(5,794)
(Loss) income from continuing operations	(41,202)	88,288	(610)	32,890
Net (loss) income	(41,202)	88,288	(610)	32,890
Net income attributable to noncontrolling interests	1,214	1,897	3,074	3,708
Net (loss) income attributable to common stockholders	(42,416)	86,391	(3,684)	29,182
Resident fees and services
Revenues:
Other revenues	658,056	535,952	1,309,177	1,064,602
Office building and other services revenue
Revenues:
Other revenues	4,326	5,381	8,275	10,331
Operating Segments
Less:
Office building and other services costs			2,723
Operating Segments | Triple-Net Leased Properties
Revenues:
Rental income	149,397	159,223	300,958	319,108
Income from loans and investments	0	0	0	0
Interest and other income	0	0	0	0
Total revenues	149,397	159,223	300,958	319,108
Less:
Interest and other income	0	0	0	0
Property-level operating expenses	3,585	4,432	7,593	9,257
Office building and other services costs	0	0	0	0
NOI	145,812	154,791	293,365	309,851
Interest and other income	0	0	0	0
Operating Segments | Triple-Net Leased Properties | Resident fees and services
Revenues:
Other revenues	0	0	0	0
Operating Segments | Triple-Net Leased Properties | Office building and other services revenue
Revenues:
Other revenues	0	0	0	0
Operating Segments | SHOP
Revenues:
Rental income	0	0	0	0
Income from loans and investments	0	0	0	0
Interest and other income	0	0	0	0
Total revenues	658,056	535,952	1,309,177	1,064,602
Less:
Interest and other income	0	0	0	0
Property-level operating expenses	507,446	424,813	982,976	842,642
Office building and other services costs	0	0	0	0
NOI	150,610	111,139	326,201	221,960
Interest and other income	0	0	0	0
Operating Segments | SHOP | Resident fees and services
Revenues:
Other revenues	658,056	535,952	1,309,177	1,064,602
Operating Segments | SHOP | Office building and other services revenue
Revenues:
Other revenues	0	0	0	0
Operating Segments | Office Operations
Revenues:
Rental income	199,241	200,388	399,781	397,843
Income from loans and investments	0	0	0	0
Interest and other income	0	0	0	0
Total revenues	199,911	202,928	401,068	402,727
Less:
Interest and other income	0	0	0	0
Property-level operating expenses	63,328	64,950	126,511	128,896
Office building and other services costs	0	658	0	1,276
NOI	136,583	137,320	274,557	272,555
Interest and other income	0	0	0	0
Operating Segments | Office Operations | Resident fees and services
Revenues:
Other revenues	0	0	0	0
Operating Segments | Office Operations | Office building and other services revenue
Revenues:
Other revenues	670	2,540	1,287	4,884
Non-Segment
Revenues:
Rental income	0	0	0	0
Income from loans and investments	10,752	17,665	20,599	36,675
Interest and other income	1,166	585	1,702	926
Total revenues	15,574	21,091	29,289	43,048
Less:
Interest and other income	1,166	585	1,702	926
Property-level operating expenses	0	0	0	0
Office building and other services costs	1,410	0	2,723	0
NOI	12,998	20,506	24,864	42,122
Interest and other income	1,166	585	1,702	926
Non-Segment | Resident fees and services
Revenues:
Other revenues	0	0	0	0
Non-Segment | Office building and other services revenue
Revenues:
Other revenues	$ 3,656	$ 2,841	$ 6,988	$ 5,447