CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
CASH FLOWS FROM OPERATING ACTIVITIES:
Net (loss) income	$ (293,572,000)	$ (15,774,000)	$ 179,926,000
Adjustments to reconcile net (loss) income to cash provided by (used in) operating activities:
Depreciation and amortization	284,083,000	239,280,000	271,131,000
Net amortization of debt premiums, discounts and issuance costs	11,811,000	8,658,000	13,408,000
Straight line rental income	1,095,000	(8,916,000)	(5,846,000)
Amortization of acquired real estate leases and assumed real estate lease obligations, net	(242,000)	245,000	(7,211,000)
Loss on modification or early extinguishment of debt	2,468,000	30,043,000	2,410,000
Impairment of assets	18,380,000	0	(174,000)
Gain on sale of properties	(1,205,000)	(321,862,000)	(492,272,000)
Gains and losses on equity securities, net	(8,126,000)	25,660,000	42,232,000
Other non-cash adjustments, net	(1,932,000)	(2,038,000)	(1,811,000)
Unconsolidated joint venture distributions	5,100,000	8,769,000	0
Equity in net losses (earnings) of investees	20,461,000	(6,055,000)	0
Change in assets and liabilities:
Deferred leasing costs, net	(9,834,000)	(7,874,000)	(20,701,000)
Other assets	10,672,000	10,946,000	(51,201,000)
Accrued interest	(6,570,000)	(428,000)	7,654,000
Other liabilities	(22,106,000)	(1,007,000)	(868,000)
Net cash provided by (used in) operating activities	10,483,000	(40,353,000)	(63,323,000)
CASH FLOWS FROM INVESTING ACTIVITIES:
Real estate acquisitions and deposits	0	(75,105,000)	0
Real estate improvements	(235,007,000)	(299,387,000)	(227,605,000)
Proceeds from sale of properties, net	18,356,000	822,000	103,257,000
Proceeds from sale of properties to joint venture, net	0	638,488,000	0
Proceeds from sale of interest in joint venture, net	0	108,424,000	367,033,000
Proceeds from insurance recoveries	534,000	14,466,000	0
Proceeds from AlerisLife Inc. tender offer	14,006,000	0	0
Distributions in excess of earnings from Affiliates Insurance Company	0	0	11,000
Net cash (used in) provided by investing activities	(202,111,000)	387,708,000	242,696,000
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of senior unsecured notes, net	0	0	492,500,000
Proceeds from issuance of senior secured notes, net	750,001,000	0	0
Proceeds from borrowings on secured credit facility	0	0	800,000,000
Repayments of borrowings on secured credit facility	(700,000,000)	(100,000,000)	0
Redemption of senior unsecured notes	(250,000,000)	(500,000,000)	(300,000,000)
Repayment of term loan	0	0	(200,000,000)
Repayment of other debt	(17,049,000)	(39,067,000)	(3,159,000)
Loss on early extinguishment of debt settled in cash	(978,000)	(24,375,000)	0
Payment of debt issuance costs	(21,699,000)	(2,817,000)	(10,347,000)
Repurchase of common shares	(393,000)	(171,000)	(383,000)
Distributions to noncontrolling interest	0	0	(22,348,000)
Distributions to shareholders	(9,595,000)	(9,568,000)	(9,540,000)
Net cash (used in) provided by financing activities	(249,713,000)	(675,998,000)	746,723,000
(Decrease) increase in cash and cash equivalents and restricted cash	(441,341,000)	(328,643,000)	926,096,000
Cash and cash equivalents and restricted cash at beginning of period	688,302,000	1,016,945,000	90,849,000
Cash and cash equivalents and restricted cash at end of period	$ 246,961,000	$ 688,302,000	$ 1,016,945,000