Segment Reporting - Income Statements (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenues:
Total revenues	$ 337,416			$ 394,339			$ 1,046,481	$ 1,247,117
Expenses:
Property operating expenses	266,073			315,650			818,096	934,150
Depreciation and amortization	68,702			67,211			202,743	204,466
General and administrative	8,870			6,988			25,538	23,132
Acquisition and certain other transaction related costs	3,108			53			15,179	803
Impairment of assets	0			64,202			(174)	106,611
Total expenses	346,753			454,104			1,061,382	1,269,162
Gain (loss) on sale of properties	200			(211)			30,838	2,403
Gains and losses on equity securities, net	(14,755)			12,510			(26,943)	14,541
Interest and other income	976			134			19,849	8,008
Interest expense	(64,493)			(58,091)			(192,241)	(143,715)
Gain on lease termination	0			0			0	22,896
Loss on early extinguishment of debt	0			0			(2,410)	(427)
Loss from continuing operations before income tax expense	(87,409)			(105,423)			(185,808)	(118,339)
Income tax expense	(595)			(365)			(1,024)	(1,048)
Net loss	(88,004)	$ (32,645)	$ (66,183)	(105,788)	$ (24,742)	$ 11,143	(186,832)	(119,387)
Net income attributable to noncontrolling interest	(1,339)			(1,100)			(4,238)	(3,838)
Net loss attributable to common shareholders	(89,343)			(106,888)			(191,070)	(123,225)
Operating Segments | Office Portfolio
Revenues:
Total revenues	91,520			94,235			277,647	288,515
Expenses:
Property operating expenses	32,386			33,448			95,000	97,047
Depreciation and amortization	32,142			32,816			96,577	97,213
General and administrative	0			0			0	0
Acquisition and certain other transaction related costs	0			0			0	0
Impairment of assets				1,334			0	8,090
Total expenses	64,528			67,598			191,577	202,350
Gain (loss) on sale of properties	0			(169)			30,638	2,613
Gains and losses on equity securities, net	0			0			0	0
Interest and other income	0			0			0	0
Interest expense	(6,053)			(6,068)			(17,984)	(18,140)
Gain on lease termination								0
Loss on early extinguishment of debt							0	(401)
Loss from continuing operations before income tax expense	20,939			20,400			98,724	70,237
Income tax expense	0			0			0	0
Net loss	20,939			20,400			98,724	70,237
Net income attributable to noncontrolling interest	(1,339)			(1,100)			(4,238)	(3,838)
Net loss attributable to common shareholders	19,600			19,300			94,486	66,399
Operating Segments | SHOP
Revenues:
Total revenues	236,013			290,101			739,926	926,174
Expenses:
Property operating expenses	233,687			282,202			723,096	837,103
Depreciation and amortization	33,688			31,570			97,587	98,385
General and administrative	0			0			0	0
Acquisition and certain other transaction related costs	0			0			0	0
Impairment of assets				62,868			(174)	98,521
Total expenses	267,375			376,640			820,509	1,034,009
Gain (loss) on sale of properties	200			(42)			200	(210)
Gains and losses on equity securities, net	0			0			0	0
Interest and other income	786			0			18,967	7,346
Interest expense	(523)			(552)			(1,576)	(1,676)
Gain on lease termination								0
Loss on early extinguishment of debt							0	0
Loss from continuing operations before income tax expense	(30,899)			(87,133)			(62,992)	(102,375)
Income tax expense	0			0			0	0
Net loss	(30,899)			(87,133)			(62,992)	(102,375)
Net income attributable to noncontrolling interest	0			0			0	0
Net loss attributable to common shareholders	(30,899)			(87,133)			(62,992)	(102,375)
Non-Segment
Revenues:
Total revenues	9,883			10,003			28,908	32,428
Expenses:
Property operating expenses	0			0			0	0
Depreciation and amortization	2,872			2,825			8,579	8,868
General and administrative	8,870			6,988			25,538	23,132
Acquisition and certain other transaction related costs	3,108			53			15,179	803
Impairment of assets				0			0	0
Total expenses	14,850			9,866			49,296	32,803
Gain (loss) on sale of properties	0			0			0	0
Gains and losses on equity securities, net	(14,755)			12,510			(26,943)	14,541
Interest and other income	190			134			882	662
Interest expense	(57,917)			(51,471)			(172,681)	(123,899)
Gain on lease termination								22,896
Loss on early extinguishment of debt							(2,410)	(26)
Loss from continuing operations before income tax expense	(77,449)			(38,690)			(221,540)	(86,201)
Income tax expense	(595)			(365)			(1,024)	(1,048)
Net loss	(78,044)			(39,055)			(222,564)	(87,249)
Net income attributable to noncontrolling interest	0			0			0	0
Net loss attributable to common shareholders	(78,044)			(39,055)			(222,564)	(87,249)
Rental income
Revenues:
Total revenues	101,403			104,238			306,555	320,943
Rental income | Operating Segments | Office Portfolio
Revenues:
Total revenues	91,520			94,235			277,647	288,515
Rental income | Operating Segments | SHOP
Revenues:
Total revenues	0			0			0	0
Rental income | Non-Segment
Revenues:
Total revenues	9,883			10,003			28,908	32,428
Residents fees and services
Revenues:
Total revenues	236,013			290,101			739,926	926,174
Residents fees and services | Operating Segments | Office Portfolio
Revenues:
Total revenues	0			0			0	0
Residents fees and services | Operating Segments | SHOP
Revenues:
Total revenues	236,013			290,101			739,926	926,174
Residents fees and services | Non-Segment
Revenues:
Total revenues	$ 0			$ 0			$ 0	$ 0