Segment Reporting (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) segment	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Segment reporting
Number of reportable segments | segment									2
Total revenues	$ 256,039	$ 255,827	$ 262,003	$ 266,286	$ 285,222	$ 278,969	$ 277,202	$ 275,770	$ 1,040,155	$ 1,117,164	$ 1,074,729
Expenses:
Property operating expenses									489,070	451,581	413,492
Depreciation and amortization									289,025	286,235	276,861
General and administrative									37,028	85,885	103,694
Acquisition and certain other transaction related costs									13,102	194	403
Impairment of assets									115,201	66,346	5,082
Total expenses									943,426	890,241	799,532
Gain on sale of properties									39,696	261,916	46,055
Dividend income									1,846	2,901	2,637
Gains and losses on equity securities, net									(41,898)	(20,724)	0
Interest and other income									941	667	406
Interest expense									(180,112)	(179,287)	(165,019)
Loss on early extinguishment of debt									(44)	(22)	(7,627)
(Loss) income from continuing operations before income tax expense and equity in earnings of an investee									(82,842)	292,374	151,649
Income tax expense									(436)	(476)	(454)
Equity in earnings of an investee									400	516	608
Net income (loss)									(82,878)	292,414	151,803
Net income attributable to noncontrolling interest									(5,356)	(5,542)	(4,193)
Net (loss) income attributable to common shareholders	(51,697)	$ (29,390)	$ (37,229)	$ 30,082	(118,543)	$ 45,805	$ 123,587	$ 236,022	(88,234)	286,872	147,610
Total assets	6,653,826				7,160,426				6,653,826	7,160,426	7,294,019
Non-Segment
Segment reporting
Total revenues									63,644	75,206	88,356
Expenses:
Property operating expenses									0	0	0
Depreciation and amortization									18,777	23,455	25,891
General and administrative									37,028	85,885	103,694
Acquisition and certain other transaction related costs									13,102	194	403
Impairment of assets									6,344	19,549	5,082
Total expenses									75,251	129,083	135,070
Gain on sale of properties									17,872	258,217	46,055
Dividend income									1,846	2,901	2,637
Gains and losses on equity securities, net									(41,898)	(20,724)
Interest and other income									941	667	406
Interest expense									(152,655)	(149,713)	(128,392)
Loss on early extinguishment of debt									(27)	76	(274)
(Loss) income from continuing operations before income tax expense and equity in earnings of an investee									(185,528)	37,547	(126,282)
Income tax expense									(436)	(476)	(454)
Equity in earnings of an investee									400	516	608
Net income (loss)									(185,564)	37,587	(126,128)
Net income attributable to noncontrolling interest									0	0	0
Net (loss) income attributable to common shareholders									(185,564)	37,587	(126,128)
Total assets	443,260				831,512				443,260	831,512	1,018,865
Office Portfolio
Segment reporting
Total revenues									405,016	412,813	382,127
Expenses:
Property operating expenses									132,348	127,732	112,930
Depreciation and amortization									137,611	141,477	128,827
General and administrative									0	0	0
Acquisition and certain other transaction related costs									0	0	0
Impairment of assets									43,035	46,797	0
Total expenses									312,994	316,006	241,757
Gain on sale of properties									6,617	0	0
Dividend income									0	0	0
Gains and losses on equity securities, net									0	0
Interest and other income									0	0	0
Interest expense									(24,399)	(24,360)	(24,919)
Loss on early extinguishment of debt									0	0	(59)
(Loss) income from continuing operations before income tax expense and equity in earnings of an investee									74,240	72,447	115,392
Income tax expense									0	0	0
Equity in earnings of an investee									0	0	0
Net income (loss)									74,240	72,447	115,392
Net income attributable to noncontrolling interest									(5,356)	(5,542)	(4,193)
Net (loss) income attributable to common shareholders									68,884	66,905	111,199
Total assets	3,165,577				3,344,581				3,165,577	3,344,581	3,367,485
SHOP
Segment reporting
Total revenues									571,495	629,145	604,246
Expenses:
Property operating expenses									356,722	323,849	300,562
Depreciation and amortization									132,637	121,303	122,143
General and administrative									0	0	0
Acquisition and certain other transaction related costs									0	0	0
Impairment of assets									65,822	0	0
Total expenses									555,181	445,152	422,705
Gain on sale of properties									15,207	3,699	0
Dividend income									0	0	0
Gains and losses on equity securities, net									0	0
Interest and other income									0	0	0
Interest expense									(3,058)	(5,214)	(11,708)
Loss on early extinguishment of debt									(17)	(98)	(7,294)
(Loss) income from continuing operations before income tax expense and equity in earnings of an investee									28,446	182,380	162,539
Income tax expense									0	0	0
Equity in earnings of an investee									0	0	0
Net income (loss)									28,446	182,380	162,539
Net income attributable to noncontrolling interest									0	0	0
Net (loss) income attributable to common shareholders									28,446	182,380	162,539
Total assets	$ 3,044,989				$ 2,984,333				3,044,989	2,984,333	2,907,669
Rental income
Segment reporting
Total revenues									606,558	700,641	681,022
Rental income | Non-Segment
Segment reporting
Total revenues									63,644	75,206	88,356
Rental income | Office Portfolio
Segment reporting
Total revenues									405,016	412,813	382,127
Rental income | SHOP
Segment reporting
Total revenues									137,898	212,622	210,539
Residents fees and services
Segment reporting
Total revenues									433,597	416,523	393,707
Residents fees and services | Non-Segment
Segment reporting
Total revenues									0	0	0
Residents fees and services | Office Portfolio
Segment reporting
Total revenues									0	0	0
Residents fees and services | SHOP
Segment reporting
Total revenues									$ 433,597	$ 416,523	$ 393,707