Segment Reporting (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($) segment	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)
Segment Reporting [Abstract]
Number of operating segments | segment	4
Number of reportable segments | segment	3
Revenues:
Total revenues	$ 266,286	$ 275,770
Expenses:
Property operating expenses	117,222	108,098
Depreciation and amortization	72,230	70,339
General and administrative	9,816	25,118
Acquisition and certain other transaction related costs	7,814	20
Impairment of assets	6,206	0
Total expenses	213,288	203,575
(Loss) gain on sale of properties	(122)	181,154
Dividend income	923	659
Unrealized gains on equity securities	22,932	27,241
Interest and other income	114	54
Interest expense	(45,611)	(43,552)
Gain on early extinguishment of debt	0	(130)
Income from continuing operations before income tax expense and equity in earnings of an investee	31,234	237,621
Income tax expense	(134)	(260)
Equity in earnings of an investee	404	44
Net income (loss)	31,504	237,405
Net income attributable to noncontrolling interest	(1,422)	(1,383)
Net income (loss) attributable to common shareholders	30,082	236,022
Assets	7,145,900		$ 7,160,426
MOBs
Revenues:
Total revenues	103,221	101,151
Expenses:
Property operating expenses	32,177	30,938
Depreciation and amortization	36,101	34,385
General and administrative	0	0
Acquisition and certain other transaction related costs	0	0
Impairment of assets	0
Total expenses	68,278	65,323
(Loss) gain on sale of properties	(122)	0
Dividend income	0	0
Unrealized gains on equity securities	0	0
Interest and other income	0	0
Interest expense	(6,030)	(5,909)
Gain on early extinguishment of debt		0
Income from continuing operations before income tax expense and equity in earnings of an investee	28,791	29,919
Income tax expense	0	0
Equity in earnings of an investee	0	0
Net income (loss)	28,791	29,919
Net income attributable to noncontrolling interest	(1,422)	(1,383)
Net income (loss) attributable to common shareholders	27,369	28,536
Assets	3,325,184		3,344,581
Triple Net Leased Senior Living Communities
Revenues:
Total revenues	50,320	67,975
Expenses:
Property operating expenses	0	0
Depreciation and amortization	19,422	20,195
General and administrative	0	0
Acquisition and certain other transaction related costs	0	0
Impairment of assets	6,206
Total expenses	25,628	20,195
(Loss) gain on sale of properties	0	181,154
Dividend income	0	0
Unrealized gains on equity securities	0	0
Interest and other income	0	0
Interest expense	(238)	(571)
Gain on early extinguishment of debt		0
Income from continuing operations before income tax expense and equity in earnings of an investee	24,454	228,363
Income tax expense	0	0
Equity in earnings of an investee	0	0
Net income (loss)	24,454	228,363
Net income attributable to noncontrolling interest	0	0
Net income (loss) attributable to common shareholders	24,454	228,363
Assets	2,030,946		2,044,939
Managed Senior Living Communities
Revenues:
Total revenues	108,045	102,042
Expenses:
Property operating expenses	85,045	77,160
Depreciation and amortization	15,760	14,811
General and administrative	0	0
Acquisition and certain other transaction related costs	0	0
Impairment of assets	0
Total expenses	100,805	91,971
(Loss) gain on sale of properties	0	0
Dividend income	0	0
Unrealized gains on equity securities	0	0
Interest and other income	0	0
Interest expense	(820)	(1,327)
Gain on early extinguishment of debt		(130)
Income from continuing operations before income tax expense and equity in earnings of an investee	6,420	8,614
Income tax expense	0	0
Equity in earnings of an investee	0	0
Net income (loss)	6,420	8,614
Net income attributable to noncontrolling interest	0	0
Net income (loss) attributable to common shareholders	6,420	8,614
Assets	1,388,949		1,395,657
All Other Operations
Revenues:
Total revenues	4,700	4,602
Expenses:
Property operating expenses	0	0
Depreciation and amortization	947	948
General and administrative	9,816	25,118
Acquisition and certain other transaction related costs	7,814	20
Impairment of assets	0
Total expenses	18,577	26,086
(Loss) gain on sale of properties	0	0
Dividend income	923	659
Unrealized gains on equity securities	22,932	27,241
Interest and other income	114	54
Interest expense	(38,523)	(35,745)
Gain on early extinguishment of debt		0
Income from continuing operations before income tax expense and equity in earnings of an investee	(28,431)	(29,275)
Income tax expense	(134)	(260)
Equity in earnings of an investee	404	44
Net income (loss)	(28,161)	(29,491)
Net income attributable to noncontrolling interest	0	0
Net income (loss) attributable to common shareholders	(28,161)	(29,491)
Assets	400,821		$ 375,249
Rental income
Revenues:
Total revenues	158,241	173,728
Rental income | MOBs
Revenues:
Total revenues	103,221	101,151
Rental income | Triple Net Leased Senior Living Communities
Revenues:
Total revenues	50,320	67,975
Rental income | Managed Senior Living Communities
Revenues:
Total revenues	0	0
Rental income | All Other Operations
Revenues:
Total revenues	4,700	4,602
Residents fees and services
Revenues:
Total revenues	108,045	102,042
Residents fees and services | MOBs
Revenues:
Total revenues	0	0
Residents fees and services | Triple Net Leased Senior Living Communities
Revenues:
Total revenues	0	0
Residents fees and services | Managed Senior Living Communities
Revenues:
Total revenues	108,045	102,042
Residents fees and services | All Other Operations
Revenues:
Total revenues	$ 0	$ 0