Real Estate Properties - Schedule of Disposal Groups (Details) $ in Thousands		1 Months Ended												12 Months Ended
	Dec. 31, 2017 USD ($) living_unit building	Dec. 31, 2019 USD ($) ft² living_unit building	Oct. 31, 2019 USD ($) ft² living_unit building	Sep. 30, 2019 USD ($) ft² living_unit building property	Aug. 31, 2019 USD ($) ft² building	Jul. 31, 2019 USD ($) ft² building	Jun. 30, 2019 USD ($) ft² building	May 31, 2019 USD ($) ft² living_unit building	Mar. 31, 2019 USD ($) ft² building	Feb. 28, 2019 USD ($) ft² building	Jun. 30, 2018 USD ($) living_unit building	May 31, 2018 USD ($) living_unit building	Mar. 31, 2018 USD ($) living_unit building	Dec. 31, 2019 USD ($) building property	Dec. 31, 2018 USD ($) building property	Dec. 31, 2017 USD ($) building
Disposal Group, Disposed of by Sale, Not Discontinued Operations
Real Estate [Line Items]
Number of Properties | building														46	5	1
Sales Price														$ 260,783	$ 334,865	$ 55,000
Gain (loss) on Sale														$ 39,696	$ 261,916
Life Science | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Florida
Real Estate [Line Items]
Number of Properties | building										1
Square Footage Of Properties Sold | ft²										60,396
Sales Price										$ 2,900
Gain (loss) on Sale										$ (69)
Life Science | Disposal Group, Disposed of by Sale, Not Discontinued Operations | New Jersey
Real Estate [Line Items]
Number of Properties | building			1
Square Footage Of Properties Sold | ft²			205,439
Sales Price			$ 47,500
Gain (loss) on Sale			$ 0
Office Portfolio
Real Estate [Line Items]
Number of Properties | property														5	13
Office Portfolio | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Massachusetts
Real Estate [Line Items]
Number of Properties | building				1	1	3	7		1
Square Footage Of Properties Sold | ft²				41,065	49,357	103,484	164,121		4,400
Sales Price				$ 2,750	$ 2,221	$ 4,955	$ 8,042		$ 75
Gain (loss) on Sale				$ 1,044	$ 812	$ 2,332	$ 1,590		$ (58)
Office Portfolio | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Colorado
Real Estate [Line Items]
Number of Properties | building								1
Square Footage Of Properties Sold | ft²								15,647
Sales Price								$ 2,590
Gain (loss) on Sale								$ 1,029
Office Portfolio | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Georgia
Real Estate [Line Items]
Number of Properties | building		1
Square Footage Of Properties Sold | ft²		95,010
Sales Price		$ 14,000
Gain (loss) on Sale		$ (63)
Skilled Nursing Facility
Real Estate [Line Items]
Number of Properties | property				15
Skilled Nursing Facility | Disposal Group, Disposed of by Sale, Not Discontinued Operations | California
Real Estate [Line Items]
Number of Properties | building								3			1
Number of Units | living_unit								278			98
Sales Price								$ 21,500			$ 6,500
Gain (loss) on Sale								$ 15,207			$ 3,699
Skilled Nursing Facility | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Various
Real Estate [Line Items]
Number of Properties | building				15
Number of Units | living_unit				964
Sales Price				$ 8,000
Gain (loss) on Sale				$ 0
Skilled Nursing Facility and Independent Living | Disposal Group, Disposed of by Sale, Not Discontinued Operations | South Dakota
Real Estate [Line Items]
Number of Properties | building			3
Number of Units | living_unit			245
Sales Price			$ 10,500
Gain (loss) on Sale			$ 6,661
Independent Living | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Various
Real Estate [Line Items]
Number of Properties | building													2
Number of Units | living_unit													843
Sales Price													$ 217,000
Gain (loss) on Sale													$ 181,154
Independent Living | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Washington
Real Estate [Line Items]
Number of Properties | building		1
Number of Units | living_unit		150
Sales Price		$ 32,500
Gain (loss) on Sale		$ 7,618
Independent Living | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Virginia
Real Estate [Line Items]
Number of Properties | building	1
Number of Units | living_unit	422
Sales Price	$ 55,000
Gain (loss) on Sale	$ 45,901
Independent Living | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Maryland
Real Estate [Line Items]
Number of Properties | building												1
Number of Units | living_unit												354
Sales Price												$ 96,000
Gain (loss) on Sale												$ 78,856
Assisted Living | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Various
Real Estate [Line Items]
Number of Properties | building		7
Number of Units | living_unit		566
Sales Price		$ 103,250
Gain (loss) on Sale		$ 3,593
Assisted Living | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Oregon
Real Estate [Line Items]
Number of Properties | building											1
Number of Units | living_unit											99
Sales Price											$ 15,365
Gain (loss) on Sale											$ (1,793)