Real Estate Transactions - Dispositions of Real Estate (Details) $ in Thousands		3 Months Ended		12 Months Ended
	Jan. 31, 2020 USD ($) property	Mar. 31, 2020 USD ($) property	Mar. 31, 2019 USD ($) property	Dec. 31, 2019 USD ($) property
Real Estate [Line Items]
Gain (loss) on sales of real estate, net		$ 164,869	$ 8,044
Undeveloped Life Science
Real Estate [Line Items]
Number of assets to be sold | property				1
SHOP
Real Estate [Line Items]
Number of assets to be sold | property		7	9	18
Medical office
Real Estate [Line Items]
Number of assets to be sold | property				10
Senior housing triple-net
Real Estate [Line Items]
Number of assets to be sold | property		18	2	2
Life science
Real Estate [Line Items]
Number of assets to be sold | property			1	1
Other non-reportable segments
Real Estate [Line Items]
Number of assets to be sold | property				2
Life science
Real Estate [Line Items]
Proceeds from sale of buildings			$ 35,000	$ 7,000
Medical office
Real Estate [Line Items]
Proceeds from sale of buildings				23,000
Senior housing triple-net
Real Estate [Line Items]
Proceeds from sale of buildings		$ 385,000	26,000	26,000
SHOP
Real Estate [Line Items]
Proceeds from sale of buildings		$ 36,000	$ 68,000	181,000
Undeveloped Life Science
Real Estate [Line Items]
Proceeds from sale of buildings				35,000
Other non-reportable segments
Real Estate [Line Items]
Proceeds from sale of buildings				$ 20,000
Brookedale MTCA
Real Estate [Line Items]
Number of properties disposed | property	18	18		18
Gain (loss) on sales of real estate, net	$ 164,000