Real Estate Transactions - Dispositions of Real Estate (Details) $ in Thousands		3 Months Ended			6 Months Ended		12 Months Ended
	Jan. 31, 2020 USD ($) property	Jun. 30, 2020 USD ($) property	Mar. 31, 2020 USD ($) property	Jun. 30, 2019 USD ($) property	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($) property	Dec. 31, 2019 property
Real Estate [Line Items]
Gain (loss) on sales of real estate, net		$ 82,863		$ 11,448	$ 247,732	$ 19,492
SHOP
Real Estate [Line Items]
Number of assets to be sold | property		2	7	1		10
Undeveloped Life Science
Real Estate [Line Items]
Number of assets to be sold | property						1
Medical office
Real Estate [Line Items]
Number of assets to be sold | property				5		5
Senior housing triple-net
Real Estate [Line Items]
Number of assets to be sold | property			18			2
Life science
Real Estate [Line Items]
Number of assets to be sold | property				1		1
Life science
Real Estate [Line Items]
Proceeds from sale of buildings				$ 7,000		$ 7,000
Medical office
Real Estate [Line Items]
Proceeds from sale of buildings				15,000		15,000
Senior housing triple-net
Real Estate [Line Items]
Proceeds from sale of buildings			$ 385,000			26,000
SHOP
Real Estate [Line Items]
Proceeds from sale of buildings		$ 28,000	36,000	$ 14,000		82,000
Gain (loss) on sales of real estate, net		$ 2,000
Undeveloped Life Science
Real Estate [Line Items]
Proceeds from sale of buildings						$ 35,000
Brookedale MTCA
Real Estate [Line Items]
Gain (loss) on sales of real estate, net	$ 164,000		$ 165,000
Number of properties disposed | property	18		18				18
San Diego | Medical office
Real Estate [Line Items]
Number of assets to be sold | property		3
San Diego | Medical office
Real Estate [Line Items]
Proceeds from sale of buildings		$ 106,000
Gain (loss) on sales of real estate, net		$ 81,000