Real Estate Transactions - 2018 Other Dispositions (Details)	1 Months Ended		3 Months Ended								12 Months Ended
	Mar. 31, 2017 USD ($) facility	Jan. 31, 2017 USD ($) facility	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($) facility	Sep. 30, 2018 USD ($) facility	Jun. 30, 2018 USD ($) facility	Mar. 31, 2018 USD ($) facility	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) facility
Real Estate [Line Items]
Gain (loss) on sales of real estate, net			$ 11,000,000	$ 0	$ 11,000,000	$ 8,000,000		$ 95,000,000	$ 25,000,000		$ 22,900,000	$ 925,985,000	$ 356,641,000
SHOP
Real Estate [Line Items]
Number of properties disposed | facility							2	11	8	2			5
Proceeds from sale of real estate							$ 15,000,000	$ 76,000,000	$ 268,000,000	$ 35,000,000
Gain (loss) on sales of real estate, net										$ 21,000,000
Senior housing triple-net
Real Estate [Line Items]
Number of properties disposed | facility	64								2				4
Proceeds from sale of real estate									$ 35,000,000
Gain (loss) on sales of real estate, net	$ 170,000,000
Medical office
Real Estate [Line Items]
Number of properties disposed | facility								2					4
Proceeds from sale of real estate							$ 4,000,000	$ 21,000,000
Gain (loss) on sales of real estate, net													$ 41,000,000
Life science
Real Estate [Line Items]
Number of properties disposed | facility		4						4					1
Proceeds from sale of real estate								$ 269,000,000
Gain (loss) on sales of real estate, net		$ 45,000,000
Land | Life science
Real Estate [Line Items]
Number of properties disposed | facility							1
Proceeds from sale of real estate							$ 3,000,000