Real Estate Transactions - 2018 Other Dispositions (Details) $ in Thousands	3 Months Ended						6 Months Ended		12 Months Ended
	Jun. 30, 2019 USD ($) facility	Mar. 31, 2019 USD ($) facility	Dec. 31, 2018 USD ($) property facility	Sep. 30, 2018 USD ($) facility	Jun. 30, 2018 USD ($) facility	Mar. 31, 2018 USD ($) facility	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($) property	Nov. 30, 2017 property
Real Estate [Line Items]
Gain (loss) on sales of real estate	$ 11,448	$ 8,000		$ 95,000	$ 46,064		$ 19,492	$ 66,879
Proceeds from sale of buildings							$ 0	$ 335,709
SHOP
Real Estate [Line Items]
Number of properties disposed (in facilities) | facility	1	9	2	11	8	2
Total consideration for disposal of real estate	$ 14,000	$ 68,000	$ 15,000	$ 76,000	$ 268,000	$ 35,000
Gain (loss) on sales of real estate						$ 21,000
Medical office
Real Estate [Line Items]
Number of properties disposed (in facilities) | facility	5		2	2
Total consideration for disposal of real estate	$ 15,000		$ 4,000	$ 21,000
Senior housing triple-net
Real Estate [Line Items]
Number of properties disposed (in facilities) | facility		2			2
Total consideration for disposal of real estate		$ 26,000			$ 35,000
Gain (loss) on sales of real estate					$ 25,000
Life science
Real Estate [Line Items]
Number of properties disposed (in facilities) | facility				4
Total consideration for disposal of real estate	$ 7,000			$ 269,000
Land | Life science
Real Estate [Line Items]
Number of properties disposed (in facilities) | facility	1	1	1
Total consideration for disposal of real estate		$ 35,000	$ 3,000
Brookedale MTCA
Real Estate [Line Items]
Number of assets to be sold (in properties) | property			19						19
Assets Leased to Others | Brookedale MTCA
Real Estate [Line Items]
Gain (loss) on sales of real estate									$ 40,000
Proceeds from sale of buildings									$ 377,000
Assets Leased to Others | Brookedale MTCA | SHOP
Real Estate [Line Items]
Number of assets to be sold (in properties) | property										4