Real Estate Transactions - Brookdale MTCA Disposition (Details)	1 Months Ended	3 Months Ended								12 Months Ended
	Mar. 31, 2017 USD ($)	Dec. 31, 2019 USD ($) property	Sep. 30, 2019 USD ($) property	Jun. 30, 2019 USD ($) property	Mar. 31, 2019 USD ($) property	Dec. 31, 2018 USD ($) property	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) property	Dec. 31, 2018 USD ($) property	Dec. 31, 2017 USD ($)	Nov. 30, 2017 property
Real Estate [Line Items]
Proceeds from sale of buildings | $										$ 0	$ 335,709,000	$ 462,242,000
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
Brookedale MTCA
Real Estate [Line Items]
Number of assets to be sold (in properties)						19					19
Assets leased to others | Brookedale MTCA
Real Estate [Line Items]
Proceeds from sale of buildings | $						$ 377,000,000
Gain (loss) on sales of real estate, net | $						$ 40,000,000
Senior housing triple-net
Real Estate [Line Items]
Number of assets to be sold (in properties)					2
Gain (loss) on sales of real estate, net | $	$ 170,000,000
Senior housing triple-net | Assets leased to others
Real Estate [Line Items]
Number of assets to be sold (in properties)													2
Senior housing triple-net | Assets leased to others | Brookedale MTCA
Real Estate [Line Items]
Number of assets to be sold (in properties)						11					11
SHOP
Real Estate [Line Items]
Number of assets to be sold (in properties)		7	1	1	9					7
Gain (loss) on sales of real estate, net | $									$ 21,000,000
SHOP | Brookedale MTCA
Real Estate [Line Items]
Number of assets to be sold (in properties)						8					8
SHOP | Assets leased to others | Brookedale MTCA
Real Estate [Line Items]
Number of assets to be sold (in properties)													4