Business - Master Lease Transactions (Details) $ in Millions		2 Months Ended	9 Months Ended	12 Months Ended
	Nov. 01, 2017 USD ($) property	Dec. 31, 2017 property	Sep. 30, 2017 facility	Dec. 31, 2016 facility	Jan. 01, 2018 USD ($) property
Senior housing triple-net
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of SH NNN facilities transitioned to RIDEA structure | facility			4	17
Affiliated Entity | Master Lease Transactions | Forecast | Assets Leased to Others | Senior housing triple-net
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Amount of annual rent cut | $					$ 5
Number of assets with annual rent cut					3
Number of SH NNN facilities transitioned to RIDEA structure		5
Affiliated Entity | Master Lease Transactions | Subsequent Event | Assets Leased to Others | Senior housing triple-net
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties	34
Properties with right to sell or transition to other operator	32
Right to sell and transfer period for operating leases	1 year
Properties transitioned to cash flow leases expiration period	2 years
Number of assets to be sold	2
Total consideration for disposition of real estate | $	$ 35
Brookdale | Affiliated Entity | Master Lease Transactions | Subsequent Event | Assets Leased to Others
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties	78