Master Transactions and Cooperation Agreement with Brookdale ("Brookdale Transaction") - Master Lease Transactions (Details) - Master Lease Transactions - Assets Leased to Others - Affiliated Entity $ in Millions	Nov. 01, 2017 USD ($) property	Jan. 01, 2018 USD ($) property
Senior housing triple-net
Lease Amendments And Terminations And Joint Venture Formations.
Number of properties	34
Properties with right to sell or transition to other operator	32
right to sell or 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
Senior housing triple-net | Subsequent Event
Lease Amendments And Terminations And Joint Venture Formations.
Amount of annual rent cut | $		$ 5
Number of assets with annual rent cut		3
Brookdale Senior Living
Lease Amendments And Terminations And Joint Venture Formations.
Number of properties	78