Debt - Debt (Details) - Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations - Mortgage notes payable - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
7 Communities Held For Sale
Debt Instrument [Line Items]
Mortgage debt	$ 23.4
15 Communities Held For Sale
Debt Instrument [Line Items]
Mortgage debt		$ 31.2