Variable Interest Entities and Investment in Unconsolidated Ventures - Schedule of Variable Interest Entities (Details) $ in Millions	Dec. 31, 2017 USD ($)
CCRC Venture opco
Variable Interest Entity [Line Items]
Maximum Exposure to Loss	$ 29.6
Carrying Amount	29.6
RIDEA Ventures
Variable Interest Entity [Line Items]
Maximum Exposure to Loss	41.3
Carrying Amount	41.3
Blackstone Venture
Variable Interest Entity [Line Items]
Maximum Exposure to Loss	37.1
Carrying Amount	$ 37.1