Acquisitions - Dispositions (Details) - HomeSmart $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)	May 13, 2016 Store
Disposal Group, Held-for-sale, Not Discontinued Operations
Business Acquisition [Line Items]
Disposal group, number of stores | Store			82
Disposal Group, Disposed of by Sale, Not Discontinued Operations
Business Acquisition [Line Items]
Disposal group, number of stores | Store			82
Charge related to write down of disposal group | $	$ 4.6
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Other operating expense (income)
Business Acquisition [Line Items]
Charge related to write down of disposal group | $		$ 4.3