Commitments and Contingencies (Details) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2017 USD ($) single_family_property	Dec. 31, 2016 USD ($) single_family_property
Long-term Purchase Commitment [Line Items]
Single-family properties sales in escrow | single_family_property	184	57
Single-family properties sales in escrow, selling price	$ 17.1	$ 6.6
Single Family Properties
Long-term Purchase Commitment [Line Items]
Commitment to acquire single-family properties | single_family_property	511	203
Purchase price of commitment to acquire single-family properties	$ 122.6	$ 41.7
Land
Long-term Purchase Commitment [Line Items]
Purchase price of commitment to acquire single-family properties	$ 13.7	$ 3.9