Commitments and Contingencies (Details 2) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) single_family_property	Dec. 31, 2015 USD ($) single_family_property	Dec. 31, 2014 USD ($)
Commitments and contingencies
Number of real estate properties held-for-sale in escrow | single_family_property	57
Expected proceeds from sale of property held-for-sale	$ 6.6
Company contributions	$ 0.7	$ 0.5	$ 0.3
Commitment to acquire properties
Commitments and contingencies
Number of properties | single_family_property	203	12
Aggregate purchase price	$ 41.7	$ 1.7