Subsequent Events (Details)	Nov. 05, 2019 USD ($) $ / shares	Sep. 30, 2019 $ / shares	Dec. 31, 2018 $ / shares
Common stock, Class A
Subsequent Event [Line Items]
Common stock, par value (in USD per share)		$ 0.01	$ 0.01
Common stock, Class B
Subsequent Event [Line Items]
Common stock, par value (in USD per share)		$ 0.01	$ 0.01
Subsequent Event | Taylor Morrison
Subsequent Event [Line Items]
Common stock, par value (in USD per share)	$ 0.00001
Subsequent Event | Merger | Merger Agreement
Subsequent Event [Line Items]
Termination fee | $	$ 18,000,000
Subsequent Event | Merger | Merger Agreement | Taylor Morrison
Subsequent Event [Line Items]
Termination fee | $	$ 40,000,000
Subsequent Event | Merger | Merger Agreement | Common stock, Class A
Subsequent Event [Line Items]
Additional cash per share, without interest (in USD per share)	$ 2.50
Subsequent Event | Merger | Merger Agreement | Common stock, Class A | Taylor Morrison
Subsequent Event [Line Items]
Conversion of shares (as a ratio)	0.8000
Subsequent Event | Merger | Merger Agreement | Common stock, Class B
Subsequent Event [Line Items]
Additional cash per share, without interest (in USD per share)	$ 2.50
Subsequent Event | Merger | Merger Agreement | Common stock, Class B | Taylor Morrison
Subsequent Event [Line Items]
Conversion of shares (as a ratio)	0.8000