Commitments and Contingencies - Land Banking Arrangements (Details)	3 Months Ended
	Mar. 31, 2018 USD ($) Project lot	Dec. 31, 2017 USD ($)
Property, Plant and Equipment [Line Items]
Real estate inventories not owned	$ 282,169,000	$ 0
Liabilities from inventories not owned	282,169,000	$ 0
Land, Banking Arrangement
Property, Plant and Equipment [Line Items]
Real estate inventories not owned	282,200,000
Liabilities from inventories not owned	$ 282,200,000
Total number of land banking projects | Project	1
Total number of lots | lot	3,053,000
Total purchase price	$ 316,452,000
Balance of lots still under option and not purchased, number of lots | lot	3,053,000
Balance of lots still under option and not purchased, purchase price	$ 316,452,000
Forfeited deposits if lots are not purchased	$ 34,283
Minimum | Land, Banking Arrangement
Property, Plant and Equipment [Line Items]
Non-refundable deposit of total purchase price, percentage	15.00%
Maximum | Land, Banking Arrangement
Property, Plant and Equipment [Line Items]
Non-refundable deposit of total purchase price, percentage	25.00%