Long-Term Debt - Notes Payable Landwell - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2014
Debt Instrument [Line Items]
Notes payable outstanding	$ 1,043,100,000	$ 893,800,000
LandWell | Note payable to the City of Henderson
Debt Instrument [Line Items]
Debt instrument			$ 3,900,000
Periodic principal payments	$ 250,000
Interest rate terms	The loan bears interest at a 3% fixed rate.
Debt instrument maturity date	Dec. 31, 2020
Frequency of debt instrument payment	semi-annual
Long-term promissory note fixed interest rate	3.00%
Notes payable outstanding	$ 2,500,000