Commitments and Contingencies (Narrative) (Details) - USD ($) $ in Millions	6 Months Ended
	Jan. 31, 2017	Jul. 31, 2016	Jan. 31, 2016
Amount outstanding in letters of credit	$ 66.1
Surety Bonds Outstanding	9.3
Holland Creek Metropolitan District [Member]
Credit-enhanced bonds issued amount	8.0
Amount outstanding in letters of credit	8.1
Red Sky Ranch Metropolitan District [Member]
Other long-term liabilities	$ 2.0	$ 2.0	$ 1.8
Estimated cessation date of capital improvement fee payment obligation	Jul. 31, 2031
Employee Housing Bonds [Member]
Amount outstanding in letters of credit	$ 53.4
Workers' Compensation and General Liability Related to Construction and Development Activities [Member]
Amount outstanding in letters of credit	$ 12.7