Commitments And Contingencies (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jan. 31, 2012	Jul. 31, 2011	Jan. 31, 2011
Holland Creek Metropolitan District [Member]
Loss Contingencies [Line Items]
Credit-enhanced bonds issued amount	$ 8.0
Amount outstanding in letters of credit	8.1
Red Sky Ranch Metropolitan District [Member]
Loss Contingencies [Line Items]
Other long-term liabilities	1.8	1.8	1.8
Estimated cessation date of capital improvement fee payment obligation	July 31, 2028
Various Other [Member]
Loss Contingencies [Line Items]
Amount outstanding in letters of credit	59.7
Employee Housing Bonds [Member]
Loss Contingencies [Line Items]
Amount outstanding in letters of credit	53.4
Workers' Compensation And General Liability Related To Construction And Development Activities [Member]
Loss Contingencies [Line Items]
Amount outstanding in letters of credit	$ 4.4