Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	Apr. 30, 2015		Jul. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	$ 31,376		$ 12,873
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		[1]		[1]
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	31,376	[2]	12,873	[2]
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		[3]		[3]

[1] quoted prices in active markets for identical assets or liabilities

[2] observable inputs other than quoted prices in active markets for identical assets and liabilities

[3] no observable pricing inputs in the market