Stock-Based Compensation - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended		12 Months Ended			1 Months Ended	12 Months Ended	1 Months Ended	12 Months Ended	1 Months Ended
	Mar. 26, 2012	Mar. 31, 2012	Jul. 31, 2014	Jul. 31, 2013	Jul. 31, 2012	Sep. 30, 2014 Subsequent Event [Member]	Jul. 31, 2014 Stock Option [Member]	Sep. 24, 2012 Straight Path IP Group, Inc. [Member]	Jul. 31, 2013 Straight Path IP Group, Inc. [Member]	Aug. 31, 2013 Class B Common Stock [Member]	Mar. 26, 2012 Class B Common Stock [Member]	Nov. 22, 2011 Class B Common Stock [Member]	Dec. 31, 2011 Class B Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock reserved for award under 2005 Stock Option and Incentive Plan			5,300,000										1,100,000
Shares of common stock authorized for award under 2014 Stock Option and Incentive Plan						500,000
Shares of common stock available for future grants			300,000
Stock option awards vesting period							3 years
Stock option awards contractual term							10 years
Weighted-average grant date fair value of options granted during the period					$ 4.97
Total intrinsic value of options exercised during the period			$ 0.2	$ 0.2
Total unrecognized compensation cost			1.4
Total unrecognized compensation cost, Weighted-average period of recognization			2 years 2 months 12 days
Percentage of reduction in the exercise price										15.29%		43.80%
Fully vested outstanding options to purchase shares of Class B common stock										32,155		500,000
Stock option expiration period extended	3 years
Extension or replacement applied to options to purchase an aggregate shares of Class B common stock											600,000
Stock-based compensation expense		0.3							0.7
Option holder shared ratably to purchase shares of Class B common stock												50,000
Total unrecognized compensation cost related to non-vested stock-based compensation arrangements			3.5
Total unrecognized compensation cost related to non-vested stock-based compensation arrangements, expected weighted-average period			10 months 24 days
Total grant date fair value of shares vested			$ 8.7	$ 3.5	$ 5.7
Percentage of grant approved by the Board of Directors								10.00%