Equity - Additional Information (Detail) (USD $)	9 Months Ended		9 Months Ended		1 Months Ended	3 Months Ended			1 Months Ended		3 Months Ended			9 Months Ended	1 Months Ended
	Apr. 30, 2014	Jul. 31, 2013	Apr. 30, 2014 Additional Paid-in Capital [Member]	Apr. 30, 2014 Straight Path [Member]	Jul. 31, 2013 Class A Common Stock [Member]	Apr. 30, 2014 Class A Common Stock [Member]	Jan. 31, 2014 Class A Common Stock [Member]	Oct. 31, 2013 Class A Common Stock [Member]	Aug. 31, 2013 Class B Common Stock [Member]	Jul. 31, 2013 Class B Common Stock [Member]	Apr. 30, 2014 Class B Common Stock [Member]	Jan. 31, 2014 Class B Common Stock [Member]	Oct. 31, 2013 Class B Common Stock [Member]	Apr. 30, 2013 Class B Common Stock [Member]	Aug. 31, 2013 Fabrix [Member]
Equity Textual [Abstract]
Date of declared dividend will be paid						Jun. 27, 2014					Jun. 27, 2014
Dividends payable		$ 1,837,000
Dividends paid	7,900,000
Dividend paid per share					$ 0.08	$ 0.17	$ 0.17	$ 0.17		$ 0.08	$ 0.17	$ 0.17	$ 0.17
Stock repurchase program, shares authorized for repurchase											8,300,000
Purchase of stock of subsidiary	1,133,000														1,100,000
Noncontrolling interests purchased percentage															2.80%
Equity method investment, ownership percentage															88.40%
Stock repurchased in a fiscal year														77,843
Aggregate purchase price of shares repurchased														800,000
Stock repurchase program, remaining number of shares authorized to be repurchased											5,100,000
Reduction in exercise price of options outstanding									15.29%
Option to purchase shares in spin-off									32,155
Additional liability			$ 1,600,000	$ 1,700,000