Equity (Details Textual) - USD ($)				1 Months Ended	12 Months Ended
	Aug. 01, 2017	Jul. 11, 2016	Jan. 16, 2015	Apr. 30, 2015	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2015	Sep. 30, 2014
Equity (Textual)
Common stock issued for exercises of stock options, value					$ 1,802,000	$ 10,000	$ 68,000
Treasury stock, shares					40,000	40,000
Sale of treasury stock							$ 65,000
Intrinsic value of warrants exercised					$ 9,005,263
Closing stock price					$ 179.40	$ 18.24	$ 23.57
Treasury Stock [Member]
Equity (Textual)
Common stock issued for exercises of stock options, value
Treasury stock, shares		2,030			39,693	39,693	41,723
Sale of treasury stock		$ 52,476			$ 427,916	$ 427,916	$ 480,392
Treasury Stock [Member] | Other officers [Member]
Equity (Textual)
Treasury stock, shares			4,105
Sale of treasury stock			$ 65,003
Class A common stock [Member] | Common Stock [Member]
Equity (Textual)
Common stock, voting rights						Class A common stock are entitled to three votes per share.
Common stock issued for compensation, shares
Common stock issued for exercises of stock options, shares
Common stock issued for exercises of stock options, value
Common stock issued for deferred stock units, shares
Class B common stock [Member]
Equity (Textual)
Common stock, voting rights						Class B common stock are entitled to one-tenth of a vote per share.
Class B common stock [Member] | Dividends [Member]
Equity (Textual)
Dividend declared				$ 5,647,342
Amount paid to minority shareholders				875,338
Unpaid dividends				4,772,004
Class B common stock [Member] | Jonas [Member]
Equity (Textual)
Common stock issued for compensation, shares					180,000	60,000
Class B common stock [Member] | Other officers [Member]
Equity (Textual)
Common stock issued for compensation, shares					108,000
Class B common stock [Member] | Consultant [Member]
Equity (Textual)
Common stock issued for compensation, shares					1,250	1,250
Class B common stock [Member] | Two Employees [Member]
Equity (Textual)
Common stock issued for compensation, shares						36,000
Class B common stock [Member] | Non employee directors [Member]
Equity (Textual)
Common stock issued for compensation, shares					24,000	24,000
Class B common stock [Member] | Directors and officers [Member]
Equity (Textual)
Common stock issued for compensation, shares							264,500
Class B common stock [Member] | Other employees (Member)
Equity (Textual)
Common stock issued for compensation, shares					56,000
Class B common stock [Member] | IDT[Member]
Equity (Textual)
Number of restricted shares issued to former employees						131	2,200
Class B common stock [Member] | Common Stock [Member]
Equity (Textual)
Common stock issued for compensation, shares					369,000
Common stock issued for exercises of stock options, shares					41,000	2,000	12,000
Common stock issued for exercises of stock options, value					$ 1,000
Common stock issued for deferred stock units, shares							20,000
Class B common stock [Member] | Treasury Stock [Member]
Equity (Textual)
Number of shares held in treasury stock value				$ 197,344				$ 348,051
Treasury stock, shares				9,982				35,846
Class B common stock [Member] | Warrant [Member]
Equity (Textual)
Common stock issued for exercises of warrants, shares					147,682
Common stock issued for exercises of stock options, value					$ 5,125,000
Class B common stock [Member] | Warrant [Member] | Subsequent Event [Member]
Equity (Textual)
Issuances of warrants to purchase	17,251
Stock options [Member]
Equity (Textual)
Common stock issued for exercises of stock options, shares					(41,114)	(1,631)	(12,053)
Stock options [Member] | Class B common stock [Member]
Equity (Textual)
Common stock issued for exercises of stock options, shares					41,114	1,631	12,053
Common stock issued for exercises of stock options, value					$ 1,801,600	$ 9,300	$ 68,000
Common stock issued for deferred stock units, shares							20,300