Fair Value Measurements (Details) - USD ($) $ in Thousands		Apr. 30, 2018	Jul. 31, 2017
Available-for-sale securities:
Marketable securities		$ 10,570	$ 58,272
Rafael Pharma Series D Note			6,300
Total			64,572
Fair Value Measurements, Recurring basis [Member] | Level 1 [Member]
Available-for-sale securities:
Marketable securities	[1]	1,794	12,151
Rafael Pharma Series D Note	[1]
Total	[1]		12,151
Fair Value Measurements, Recurring basis [Member] | Level 2 [Member]
Available-for-sale securities:
Marketable securities	[2]	8,776	46,121
Rafael Pharma Series D Note	[2]
Total	[2]		46,121
Fair Value Measurements, Recurring basis [Member] | Level 3 [Member]
Available-for-sale securities:
Marketable securities	[3]
Rafael Pharma Series D Note	[3]		6,300
Total	[3]		$ 6,300

[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