Fair Value Measurements (Details) - USD ($) $ in Thousands	Oct. 31, 2019	Jul. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	$ 9,894	$ 2,534
Equity investments included in current assets	5,710	5,688
Equity investments included in noncurrent assets	3,637	3,619
Total	19,241	11,841
Fair Value Measurements, Recurring basis [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities			[1]
Equity investments included in current assets	5,710	5,688	[1]
Equity investments included in noncurrent assets			[1]
Total	5,710	5,688	[1]
Fair Value Measurements, Recurring basis [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	9,894	2,534	[2]
Equity investments included in current assets			[2]
Equity investments included in noncurrent assets			[2]
Total	9,894	2,534	[2]
Fair Value Measurements, Recurring basis [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities			[3]
Equity investments included in current assets			[3]
Equity investments included in noncurrent assets	3,637	3,619	[3]
Total	$ 3,637	$ 3,619	[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