Fair Value of Financial Instruments (Details 2) - USD ($) $ in Thousands	Oct. 31, 2020	Jul. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Less than 12 Months	$ 1,086,147
12 Months or Greater	253,953
Total	1,340,100	$ 1,357,945
U.S. Government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Less than 12 Months	143,491
12 Months or Greater	65,625
Total	209,116	242,274
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Less than 12 Months	225,521
12 Months or Greater	0
Total	225,521	222,578
Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Less than 12 Months	339,403
12 Months or Greater	109,727
Total	449,130	478,056
U.S. Government bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Less than 12 Months	134,771
12 Months or Greater	20,355
Total	155,126	68,808
Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Less than 12 Months	2,494
12 Months or Greater	45,024
Total	47,518	58,870
Foreign government bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Less than 12 Months	0
12 Months or Greater	7,472
Total	7,472
Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Less than 12 Months	67,398
12 Months or Greater	5,750
Total	73,148	56,296
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Less than 12 Months	173,069
12 Months or Greater	0
Total	$ 173,069	$ 231,063