Fair Value of Financial Instruments (Details 1) - USD ($) $ in Thousands	Jan. 31, 2021	Jul. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	$ 1,279,180	$ 1,354,632
Unrealized Gains	1,994	4,432
Unrealized Losses	(62)	(119)
Total	1,281,112	1,358,945
U.S. Government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	180,916	242,153
Unrealized Gains	115	202
Unrealized Losses	(37)	(81)
Total	180,994	242,274
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	304,059	222,578
Unrealized Gains	0	0
Unrealized Losses	0	0
Total	304,059	222,578
Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	397,727	474,646
Unrealized Gains	1,517	3,448
Unrealized Losses	(25)	(38)
Total	399,219	478,056
U.S. Government bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	147,582	68,332
Unrealized Gains	258	476
Unrealized Losses	0	0
Total	147,840	68,808
Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	44,095	58,564
Unrealized Gains	94	306
Unrealized Losses	0	0
Total	44,189	58,870
Foreign government bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	7,445
Unrealized Gains	10
Unrealized Losses	0
Total	7,455
Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	76,724	56,296
Unrealized Gains	0	0
Unrealized Losses	0	0
Total	76,724	56,296
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	119,632	231,063
Unrealized Gains	0	0
Unrealized Losses	0	0
Total	119,632	231,063
Strategic convertible debt investment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	1,000	1,000
Unrealized Gains	0	0
Unrealized Losses	0	0
Total	$ 1,000	$ 1,000