FAIR VALUE MEASUREMENTS - Fair Value of Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Apr. 30, 2020	Jul. 31, 2019
Financial Assets:
Short-term investments:	$ 469,806	$ 512,156
Recurring
Financial Assets:
Total measured at fair value	581,348	778,270
Cash	150,789	130,564
Total cash, cash equivalents and short-term investments	732,137	908,834
Recurring \| Corporate bonds
Financial Assets:
Short-term investments:	370,210	354,549
Recurring \| Commercial paper
Financial Assets:
Short-term investments:	46,375	92,851
Recurring \| U.S. government securities
Financial Assets:
Short-term investments:	53,221	64,756
Recurring \| Money market funds
Financial Assets:
Cash equivalents:	100,550	33,156
Recurring \| Commercial paper
Financial Assets:
Cash equivalents:	10,992	103,029
Recurring \| U.S. government securities
Financial Assets:
Cash equivalents:		119,933
Recurring \| Corporate bonds
Financial Assets:
Cash equivalents:		9,996
Recurring \| Level I
Financial Assets:
Total measured at fair value	100,550	33,156
Recurring \| Level I \| Corporate bonds
Financial Assets:
Short-term investments:	0	0
Recurring \| Level I \| Commercial paper
Financial Assets:
Short-term investments:	0	0
Recurring \| Level I \| U.S. government securities
Financial Assets:
Short-term investments:	0	0
Recurring \| Level I \| Money market funds
Financial Assets:
Cash equivalents:	100,550	33,156
Recurring \| Level I \| Commercial paper
Financial Assets:
Cash equivalents:	0	0
Recurring \| Level I \| U.S. government securities
Financial Assets:
Cash equivalents:		0
Recurring \| Level I \| Corporate bonds
Financial Assets:
Cash equivalents:		0
Recurring \| Level II
Financial Assets:
Total measured at fair value	480,798	745,114
Recurring \| Level II \| Corporate bonds
Financial Assets:
Short-term investments:	370,210	354,549
Recurring \| Level II \| Commercial paper
Financial Assets:
Short-term investments:	46,375	92,851
Recurring \| Level II \| U.S. government securities
Financial Assets:
Short-term investments:	53,221	64,756
Recurring \| Level II \| Money market funds
Financial Assets:
Cash equivalents:	0	0
Recurring \| Level II \| Commercial paper
Financial Assets:
Cash equivalents:	10,992	103,029
Recurring \| Level II \| U.S. government securities
Financial Assets:
Cash equivalents:		119,933
Recurring \| Level II \| Corporate bonds
Financial Assets:
Cash equivalents:		9,996
Recurring \| Level III
Financial Assets:
Total measured at fair value	0	0
Recurring \| Level III \| Corporate bonds
Financial Assets:
Short-term investments:	0	0
Recurring \| Level III \| Commercial paper
Financial Assets:
Short-term investments:	0	0
Recurring \| Level III \| U.S. government securities
Financial Assets:
Short-term investments:	0	0
Recurring \| Level III \| Money market funds
Financial Assets:
Cash equivalents:	0	0
Recurring \| Level III \| Commercial paper
Financial Assets:
Cash equivalents:	$ 0	0
Recurring \| Level III \| U.S. government securities
Financial Assets:
Cash equivalents:		0
Recurring \| Level III \| Corporate bonds
Financial Assets:
Cash equivalents:		$ 0

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), classified as current.

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Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Excludes cash and cash equivalents within disposal group and discontinued operation.

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Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

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