Cash Equivalents and Investments (Available-for-Sale Securities) (Details) - USD ($) $ in Millions	Oct. 31, 2020	Jul. 31, 2020
Debt Securities, Available-for-sale
Amortized Cost	$ 2,503.2
Fair Value	2,506.4
Cash equivalents:
Debt Securities, Available-for-sale
Amortized Cost	557.6	$ 342.0
Unrealized Gains	0.0	0.0
Unrealized Losses	0.0	0.0
Fair Value	557.6	342.0
Cash equivalents: \| Certificates of deposit
Debt Securities, Available-for-sale
Amortized Cost	150.0
Unrealized Gains	0.0
Unrealized Losses	0.0
Fair Value	150.0
Cash equivalents: \| U.S. government and agency securities
Debt Securities, Available-for-sale
Amortized Cost	407.6	342.0
Unrealized Gains	0.0	0.0
Unrealized Losses	0.0	0.0
Fair Value	407.6	342.0
Investments:
Debt Securities, Available-for-sale
Amortized Cost	1,945.6	1,339.7
Unrealized Gains	3.3	4.6
Unrealized Losses	(0.1)	(0.1)
Fair Value	1,948.8	1,344.2
Investments: \| Certificates of deposit
Debt Securities, Available-for-sale
Amortized Cost	31.1	31.9
Unrealized Gains	0.0	0.0
Unrealized Losses	0.0	0.0
Fair Value	31.1	31.9
Investments: \| Commercial paper
Debt Securities, Available-for-sale
Amortized Cost	10.0
Unrealized Gains	0.0
Unrealized Losses	0.0
Fair Value	10.0
Investments: \| Corporate debt securities
Debt Securities, Available-for-sale
Amortized Cost	330.7	190.1
Unrealized Gains	1.3	1.8
Unrealized Losses	0.0	0.0
Fair Value	332.0	191.9
Investments: \| U.S. government and agency securities
Debt Securities, Available-for-sale
Amortized Cost	1,492.6	1,090.3
Unrealized Gains	2.0	2.8
Unrealized Losses	(0.1)	(0.1)
Fair Value	1,494.5	1,093.0
Investments: \| Non-U.S. government and agency securities
Debt Securities, Available-for-sale
Amortized Cost	81.2	27.4
Unrealized Gains	0.0	0.0
Unrealized Losses	0.0	0.0
Fair Value	$ 81.2	$ 27.4

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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