Financial Instruments (Contractual Maturities of Types of Securities) (Details) $ in Millions	Jul. 31, 2018 USD ($)
Cost
Due within 1 year	$ 220.3
Due in 1 year through 5 years	124.3
Due in 5 years through 10 years	3.7
Due after 10 years	1.0
Amortized Cost	349.3
Fair Value
Due within 1 year	219.0
Due in 1 year through 5 years	123.4
Due in 5 years through 10 years	3.7
Due after 10 years	1.0
Total	$ 347.1

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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