Stock-Based Compensation (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	6 Months Ended
Jan. 31, 2019	Jan. 31, 2018	Jan. 31, 2019	Jan. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total intrinsic value of options exercised			$ 23.1	$ 11.8
Options granted, grant date fair value (in usd per share)			$ 12.27	$ 9.29
Aggregate intrinsic value of options outstanding	$ 65.7		$ 65.7
Aggregate intrinsic value of options exercisable	63.0		63.0
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	2.0	$ 1.7	6.9	$ 5.5
Tax benefit associated with stock options	0.3	0.1	1.4	1.3
Unrecognized compensation expense related to non-vested stock options granted	11.2		11.2
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 1.3	$ 1.0	$ 3.0	$ 3.7

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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Unrecognized cost of unvested share-based compensation awards.

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The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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