Accounting for Stock-Based Compensation (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	6 Months Ended
Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2016	Jan. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options awarded			941,350
Weighted average fair value for options granted, per share (in usd per share)			$ 7.08	$ 9.95
Pre-tax stock-based compensation expense associated with stock options	$ 3.3	$ 5.6	$ 4.4	$ 6.9
Tax benefit associated with stock options	1.1	$ 1.9	1.4	2.3
Total intrinsic value of options exercised			4.5	$ 13.4
Aggregate intrinsic value of options outstanding	21.0		21.0
Aggregate intrinsic value of options exercisable	20.9		20.9
2010 Master Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to non-vested stock options granted	$ 9.2		$ 9.2

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.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 14.F)
-URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 14
-Section F

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Unrecognized cost of unvested share-based compensation awards.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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- Definition

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

+ References

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-Publisher FASB
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

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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-Publisher FASB
-Name Accounting Standards Codification
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- Definition

Net number of share options (or share units) granted during the period.

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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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