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
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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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- Definition

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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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.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
-Paragraph 2
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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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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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-Paragraph 2
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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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No definition available.

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Accounting for Stock-Based Compensation (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended			9 Months Ended
	Jun. 30, 2017	Feb. 28, 2018	Aug. 31, 2017	Feb. 28, 2017	Feb. 28, 2018	Feb. 28, 2017
Restricted stock
Stock options, additional disclosures
Compensation expense		$ 2.0		$ 1.6	$ 4.9	$ 4.2
Performance-based restricted stock
Stock options, additional disclosures
Granted (in shares)			98,750
Granted (in dollars per share)			$ 35.26
Time-based restricted stock
Stock options, additional disclosures
Granted (in shares)			24,425
Granted (in dollars per share)			$ 35.26
Time-based restricted stock \| Board of Directors
Stock options, additional disclosures
Granted (in shares)	55,000
Granted (in dollars per share)	$ 34.95
Stock options
Stock options, additional disclosures
Granted (in shares)			453,450
Granted (in dollars per share)			$ 35.26
Weighted average fair value of stock options granted (in dollars per share)			$ 9.27
Total intrinsic value of stock options exercised					12.0	3.3
Compensation expense		$ 1.4		$ 1.1	$ 3.8	$ 3.4