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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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).

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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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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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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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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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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, 2018	Feb. 28, 2019	Aug. 31, 2018	Feb. 28, 2018	Feb. 28, 2019	Feb. 28, 2018
Restricted stock
Stock options, additional disclosures
Compensation expense		$ 2.7		$ 2.0	$ 5.7	$ 4.9
Performance-based restricted stock
Stock options, additional disclosures
Granted (in shares)			43,680
Granted (in dollars per share)			$ 48.09
Time-based restricted stock
Stock options, additional disclosures
Granted (in shares)			38,760
Granted (in dollars per share)			$ 48.09
Time-based restricted stock \| Board of Directors
Stock options, additional disclosures
Granted (in shares)	29,128
Granted (in dollars per share)	$ 45.32
Employee stock options
Stock options, additional disclosures
Granted (in shares)			290,340
Granted (in dollars per share)			$ 48.09
Weighted average fair value of stock options granted (in dollars per share)			$ 13.67
Total intrinsic value of stock options exercised					12.0	12.0
Compensation expense		$ 1.0		$ 1.4	$ 3.2	$ 3.8