Stock-Based Compensation, Stock Options (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Compensation expense [Abstract]
Stock-based compensation cost	$ 9.5	$ 7.4	$ 4.9
Stock Options [Member]
Compensation expense [Abstract]
Stock-based compensation cost	1.2	1.1	0.9
Fair value of awards vesting	1.2	$ 1.0	$ 0.9
Unrecognized compensation costs	$ 2.2
Weighted average period recognized	2 years 6 months
Assumptions for stock awards granted [Abstract]
Fair value of options (in dollars per share)	$ 7.30	$ 4.60	$ 7.11
Expected life of awards in years	6 years 4 months 24 days	6 years 4 months 24 days	6 years 3 months 18 days
Risk-free interest rate	1.90%	1.40%	1.90%
Expected volatility of the Company's stock	44.30%	45.50%	66.90%
Expected dividend yield on the Company's stock	0.00%	0.00%	0.00%
Annual vesting percentage	25.00%
Award performance period	4 years
Stock options activity [Rollforward]
Outstanding, beginning (in shares)	1.5
Granted (in shares)	0.2
Exercised (in shares)	(0.4)
Forfeited or expired (in shares)	(0.1)
Outstanding, ending (in shares)	1.2	1.5
Exercisable, ending (in shares)	0.7
Weighted average exercise price [Rollforward]
Outstanding, beginning (in dollars per share)	$ 9.83
Granted (in dollars per share)	15.90
Exercised (in dollars per share)	8.89
Forfeited or expired (in dollars per share)	12.64
Outstanding, ending (in dollars per share)	11.16	$ 9.83
Exercisable, ending (in dollars per share)	$ 9.99
Summary of stock option activity [Abstract]
Options, Outstanding, Weighted average remaining contractual term	6 years 1 month 6 days
Options, Outstanding, Aggregate intrinsic value	$ 12.2
Options, Exercisable, Weighted average remaining contractual term	4 years 7 months 6 days
Options, Exercisable, Aggregate intrinsic value	$ 8.0
Additional information related to stock options exercised [Abstract]
Intrinsic value of stock options exercised	4.9	$ 0.5	$ 0.4
Proceeds from stock options exercised	$ 4.3	$ 0.9	$ 0.5
Stock Options [Member] \| Maximum [Member]
Assumptions for stock awards granted [Abstract]
Stock option term	10 years

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Amount of cash inflow from exercise of stock options granted under share-based compensation arrangement.

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The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method.

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The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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The risk-free interest rate assumption that is used in valuing an option on its own shares.

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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For presentations that combine terminations, the number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan or that expired.

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Gross 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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Number of options outstanding, including both vested and non-vested options.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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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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Percentage of vesting of share-based compensation awards.

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Fair value of options vested. Excludes equity instruments other than options, for example, but not limited to, share units, stock appreciation rights, restricted stock.

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