Share-Based Compensation (Stock Option Activity) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	6 Months Ended
Sep. 30, 2013	Sep. 30, 2012
Shares
Outstanding, beginning of period (in shares)	1,386,400	1,745,400
Granted (in shares)	227,700	444,900
Exercised (in shares)	(539,400)	(6,800)
Forfeited or expired (in shares)	(8,000)	(11,700)
Outstanding, end of period (in shares)	1,066,700	2,171,800
Exercisable, end of period (in shares)	225,500	1,027,700
Weighted- Average Exercise Price
Outstanding, beginning of period, weighted-average exercise price (in USD per share)	$ 10.43	$ 8.44
Granted, weighted-average exercise price (in USD per share)	$ 29.94	$ 13.36
Exercised, weighted-average exercise price (in USD per share)	$ 9.54	$ 11.84
Forfeited or expired, weighted-average exercise price (in USD per share)	$ 13.24	$ 10.99
Outstanding, end of period, weighted-average exercise price (in USD per share)	$ 15.02	$ 9.43
Exercisable, end of period, weighted-average exercise price (in USD per share)	$ 11.42	$ 8.39
Options, Additional Disclosures:
Outstanding, end of period, weighted-average remaining contractual term	6 years 6 months	7 years 7 months 0 days
Exercisable, end of period, weighted-average remaining contractual term	7 years 8 months 12 days	6 years 11 months 0 days
Outstanding, end of period, aggregate intrinsic value	$ 16,110	$ 16,602
Exercisable, end of period, aggregate intrinsic value	$ 4,216	$ 7,132

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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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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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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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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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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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Weighted average price of options that were either forfeited or expired.

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

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The number of shares reserved for issuance under stock option agreements awarded under the plan that validly exist and are outstanding as of the balance sheet date, including vested options.

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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

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