Stock-Based Compensation Information regarding unvested and exercised stock options (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense	$ 3,178	$ 3,730	$ 4,681
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares	1,905	1,962
Proceeds from Stock Options Exercised	$ 8,988	$ 9,516	22,069
Employee Service Share-based Compensation, Tax Benefit Realized from Exercise of Stock Options	$ 725	$ 1,962	$ 4,856
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value	$ 42.54	$ 11.48
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	753
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 31.31
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Number of Shares	(759)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Weighted Average Grant Date Fair Value	$ 41.57
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested Options Forfeited, Number of Shares	(51)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested Options Forfeited, Weighted Average Grant Date Fair Value	$ 47.13
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	1 year 183 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares	1,905
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized	$ 11,727
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	753	876	918
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 7.78	$ 11.26	$ 12.03

Unrecognized cost of unvested share-based compensation awards.

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- Definition

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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- Definition

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

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- Definition

Disclosure of the aggregate tax benefit realized from the exercise of stock options and the conversion of similar instruments during the annual period.

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- Definition

The cash inflow associated with the amount received from holders exercising their stock options. This item inherently excludes any excess tax benefit, which the entity may have realized and reported separately.

+ References

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

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3255-108585

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Financing Activities
-URI http://asc.fasb.org/extlink&oid=6513228

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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

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

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No definition available.

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- Definition

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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- Definition

Number of non-vested options outstanding.

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No definition available.

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- Definition

Number of non-vested options forfeited.

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- Definition

Weighted average grant-date fair value of non-vested options forfeited.

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No definition available.

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- Definition

Weighted average grant-date fair value of non-vested options outstanding.

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No definition available.

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- Definition

Number of options vested.

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Weighted average grant-date fair value of options vested.

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