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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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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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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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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No definition available.

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The floor of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

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The ceiling of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

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

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Stock Options and Stock-Based Compensation - Stock Options Outstanding and Exercisable (Detail) - $ / shares	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Outstanding Options	937,158	1,029,103	1,058,411	1,064,439
Weighted Average Remaining Contractual Life	3 years 4 months 2 days
Outstanding Options – Weighted Average Exercise Price	$ 64.28	$ 54.87	$ 45.17
Exercisable Options – Number of Exercisable Options	421,964
Exercisable Options – Weighted Average Exercise Price	$ 50.95
Range of Exercise Price, $21.87 to $49.40 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, lower limit	21.87
Range of Exercise Price, upper limit	$ 49.40
Number of Outstanding Options	253,107
Weighted Average Remaining Contractual Life	2 years 2 months 4 days
Outstanding Options – Weighted Average Exercise Price	$ 39.70
Exercisable Options – Number of Exercisable Options	226,736
Exercisable Options – Weighted Average Exercise Price	$ 38.65
Range of Exercise Price, $49.41 to $59.32 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, lower limit	49.41
Range of Exercise Price, upper limit	$ 59.32
Number of Outstanding Options	247,080
Weighted Average Remaining Contractual Life	2 years 10 months 9 days
Outstanding Options – Weighted Average Exercise Price	$ 57.14
Exercisable Options – Number of Exercisable Options	122,803
Exercisable Options – Weighted Average Exercise Price	$ 57.97
Range of Exercise Price, $59.33 to $87.49 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, lower limit	59.33
Range of Exercise Price, upper limit	$ 87.49
Number of Outstanding Options	263,715
Weighted Average Remaining Contractual Life	4 years 1 month 9 days
Outstanding Options – Weighted Average Exercise Price	$ 77.66
Exercisable Options – Number of Exercisable Options	65,983
Exercisable Options – Weighted Average Exercise Price	$ 76.49
Range of Exercise Price, $87.50 to $103.31 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, lower limit	87.50
Range of Exercise Price, upper limit	$ 103.31
Number of Outstanding Options	173,256
Weighted Average Remaining Contractual Life	4 years 6 months 7 days
Outstanding Options – Weighted Average Exercise Price	$ 89.97
Exercisable Options – Number of Exercisable Options	6,442
Exercisable Options – Weighted Average Exercise Price	$ 88.22