Percentage of average return on invested capital on share based compensation arrangement.

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- Definition

Reduced percentage of restricted shares.

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- Definition

Reduced percentage of shares earned in stock option plan.

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- Definition

Share based compensation arrangement by share based payment award equity instruments other than options vesting date.

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- Definition

Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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- Definition

Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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- Definition

Amount of cost to be recognized for nonvested award under share-based payment arrangement. Excludes share and unit options.

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- Definition

Amount of noncash expense for award of restricted stock or unit under share-based payment arrangement.

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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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Description of terms of share-based payment arrangement. Includes, but is not limited to, type of award or grantee and reason for issuance.

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- Definition

Date the equity-based award expires, in CCYY-MM-DD format.

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- Definition

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

Number of shares authorized for issuance under share-based payment arrangement.

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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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- Definition

Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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- Definition

Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

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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- Definition

Amount of noncash expense for option under share-based payment arrangement.

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Share-Based Employee Compensation - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	May 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Aug. 31, 2020	Aug. 07, 2013
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for future grant		3,458,865		3,458,865			3,000,000
Stock option expense		$ 1.1	$ 1.2	$ 3.9	$ 3.5
Aggregate intrinsic value for outstanding options		24.5		24.5
Aggregate intrinsic value for exercisable options		15.4		15.4
Total intrinsic value of options exercised				6.3
Restricted stock or unit expense		2.8	$ 3.1	$ 8.2	$ 12.9
Stock Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for future grant							1,500,000
Performance Vesting Stock Options [Member] \| Long Term Compensation Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for future grant	96,476
Reduced percentage of shares earned in stock options plan				66.70%
Stock based compensation plan, description				The performance criteria for the Fiscal 2021 Employee Performance Stock Option Grant is based upon the achievement of certain levels of return on equity (as defined in the option agreements), ranging from 10.0% to 20.0%, for the fiscal year ending March 31, 2021. All stock options will be earned if the return on equity is 20.0% or greater, and the percentage of shares earned will be reduced proportionately to approximately 66.7% if the return on equity is 10.0%. If the Company does not achieve a return on equity of at least 10.0%, all granted stock options will be forfeited.
Share-based compensation vesting period	4 years
Share-based compensation award expiration term	10 years
Performance Vesting Stock Options [Member] \| Long Term Compensation Plan [Member] \| Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of average return on invested capital	10.00%
Share-based compensation expiration date				Mar. 31, 2022
Performance Vesting Stock Options [Member] \| Long Term Compensation Plan [Member] \| Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of average return on invested capital	20.00%
Share-based compensation expiration date				Mar. 31, 2024
Time Vesting Stock Options [Member] \| Long Term Compensation Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for future grant	80,396
Share-based compensation vesting period	4 years
Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation cost, stock options		7.7		$ 7.7
Weighted-average period of recognition of unrecognized compensation cost				2 years 5 months
Performance Vesting Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for future grant	82,722
Stock based compensation plan, description				The performance criteria for the Fiscal 2021 Employee Restricted Stock Performance Award is based upon the achievement of certain levels of return on equity (as defined in the award agreement), ranging from 10.0% to 20.0%, for the fiscal year ending March 31, 2021. All restricted shares will be earned if the return on equity is 20.0% or greater, and the percentage of shares earned will be reduced proportionately to approximately 66.7% if the return on equity is 10.0%. If the Company does not achieve a return on equity of at least 10.0%, all awards will be forfeited.
Share-based compensation vesting period	4 years
Reduced percentage of restricted shares				66.70%
Performance Vesting Restricted Stock [Member] \| Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of average return on invested capital	10.00%
Share-based compensation vesting date				Mar. 31, 2021
Performance Vesting Restricted Stock [Member] \| Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of average return on invested capital	20.00%
Share-based compensation vesting date				Mar. 31, 2022
Time Vesting Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for future grant	68,936
Share-based compensation vesting period	4 years
Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for future grant						26,064
Weighted-average period of recognition of unrecognized compensation cost				2 years 2 months 12 days
Unrecognized compensation cost		$ 14.7		$ 14.7