Change in Plan Assets and Obligations (Detail) (USD $)	12 Months Ended
Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2015
Schedule of Pension and Other Postretirement Benefits Changes in Benefit Obligation and Fair Value of Plan Assets [Line Items]
Fair value of plan assets	$ 56,896,000		$ 59,485,000
Benefit obligation	(84,067,000)		(96,308,000)
Fair value of plan assets at end of year	56,896,000		59,485,000
Benefit obligation at end of year	84,067,000		96,308,000
Pension Plans, Defined Benefit
Schedule of Pension and Other Postretirement Benefits Changes in Benefit Obligation and Fair Value of Plan Assets [Line Items]
Fair value of plan assets	(56,002,000)		(58,619,000)
Employer contributions	0	0
Fair value of plan assets at end of year	(56,002,000)		(58,619,000)
Current liabilities	(1,162,000)		(1,306,000)
Noncurrent liabilities	(26,009,000)		(35,517,000)
Net amount recognized	(27,171,000)		(36,823,000)
Pension Plans, Defined Benefit \| Change in Benefit Obligations
Schedule of Pension and Other Postretirement Benefits Changes in Benefit Obligation and Fair Value of Plan Assets [Line Items]
Benefit obligation at beginning of year	88,238,000		84,067,000
Service cost	790,000		825,000
Benefit obligation	(84,067,000)		(96,308,000)
Interest cost	3,581,000		3,873,000
Plan settlement	0		0
Benefits paid	(4,250,000)		(4,405,000)
Actuarial (gain) loss	(4,292,000)		11,948,000
Benefit obligation at end of year	84,067,000		96,308,000
Pension Plans, Defined Benefit \| Change in Plan Assets
Schedule of Pension and Other Postretirement Benefits Changes in Benefit Obligation and Fair Value of Plan Assets [Line Items]
Fair value of plan assets at beginning of year	59,431,000		56,896,000
Fair value of plan assets	56,896,000		59,485,000
Actual return	776,000		6,069,000
Employer contributions	939,000		925,000
Plan settlement	0		0
Benefits paid	(4,250,000)		(4,405,000)
Fair value of plan assets at end of year	56,896,000		59,485,000
Pension Plans, Defined Benefit \| Reconciliation of Funded Status
Schedule of Pension and Other Postretirement Benefits Changes in Benefit Obligation and Fair Value of Plan Assets [Line Items]
Fair value of plan assets	56,896,000		59,485,000
Benefit obligation	84,067,000		96,308,000
Unfunded status	(27,171,000)		(36,823,000)
Fair value of plan assets at end of year	56,896,000		59,485,000
Benefit obligation at end of year	(84,067,000)		(96,308,000)
Other Pension Plans, Defined Benefit
Schedule of Pension and Other Postretirement Benefits Changes in Benefit Obligation and Fair Value of Plan Assets [Line Items]
Current liabilities	(1,129,000)		(908,000)
Noncurrent liabilities	(22,985,000)		(23,018,000)
Net amount recognized	(24,114,000)		(23,926,000)
Other Pension Plans, Defined Benefit \| Change in Benefit Obligations
Schedule of Pension and Other Postretirement Benefits Changes in Benefit Obligation and Fair Value of Plan Assets [Line Items]
Benefit obligation at beginning of year	29,006,000		24,114,000
Service cost	405,000		273,000
Benefit obligation	(24,114,000)		(23,926,000)
Interest cost	1,048,000		904,000
Participant contributions	436,000		430,000
ERRP reimbursement	(26,000)
Plan settlement	0		0
Benefits paid	(962,000)		(863,000)
Actuarial (gain) loss	(5,793,000)		(932,000)
Benefit obligation at end of year	24,114,000		23,926,000
Other Pension Plans, Defined Benefit \| Change in Plan Assets
Schedule of Pension and Other Postretirement Benefits Changes in Benefit Obligation and Fair Value of Plan Assets [Line Items]
Employer contributions	552,000		433,000
Participant contributions	436,000		430,000
ERRP reimbursement	(26,000)
Plan settlement	0		0
Benefits paid	(962,000)		(863,000)
Other Pension Plans, Defined Benefit \| Reconciliation of Funded Status
Schedule of Pension and Other Postretirement Benefits Changes in Benefit Obligation and Fair Value of Plan Assets [Line Items]
Benefit obligation	24,114,000		23,926,000
Unfunded status	(24,114,000)		(23,926,000)
Benefit obligation at end of year	$ (24,114,000)		$ (23,926,000)

Defined Benefit Plan, Reimbursement on Plan Assets

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The difference between fair value of plan assets at the end of the period and the fair value at the beginning of the period, adjusted for contributions and payments of benefits during the period, and after adjusting for taxes and other expenses, as applicable.

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-Glossary Actual Return on Plan Assets (Component of Net Periodic Postretirement Benefit Cost)

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Amount of gain (loss) related to change in benefit obligation resulting from changes in actuarial assumptions, for example, but not limited to, interest, mortality, employee turnover, salary, and temporary deviation from the substantive plan.

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The aggregate net amount recognized in the balance sheet associated with the defined benefit plan(s). Will normally be the same as the Defined Benefit Plan, Funded Status of Plan, Total.

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1) For defined benefit pension plans, the benefit obligation is the projected benefit obligation, which is the actuarial present value as of a date of all benefits attributed by the pension benefit formula to employee service rendered prior to that date. 2) For other postretirement defined benefit plans, the benefit obligation is the accumulated postretirement benefit obligation, which is the actuarial present value of benefits attributed to employee service rendered to a particular date.

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The amount of payments made for which participants are entitled under a pension plan, including pension benefits, death benefits, and benefits due on termination of employment. Also includes payments made under a postretirement benefit plan, including prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services. This item represents a periodic decrease to the plan obligations and a decrease to plan assets.

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The increase in the fair value of plan assets from contributions made by the employer.

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The amount of contributions made by plan participants. This item represents a periodic increase to the plan obligation and an increase to plan assets.

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Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. If a plan has liabilities other than for benefits, those non-benefit obligations may be considered as reductions of plan assets.

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The funded status is measured as the difference between the fair value of plan assets and the benefit obligation. Will normally be the same as the net Defined Benefit Plan, Amounts Recognized in Balance Sheet, Total.

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The increase in a defined benefit pension plan's projected benefit obligation or a defined benefit postretirement plan's accumulated postretirement benefit obligation due to the passage of time.

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The actuarial present value of benefits attributed by the pension benefit formula to services rendered by employees during the period. The portion of the expected postretirement benefit obligation attributed to employee service during the period. The service cost component is a portion of the benefit obligation and is unaffected by the funded status of the plan.

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The amount that relates to an irrevocable action that relieves the employer (or the plan) of primary responsibility for a benefit obligation and eliminates significant risks related to the obligation and the assets used to effect the settlement. Examples of transactions that constitute a settlement include (a) making lump-sum cash payments to plan participants in exchange for their rights to receive specified benefits and (b) purchasing nonparticipating annuity contracts.

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For a classified balance sheet, the amount recognized in balance sheet as a current liability associated with an underfunded defined benefit plan.

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This represents the noncurrent liability for underfunded plans recognized in the balance sheet that is associated with the defined benefit pension plans and other postretirement defined benefit plans.

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