Schedule of Fair Value Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Mar. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	$ 57,146	$ 57,174
Total fair value of plan assets	8,759	8,811
Pension Plans, Defined Benefit
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	56,465	56,352
Accrued income	681	822
Total fair value of plan assets	57,146	57,174
Supplemental Executive Retirement Plan
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	8,760	8,551
Other pending transactions		260
Total fair value of plan assets	8,760	8,811
Measured At Net Asset Value | Supplemental Executive Retirement Plan
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	1,720	1,711
Other pending transactions		18
Total fair value of plan assets	1,720	1,729
US Government Agencies Debt Securities | Pension Plans, Defined Benefit
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	3,770	3,104
US Government Agencies Debt Securities | Supplemental Executive Retirement Plan
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	1,613	1,711
Collateralized mortgage securities | Pension Plans, Defined Benefit
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	2,537	47
Corporate Debt Securities | Pension Plans, Defined Benefit
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	47,871	48,378
Foreign Debt Securities | Pension Plans, Defined Benefit
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets		1,499
Cash and Cash Equivalents | Pension Plans, Defined Benefit
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	989	2,247
Cash and Cash Equivalents | Supplemental Executive Retirement Plan
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	323	343
Cash and Cash Equivalents | Measured At Net Asset Value | Supplemental Executive Retirement Plan
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	72	48
Common stock | Supplemental Executive Retirement Plan
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	3,561	3,290
Foreign Stock | Supplemental Executive Retirement Plan
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	132	159
American Depository Receipts | Supplemental Executive Retirement Plan
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	1,387	1,311
Preferred American Depository Receipts | Supplemental Executive Retirement Plan
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	20	13
Real Estate Investment Trusts | Supplemental Executive Retirement Plan
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	76	61
Open Ended Mutual Funds | Supplemental Executive Retirement Plan
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	1,648	1,663
Open Ended Mutual Funds | Measured At Net Asset Value | Supplemental Executive Retirement Plan
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	1,648	1,663
Other | Pension Plans, Defined Benefit
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	1,298	1,077
Quoted Prices In Active Markets (Level 1) | Pension Plans, Defined Benefit
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	4,215	3,514
Accrued income	681	822
Total fair value of plan assets	4,896	4,336
Quoted Prices In Active Markets (Level 1) | Supplemental Executive Retirement Plan
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	6,023	5,819
Other pending transactions		291
Total fair value of plan assets	6,023	6,110
Quoted Prices In Active Markets (Level 1) | US Government Agencies Debt Securities | Pension Plans, Defined Benefit
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	3,770	3,104
Quoted Prices In Active Markets (Level 1) | US Government Agencies Debt Securities | Supplemental Executive Retirement Plan
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	832	972
Quoted Prices In Active Markets (Level 1) | Cash and Cash Equivalents | Pension Plans, Defined Benefit
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	345	346
Quoted Prices In Active Markets (Level 1) | Cash and Cash Equivalents | Supplemental Executive Retirement Plan
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	15	13
Quoted Prices In Active Markets (Level 1) | Common stock | Supplemental Executive Retirement Plan
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	3,561	3,290
Quoted Prices In Active Markets (Level 1) | Foreign Stock | Supplemental Executive Retirement Plan
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	132	159
Quoted Prices In Active Markets (Level 1) | American Depository Receipts | Supplemental Executive Retirement Plan
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	1,387	1,311
Quoted Prices In Active Markets (Level 1) | Preferred American Depository Receipts | Supplemental Executive Retirement Plan
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	20	13
Quoted Prices In Active Markets (Level 1) | Real Estate Investment Trusts | Supplemental Executive Retirement Plan
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	76	61
Quoted Prices In Active Markets (Level 1) | Other | Pension Plans, Defined Benefit
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	100	64
Significant Observable Inputs (Level 2) | Pension Plans, Defined Benefit
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	52,250	52,838
Total fair value of plan assets	52,250	52,838
Significant Observable Inputs (Level 2) | Supplemental Executive Retirement Plan
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	1,017	1,021
Other pending transactions		(49)
Total fair value of plan assets	1,017	972
Significant Observable Inputs (Level 2) | US Government Agencies Debt Securities | Supplemental Executive Retirement Plan
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	781	739
Significant Observable Inputs (Level 2) | Collateralized mortgage securities | Pension Plans, Defined Benefit
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	2,537	47
Significant Observable Inputs (Level 2) | Corporate Debt Securities | Pension Plans, Defined Benefit
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	47,871	48,378
Significant Observable Inputs (Level 2) | Foreign Debt Securities | Pension Plans, Defined Benefit
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets		1,499
Significant Observable Inputs (Level 2) | Cash and Cash Equivalents | Pension Plans, Defined Benefit
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	644	1,901
Significant Observable Inputs (Level 2) | Cash and Cash Equivalents | Supplemental Executive Retirement Plan
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	236	282
Significant Observable Inputs (Level 2) | Other | Pension Plans, Defined Benefit
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	$ 1,198	$ 1,013