Schedule of Fair Value Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Mar. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	$ 57,174	$ 59,485
Pension Plans, Defined Benefit
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	56,352	58,619
Accrued income	822	866
Total fair value of plan assets	57,174	59,485
Supplemental Executive Retirement Plan
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	8,551	10,038
Other pending transactions	260	(123)
Total fair value of plan assets	8,811	9,915
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	3,104	3,116
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	1,711	1,926
Collateralized mortgage securities | Pension Plans, Defined Benefit
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	47	400
Corporate Debt Securities | Pension Plans, Defined Benefit
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	48,378	51,758
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	1,529
Cash and Cash Equivalents | Pension Plans, Defined Benefit
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	2,247	1,816
Cash and Cash Equivalents | Supplemental Executive Retirement Plan
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	343	377
Common stock | Supplemental Executive Retirement Plan
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	3,290	3,859
Foreign Stock | Supplemental Executive Retirement Plan
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	159	201
American Depository Receipts | Supplemental Executive Retirement Plan
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	1,311	1,685
Preferred American Depository Receipts | Supplemental Executive Retirement Plan
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	13	15
Real Estate Investment Trusts | Supplemental Executive Retirement Plan
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	61	59
Open Ended Mutual Funds | Supplemental Executive Retirement Plan
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	1,663	1,916
Other | Pension Plans, Defined Benefit
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	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	3,514	3,116
Accrued income	822	866
Total fair value of plan assets	4,336	3,982
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	5,819	7,268
Other pending transactions	291	(123)
Total fair value of plan assets	6,110	7,145
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	3,104	3,116
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	972	1,377
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	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	13	72
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	3,290	3,859
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	159	201
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	1,311	1,685
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	13	15
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	61	59
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	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	52,838	55,503
Total fair value of plan assets	52,838	55,503
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	1,021	810
Other pending transactions	(49)
Total fair value of plan assets	972	810
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	739	549
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	47	400
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	48,378	51,758
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	1,529
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	1,901	1,816
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	282	261
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	1,013
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	1,711	1,960
Other pending transactions	18
Total fair value of plan assets	1,729	1,960
Measured At Net Asset Value | Cash and Cash Equivalents | Supplemental Executive Retirement Plan
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	48	44
Measured At Net Asset Value | Open Ended Mutual Funds | Supplemental Executive Retirement Plan
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of plan assets	$ 1,663	$ 1,916