Schedule of Fair Values of Defined Benefit Plans Determined Using Fair Value Hierarchy of Inputs (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plans	$ 22,055	$ 21,189	$ 18,693
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plans	13,510	13,973
Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plans	7,985	6,526
Real Estate Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plans	133	130
Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plans	303	390
Commodity Linked Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plans	124	170
Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plans	303	390
Fair Value, Inputs, Level 1 | Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plans	303	390
Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plans	21,752	20,799
Fair Value, Inputs, Level 2 | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plans	13,510	13,973
Fair Value, Inputs, Level 2 | Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plans	7,985	6,526
Fair Value, Inputs, Level 2 | Real Estate Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plans	133	130
Fair Value, Inputs, Level 2 | Commodity Linked Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plans	$ 124	$ 170