Employee Benefit Plans - Components of Net Periodic Benefit Cost (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 8	$ 9	$ 15	$ 17
Amortization of net loss	7	2	15	4
Net periodic cost	15	11	30	21
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Interest cost	28	34	56	69
Amortization of net loss
Net periodic cost	$ 28	$ 34	$ 56	$ 69