Employee Benefit Plans - Components of Net Periodic Benefit Cost (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2011
Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 8	$ 9	$ 25	$ 28
Amortization of net (gain) loss	1	4	5	11
Net periodic cost	9	13	30	39
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	36	40	105	125
Amortization of net (gain) loss
Net periodic cost	$ 36	$ 40	$ 105	$ 125