Employee Benefit Plans - Components of Net Periodic Benefit Cost (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 7	$ 8
Amortization of net loss	8	2
Net periodic cost	15	10
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	28	35
Amortization of net loss
Net periodic cost	$ 28	$ 35