Quarterly report pursuant to Section 13 or 15(d)

Employee Benefit Plans - Components of Postretirement Benefit Cost (Income) and Pension Benefit Income (Detail)

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Employee Benefit Plans - Components of Postretirement Benefit Cost (Income) and Pension Benefit Income (Detail) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2015
Dec. 31, 2014
Pension Plans, Defined Benefit [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Service cost $ 130 $ 136 $ 391 $ 409
Interest cost 360 359 1,078 1,076
Expected return on assets (795) (758) (2,385) (2,275)
Amortization of prior service benefit   1   3
Amortization of actuarial loss 293 145 880 435
Net pension benefit income and postretirement benefit cost (income) (12) (117) (36) (352)
Other Postretirement Benefit Plans [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Interest cost 7 8 20 24
Amortization of prior service benefit   (26)   (79)
Amortization of actuarial loss 10 10 30 30
Net pension benefit income and postretirement benefit cost (income) $ 17 $ (8) $ 50 $ (25)