Annual report pursuant to Section 13 and 15(d)

Employee Benefit Plans - Summary of Increase (Decrease) in Accumulated Other Comprehensive Loss, Net of Income Tax (Detail)

v3.8.0.1
Employee Benefit Plans - Summary of Increase (Decrease) in Accumulated Other Comprehensive Loss, Net of Income Tax (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Mar. 31, 2016
Defined Benefit Plan Disclosure [Line Items]      
Total $ (1,668) $ (2,493) $ 1,470
Pension Plans, Defined Benefit [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Net actuarial loss (gain) arising during the year (794) (1,609)  
Reclassification of stranded tax effects related to the Tax Act 1,771    
Amortization of actuarial loss (788) (873)  
Total 189 (2,482)  
Other Postretirement Benefit Plans [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Net actuarial loss (gain) arising during the year (57) 13  
Reclassification of stranded tax effects related to the Tax Act 57    
Amortization of actuarial loss (29) (24)  
Total $ (29) $ (11)