Annual report pursuant to Section 13 and 15(d)

Employee Benefit Plans - Fair Values of Company's Pension Plan Assets by Asset Category (Detail)

v3.8.0.1
Employee Benefit Plans - Fair Values of Company's Pension Plan Assets by Asset Category (Detail) - Pension Plans, Defined Benefit [Member] - USD ($)
$ in Thousands
Mar. 31, 2018
Mar. 31, 2017
Mar. 31, 2016
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets $ 38,810 $ 37,800 $ 36,471
Cash [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets 98 154  
U.S. companies, Equity Securities [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets 20,663 20,570  
International companies, Equity Securities [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets 5,181 5,071  
Fixed income, Corporate bond funds, Intermediate-term [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets 10,283 9,585  
Fixed income, Corporate bond funds, Short-term [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets 2,585 2,420  
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets 38,810 37,800  
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Cash [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets 98 154  
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | U.S. companies, Equity Securities [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets 20,663 20,570  
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | International companies, Equity Securities [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets 5,181 5,071  
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fixed income, Corporate bond funds, Intermediate-term [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets 10,283 9,585  
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fixed income, Corporate bond funds, Short-term [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets $ 2,585 $ 2,420