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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, 2019 | Mar. 31, 2018 | Mar. 31, 2017
--- | --- | --- | ---
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | $ 38,416 | $ 38,810 | $ 37,800
Cash [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 87 | 98 |
U.S. companies, Equity Securities [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 15,130 | 20,663 |
International companies, Equity Securities [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 3,795 | 5,181 |
Fixed income, Corporate bond funds, Long-term [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 19,404 |  |
Fixed income, Corporate bond funds, Intermediate-term [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets |  | 10,283 |
Fixed income, Corporate bond funds, Short-term [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets |  | 2,585 |
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 38,416 | 38,810 |
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Cash [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 87 | 98 |
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 | 15,130 | 20,663 |
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 | 3,795 | 5,181 |
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fixed income, Corporate bond funds, Long-term [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | $ 19,404 |  |
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 |
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 |

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