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Changes in Accumulated Other Comprehensive Loss - Reclassifications Out of Accumulated Other Comprehensive Loss by Component (Detail) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2018 | Sep. 30, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |  |  |
Income before provision for income taxes | $ 2,005 | $ (26) | $ 5,030 | $ 1,307
Provision for income taxes | 178 | (36) | 880 | 362
Net income | 1,827 | 10 | 4,150 | 945
Reclassifications Out of Accumulated Other Comprehensive Loss [Member] | Amortization of Actuarial Loss [Member] |  |  |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |  |  |
Income before provision for income taxes | (218) | (263) | (437) | (526)
Reclassifications Out of Accumulated Other Comprehensive Loss [Member] | Pension and Other Postretirement Benefits Items [Member] |  |  |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |  |  |
Provision for income taxes | (48) | (93) | (97) | (186)
Net income | $ (170) | $ (170) | $ (340) | $ (340)

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