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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 | 12 Months Ended
--- | --- | ---
Mar. 31, 2016 | Dec. 31, 2015 | Sep. 30, 2015 | Jun. 30, 2015 | Mar. 31, 2015 | Dec. 31, 2014 | Sep. 30, 2014 | Jun. 30, 2014 | Mar. 31, 2016 | Mar. 31, 2015 | Mar. 31, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |  |  |  |  |  |  |  |  |  |
Income before provision for income taxes |  |  |  |  |  |  |  |  | $ 8,730 | $ 21,752 | $ 14,710
Provision for income taxes |  |  |  |  |  |  |  |  | 2,599 | 7,017 | 4,565
Net income | $ 520 | $ 1,274 | $ 1,976 | $ 2,361 | $ 4,165 | $ 3,992 | $ 4,186 | $ 2,392 | 6,131 | 14,735 | $ 10,145
Reclassifications Out of Accumulated Other Comprehensive Loss [Member] | Amortization of Unrecognized Prior Service Benefit [Member] |  |  |  |  |  |  |  |  |  |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |  |  |  |  |  |  |  |  |  |
Income before provision for income taxes |  |  |  |  |  |  |  |  |  | 102 |
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 |  |  |  |  |  |  |  |  | (1,214) | (616) |
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] |  |  |  |  |  |  |  |  |  |  |
Income before provision for income taxes |  |  |  |  |  |  |  |  | (1,214) | (514) |
Provision for income taxes |  |  |  |  |  |  |  |  | (429) | (182) |
Net income |  |  |  |  |  |  |  |  | $ (785) | $ (332) |

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