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Quarterly Financial Data (Unaudited) - Summary of Company's Unaudited Quarterly Results (Parenthetical) (Detail) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2018 | Dec. 31, 2017 | Sep. 30, 2017 | Sep. 30, 2016 | Jun. 30, 2016 | Mar. 31, 2018 | Mar. 31, 2017 | Mar. 31, 2016
Restructuring charge |  |  | $ 316 | $ 75 | $ 555 | $ 316 | $ 630 |
Income tax benefit related to restructuring charge |  |  | $ 92 | $ 17 | $ 172 |  |  |
Loss from impairment of goodwill and intangible assets |  | $ 14,816 |  |  |  | 14,816 |  |
Income tax benefit on goodwill and intangible assets impairment |  | 2,802 |  |  |  |  |  |
Income tax benefit |  |  |  |  |  | $ 3,010 | $ (2,026) | $ (2,599)
Income tax benefit related to Tax Act | $ 209 | 577 |  |  |  |  |  |
Commercial Nuclear Business [Member] |  |  |  |  |  |  |  |
Other charges |  | 280 |  |  |  |  |  |
Income tax benefit |  | $ 87 |  |  |  |  |  |

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