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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, 2019 | Dec. 31, 2018 | Mar. 31, 2018 | Dec. 31, 2017 | Sep. 30, 2017 | Mar. 31, 2019 | Mar. 31, 2018 | Mar. 31, 2017
Loss from impairment of goodwill and intangible assets | $ 6,449 | $ 0 |  | $ 14,816 |  | $ 6,449 | $ 14,816 |
Income tax benefit on goodwill and intangible assets impairment | 1,129 |  |  | 2,802 |  |  |  |
Restructuring charge |  |  |  |  | $ 316 |  | 316 | $ 630
Income tax benefit related to restructuring charge |  |  |  |  | $ 92 |  |  |
Income tax benefit |  |  |  |  |  | $ (163) | $ 3,010 | $ (2,026)
Income tax benefit related to Tax Act |  |  | $ 209 | 577 |  |  |  |
Commercial Nuclear Utility Business [Member] |  |  |  |  |  |  |  |
Loss from impairment of goodwill and intangible assets | $ 6,449 |  |  |  |  |  |  |
Other charges |  |  |  | 280 |  |  |  |
Income tax benefit |  |  |  | $ 87 |  |  |  |

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