Annual report pursuant to Section 13 and 15(d)

Quarterly Financial Data (Unaudited) - Summary of Company's Unaudited Quarterly Results (Parenthetical) (Detail)

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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