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Debt and Financing Arrangements (Bank Debt) - Additional Information (Detail) - USD ($)
$ in Thousands
Mar. 31, 2018
Dec. 31, 2017
Debt Disclosure [Abstract]    
Outstanding balance under applicable credit facility $ 214,700 $ 178,500
Available funds under credit facility 175,000  
Outstanding letters of credit $ 2,300 $ 2,300