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Pension and Other Postretirement Benefit Plans - Information Related to Multi-Employer Pension Plans (Detail) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
516099782-001      
Multiemployer Plans [Line Items]      
Contributions to multiemployer pension plan $ 0.6 $ 0.6 $ 0.5
13-6130178      
Multiemployer Plans [Line Items]      
Contributions to multiemployer pension plan $ 0.4 $ 0.4 $ 0.3