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Pension Plans - Weighted Average Assumptions Used to Determine Benefit Obligation (Detail) - Pension Plan [Member]
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]      
Discount rate 3.30% 3.72% 3.90%
Rate of compensation increase 0.00% 0.00% 0.00%