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Weighted Average Assumptions Used in Determining Net Periodic Benefit Cost for Pension (Detail) - Pension Benefits
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]      
Discount rate 4.10% 3.40% 3.90%
Expected rate of return on plan assets 6.80% 7.00% 7.50%