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Benefit Plans - Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rate (Detail) - Post-retirement
$ in Thousands
12 Months Ended
Dec. 31, 2020
USD ($)
Defined Benefit Plan Disclosure [Line Items]  
Effect on total service cost and interest cost, 1% increase $ 140
Effect on post-retirement benefits obligation, 1% increase 3,900
Effect on total service cost and interest cost, 1% decrease 110
Effect on post-retirement benefits obligation, 1% decrease $ 3,100