Pension and Other Postretirement Benefits - Asset Categories Based on the Nature and Risks of the Plan Assets (Parenthetical) (Detail) - Defined Benefit Pension Plan [Member] - U.S. [Member]	Dec. 31, 2019	Dec. 31, 2018
Alternative Investments, Managed Funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Target Allocation	81.00%	74.00%
Alternative Investments, Cash and Cash Equivalents [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Target Allocation	19.00%	26.00%