Pensions and Postretirement Benefits Other Than Pensions - Weighted Average Asset Allocations for Domestic and U.K. Pension Plans' Assets (Detail)	Dec. 31, 2020	Dec. 31, 2019
United States
Defined Benefit Plan Disclosure [Line Items]
Plan asset allocations (as a percent)	100.00%	100.00%
United States | Fixed Income Collective Trust Funds and Securities
Defined Benefit Plan Disclosure [Line Items]
Plan asset allocations (as a percent)	64.00%	65.00%
United States | Equity Collective Trust Funds and Securities
Defined Benefit Plan Disclosure [Line Items]
Plan asset allocations (as a percent)	29.00%	30.00%
United States | Other Investment Collective Trust Funds and Securities
Defined Benefit Plan Disclosure [Line Items]
Plan asset allocations (as a percent)	3.00%	3.00%
United States | Cash
Defined Benefit Plan Disclosure [Line Items]
Plan asset allocations (as a percent)	4.00%	2.00%
Foreign Plan
Defined Benefit Plan Disclosure [Line Items]
Plan asset allocations (as a percent)	100.00%	100.00%
Foreign Plan | Fixed Income Collective Trust Funds and Securities
Defined Benefit Plan Disclosure [Line Items]
Plan asset allocations (as a percent)	70.00%	68.00%
Foreign Plan | Equity Collective Trust Funds and Securities
Defined Benefit Plan Disclosure [Line Items]
Plan asset allocations (as a percent)	18.00%	19.00%
Foreign Plan | Other Investment Collective Trust Funds and Securities
Defined Benefit Plan Disclosure [Line Items]
Plan asset allocations (as a percent)	11.00%	12.00%
Foreign Plan | Cash
Defined Benefit Plan Disclosure [Line Items]
Plan asset allocations (as a percent)	1.00%	1.00%