Pensions and Postretirement Benefits Other than Pensions - Weighted Average Assumptions Used to Determine Benefit Obligations (Detail)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Discount rate	2.00%	2.78%
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Discount rate	2.36%	3.12%
United States | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Discount rate	2.28%	3.09%
United States | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Discount rate	2.36%	3.12%
Foreign Plan | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Discount rate	1.29%	1.99%
Foreign Plan | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Discount rate	0.00%	0.00%