Pension and Other Postretirement Benefits - Schedule of Weighted Average Assumptions Used to Determine Benefit Obligations and Net Periodic Benefit Cost (Detail)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.12%	4.21%
Rate of compensation increase	3.25%	3.26%
Discount rate	3.89%	3.59%	3.61%
Expected long-term rate of return on plan assets	6.59%	6.89%	7.47%
Rate of compensation increase	3.26%	3.28%	3.61%
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.12%	4.25%
Discount rate	3.94%	3.18%	3.30%