Retirement Plans and Other Post-Retirement Benefits - Schedule of Defined Benefit Plan Weighted-Average Assumptions Used in Computing Net Periodic Benefit Cost (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate - benefit expense	3.85%	4.44%	4.65%
Future compensation growth rate	3.00%	3.00%	3.50%
Expected long-term rate of return on plan assets	7.25%	7.25%	7.75%
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate - benefit expense	3.68%	4.18%	4.38%