Benefit Plans - Schedule of Assumptions (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Pension plans
Benefit obligation assumptions
Discount rate	3.73%	4.00%	3.92%
Rate of compensation increase	3.77%	3.96%	3.95%
Net periodic benefit expense assumptions
Discount rate	4.00%	3.94%	4.12%
Expected long-term return on plan assets	4.17%	4.05%	4.19%
Rate of compensation increase	3.96%	3.96%	3.93%
Other post-retirement plans
Benefit obligation assumptions
Discount rate	3.95%	3.40%	3.80%
Net periodic benefit expense assumptions
Discount rate	3.40%	3.80%	3.95%