Pension and Postretirement Benefit Plans - Weighted Average Assumptions Used to Determine Benefit Plans' Obligations (Details)	Dec. 31, 2018	Dec. 31, 2017
Pension
Benefit obligations weighted-average assumptions:
Discount rate (percent)	4.12%	3.50%
Rates of increase in compensation levels (percent)	3.25%	3.25%
Postretirement
Benefit obligations weighted-average assumptions:
Discount rate (percent)	4.12%	3.50%
Rates of increase in compensation levels (percent)	0.00%	0.00%