Pension and Other Postretirement Benefit Plans - Assumptions Used to Determine Benefit Obligation and Net Periodic Benefit Costs (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Minimum [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	3.81%	4.53%	4.72%
Maximum [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	3.96%	4.57%	4.73%
Pension [Member]
Assumptions Used to Determine Net Periodic Benefit Costs [Abstract]
Expected Long-Term Return on Plan Assets	7.50%	7.50%	8.00%
Pension [Member] | Minimum [Member]
Assumptions Used to Determine Benefit Obligation [Abstract]
Discount Rate	4.39%	3.81%
Rate of Compensation Increase	3.70%	3.70%
Assumptions Used to Determine Net Periodic Benefit Costs [Abstract]
Rate of Compensation Increase	3.70%	3.70%	3.70%
Pension [Member] | Maximum [Member]
Assumptions Used to Determine Benefit Obligation [Abstract]
Discount Rate	4.53%	3.96%
Rate of Compensation Increase	4.10%	4.10%
Assumptions Used to Determine Net Periodic Benefit Costs [Abstract]
Rate of Compensation Increase	4.10%	4.30%	4.30%
Postretirement Health and Life [Member]
Assumptions Used to Determine Benefit Obligation [Abstract]
Discount Rate	4.47%	3.86%
Health Care Trend Rates [Abstract]
Ultimate Trend Rate	4.50%	4.50%
Year Ultimate Trend Rate Effective	2038	2038
Postretirement Health and Life [Member] | Minimum [Member]
Health Care Trend Rates [Abstract]
Trend Rate	5.00%	5.00%
Assumptions Used to Determine Net Periodic Benefit Costs [Abstract]
Expected Long-Term Return on Plan Assets	6.00%	6.00%	6.40%
Postretirement Health and Life [Member] | Maximum [Member]
Health Care Trend Rates [Abstract]
Trend Rate	6.46%	6.73%
Assumptions Used to Determine Net Periodic Benefit Costs [Abstract]
Expected Long-Term Return on Plan Assets	7.50%	7.50%	8.00%