Pensions and Postretirement Benefits (Summary of Pension Plan Weighted-Average Asset Allocation) (Details)	Dec. 31, 2017	Dec. 31, 2016
Summary of pension plan weighted-average asset allocation/summary of reconciliation of level 3 assets
Target allocation	100.00%
Weighted-average asset allocations	100.00%	100.00%
Equity securities
Summary of pension plan weighted-average asset allocation/summary of reconciliation of level 3 assets
Weighted-average asset allocations	65.00%	61.90%
Debt securities
Summary of pension plan weighted-average asset allocation/summary of reconciliation of level 3 assets
Weighted-average asset allocations	23.60%	24.60%
Other
Summary of pension plan weighted-average asset allocation/summary of reconciliation of level 3 assets
Weighted-average asset allocations	11.40%	13.50%
Minimum | Equity securities
Summary of pension plan weighted-average asset allocation/summary of reconciliation of level 3 assets
Target allocation	45.00%
Minimum | Debt securities
Summary of pension plan weighted-average asset allocation/summary of reconciliation of level 3 assets
Target allocation	20.00%
Minimum | Other
Summary of pension plan weighted-average asset allocation/summary of reconciliation of level 3 assets
Target allocation	0.00%
Maximum | Equity securities
Summary of pension plan weighted-average asset allocation/summary of reconciliation of level 3 assets
Target allocation	75.00%
Maximum | Debt securities
Summary of pension plan weighted-average asset allocation/summary of reconciliation of level 3 assets
Target allocation	40.00%
Maximum | Other
Summary of pension plan weighted-average asset allocation/summary of reconciliation of level 3 assets
Target allocation	20.00%