Retirement Benefits (Details 13) - Pension Benefits [Member]	12 Months Ended
	Dec. 31, 2017
Minimum [Member] | U.S. equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	0.18
Minimum [Member] | International equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	.10
Minimum [Member] | Global debt securities and cash [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	.15
Minimum [Member] | Private equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	0
Minimum [Member] | Hedge funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	.10
Minimum [Member] | Real estate and other [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	0
Maximum [Member] | U.S. equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	.40
Maximum [Member] | International equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	.3
Maximum [Member] | Global debt securities and cash [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	.4
Maximum [Member] | Private equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	.15
Maximum [Member] | Hedge funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	.2
Maximum [Member] | Real estate and other [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	0.1