Retirement Benefits - Schedule of Pension Plan's Asset Allocations by Asset Category (Details)	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Pension plans weighted average asset allocation	100.00%	100.00%
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plans weighted average asset allocation	26.00%	36.00%
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Pension plans weighted average asset allocation	43.00%	34.00%
Fixed income:
Defined Benefit Plan Disclosure [Line Items]
Pension plans weighted average asset allocation	15.00%	13.00%
Private assets
Defined Benefit Plan Disclosure [Line Items]
Pension plans weighted average asset allocation	8.00%	6.00%
Hedge funds
Defined Benefit Plan Disclosure [Line Items]
Pension plans weighted average asset allocation	8.00%	11.00%