Defined Benefit Pension Plans (Details) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2017 USD ($)	Sep. 30, 2017 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer		$ 75
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year	$ 6	6
Defined Benefit Plan, Expected Future Employer Contributions, Current Fiscal Year	81	$ 81
Pension Plan [Member] | Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 59