Benefit Plans (Estimated Net Loss and Prior Service Cost (Credit) Expected to be Amortized in 2017) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($)
Pension [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Estimated future net loss	$ 200
Estimated future prior service cost (credit)	4
Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Estimated future net loss	32
Estimated future prior service cost (credit)	$ (38)