Benefit Plans (Schedule of estimated amounts to be recognized from Accumulated other comprehensive income into net periodic cost (benefit) during next fiscal year) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($)
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service cost (credit) during 2016	$ 0
Amortization of net actuarial (gain) loss during 2016	37
Total estimated amounts to be recognized during 2016	37
Other Postretirement Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service cost (credit) during 2016	(2)
Amortization of net actuarial (gain) loss during 2016	0
Total estimated amounts to be recognized during 2016	$ (2)