Benefit Plans (Schedule of estimated amounts to be recognized from Accumulated other comprehensive income into net periodic cost (benefit) during next fiscal year) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2015
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service cost (credit)	$ 0
Amortization of net actuarial (gain) loss	38
Total estimated amounts to be recognized	38
Other Postretirement Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service cost (credit)	(2)
Amortization of net actuarial (gain) loss	1
Total estimated amounts to be recognized	$ (1)