Retirement Benefits and Trusteed Assets (Schedule of Defined Benefit Plans Disclosures) (Details) - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
	Feb. 17, 2015	Dec. 31, 2015	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Contribution of common stock to pension plan			$ 200
Other Postretirement Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Contribution of common stock to pension plan		$ 117
VEBA Trust | Other Postretirement Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Contribution of common stock to pension plan (in shares)	1,427,835
Share Price	$ 81.91
Contribution of common stock to pension plan	$ 117