Pension and Other Postemployment Benefits (Details 11) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Pension
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net Periodic Cost (Credit)	$ 377	$ 485	$ 1,350
Pension | FES
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net Periodic Cost (Credit)	(5)	10	150
OPEB
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net Periodic Cost (Credit)	(60)	(108)	(154)
OPEB | FES
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net Periodic Cost (Credit)	$ (26)	$ (22)	$ (24)