Fair Value Measurements (Details 1) (Level 3, USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
NUG contracts
Reconciliation of changes in the fair value of NUG contracts
Beginning Balance, Derivative Assets	$ 20	$ 36
Beginning Balance, Derivative Liabilities	(222)	(290)
Beginning Balance, Net	(202)	(254)
Unrealized gain (loss), Derivative Assets	2	(8)
Unrealized gain (loss), Derivative Liabilities	(2)	(17)
Unrealized gain (loss), Net	0	(25)
Purchases, Derivative Assets	0	0
Purchases, Derivative Liabilities	0	0
Purchases, Net	0	0
Terminations, Derivative Assets		0
Terminations, Derivative Liability		0
Terminations, Net		0
Settlements, Derivative Assets	(20)	(8)
Settlements, Derivative Liabilities	71	85
Settlements, Net	51	77
Ending Balance, Derivative Assets	2	20
Ending Balance, Derivative Liabilities	(153)	(222)
Ending Balance, Net	(151)	(202)
LCAPP Contracts
Reconciliation of changes in the fair value of NUG contracts
Beginning Balance, Derivative Assets	0	0
Beginning Balance, Derivative Liabilities	0	(144)
Beginning Balance, Net	0	(144)
Unrealized gain (loss), Derivative Assets	0	0
Unrealized gain (loss), Derivative Liabilities	0	(22)
Unrealized gain (loss), Net	0	(22)
Purchases, Derivative Assets	0	0
Purchases, Derivative Liabilities	0	0
Purchases, Net	0	0
Terminations, Derivative Assets		0
Terminations, Derivative Liability		166
Terminations, Net		166
Settlements, Derivative Assets	0	0
Settlements, Derivative Liabilities	0	0
Settlements, Net	0	0
Ending Balance, Derivative Assets	0	0
Ending Balance, Derivative Liabilities	0	0
Ending Balance, Net	0	0
FTRs
Reconciliation of changes in the fair value of NUG contracts
Beginning Balance, Derivative Assets	4	8
Beginning Balance, Derivative Liabilities	(12)	(9)
Beginning Balance, Net	(8)	(1)
Unrealized gain (loss), Derivative Assets	47	3
Unrealized gain (loss), Derivative Liabilities	(1)	1
Unrealized gain (loss), Net	46	4
Purchases, Derivative Assets	26	6
Purchases, Derivative Liabilities	(16)	(15)
Purchases, Net	10	(9)
Terminations, Derivative Assets		0
Terminations, Derivative Liability		0
Terminations, Net		0
Settlements, Derivative Assets	(38)	(13)
Settlements, Derivative Liabilities	15	11
Settlements, Net	(23)	(2)
Ending Balance, Derivative Assets	39	4
Ending Balance, Derivative Liabilities	(14)	(12)
Ending Balance, Net	25	(8)
FES | FTRs
Reconciliation of changes in the fair value of NUG contracts
Beginning Balance, Derivative Assets	3	6
Beginning Balance, Derivative Liabilities	(11)	(6)
Beginning Balance, Net	(8)	0
Unrealized gain (loss), Derivative Assets	34	0
Unrealized gain (loss), Derivative Liabilities	(1)	(2)
Unrealized gain (loss), Net	33	(2)
Purchases, Derivative Assets	15	5
Purchases, Derivative Liabilities	(16)	(12)
Purchases, Net	(1)	(7)
Settlements, Derivative Assets	(25)	(8)
Settlements, Derivative Liabilities	15	9
Settlements, Net	(10)	1
Ending Balance, Derivative Assets	27	3
Ending Balance, Derivative Liabilities	(13)	(11)
Ending Balance, Net	$ 14	$ (8)