Fair Value Measurements (Details 1) (Level 3, USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2014		Dec. 31, 2013
Non Utility Generation Contract
Fair Value, Assets and Liabilities Measured on Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value Measurement With Unobservable Inputs Reconciliation,Recurring Basis, Asset, Terminations			$ 0	[1],[2]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Liabilities, Terminations			0	[1],[2]
Fair Value Measurement With Unobservable Inputs, Reconciliation, Recurring Basis, Asset And Liability Terminations			0	[1],[2]
Reconciliation of changes in the fair value of NUG contracts
Beginning Balance, Derivative Assets	20	[2]	36	[2]
Beginning Balance, Derivative Liabilities	(222)	[2]	(290)	[2]
Beginning Balance, Net	(202)	[2]	(254)	[2]
Unrealized gain (loss), Derivative Assets	0	[2]	(8)	[2]
Unrealized gain (loss), Derivative Liabilities	27	[2]	(17)	[2]
Unrealized gain (loss), Net	27	[2]	(25)	[2]
Purchases, Derivative Assets			0	[2]
Purchases, Derivative Liabilities			0	[2]
Purchases, Net			0	[2]
Settlements, Derivative Assets	(17)	[2]	(8)	[2]
Settlements, Derivative Liabilities	7	[2]	85	[2]
Settlements, Net	(10)	[2]	77	[2]
Ending Balance, Derivative Assets	3	[2]	20	[2]
Ending Balance, Derivative Liabilities	(188)	[2]	(222)	[2]
Ending Balance, Net	(185)	[2]	(202)	[2]
LCAPP Contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value Measurement With Unobservable Inputs Reconciliation,Recurring Basis, Asset, Terminations			0	[1],[2]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Liabilities, Terminations			166	[1],[2]
Fair Value Measurement With Unobservable Inputs, Reconciliation, Recurring Basis, Asset And Liability Terminations			166	[1],[2]
Reconciliation of changes in the fair value of NUG contracts
Beginning Balance, Derivative Assets	0	[2]	0	[2]
Beginning Balance, Derivative Liabilities	0	[2]	(144)	[2]
Beginning Balance, Net	0	[2]	(144)	[2]
Unrealized gain (loss), Derivative Assets	0	[2]	0	[2]
Unrealized gain (loss), Derivative Liabilities	0	[2]	(22)	[2]
Unrealized gain (loss), Net	0	[2]	(22)	[2]
Purchases, Derivative Assets			0	[2]
Purchases, Derivative Liabilities			0	[2]
Purchases, Net			0	[2]
Settlements, Derivative Assets	0	[2]	0	[2]
Settlements, Derivative Liabilities	0	[2]	0	[2]
Settlements, Net	0	[2]	0	[2]
Ending Balance, Derivative Assets	0	[2]	0	[2]
Ending Balance, Derivative Liabilities	0	[2]	0	[2]
Ending Balance, Net	0	[2]	0	[2]
FTRs
Fair Value, Assets and Liabilities Measured on Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value Measurement With Unobservable Inputs Reconciliation,Recurring Basis, Asset, Terminations			0	[1]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Liabilities, Terminations			0	[1]
Fair Value Measurement With Unobservable Inputs, Reconciliation, Recurring Basis, Asset And Liability Terminations			0	[1]
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	6		3
Unrealized gain (loss), Derivative Liabilities	2		1
Unrealized gain (loss), Net	8		4
Purchases, Derivative Assets			6
Purchases, Derivative Liabilities			(15)
Purchases, Net			(9)
Settlements, Derivative Assets	(3)		(13)
Settlements, Derivative Liabilities	2		11
Settlements, Net	(1)		(2)
Ending Balance, Derivative Assets	7		4
Ending Balance, Derivative Liabilities	(8)		(12)
Ending Balance, Net	(1)		(8)
FTRs | FES
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	3		0
Unrealized gain (loss), Derivative Liabilities	1		(2)
Unrealized gain (loss), Net	4		(2)
Purchases, Derivative Assets			5
Purchases, Derivative Liabilities			(12)
Purchases, Net			(7)
Settlements, Derivative Assets	(2)		(8)
Settlements, Derivative Liabilities	2		9
Settlements, Net	0		1
Ending Balance, Derivative Assets	4		3
Ending Balance, Derivative Liabilities	(8)		(11)
Ending Balance, Net	$ (4)		$ (8)

[1] See Note 8, Derivative Instruments

[2] Changes in the fair value of NUG and LCAPP contracts are generally subject to regulatory accounting treatment and do not impact earnings.