Fair Value Measurements (Details) (Recurring, USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Assets
Fair value, assets	$ 2,832	$ 2,865
Liabilities
Fair value, liabilities	(334)	(347)
Net assets (liabilities)	2,498	2,518
FES
Assets
Fair value, assets	1,520	1,485
Liabilities
Fair value, liabilities	(180)	(124)
Net assets (liabilities)	1,340	1,361
Commodity contracts | Derivative Liabilities
Liabilities
Fair value, liabilities	(167)	(113)
Commodity contracts | Derivative Liabilities | FES
Liabilities
Fair value, liabilities	(167)	(113)
FTRs | Derivative Liabilities
Liabilities
Fair value, liabilities	(14)	(12)
FTRs | Derivative Liabilities | FES
Liabilities
Fair value, liabilities	(13)	(11)
NUG contracts | Derivative Liabilities
Liabilities
Fair value, liabilities	(153)	(222)
Corporate debt securities
Assets
Fair value, assets	1,221	1,365
Corporate debt securities | FES
Assets
Fair value, assets	655	792
Commodity contracts | Derivative Assets
Assets
Fair value, assets	172	215
Commodity contracts | Derivative Assets | FES
Assets
Fair value, assets	172	215
FTRs | Derivative Assets
Assets
Fair value, assets	39	4
FTRs | Derivative Assets | FES
Assets
Fair value, assets	27	3
NUG contracts | Derivative Assets
Assets
Fair value, assets	2	20
Equity securities
Assets
Fair value, assets	592	317
Equity securities | FES
Assets
Fair value, assets	360	207
Foreign government debt securities
Assets
Fair value, assets	76	109
Foreign government debt securities | FES
Assets
Fair value, assets	57	65
U.S. government debt securities
Assets
Fair value, assets	182	165
U.S. government debt securities | FES
Assets
Fair value, assets	46	27
U.S. state debt securities
Assets
Fair value, assets	237	228
U.S. state debt securities | FES
Assets
Fair value, assets	4	0
Other
Assets
Fair value, assets	311	442
Other | FES
Assets
Fair value, assets	199	176
Level 1
Assets
Fair value, assets	648	511
Liabilities
Fair value, liabilities	(26)	(13)
Net assets (liabilities)	622	498
Level 1 | FES
Assets
Fair value, assets	361	214
Liabilities
Fair value, liabilities	(26)	(13)
Net assets (liabilities)	335	201
Level 1 | Commodity contracts | Derivative Liabilities
Liabilities
Fair value, liabilities	(26)	(13)
Level 1 | Commodity contracts | Derivative Liabilities | FES
Liabilities
Fair value, liabilities	(26)	(13)
Level 1 | FTRs | Derivative Liabilities
Liabilities
Fair value, liabilities	0	0
Level 1 | FTRs | Derivative Liabilities | FES
Liabilities
Fair value, liabilities	0	0
Level 1 | NUG contracts | Derivative Liabilities
Liabilities
Fair value, liabilities	0	0
Level 1 | Corporate debt securities
Assets
Fair value, assets	0	0
Level 1 | Corporate debt securities | FES
Assets
Fair value, assets	0	0
Level 1 | Commodity contracts | Derivative Assets
Assets
Fair value, assets	1	7
Level 1 | Commodity contracts | Derivative Assets | FES
Assets
Fair value, assets	1	7
Level 1 | FTRs | Derivative Assets
Assets
Fair value, assets	0	0
Level 1 | FTRs | Derivative Assets | FES
Assets
Fair value, assets	0	0
Level 1 | NUG contracts | Derivative Assets
Assets
Fair value, assets	0	0
Level 1 | Equity securities
Assets
Fair value, assets	592	317
Level 1 | Equity securities | FES
Assets
Fair value, assets	360	207
Level 1 | Foreign government debt securities
Assets
Fair value, assets	0	0
Level 1 | Foreign government debt securities | FES
Assets
Fair value, assets	0	0
Level 1 | U.S. government debt securities
Assets
Fair value, assets	0	0
Level 1 | U.S. government debt securities | FES
Assets
Fair value, assets	0	0
Level 1 | U.S. state debt securities
Assets
Fair value, assets	0	0
Level 1 | U.S. state debt securities | FES
Assets
Fair value, assets	0	0
Level 1 | Other
Assets
Fair value, assets	55	187
Level 1 | Other | FES
Assets
Fair value, assets	0	0
Level 2
Assets
Fair value, assets	2,143	2,330
Liabilities
Fair value, liabilities	(141)	(100)
Net assets (liabilities)	2,002	2,230
Level 2 | FES
Assets
Fair value, assets	1,132	1,268
Liabilities
Fair value, liabilities	(141)	(100)
Net assets (liabilities)	991	1,168
Level 2 | Commodity contracts | Derivative Liabilities
Liabilities
Fair value, liabilities	(141)	(100)
Level 2 | Commodity contracts | Derivative Liabilities | FES
Liabilities
Fair value, liabilities	(141)	(100)
Level 2 | FTRs | Derivative Liabilities
Liabilities
Fair value, liabilities	0	0
Level 2 | FTRs | Derivative Liabilities | FES
Liabilities
Fair value, liabilities	0	0
Level 2 | NUG contracts | Derivative Liabilities
Liabilities
Fair value, liabilities	0	0
Level 2 | Corporate debt securities
Assets
Fair value, assets	1,221	1,365
Level 2 | Corporate debt securities | FES
Assets
Fair value, assets	655	792
Level 2 | Commodity contracts | Derivative Assets
Assets
Fair value, assets	171	208
Level 2 | Commodity contracts | Derivative Assets | FES
Assets
Fair value, assets	171	208
Level 2 | FTRs | Derivative Assets
Assets
Fair value, assets	0	0
Level 2 | FTRs | Derivative Assets | FES
Assets
Fair value, assets	0	0
Level 2 | NUG contracts | Derivative Assets
Assets
Fair value, assets	0	0
Level 2 | Equity securities
Assets
Fair value, assets	0	0
Level 2 | Equity securities | FES
Assets
Fair value, assets	0	0
Level 2 | Foreign government debt securities
Assets
Fair value, assets	76	109
Level 2 | Foreign government debt securities | FES
Assets
Fair value, assets	57	65
Level 2 | U.S. government debt securities
Assets
Fair value, assets	182	165
Level 2 | U.S. government debt securities | FES
Assets
Fair value, assets	46	27
Level 2 | U.S. state debt securities
Assets
Fair value, assets	237	228
Level 2 | U.S. state debt securities | FES
Assets
Fair value, assets	4	0
Level 2 | Other
Assets
Fair value, assets	256	255
Level 2 | Other | FES
Assets
Fair value, assets	199	176
Level 3
Assets
Fair value, assets	41	24
Liabilities
Fair value, liabilities	(167)	(234)
Net assets (liabilities)	(126)	(210)
Level 3 | FES
Assets
Fair value, assets	27	3
Liabilities
Fair value, liabilities	(13)	(11)
Net assets (liabilities)	14	(8)
Level 3 | Commodity contracts | Derivative Liabilities
Liabilities
Fair value, liabilities	0	0
Level 3 | Commodity contracts | Derivative Liabilities | FES
Liabilities
Fair value, liabilities	0	0
Level 3 | FTRs | Derivative Liabilities
Liabilities
Fair value, liabilities	(14)	(12)
Level 3 | FTRs | Derivative Liabilities | FES
Liabilities
Fair value, liabilities	(13)	(11)
Level 3 | NUG contracts | Derivative Liabilities
Liabilities
Fair value, liabilities	(153)	(222)
Level 3 | Corporate debt securities
Assets
Fair value, assets	0	0
Level 3 | Corporate debt securities | FES
Assets
Fair value, assets	0	0
Level 3 | Commodity contracts | Derivative Assets
Assets
Fair value, assets	0	0
Level 3 | Commodity contracts | Derivative Assets | FES
Assets
Fair value, assets	0	0
Level 3 | FTRs | Derivative Assets
Assets
Fair value, assets	39	4
Level 3 | FTRs | Derivative Assets | FES
Assets
Fair value, assets	27	3
Level 3 | NUG contracts | Derivative Assets
Assets
Fair value, assets	2	20
Level 3 | Equity securities
Assets
Fair value, assets	0	0
Level 3 | Equity securities | FES
Assets
Fair value, assets	0	0
Level 3 | Foreign government debt securities
Assets
Fair value, assets	0	0
Level 3 | Foreign government debt securities | FES
Assets
Fair value, assets	0	0
Level 3 | U.S. government debt securities
Assets
Fair value, assets	0	0
Level 3 | U.S. government debt securities | FES
Assets
Fair value, assets	0	0
Level 3 | U.S. state debt securities
Assets
Fair value, assets	0	0
Level 3 | U.S. state debt securities | FES
Assets
Fair value, assets	0	0
Level 3 | Other
Assets
Fair value, assets	0	0
Level 3 | Other | FES
Assets
Fair value, assets	$ 0	$ 0