Fair Value Measurements (Details) - Recurring - USD ($)
$ in Millions |
Sep. 30, 2016 |
Dec. 31, 2015 |
| Assets |
|
|
| Fair value, assets |
$ 3,582
|
$ 2,876
|
| Liabilities |
|
|
| Fair value, liabilities |
(259)
|
(281)
|
| Net assets (liabilities) |
3,323
|
2,595
|
| FES |
|
|
| Assets |
|
|
| Fair value, assets |
1,787
|
1,559
|
| Liabilities |
|
|
| Fair value, liabilities |
(139)
|
(142)
|
| Net assets (liabilities) |
1,648
|
1,417
|
| Derivative liabilities - commodity contracts | Derivative Liabilities |
|
|
| Liabilities |
|
|
| Fair value, liabilities |
(134)
|
(131)
|
| Derivative liabilities - commodity contracts | Derivative Liabilities | FES |
|
|
| Liabilities |
|
|
| Fair value, liabilities |
(134)
|
(131)
|
| Derivative liabilities - FTRs | Derivative Liabilities |
|
|
| Liabilities |
|
|
| Fair value, liabilities |
(7)
|
(13)
|
| Derivative liabilities - FTRs | Derivative Liabilities | FES |
|
|
| Liabilities |
|
|
| Fair value, liabilities |
(5)
|
(11)
|
| Derivative liabilities - NUG contracts | Derivative Liabilities |
|
|
| Liabilities |
|
|
| Fair value, liabilities |
(118)
|
(137)
|
| Corporate debt securities |
|
|
| Assets |
|
|
| Fair value, assets |
1,242
|
1,245
|
| Corporate debt securities | FES |
|
|
| Assets |
|
|
| Fair value, assets |
714
|
678
|
| Derivative liabilities - commodity contracts | Derivative Assets |
|
|
| Assets |
|
|
| Fair value, assets |
237
|
228
|
| Derivative liabilities - commodity contracts | Derivative Assets | FES |
|
|
| Assets |
|
|
| Fair value, assets |
237
|
228
|
| Derivative liabilities - FTRs | Derivative Assets |
|
|
| Assets |
|
|
| Fair value, assets |
13
|
8
|
| Derivative liabilities - FTRs | Derivative Assets | FES |
|
|
| Assets |
|
|
| Fair value, assets |
7
|
5
|
| Derivative liabilities - NUG contracts | Derivative Assets |
|
|
| Assets |
|
|
| Fair value, assets |
0
|
1
|
| Equity securities |
|
|
| Assets |
|
|
| Fair value, assets |
908
|
576
|
| Equity securities | FES |
|
|
| Assets |
|
|
| Fair value, assets |
624
|
378
|
| Foreign government debt securities |
|
|
| Assets |
|
|
| Fair value, assets |
77
|
75
|
| Foreign government debt securities | FES |
|
|
| Assets |
|
|
| Fair value, assets |
59
|
59
|
| U.S. government debt securities |
|
|
| Assets |
|
|
| Fair value, assets |
173
|
180
|
| U.S. government debt securities | FES |
|
|
| Assets |
|
|
| Fair value, assets |
53
|
23
|
| U.S. state debt securities |
|
|
| Assets |
|
|
| Fair value, assets |
255
|
246
|
| U.S. state debt securities | FES |
|
|
| Assets |
|
|
| Fair value, assets |
4
|
4
|
| Other |
|
|
| Assets |
|
|
| Fair value, assets |
677
|
317
|
| Other | FES |
|
|
| Assets |
|
|
| Fair value, assets |
89
|
184
|
| Level 1 |
|
|
| Assets |
|
|
| Fair value, assets |
1,466
|
685
|
| Liabilities |
|
|
| Fair value, liabilities |
(12)
|
(9)
|
| Net assets (liabilities) |
1,454
|
676
|
| Level 1 | FES |
|
|
| Assets |
|
|
| Fair value, assets |
633
|
382
|
| Liabilities |
|
|
| Fair value, liabilities |
(12)
|
(9)
|
| Net assets (liabilities) |
621
|
373
|
| Level 1 | Derivative liabilities - commodity contracts | Derivative Liabilities |
|
|
| Liabilities |
|
|
| Fair value, liabilities |
(12)
|
(9)
|
| Level 1 | Derivative liabilities - commodity contracts | Derivative Liabilities | FES |
|
|
| Liabilities |
|
|
| Fair value, liabilities |
(12)
|
(9)
|
| Level 1 | Derivative liabilities - FTRs | Derivative Liabilities |
|
|
| Liabilities |
|
|
| Fair value, liabilities |
0
|
0
|
| Level 1 | Derivative liabilities - FTRs | Derivative Liabilities | FES |
|
|
| Liabilities |
|
|
| Fair value, liabilities |
0
|
0
|
| Level 1 | Derivative liabilities - 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 | Derivative liabilities - commodity contracts | Derivative Assets |
|
|
| Assets |
|
|
| Fair value, assets |
7
|
4
|
| Level 1 | Derivative liabilities - commodity contracts | Derivative Assets | FES |
|
|
| Assets |
|
|
| Fair value, assets |
7
|
4
|
| Level 1 | Derivative liabilities - FTRs | Derivative Assets |
|
|
| Assets |
|
|
| Fair value, assets |
0
|
0
|
| Level 1 | Derivative liabilities - FTRs | Derivative Assets | FES |
|
|
| Assets |
|
|
| Fair value, assets |
0
|
0
|
| Level 1 | Derivative liabilities - NUG contracts | Derivative Assets |
|
|
| Assets |
|
|
| Fair value, assets |
0
|
0
|
| Level 1 | Equity securities |
|
|
| Assets |
|
|
| Fair value, assets |
908
|
576
|
| Level 1 | Equity securities | FES |
|
|
| Assets |
|
|
| Fair value, assets |
624
|
378
|
| 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 |
551
|
105
|
| Level 1 | Other | FES |
|
|
| Assets |
|
|
| Fair value, assets |
2
|
0
|
| Level 2 |
|
|
| Assets |
|
|
| Fair value, assets |
2,103
|
2,182
|
| Liabilities |
|
|
| Fair value, liabilities |
(122)
|
(122)
|
| Net assets (liabilities) |
1,981
|
2,060
|
| Level 2 | FES |
|
|
| Assets |
|
|
| Fair value, assets |
1,147
|
1,172
|
| Liabilities |
|
|
| Fair value, liabilities |
(122)
|
(122)
|
| Net assets (liabilities) |
1,025
|
1,050
|
| Level 2 | Derivative liabilities - commodity contracts | Derivative Liabilities |
|
|
| Liabilities |
|
|
| Fair value, liabilities |
(122)
|
(122)
|
| Level 2 | Derivative liabilities - commodity contracts | Derivative Liabilities | FES |
|
|
| Liabilities |
|
|
| Fair value, liabilities |
(122)
|
(122)
|
| Level 2 | Derivative liabilities - FTRs | Derivative Liabilities |
|
|
| Liabilities |
|
|
| Fair value, liabilities |
0
|
0
|
| Level 2 | Derivative liabilities - FTRs | Derivative Liabilities | FES |
|
|
| Liabilities |
|
|
| Fair value, liabilities |
0
|
0
|
| Level 2 | Derivative liabilities - NUG contracts | Derivative Liabilities |
|
|
| Liabilities |
|
|
| Fair value, liabilities |
0
|
0
|
| Level 2 | Corporate debt securities |
|
|
| Assets |
|
|
| Fair value, assets |
1,242
|
1,245
|
| Level 2 | Corporate debt securities | FES |
|
|
| Assets |
|
|
| Fair value, assets |
714
|
678
|
| Level 2 | Derivative liabilities - commodity contracts | Derivative Assets |
|
|
| Assets |
|
|
| Fair value, assets |
230
|
224
|
| Level 2 | Derivative liabilities - commodity contracts | Derivative Assets | FES |
|
|
| Assets |
|
|
| Fair value, assets |
230
|
224
|
| Level 2 | Derivative liabilities - FTRs | Derivative Assets |
|
|
| Assets |
|
|
| Fair value, assets |
0
|
0
|
| Level 2 | Derivative liabilities - FTRs | Derivative Assets | FES |
|
|
| Assets |
|
|
| Fair value, assets |
0
|
0
|
| Level 2 | Derivative liabilities - 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 |
77
|
75
|
| Level 2 | Foreign government debt securities | FES |
|
|
| Assets |
|
|
| Fair value, assets |
59
|
59
|
| Level 2 | U.S. government debt securities |
|
|
| Assets |
|
|
| Fair value, assets |
173
|
180
|
| Level 2 | U.S. government debt securities | FES |
|
|
| Assets |
|
|
| Fair value, assets |
53
|
23
|
| Level 2 | U.S. state debt securities |
|
|
| Assets |
|
|
| Fair value, assets |
255
|
246
|
| Level 2 | U.S. state debt securities | FES |
|
|
| Assets |
|
|
| Fair value, assets |
4
|
4
|
| Level 2 | Other |
|
|
| Assets |
|
|
| Fair value, assets |
126
|
212
|
| Level 2 | Other | FES |
|
|
| Assets |
|
|
| Fair value, assets |
87
|
184
|
| Level 3 |
|
|
| Assets |
|
|
| Fair value, assets |
13
|
9
|
| Liabilities |
|
|
| Fair value, liabilities |
(125)
|
(150)
|
| Net assets (liabilities) |
(112)
|
(141)
|
| Level 3 | FES |
|
|
| Assets |
|
|
| Fair value, assets |
7
|
5
|
| Liabilities |
|
|
| Fair value, liabilities |
(5)
|
(11)
|
| Net assets (liabilities) |
2
|
(6)
|
| Level 3 | Derivative liabilities - commodity contracts | Derivative Liabilities |
|
|
| Liabilities |
|
|
| Fair value, liabilities |
0
|
0
|
| Level 3 | Derivative liabilities - commodity contracts | Derivative Liabilities | FES |
|
|
| Liabilities |
|
|
| Fair value, liabilities |
0
|
0
|
| Level 3 | Derivative liabilities - FTRs | Derivative Liabilities |
|
|
| Liabilities |
|
|
| Fair value, liabilities |
(7)
|
(13)
|
| Level 3 | Derivative liabilities - FTRs | Derivative Liabilities | FES |
|
|
| Liabilities |
|
|
| Fair value, liabilities |
(5)
|
(11)
|
| Level 3 | Derivative liabilities - NUG contracts | Derivative Liabilities |
|
|
| Liabilities |
|
|
| Fair value, liabilities |
(118)
|
(137)
|
| 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 | Derivative liabilities - commodity contracts | Derivative Assets |
|
|
| Assets |
|
|
| Fair value, assets |
0
|
0
|
| Level 3 | Derivative liabilities - commodity contracts | Derivative Assets | FES |
|
|
| Assets |
|
|
| Fair value, assets |
0
|
0
|
| Level 3 | Derivative liabilities - FTRs | Derivative Assets |
|
|
| Assets |
|
|
| Fair value, assets |
13
|
8
|
| Level 3 | Derivative liabilities - FTRs | Derivative Assets | FES |
|
|
| Assets |
|
|
| Fair value, assets |
7
|
5
|
| Level 3 | Derivative liabilities - NUG contracts | Derivative Assets |
|
|
| Assets |
|
|
| Fair value, assets |
0
|
1
|
| 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
|