Financial Information by Business Segment (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Segment Reporting Information [Line Items]
Unaffiliated	$ 2,273	$ 2,256	$ 4,365	$ 4,423
Intersegment	0	0	0	0
Total revenues	2,273	2,256	4,365	4,423
Depreciation, amortization and accretion	231	179	397	333
Interest income	1	0	2	1
Total interest charges, net	192	180	377	370
Ongoing Earnings	80	211	223	413
Total assets	35,724		35,724		35,059
PEC
Segment Reporting Information [Line Items]
Unaffiliated	1,082	1,060	2,167	2,193
Intersegment	0	0	0	0
Total revenues	1,082	1,060	2,167	2,193
Ongoing Earnings	42	112	103	251
Total assets	16,957		16,957
PEF
Segment Reporting Information [Line Items]
Unaffiliated	1,189	1,193	2,193	2,224
Intersegment	0	0	1	1
Total revenues	1,189	1,193	2,194	2,225
Ongoing Earnings	85	141	214	252
Total assets	14,657		14,657
Corporate and Other
Segment Reporting Information [Line Items]
Unaffiliated	2	3	5	6
Intersegment	72	60	130	134
Total revenues	74	63	135	140
Ongoing Earnings	(47)	(42)	(94)	(90)
Total assets	20,668		20,668
Eliminations
Segment Reporting Information [Line Items]
Unaffiliated	0	0	0	0
Intersegment	(72)	(60)	(131)	(135)
Total revenues	(72)	(60)	(131)	(135)
Ongoing Earnings	0	0	0	0
Total assets	$ (16,558)		$ (16,558)