Financial Information by Business Segment (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Segment Reporting Information [Line Items]
Unaffiliated	$ 2,092	$ 2,167
Intersegment	0	0
Total revenues	2,092	2,167
Depreciation, amortization and accretion	166	154
Interest income	1	1
Total interest charges, net	185	190
Ongoing Earnings	143	202
Total assets	35,975		35,059
PEC
Segment Reporting Information [Line Items]
Unaffiliated	1,085	1,133
Intersegment	0	0
Total revenues	1,085	1,133
Ongoing Earnings	60	139
Total assets	16,424
PEF
Segment Reporting Information [Line Items]
Unaffiliated	1,005	1,032
Intersegment	0	0
Total revenues	1,005	1,032
Ongoing Earnings	130	111
Total assets	14,732
Corporate and Other
Segment Reporting Information [Line Items]
Unaffiliated	2	2
Intersegment	59	74
Total revenues	61	76
Ongoing Earnings	(47)	(48)
Total assets	21,248
Eliminations
Segment Reporting Information [Line Items]
Unaffiliated	0	0
Intersegment	(59)	(74)
Total revenues	(59)	(74)
Ongoing Earnings	0	0
Total assets	$ (16,429)