Financial Information by Business Segment (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Segment Reporting Information [Line Items]
Unaffiliated									$ 8,907	$ 10,190	$ 9,885
Total revenues	1,737	2,747	2,256	2,167	2,321	2,962	2,372	2,535	8,907	10,190	9,885
Depreciation, amortization and accretion									701	920	986
Interest income									2	7	14
Total interest charges, net									725	747	679
Income tax expense (benefit)									480	522	416
Ongoing Earnings									871	889	846
Total assets	35,059				33,054				35,059	33,054	31,236
Capital and investment expenditures									2,150	2,382	2,503
PEC
Segment Reporting Information [Line Items]
Unaffiliated									4,528	4,922	4,627
Total revenues									4,528	4,922	4,627
Depreciation, amortization and accretion									514	479	470
Interest income									1	3	5
Total interest charges, net									184	186	195
Income tax expense (benefit)									268	342	295
Ongoing Earnings									541	618	540
Total assets	16,102				14,899				16,102	14,899	13,502
Capital and investment expenditures									1,423	1,382	962
PEF
Segment Reporting Information [Line Items]
Unaffiliated									4,367	5,252	5,249
Intersegment									2	2	2
Total revenues									4,369	5,254	5,251
Depreciation, amortization and accretion									169	426	502
Interest income									1	1	4
Total interest charges, net									239	258	231
Income tax expense (benefit)									311	267	209
Ongoing Earnings									530	462	460
Total assets	14,484				14,056				14,484	14,056	13,100
Capital and investment expenditures									710	991	1,532
Corporate and Other
Segment Reporting Information [Line Items]
Unaffiliated									12	16	9
Intersegment									272	248	234
Total revenues									284	264	243
Depreciation, amortization and accretion									18	15	14
Interest income									22	31	38
Total interest charges, net									324	331	286
Income tax expense (benefit)									(99)	(87)	(88)
Ongoing Earnings									(200)	(191)	(154)
Total assets	20,926				21,110				20,926	21,110	20,538
Capital and investment expenditures									17	33	21
Eliminations
Segment Reporting Information [Line Items]
Intersegment									(274)	(250)	(236)
Total revenues									(274)	(250)	(236)
Interest income									(22)	(28)	(33)
Total interest charges, net									(22)	(28)	(33)
Total assets	(16,453)				(17,011)				(16,453)	(17,011)	(15,904)
Capital and investment expenditures									$ 0	$ (24)	$ (12)