Fair Value (Details) (USD $) In Millions	Jun. 30, 2011	Dec. 31, 2010
Assets:
Nuclear decommissioning trusts	$ 975	$ 939
Other Investments	109	111
Derivative assets	158	208
Total Assets	1,242	1,258
Current	109	131
Noncurrent	1,133	1,127
Net Assets	1,058	1,006
Liabilities:
Current	(110)	(142)
Noncurrent	(74)	(110)
Total Liabilities	(184)	(252)
Derivative liabilities	(184)	(252)
Fair Value Inputs Level 1 [Member]
Assets:
Nuclear decommissioning trusts	626	599
Other Investments	56	56
Derivative assets	1,179	1,914
Total Assets	1,861	2,569
Current	818	1,299
Noncurrent	1,043	1,270
Net Assets	700	662
Fair Value Inputs Level 1 [Member] | Foreign currency exchange contracts [Member]
Assets:
Derivative assets	0	0
Fair Value Inputs Level 1 [Member] | Natural Gas [Member]
Assets:
Derivative assets	1,151	1,846
Fair Value Inputs Level 1 [Member] | Electricity [Member]
Assets:
Derivative assets	0	0
Fair Value Inputs Level 1 [Member] | Other [Member]
Assets:
Derivative assets	28	68
Fair Value Inputs Level 1 [Member]
Liabilities:
Current	(817)	(1,290)
Noncurrent	(344)	(617)
Total Liabilities	(1,161)	(1,907)
Derivative liabilities	(1,161)	(1,907)
Fair Value Inputs Level 1 [Member] | Foreign currency exchange contracts [Member]
Liabilities:
Derivative liabilities	0	0
Fair Value Inputs Level 1 [Member] | Interest rate contracts [Member]
Liabilities:
Derivative liabilities	0	0
Fair Value Inputs Level 1 [Member] | Natural Gas [Member]
Liabilities:
Derivative liabilities	(1,141)	(1,844)
Fair Value Inputs Level 1 [Member] | Electricity [Member]
Liabilities:
Derivative liabilities	0	0
Fair Value Inputs Level 1 [Member] | Other [Member]
Liabilities:
Derivative liabilities	(20)	(63)
Fair Value Inputs Level 2 [Member]
Assets:
Nuclear decommissioning trusts	349	340
Other Investments	53	55
Derivative assets	463	801
Total Assets	865	1,196
Current	342	663
Noncurrent	523	533
Net Assets	265	241
Fair Value Inputs Level 2 [Member] | Foreign currency exchange contracts [Member]
Assets:
Derivative assets	16	20
Fair Value Inputs Level 2 [Member] | Natural Gas [Member]
Assets:
Derivative assets	78	128
Fair Value Inputs Level 2 [Member] | Electricity [Member]
Assets:
Derivative assets	367	649
Fair Value Inputs Level 2 [Member] | Other [Member]
Assets:
Derivative assets	2	4
Fair Value Inputs Level 2 [Member]
Liabilities:
Current	(430)	(730)
Noncurrent	(170)	(225)
Total Liabilities	(600)	(955)
Derivative liabilities	(600)	(955)
Fair Value Inputs Level 2 [Member] | Foreign currency exchange contracts [Member]
Liabilities:
Derivative liabilities	(26)	(30)
Fair Value Inputs Level 2 [Member] | Interest rate contracts [Member]
Liabilities:
Derivative liabilities	(1)	(1)
Fair Value Inputs Level 2 [Member] | Natural Gas [Member]
Liabilities:
Derivative liabilities	(187)	(263)
Fair Value Inputs Level 2 [Member] | Electricity [Member]
Liabilities:
Derivative liabilities	(384)	(653)
Fair Value Inputs Level 2 [Member] | Other [Member]
Liabilities:
Derivative liabilities	(2)	(8)
Fair Value Inputs Level 3 [Member]
Assets:
Nuclear decommissioning trusts	0	0
Other Investments	0	0
Derivative assets	153	133
Total Assets	153	133
Current	117	49
Noncurrent	36	84
Net Assets	65	59
Fair Value Inputs Level 3 [Member] | Foreign currency exchange contracts [Member]
Assets:
Derivative assets	0	0
Fair Value Inputs Level 3 [Member] | Natural Gas [Member]
Assets:
Derivative assets	10	12
Fair Value Inputs Level 3 [Member] | Electricity [Member]
Assets:
Derivative assets	136	117
Fair Value Inputs Level 3 [Member] | Other [Member]
Assets:
Derivative assets	7	4
Fair Value Inputs Level 3 [Member]
Liabilities:
Current	(65)	(21)
Noncurrent	(23)	(53)
Total Liabilities	(88)	(74)
Derivative liabilities	(88)	(74)
Fair Value Inputs Level 3 [Member] | Foreign currency exchange contracts [Member]
Liabilities:
Derivative liabilities	0	0
Fair Value Inputs Level 3 [Member] | Interest rate contracts [Member]
Liabilities:
Derivative liabilities	0	0
Fair Value Inputs Level 3 [Member] | Natural Gas [Member]
Liabilities:
Derivative liabilities	(9)	(11)
Fair Value Inputs Level 3 [Member] | Electricity [Member]
Liabilities:
Derivative liabilities	(79)	(63)
Fair Value Inputs Level 3 [Member] | Other [Member]
Liabilities:
Derivative liabilities	0	0
Netting Adjustments [Member]
Assets:
Nuclear decommissioning trusts	0	0
Other Investments	0	0
Derivative assets	(1,637)	(2,640)
Total Assets	(1,637)	(2,640)
Current	(1,168)	(1,880)
Noncurrent	(469)	(760)
Net Assets	28	44
Netting Adjustments [Member] | Foreign currency exchange contracts [Member]
Assets:
Derivative assets	(16)	(20)
Netting Adjustments [Member] | Natural Gas [Member]
Assets:
Derivative assets	(1,224)	(1,960)
Netting Adjustments [Member] | Electricity [Member]
Assets:
Derivative assets	(369)	(589)
Netting Adjustments [Member] | Other [Member]
Assets:
Derivative assets	(28)	(71)
Netting Adjustments [Member]
Liabilities:
Current	1,202	1,899
Noncurrent	463	785
Total Liabilities	1,665	2,684
Derivative liabilities	1,665	2,684
Netting Adjustments [Member] | Foreign currency exchange contracts [Member]
Liabilities:
Derivative liabilities	16	20
Netting Adjustments [Member] | Interest rate contracts [Member]
Liabilities:
Derivative liabilities	0	0
Netting Adjustments [Member] | Natural Gas [Member]
Liabilities:
Derivative liabilities	1,212	1,955
Netting Adjustments [Member] | Electricity [Member]
Liabilities:
Derivative liabilities	417	643
Netting Adjustments [Member] | Other [Member]
Liabilities:
Derivative liabilities	20	66
Foreign currency exchange contracts [Member]
Assets:
Derivative assets	0	0
Liabilities:
Derivative liabilities	(10)	(10)
Interest rate contracts [Member]
Liabilities:
Derivative liabilities	(1)	(1)
Natural Gas [Member]
Assets:
Derivative assets	15	26
Liabilities:
Derivative liabilities	(125)	(163)
Electricity [Member]
Assets:
Derivative assets	134	177
Liabilities:
Derivative liabilities	(46)	(73)
Other [Member]
Assets:
Derivative assets	9	5
Liabilities:
Derivative liabilities	$ (2)	$ (5)