Fair Value (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended																																																3 Months Ended		9 Months Ended									3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010	Sep. 30, 2011 Carrying Amount	Dec. 31, 2010 Carrying Amount	Sep. 30, 2011 Fair Value	Dec. 31, 2010 Fair Value	Sep. 30, 2011 Level 1	Dec. 31, 2010 Level 1	Sep. 30, 2011 Level 1 Recurring	Dec. 31, 2010 Level 1 Recurring	Sep. 30, 2011 Level 1 Nonrecurring Long Lived Assets Held And Used [Member] Kelanitissa [Member]	Sep. 30, 2010 Level 1 Nonrecurring Long Lived Assets Held And Used [Member] Southland Huntington Beach Subsidiary [Member]	Sep. 30, 2010 Level 1 Nonrecurring Long Lived Assets Held And Used [Member] Tisza I I Subsidiary [Member]	Sep. 30, 2011 Level 1 Nonrecurring Long Lived Assets Held And Used [Member] Wind Turbines And Deposits [Member]	Sep. 30, 2011 Level 1 Nonrecurring Long Lived Assets Held And Used [Member] Carbon Reduction Projects [Member]	Sep. 30, 2011 Level 1 Nonrecurring Long Lived Assets Held And Used [Member] Bohemia [Member]	Sep. 30, 2010 Level 1 Nonrecurring Goodwill [Member] Deepwater Subsidiary [Member]	Sep. 30, 2011 Level 1 Nonrecurring Goodwill [Member] Chigen [Member]	Sep. 30, 2011 Level 1 Nonrecurring Equity Method Affiliate [Member] Yangcheng [Member]	Sep. 30, 2011 Level 2	Dec. 31, 2010 Level 2	Sep. 30, 2011 Level 2 Recurring	Dec. 31, 2010 Level 2 Recurring	Sep. 30, 2011 Level 2 Nonrecurring Long Lived Assets Held And Used [Member] Kelanitissa [Member]	Sep. 30, 2010 Level 2 Nonrecurring Long Lived Assets Held And Used [Member] Southland Huntington Beach Subsidiary [Member]	Sep. 30, 2010 Level 2 Nonrecurring Long Lived Assets Held And Used [Member] Tisza I I Subsidiary [Member]	Sep. 30, 2011 Level 2 Nonrecurring Long Lived Assets Held And Used [Member] Wind Turbines And Deposits [Member]	Sep. 30, 2011 Level 2 Nonrecurring Long Lived Assets Held And Used [Member] Carbon Reduction Projects [Member]	Sep. 30, 2011 Level 2 Nonrecurring Long Lived Assets Held And Used [Member] Bohemia [Member]	Sep. 30, 2010 Level 2 Nonrecurring Goodwill [Member] Deepwater Subsidiary [Member]	Sep. 30, 2011 Level 2 Nonrecurring Goodwill [Member] Chigen [Member]	Sep. 30, 2011 Level 2 Nonrecurring Equity Method Affiliate [Member] Yangcheng [Member]	Sep. 30, 2011 Level 3	Dec. 31, 2010 Level 3	Sep. 30, 2011 Level 3 Recurring	Dec. 31, 2010 Level 3 Recurring	Sep. 30, 2011 Level 3 Nonrecurring Long Lived Assets Held And Used [Member] Kelanitissa [Member]	Sep. 30, 2010 Level 3 Nonrecurring Long Lived Assets Held And Used [Member] Southland Huntington Beach Subsidiary [Member]	Sep. 30, 2010 Level 3 Nonrecurring Long Lived Assets Held And Used [Member] Tisza I I Subsidiary [Member]	Sep. 30, 2011 Level 3 Nonrecurring Long Lived Assets Held And Used [Member] Wind Turbines And Deposits [Member]	Sep. 30, 2011 Level 3 Nonrecurring Long Lived Assets Held And Used [Member] Carbon Reduction Projects [Member]	Sep. 30, 2011 Level 3 Nonrecurring Long Lived Assets Held And Used [Member] Bohemia [Member]	Sep. 30, 2010 Level 3 Nonrecurring Goodwill [Member] Deepwater Subsidiary [Member]	Sep. 30, 2011 Level 3 Nonrecurring Goodwill [Member] Chigen [Member]	Sep. 30, 2011 Level 3 Nonrecurring Equity Method Affiliate [Member] Yangcheng [Member]	Sep. 30, 2011 Recurring	Dec. 31, 2010 Recurring	Sep. 30, 2011 Nonrecurring Long Lived Assets Held And Used [Member] Kelanitissa [Member]	Jun. 30, 2011 Nonrecurring Long Lived Assets Held And Used [Member] Kelanitissa [Member]	Sep. 30, 2011 Nonrecurring Long Lived Assets Held And Used [Member] Kelanitissa [Member]	Sep. 30, 2010 Nonrecurring Long Lived Assets Held And Used [Member] Southland Huntington Beach Subsidiary [Member]	Sep. 30, 2010 Nonrecurring Long Lived Assets Held And Used [Member] Tisza I I Subsidiary [Member]	Sep. 30, 2011 Nonrecurring Long Lived Assets Held And Used [Member] Wind Turbines And Deposits [Member]	Sep. 30, 2011 Nonrecurring Long Lived Assets Held And Used [Member] Carbon Reduction Projects [Member]	Sep. 30, 2011 Nonrecurring Long Lived Assets Held And Used [Member] Bohemia [Member]	Sep. 30, 2010 Nonrecurring Goodwill [Member] Deepwater Subsidiary [Member]	Sep. 30, 2011 Nonrecurring Goodwill [Member] Chigen [Member]	Sep. 30, 2011 Nonrecurring Equity Method Affiliate [Member] Yangcheng [Member] mw	Sep. 30, 2011 Interest Rate Derivatives	Sep. 30, 2010 Interest Rate Derivatives	Sep. 30, 2011 Interest Rate Derivatives	Sep. 30, 2010 Interest Rate Derivatives	Sep. 30, 2011 Cross Currency Swaps	Sep. 30, 2010 Cross Currency Swaps	Sep. 30, 2011 Cross Currency Swaps	Sep. 30, 2010 Cross Currency Swaps	Sep. 30, 2011 Foreign Currency	Sep. 30, 2010 Foreign Currency	Sep. 30, 2011 Foreign Currency	Sep. 30, 2010 Foreign Currency	Sep. 30, 2011 Commodity & Other	Sep. 30, 2010 Commodity & Other	Sep. 30, 2011 Commodity & Other	Sep. 30, 2010 Commodity & Other	Sep. 30, 2011 Debt securities	Sep. 30, 2010 Debt securities	Sep. 30, 2011 Debt securities	Sep. 30, 2010 Debt securities
Fair Value Disclosures Details [Abstract]
An input assumption is considered significant if it affects the fair value by at least 10%.	10.00%		10.00%
Assets
Marketable securities	$ 1,093		$ 1,093		$ 1,767	$ 1,093	$ 1,767	$ 1,093	$ 1,767	$ 12	$ 18												$ 1,041	$ 1,707												$ 40	$ 42
Derivatives	117		117		124	117	124	117	124
Total assets						1,210	1,891	1,210	1,891
Liabilities
Debt						20,878	19,550	21,101	20,137
Derivatives	688		688		423	688	423	688	423
Total liabilities						21,566	19,973	21,789	20,560
Fair Value Assets And Liabilities Measured On Recurring Basis Abstract
Available-for-sale securities												2	8												1,041	1,707												40	42										1,083	1,757
Trading securities												10	10												0	0												0	0										10	10
Derivatives												0	0												57	63												60	61										117	124
Total assets												12	18												1,098	1,770												100	103										1,210	1,891
Derivatives												0	0												419	411												269	12										688	423
Total liabilities												0	0												419	411												269	12										688	423
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Carrying Amount, Nonrecurring																																																			66		66	288	160	161	49	14	18	17	100
Fair Value, Nonrecurring														0	0	0	0	0	0	0	0	0					0	0	0	45	0	5	0	0	0					29	88	75	0	11	0	0	0	26
(Gain) loss on disposal and impairment write-down - discontinued operations			(1)	102
Asset Impairment Charges	163	296	196	297																																															4	33	37	200	85	116	33	9
Goodwill impairment	17	18	17	18																																																							18	17
Generation Capacity (MW)																																																													2,100
Ownership Interest In Subsidiary																																																													25.00%
Other non-operating expense	82	2	82	7																																																									74
Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	10	(223)	49	0																																																										(60)	(226)	(1)	(12)	15	(34)	10	(12)	38	18	22	0	17	19	18	24
Included in earnings	(43)	(5)	(34)	25																																																										0	(2)	0	1	(3)	0	(5)	4	4	0	21	19	(44)	(3)	(50)	1
Included in other comprehensive income	(73)	(40)	(37)	(25)																																																										(36)	(63)	(3)	(20)	(37)	24	(34)	(5)	0	(1)	0	0	0	0	0	0
Included in regulatory (assets) liabilities	(3)	(5)	3	(4)																																																										0	(3)	0	(6)	0	0	0	0	0	0	0	0	(3)	(2)	3	2
Settlements	(1)	13	(3)	(7)																																																										4	15	0	6	4	1	8	4	(1)	0	(2)	(1)	(8)	(3)	(9)	(16)
Transfers of assets (liabilities) into Level 3	(101)	(3)	(189)	(252)																																																										(101)	(3)	(189)	(251)	0	0	0	0	0	0	0	(1)	0	0	0	0
Transfers of (assets) liabilities out of Level 3	2	26	2	26																																																										2	26	2	26	0	0	0	0	0	0	0	0	0	0	0	0
Balance at end of period	(209)	(237)	(209)	(237)																																																										(191)	(256)	(191)	(256)	(21)	(9)	(21)	(9)	41	17	41	17	(38)	11	(38)	11
Total gains/(losses) for the period included in earnings attributable to the change in unrealized gains/(losses) relating to assets and liabilities held at the end of the period	(52)	(1)	(40)	13																																																										0	(1)	0	(2)	(2)	0	(2)	5	2	0	18	20	(52)	0	(56)	(10)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period																																																																														40	42	42	42
Settlements																																																																														0	0	(2)	0
Balance at end of period																																																																														40	42	40	42
Total gains/(losses) for the period included in earnings attributable to the change in unrealized gains/losses relating to assets held at the end of the period																																																																														$ 0	$ 0	$ 0	$ 0