Fair Value (Level 3 Reconciliation) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance at beginning of period	$ (4)	$ (341)
Total gains (losses) (realized and unrealized):
Included in earnings	25	3
Included in other comprehensive income - derivative activity	(65)	(21)
Included in other comprehensive income - foreign currency translation activity	(18)	1
Included in regulatory (assets) liabilities	(3)	(2)
Settlements	8	22
Transfers of (assets) liabilities out of Level 3	71	334
Balance at end of period	14	(4)
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	25	2
Interest Rate [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance at beginning of period	(101)	(412)
Total gains (losses) (realized and unrealized):
Included in earnings	0	0
Included in other comprehensive income - derivative activity	(64)	(21)
Included in other comprehensive income - foreign currency translation activity	0	4
Included in regulatory (assets) liabilities	0	0
Settlements	8	23
Transfers of (assets) liabilities out of Level 3	70	334
Balance at end of period	(87)	(72)
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	0	0
Foreign currency derivatives [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance at beginning of period	93	72
Total gains (losses) (realized and unrealized):
Included in earnings	26	3
Included in other comprehensive income - derivative activity	(1)	0
Included in other comprehensive income - foreign currency translation activity	(18)	(3)
Included in regulatory (assets) liabilities	0	0
Settlements	0	(1)
Transfers of (assets) liabilities out of Level 3	1	0
Balance at end of period	101	71
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	26	2
Commodity [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance at beginning of period	4	(1)
Total gains (losses) (realized and unrealized):
Included in earnings	(1)	0
Included in other comprehensive income - derivative activity	0	0
Included in other comprehensive income - foreign currency translation activity	0	0
Included in regulatory (assets) liabilities	(3)	(2)
Settlements	0	0
Transfers of (assets) liabilities out of Level 3	0	0
Balance at end of period	0	(3)
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	$ (1)	$ 0