Reconciliation of Changes in Fair Value of Financial Assets and Liabilities Classified as Level Three In Fair Value Hierarchy (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 151	$ 103	$ 78
Included in earnings	(90)	135	87
Included in other comprehensive income (loss)	10	4	4
Settlements	(45)	(91)	(66)
Transfers in and out of Level 3	0	0	0
Ending Balance	26	151	103
Change in unrealized gains (losses) relating to investments and derivatives still held	(16)	82	56
Derivatives [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance		71	48
Included in earnings		135	87
Included in other comprehensive income (loss)		0	0
Settlements		(91)	(64)
Transfers in and out of Level 3		0	0
Ending Balance		115	71
Change in unrealized gains (losses) relating to investments and derivatives still held		82	56
Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	36	32	30
Included in earnings	(6)	0	0
Included in other comprehensive income (loss)	10	4	4
Settlements	(1)	0	(2)
Transfers in and out of Level 3	0	0	0
Ending Balance	39	36	32
Change in unrealized gains (losses) relating to investments and derivatives still held	$ (6)	$ 0	$ 0