Fair Value Measurements - Reconciliation of Changes in Level 3 Balances (Details) (Fair Value, Measurements, Recurring [Member], Level 3 [Member], USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	$ 0	$ 85	$ 137	$ (108)
Realized/unrealized gains/(losses) [Abstract]
Other income, net (assets and liabilities, net)	0	397	(81)	385
Other comprehensive income/(loss) (assets and liabilities, net)	0	2	0	(1)
Interest income/(expense) (assets and liabilities, net)	0	40	0	65
Total realized/unrealized gains/(losses) (assets and liabilities, net)	0	439	(81)	449
Purchases, issues, sales and settlements [Abstract]
Purchases (assets and liabilities, net)	0	0	0	5
Issues (assets and liabilities, net)	0	0	0	73
Sales (assets and liabilities, net)	0	0	0	0
Settlements (assets and liabilites, net)	0	6	(56)	112
Total purchases, issues, sales, settlements (assets and liabilities, net)	0	6	(56)	190
Transfers into Level 3 (assets and liabilities, net)	0	0	0	0
Transfers out of Level 3 (assets and liabilities, net)	0	(5)	0	(6)
Ending balance	0	525	0	525
Unrealized gains/(losses) on instruments still held	0	436	0	475
Marketable Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Fair Value Beginning balance	0	5	0	1
Realized/unrealized gains/(losses) [Abstract]
Other income, net (assets)	0	0	0	0
Other comprehensive income/(loss) (assets)	0	0	0	0
Interest income/(expense) (assets)	0	0	0	0
Total realized/unrealized gains/(losses) (assets)	0	0	0	0
Purchases, issues, sales and settlements [Abstract]
Purchases (assets)	0	0	0	5
Issues (assets)	0	0	0	0
Sales (assets)	0	0	0	0
Settlements (assets)	0	0	0	0
Total purchases, issues, sales, settlements (assets)	0	0	0	5
Transfers into Level 3 (assets and liabilities, net)	0	0	0	0
Transfers out of Level 3 (assets and liabilities, net)	0	(5)	0	(6)
Fair Value Ending balance	0	0	0	0
Unrealized gains/(losses) on instruments still held	0	0	0	0
Derivative Financial Instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	0	80	137	(109)
Realized/unrealized gains/(losses) [Abstract]
Other income, net (assets and liabilities, net)	0	397	(81)	385
Other comprehensive income/(loss) (assets and liabilities, net)	0	2	0	(1)
Interest income/(expense) (assets and liabilities, net)	0	40	0	65
Total realized/unrealized gains/(losses) (assets and liabilities, net)	0	439	(81)	449
Purchases, issues, sales and settlements [Abstract]
Purchases (assets and liabilities, net)	0	0	0	0
Issues (assets and liabilities, net)	0	0	0	73
Sales (assets and liabilities, net)	0	0	0	0
Settlements (assets and liabilites, net)	0	6	(56)	112
Total purchases, issues, sales, settlements (assets and liabilities, net)	0	6	(56)	185
Transfers into Level 3 (assets and liabilities, net)	0	0	0	0
Transfers out of Level 3 (assets and liabilities, net)	0	0	0	0
Ending balance	0	525	0	525
Unrealized gains/(losses) on instruments still held	$ 0	$ 436	$ 0	$ 475