Financial Instruments, Derivatives, Guarantees and Concentration of Credit Risk (Details 3) (USD $) In Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Pre-tax gains and losses for energy commodity derivatives designated as cash flow hedges, as recognized in accumulated other comprehensive income (loss) (AOCI) or revenues
Net gain (loss) recognized in other comprehensive income (loss) (effective portion)	$ 75	$ 32	$ 52	$ 310
Net gain (loss) reclassified from accumulated other comprehensive income (loss) into income (effective portion)	63	100	138	125
Gain (loss) recognized in income (ineffective portion)		$ (2)		$ 3