Derivative Financial Instruments and Risk Management (Details 3) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Derivative
Balance at beginning of period, net of tax			$ (6)	$ (14)
Gains (losses) deferred, net of tax	(3)	(3)	(4)	(4)
(Gains) losses reclassified to earnings, net of tax	1	2	2	11
Balance at end of period, net of tax	(8)	(7)	(8)	(7)
Beginning balance, tax			(3)	(6)
Gains (losses) deferred, tax	(1)	(1)	(2)	(1)
(Gains) losses reclassified to earnings, tax	0	1	1	4
Ending balance, tax	$ (4)	$ (3)	$ (4)	$ (3)