Basis of Presentation (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended	9 Months Ended			12 Months Ended		3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2012 Change in estimates of capitalized labor Adjustments Minimum	Sep. 30, 2012 Change in estimates of capitalized labor Adjustments Maximum	Dec. 31, 2012 Change in estimates of capitalized labor Expected Minimum	Dec. 31, 2012 Change in estimates of capitalized labor Expected Maximum	Sep. 30, 2012 Change in estimates of economic lives and salvage value Adjustments	Sep. 30, 2012 Change in estimates of economic lives and salvage value Adjustments	Dec. 31, 2012 Change in estimates of economic lives and salvage value Expected
Change in accounting estimates
Labor capitalized as an asset					$ 30	$ 45
Operating expenses	(1,724)	(1,778)	(3,639)	(5,258)	(30)	(45)	(35)	(60)
Depreciation expense									13	39	52
Net income	$ 212	$ 199	$ 364	$ 608	$ 18	$ 27	$ 21	$ 36	$ 8	$ 23	$ 31