Segment Information Summarized Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Segment Reporting Information
Revenue	$ 1,614	$ 1,590	$ 1,586	$ 1,586	$ 1,579	$ 927	$ 913	$ 914	$ 6,376	$ 4,333	$ 3,591
Capital expenditures									743	494	435
Depreciation and amortization									749	805	870
Total Assets	13,307				13,188				13,307	13,188
Segment Reporting Information
Segment Reporting Information
Revenue									6,376	4,333	3,591
Capital expenditures									743	494	435
Depreciation and amortization									749	805	870
Total Assets	$ 13,307				$ 13,188				$ 13,307	$ 13,188