Segment Disclosures (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Revenues from external customers:
Revenues from external customers - United States	$ 7,728	$ 6,470	$ 5,163
Revenues from external customers - Other	202	168	115
Total revenues	7,930	6,638	5,278
Long-lived assets:
Long-lived assets	12,624	11,792	11,374
United States [Member]
Long-lived assets:
Long-lived assets	12,041	11,384	11,064
Other Countries [Member]
Long-lived assets:
Long-lived assets	$ 583	$ 408	$ 310