Operating Segments, Geographic Analysis and Major Customers (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 segment	Dec. 31, 2010	Dec. 31, 2009
Operating Segments, Geographic Analysis and Major Customers
Number of operating segments	2
Segments, Geographical Analysis and Major Customers
Operating revenues	$ 9,142	$ 9,466	$ 11,441
U.S.
Segments, Geographical Analysis and Major Customers
Operating revenues	1,975	2,087	2,209
U.K.
Segments, Geographical Analysis and Major Customers
Operating revenues	1,211	1,183	1,563
Brazil
Segments, Geographical Analysis and Major Customers
Operating revenues	1,019	1,288	1,108
Other countries
Segments, Geographical Analysis and Major Customers
Operating revenues	$ 4,937	$ 4,908	$ 6,561
Threshold of operating revenues for reporting individually as a country (as a percent)	10.00%