Income Taxes (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income from continuing operations before income taxes:
Income from continuing operations before income taxes	$ 1,381	$ 1,384	$ 1,059
Current:
Total current	455	235	228
Deferred:
Total deferred	(95)	143	72
Total income taxes expenses	360	378	300
U.K.
Income from continuing operations before income taxes:
Income from continuing operations before income taxes	36	222	147
Current:
Total current	(10)	13	(9)
Deferred:
Total deferred	46	32	57
U.S.
Income from continuing operations before income taxes:
Income from continuing operations before income taxes	469	301	21
Current:
Total current	170	(17)	16
Deferred:
Total deferred	(83)	109	47
U.S. state and local
Current:
Total current	57	35	10
Deferred:
Total deferred	(10)	14	13
Other
Income from continuing operations before income taxes:
Income from continuing operations before income taxes	876	861	891
Current:
Total current	238	204	211
Deferred:
Total deferred	$ (48)	$ (12)	$ (45)