Taxation (Reconciliation of Unrecognized Tax Benefits) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefits, beginning of year	$ 134	$ 139
Additions based on tax provisions related to the current year	19	1
Reduction for tax positions of prior years	0	(6)
Reductions for settlements with tax authorities	(16)	0
Reductions for the lapse of the applicable statutes of limitations	(111)	0
Unrecognized Tax Benefits, end of year	$ 26	$ 134