Employee Benefits (Details 6) (USD $) In Millions, unless otherwise specified	12 Months Ended																	12 Months Ended
	Dec. 31, 2012 U.K. And non-U.S. Pension Plan	Dec. 31, 2011 U.K. And non-U.S. Pension Plan	Dec. 31, 2012 U.K. And non-U.S. Pension Plan Equity investments	Dec. 31, 2012 U.K. And non-U.S. Pension Plan Fixed income investments	Dec. 31, 2012 U.K. And non-U.S. Pension Plan Significant Unobservable Inputs (Level 3)	Dec. 31, 2011 U.K. And non-U.S. Pension Plan Significant Unobservable Inputs (Level 3)	Dec. 31, 2011 U.K. And non-U.S. Pension Plan Significant Unobservable Inputs (Level 3) Global	Dec. 31, 2011 U.K. And non-U.S. Pension Plan Significant Unobservable Inputs (Level 3) Fixed	Dec. 31, 2012 U.K. And non-U.S. Pension Plan Significant Unobservable Inputs (Level 3) Annuities	Dec. 31, 2011 U.K. And non-U.S. Pension Plan Significant Unobservable Inputs (Level 3) Annuities	Dec. 31, 2012 U.K. And non-U.S. Pension Plan Significant Unobservable Inputs (Level 3) Real Estate	Dec. 31, 2011 U.K. And non-U.S. Pension Plan Significant Unobservable Inputs (Level 3) Real Estate	Dec. 31, 2012 U.K. And non-U.S. Pension Plan Significant Unobservable Inputs (Level 3) Alternative investments	Dec. 31, 2011 U.K. And non-U.S. Pension Plan Significant Unobservable Inputs (Level 3) Alternative investments	Dec. 31, 2012 U.S. Pension Plan	Dec. 31, 2011 U.S. Pension Plan	Dec. 31, 2010 U.S. Pension Plan	Dec. 31, 2012 U.S. Pension Plan Equity investments	Dec. 31, 2012 U.S. Pension Plan Fixed income investments	Dec. 31, 2012 U.S. Pension Plan Other Investments	Dec. 31, 2012 U.S. Pension Plan Significant Unobservable Inputs (Level 3)	Dec. 31, 2011 U.S. Pension Plan Significant Unobservable Inputs (Level 3)	Dec. 31, 2012 U.S. Pension Plan Significant Unobservable Inputs (Level 3) Alternative investments	Dec. 31, 2011 U.S. Pension Plan Significant Unobservable Inputs (Level 3) Alternative investments
Change in fair value of plan assets
Balance at the beginning of the period	$ 5,098	$ 4,288			$ 899	$ 927	$ 162	$ 40	$ 419	$ 380	$ 134	$ 127	$ 346	$ 218	$ 1,631	$ 1,325	$ 1,244				$ 191	$ 193	$ 262	$ 191
Actual return on plan assets
Relating to assets still held at the end of the year					14	38			(4)	35	(1)	3	19								22	(8)
Relating to assets sold during the year					12	1					1		11	1							1	1
Purchases, sales and settlements - net					173	88			137		(32)	2	68	86							48	5
Transfer in/(out) of Level 3					(18)	(160)	(162)	(40)			(18)	1		41
Foreign exchange	161	18			32	5			16	4	3	1	13
Balance at the end of the period	$ 5,869	$ 5,098			$ 1,112	$ 899			$ 568	$ 419	$ 87	$ 134	$ 457	$ 346	$ 1,631	$ 1,325	$ 1,244				$ 262	$ 191	$ 262	$ 191
Target asset allocations
Target allocation percentage			45.00%	55.00%														49.00%	30.00%	21.00%