Employee Benefits (Fair Value Measurements Using Significant Unobservable Inputs) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value, beginning balance, Assets	$ 8,691	$ 5,761
Unrealized gains (losses)	93	(22)
Fair Value, ending balance, Assets	6,980	8,691
U.S. Pension Plan [Member] | Private Equity [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value, beginning balance, Assets	2	2
Purchases and sales, net	0	0
Unrealized gains (losses)	0	0
Fair Value, ending balance, Assets	2	2
U.S. Pension Plan [Member] | Alternative Investments [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value, beginning balance, Assets	19	19
Purchases and sales, net	0	0
Unrealized gains (losses)	0	0
Fair Value, ending balance, Assets	19	19
U.K. Pension Plan [Member] | Alternative Investments [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value, beginning balance, Assets	32	33
Purchases and sales, net	3	(1)
Unrealized gains (losses)	4	0
Fair Value, ending balance, Assets	39	32
Non-US Pension Plan (Excluding U.K.) [Member] | Insurance Group Annuity Contract [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value, beginning balance, Assets	57	36
Purchases and sales, net	4	24
Unrealized gains (losses)	0	(3)
Fair Value, ending balance, Assets	$ 61	$ 57