Employee Benefits (Details Textual) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended																					12 Months Ended		2 Months Ended			12 Months Ended
	Dec. 31, 2012 trust	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Retirement Plans [Member]		Dec. 31, 2011 Retirement Plans [Member]		Dec. 31, 2010 Retirement Plans [Member]		Dec. 31, 2012 United States Retirement Plans [Member]	Dec. 31, 2012 United Kingdom Retirement Plan [Member]	Dec. 31, 2011 United Kingdom Retirement Plan [Member]	Dec. 31, 2010 United Kingdom Retirement Plan [Member]	Dec. 31, 2012 Postretirement Plans [Member]		Dec. 31, 2011 Postretirement Plans [Member]		Dec. 31, 2010 Postretirement Plans [Member]		Dec. 31, 2012 U.S. Pension Trust [Member]	Dec. 31, 2011 U.S. Pension Trust [Member]	Dec. 31, 2012 U.K. Pension Trust [Member]	Dec. 31, 2011 U.K. Pension Trust [Member]	Feb. 28, 2013 Subsequent Event [Member] Retirement Plans [Member]	Feb. 28, 2013 Subsequent Event [Member] United States Retirement Plans [Member]	Feb. 28, 2013 Subsequent Event [Member] United Kingdom Retirement Plan [Member]	Dec. 31, 2012 Equity Securities, Domestic [Member] U.S. Pension Trust [Member]	Dec. 31, 2012 UNITED STATES trust	Dec. 31, 2012 UNITED KINGDOM trust
Employee Benefits (Textual) [Abstract]
Total cost for retirement plans	$ 129	$ 175	$ 156
Defined contribution plan cost	86	88	83
Assumed weighted-average healthcare cost trend rate	7.50%
Ultimate healthcare cost trend rate	5.00%													7.50%	[1]	8.00%	[1]	8.00%	[1]
Shares purchased by US plan under defined contribution plan	620,455	695,632
Shares sold by US plan under defined contribution plan	869,199	796,934
Shares held by the US plan under defined contribution plan	3,700,000	4,000,000
Shares held by the US plan under defined contribution plan, market value	200	178
Dividend received by the plan	13	4
Decrease in pension benefit liabilities		(129)		0	[2]	(129)	[2]							0	[2]	0	[2]
Decrease in accumulated other comprehensive loss after tax		82
Defined Benefit Plan Disclosure [Line Items]
Number of Pension Trust Accounts	2																											1	1
Actuarial loss that will be amortized in next year from accumulated Other comprehensive Income				25										0
Prior service cost that will be amortized in next year from accumulated Other comprehensive Income				1
Net periodic benefit cost				24		70		58			3	3	6	7		8		9
Change in discount rate on retirement plans				5.10%	[3]	5.40%	[3]	5.95%	[3]	4.10%	4.80%			4.45%	[3]	4.65%	[3]	5.30%	[3]						5.10%	5.10%
Change in return on assets				7.25%
Return on assets				7.75%	[4]	8.00%	[4]	8.00%	[4]															7.75%
Expected required employer contribution				30										12
Plan assets by asset category, Total	$ 1,851	$ 1,505		$ 1,851		$ 1,505		$ 1,567						$ 0		$ 0		$ 0		$ 1,500	$ 1,200	$ 318	$ 258
Target allocations of equity securities																						78.00%					50.00%
Target allocations of fixed income																						16.00%
Target allocations of international equity securities																				16.00%
Target allocations of debt securities and short term investment																				34.00%
Target allocations of UK Real Estate																						6.00%

[1] The assumed weighted-average healthcare cost trend rate will decrease ratably from 7.5% in 2012 to 5% in 2018 and remain at that level thereafter. Assumed healthcare cost trends have an effect on the amounts reported for the healthcare plans. A one percentage point change in assumed healthcare cost trend creates the following effects:(in millions)1% pointincrease 1% pointdecreaseEffect on postretirement obligation$4 $(4)

[2] In December 2011, our Board of Directors approved a plan amendment that froze our U.S. ERP effective on April 1, 2012. This amendment decreased our pension benefit liabilities by $129 million, and resulted in an after-tax decrease in accumulated other comprehensive loss of $82 million. We also recorded an immaterial amount of pension plan curtailment expense in 2011 as a result of the plan amendment.

[3] Effective January 1, 2013, we changed our discount rate assumption on our U.S. retirement plans to 4.1% from 5.1% in 2012 and changed our discount rate assumption on our U.K. plan to 4.8% from 5.1% in 2012.

[4] The expected return on assets assumption is calculated based on the plan’s asset allocation strategy and projected market returns over the long-term. Effective January 1, 2013, we changed our return on assets assumption to 7.25% from 7.75% in 2012.