Employee Benefits (Details 4) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
U.K. And non-U.S. Pension Plan
Defined Benefit Plan Disclosure
Service cost	$ 15	$ 19	$ 15
Interest cost	265	267	249
Expected return on plan assets	(323)	(287)	(240)
Amortization of prior-service cost	1	1	1
Amortization of net actuarial loss	60	53	54
Net periodic benefit cost	18	53	79
Amounts in accumulated other comprehensive loss expected to be recognized as components of net periodic benefit cost during next fiscal year
Amounts in accumulated other comprehensive loss expected to be recognized as components of net periodic benefit cost during next fiscal year	75
U.K. And non-U.S. Pension Plan | Minimum
Weighted-average assumptions used to determine future benefit obligations
Discount rate (as a percent)	3.25%	4.40%
Rate of compensation increase (as a percent)	2.25%	2.25%
Weighted-average assumptions used to determine the net periodic benefit cost
Discount rate (as a percent)	4.40%	4.70%	4.00%
Expected return on plan assets (as a percent)	4.90%	3.20%	4.70%
Rate of compensation increase (as a percent)	2.25%	2.00%	2.50%
U.K. And non-U.S. Pension Plan | Maximum
Weighted-average assumptions used to determine future benefit obligations
Discount rate (as a percent)	4.45%	4.94%
Rate of compensation increase (as a percent)	3.85%	3.55%
Weighted-average assumptions used to determine the net periodic benefit cost
Discount rate (as a percent)	4.94%	5.50%	6.19%
Expected return on plan assets (as a percent)	6.75%	7.20%	7.00%
Rate of compensation increase (as a percent)	3.55%	4.00%	3.60%
U.S. Pension Plan
Defined Benefit Plan Disclosure
Interest cost	119	122	124
Expected return on plan assets	(127)	(120)	(118)
Amortization of net actuarial loss	43	31	24
Net periodic benefit cost	35	33	30
Expenses recognized as a result of an error, net of taxes			29
Pretax expenses recognized as a result of an error			(49)
Weighted-average assumptions used to determine the net periodic benefit cost
Expected return on plan assets (as a percent)	8.80%	8.80%	8.80%
Amounts in accumulated other comprehensive loss expected to be recognized as components of net periodic benefit cost during next fiscal year
Amounts in accumulated other comprehensive loss expected to be recognized as components of net periodic benefit cost during next fiscal year	52
U.S. Pension Plan | Minimum
Weighted-average assumptions used to determine future benefit obligations
Discount rate (as a percent)	3.73%	4.33%
Weighted-average assumptions used to determine the net periodic benefit cost
Discount rate (as a percent)	4.33%	4.35%	5.22%
U.S. Pension Plan | Maximum
Weighted-average assumptions used to determine future benefit obligations
Discount rate (as a percent)	4.05%	4.60%
Weighted-average assumptions used to determine the net periodic benefit cost
Discount rate (as a percent)	4.60%	5.34%	5.98%
U.S. and Canadian Other Post-Retirement Benefits
Defined Benefit Plan Disclosure
Net periodic benefit cost	1	6	4
Amounts in accumulated other comprehensive loss expected to be recognized as components of net periodic benefit cost during next fiscal year
Net loss (gain)	1
Prior service credit	$ 5
U.S. and Canadian Other Post-Retirement Benefits | Minimum
Weighted-average assumptions used to determine future benefit obligations
Discount rate (as a percent)	3.67%	4.33%	4.92%
Weighted-average assumptions used to determine the net periodic benefit cost
Discount rate (as a percent)	4.33%	4.92%	5.90%
U.S. and Canadian Other Post-Retirement Benefits | Maximum
Weighted-average assumptions used to determine future benefit obligations
Discount rate (as a percent)	4.00%	5.00%	6.00%
Weighted-average assumptions used to determine the net periodic benefit cost
Discount rate (as a percent)	5.00%	6.00%	6.19%