Employee Benefits (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
U.K. and Non-U.S. Pension Plan [Member]
Defined Benefit Plan Disclosure
Service cost	$ 4	$ 4	$ 9	$ 8
Interest cost	62	66	126	132
Expected return on plan assets	(88)	(81)	(178)	(161)
Amortization of net actuarial loss	19	15	37	29
Net periodic benefit cost	(3)	4	(6)	8
Estimate of contributions to defined benefit pension plans for the current fiscal year	381		381
Contributions made to defined benefit pension plans	64		231
U.S. Pension Plan [Member]
Defined Benefit Plan Disclosure
Service cost	0	0	0	0
Interest cost	28	30	56	60
Expected return on plan assets	(35)	(32)	(69)	(64)
Amortization of net actuarial loss	13	11	26	22
Net periodic benefit cost	6	9	13	18
Estimate of contributions to defined benefit pension plans for the current fiscal year	167		167
Contributions made to defined benefit pension plans	$ 35		$ 68