Employee Benefits (Details 1) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Other changes in plan assets and benefit obligations recognized in other comprehensive income, net of tax
Total recognized	$ 101	$ 36	$ 26
Retirement Plans [Member]
Components of net periodic cost for retirement plans and post-retirement plans
Service cost	24	67	61
Interest cost	93	99	94
Expected return on assets	(124)	(127)	(112)
Amortization of actuarial (gain) loss	32	31	15
Prior service credit	(1)	0	0
Net periodic benefit cost	24	70	58
Other changes in plan assets and benefit obligations recognized in other comprehensive income, net of tax
Net actuarial loss (gain)	116	65	41
Recognized actuarial gain	(20)	(18)	(9)
Amortization of prior service credit	2	0	0
Total recognized	98	47	32
Postretirement Plans [Member]
Components of net periodic cost for retirement plans and post-retirement plans
Service cost	3	3	3
Interest cost	5	6	7
Expected return on assets	0	0	0
Amortization of actuarial (gain) loss	0	0	0
Prior service credit	(1)	(1)	(1)
Net periodic benefit cost	7	8	9
Other changes in plan assets and benefit obligations recognized in other comprehensive income, net of tax
Net actuarial loss (gain)	2	(12)	(6)
Recognized actuarial gain	0	0	0
Amortization of prior service credit	1	1	1
Total recognized	$ 3	$ (11)	$ (5)