Employee Benefits (Details 3) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Components of pre-tax AOCI not yet recognized as net postretirement benefit cost
Total unrecognized AOCI	$ 634	$ 525
Pension Plans, Defined Benefit [Member]
Changes in the fair values of Level 3 plan assets
FVA at beginning of year	914	839
Defined Benefit Plan, Actual Return on Plan Assets [Abstract]
FVA at end of year	918	914	839
Net postretirement benefit cost for all funded and unfunded plans
Service cost of benefits earned			50
Interest cost on PBO/APBO	57	60	58
Expected return on plan assets	(81)	(72)	(65)
Amortization of prior service cost			(1)
Net pension/postretirement benefit cost	(13)	0	91
Other changes in plan assets and benefit obligations recognized in OCI:
Net (gain) loss	120	54	28
Prior service cost (benefit)			(1)
Total recognized in comprehensive income	109	42	(20)
Other Postretirement Benefit Plans, Defined Benefit [Member]
Changes in the fair values of Level 3 plan assets
FVA at beginning of year	61	58
Defined Benefit Plan, Actual Return on Plan Assets [Abstract]
FVA at end of year	57	61	58
Components of pre-tax AOCI not yet recognized as net postretirement benefit cost
Net unrecognized losses (gains)	8	0
Net unrecognized prior service benefit	(8)	(9)
Total unrecognized AOCI	0	(9)
Net postretirement benefit cost for all funded and unfunded plans
Service cost of benefits earned	1	1	1
Interest cost on PBO/APBO	3	3	4
Expected return on plan assets	(3)	(3)	(3)
Amortization of prior service cost	1	1	1
Net pension/postretirement benefit cost	0	0	1
Other changes in plan assets and benefit obligations recognized in OCI:
Net (gain) loss	8	1	(4)
Prior service cost (benefit)	0		2
Amortization of prior service cost	1	1	1
Total recognized in comprehensive income	9	2	(1)
Total recognized in net postretirement benefit cost and comprehensive income	9	2	0
Level 3 [Member] | Pension Plans, Defined Benefit [Member]
Changes in the fair values of Level 3 plan assets
FVA at beginning of year	17	37
Defined Benefit Plan, Actual Return on Plan Assets [Abstract]
Relating to assets held at reporting date	4
Relating to assets sold during the period	(4)
Sales	(1)	(20)
FVA at end of year	16	17
Insurance Company Contracts [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Actual Return on Plan Assets [Abstract]
FVA at end of year	12	11
Insurance Company Contracts [Member] | Level 3 [Member] | Pension Plans, Defined Benefit [Member]
Changes in the fair values of Level 3 plan assets
FVA at beginning of year	11	11
Defined Benefit Plan, Actual Return on Plan Assets [Abstract]
Relating to assets held at reporting date	1
Relating to assets sold during the period	0
Sales	0	0
FVA at end of year	12	11
Multi Strategy Investment Funds [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Actual Return on Plan Assets [Abstract]
FVA at end of year	4	6
Multi Strategy Investment Funds [Member] | Level 3 [Member] | Pension Plans, Defined Benefit [Member]
Changes in the fair values of Level 3 plan assets
FVA at beginning of year	6	26
Defined Benefit Plan, Actual Return on Plan Assets [Abstract]
Relating to assets held at reporting date	3
Relating to assets sold during the period	(4)
Sales	(1)	(20)
FVA at end of year	$ 4	$ 6