Employment Benefit Plans Change in Benefit Obligation (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Pension Plan, Defined Benefit
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Projected benefit obligation at beginning of period	$ 2,517	$ 2,324
Service cost	47	39	32
Interest cost	89	100	102
Actuarial (gain) loss	(234)	212
Plan amendment	(7)	0
Benefits paid	(176)	(141)
Administrative expenses	(1)	(1)
Settlements	(15)	(16)
Projected benefit obligation at end of period	2,220	2,517	2,324
Component representing future salary increases	(106)	(130)
Accumulated benefit obligation at end of period	2,114	2,387
Retiree Health and Welfare Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Projected benefit obligation at beginning of period	314	293
Service cost	1	1	1
Interest cost	12	13	14
Actuarial (gain) loss	(29)	31
Plan amendment	0	(5)
Prior service credits	(7)	0	0
Benefits paid	(22)	(26)
Plan participants' contributions	3	5
Medicare Subsidy	0	2
Projected benefit obligation at end of period	$ 272	$ 314	$ 293