Employment Benefit Plans Change in Benefit Obligation (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pension Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Projected benefit obligation at beginning of period	$ 2,220	$ 2,517
Service cost	38	47	39
Interest cost	95	89	100
Actuarial loss (gain)	256	(234)
Plan amendment	0	(7)
Benefits paid	(141)	(176)
Administrative expenses	(1)	(1)
Settlements	(15)	(15)
Projected benefit obligation at end of period	2,452	2,220	2,517
Component representing future salary increases	(146)	(106)
Accumulated benefit obligation at end of period	2,306	2,114
Retiree Health and Welfare Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Projected benefit obligation at beginning of period	272	314
Service cost	1	1	1
Interest cost	11	12	13
Actuarial loss (gain)	13	(29)
Benefits paid	(23)	(22)
Plan participants' contributions	6	3
Prior service credits	0	(7)	0
Projected benefit obligation at end of period	$ 280	$ 272	$ 314

Component representing future salary increases

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- Definition

Amount before tax of cost (credit) of benefit changes attributable to plan participants' prior service resulting from a plan design change that has not been recognized in net periodic benefit cost (credit).

+ References

No definition available.

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- Definition

Amount of gain (loss) related to change in benefit obligation resulting from changes in actuarial assumptions, for example, but not limited to, interest, mortality, employee turnover, salary, and temporary deviation from the substantive plan.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

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- Definition

Amount of plan administration expenses deducted from total plan assets.

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- Definition

1) For defined benefit pension plans, the benefit obligation is the projected benefit obligation, which is the actuarial present value as of a date of all benefits attributed by the pension benefit formula to employee service rendered prior to that date. 2) For other postretirement defined benefit plans, the benefit obligation is the accumulated postretirement benefit obligation, which is the actuarial present value of benefits attributed to employee service rendered to a particular date.

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-Glossary Projected Benefit Obligation

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-Glossary Accumulated Postretirement Benefit Obligation

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- Definition

The amount of payments made for which participants are entitled under a pension plan, including pension benefits, death benefits, and benefits due on termination of employment. Also includes payments made under a postretirement benefit plan, including prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services. This item represents a periodic decrease to the plan obligations and a decrease to plan assets.

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- Definition

The amount of contributions made by plan participants. This item represents a periodic increase to the plan obligation and an increase to plan assets.

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- Definition

The increase in a defined benefit pension plan's projected benefit obligation or a defined benefit postretirement plan's accumulated postretirement benefit obligation due to the passage of time.

+ References

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- Definition

If aggregate disclosures are presented, the aggregate pension accumulated benefit obligation for pension plans with accumulated benefit obligations in excess of plan assets as of the measurement date of each statement of financial position presented.

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- Definition

The amount of increase or decrease due to a change in the terms of an existing plan or the initiation of a new plan. A plan amendment may increase or decrease benefits, including those attributed to years of service already rendered.

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- Definition

The actuarial present value of benefits attributed by the pension benefit formula to services rendered by employees during the period. The portion of the expected postretirement benefit obligation attributed to employee service during the period. The service cost component is a portion of the benefit obligation and is unaffected by the funded status of the plan.

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- Definition

The amount of decrease that relates to an irrevocable action that relieves the employer (or the plan) of primary responsibility for a benefit obligation and eliminates significant risks related to the obligation and the assets used to effect the settlement. Examples of transactions that constitute a settlement include (a) making lump-sum cash payments to plan participants in exchange for their rights to receive specified benefits and (b) purchasing nonparticipating annuity contracts.

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