Retirement Plans (Narrative) (Details) (USD $) Share data in Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014 plan	Dec. 31, 2013	Dec. 31, 2012
Compensation And Retirement Disclosure Line Items
Defined contribution plan, cost recognized	$ 238,000,000	$ 204,000,000	$ 201,000,000
Common stock, shares held in employee trust, shares	25	27
Percentage of defined contribution plans held from outstanding shares	7.00%	8.00%
Number Of Noncontributory Defined Benefit Pension Plans Covering Government Business Employees	6
Number Of Contributory Defined Benefit Pension Plans Covering Government Business Employees	6
Number Of Noncontributory Defined Benefit Pension Plans Covering Commercial Business Employees	2
Number Of Contributory Defined Benefit Pension Plans Covering Commercial Business Employees	4
Number of non-qualified supplemental executive plans	1
Period in which the difference between the actual and expected return on plan assets for qualified plans are recognized in years	5 years
Defined benefit plan, effect of one percentage point increase on service and interest cost components	6,000,000
Defined benefit plan, effect of one percentage point decrease on service and interest cost components	(5,000,000)
Defined Benefit Plan, Effect of One Percentage Point Increase on Accumulated Postretirement Benefit Obligation	94,000,000
Defined Benefit Plan, Effect of One Percentage Point Decrease on Accumulated Postretirement Benefit Obligation	(75,000,000)
Percentage of pension plan assets held in a single trust for primary domestic government and commercial pension plans	90.00%
Pension Benefits
Compensation And Retirement Disclosure Line Items
Defined Benefit Plan, Actuarial Gain (Loss)	566,000,000
Defined Benefit Plan, Contributions by Employer	513,000,000
Expected contribution to defined benefit contribution plans	185,000,000
Defined benefit plan, accumulated benefit obligation	12,800,000,000	10,600,000,000
Other Postretirement Benefit Plans, Defined Benefit
Compensation And Retirement Disclosure Line Items
Defined Benefit Plan, Actuarial Gain (Loss)	$ 28,000,000

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Number Of Contributory Defined Benefit Pension Plans Covering Commercial Business Employees

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Number Of Contributory Defined Benefit Pension Plans Covering Government Business Employees

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Number Of Noncontributory Defined Benefit Pension Plans Covering Commercial Business Employees

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Number Of Noncontributory Defined Benefit Pension Plans Covering Government Business Employees

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Number of Non-qualified Supplemental Executive Plans

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Percentage Of Defined Contribution Plans Held From Outstanding Shares

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Percentage of pension plan assets held in a single trust for primary domestic government and commercial pension plans

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Period in which the difference between the actual and expected return on plan assets for qualified plans are recognized in years

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Number of common stock held in a trust that has been set up specifically to accumulate stock for the sole purpose of distribution to participating employees but not yet earned.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 40

-Section 25

-Paragraph 12

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For defined benefit pension plans, the actuarial present value of benefits (whether vested or nonvested) attributed by the pension benefit formula to employee service rendered before a specified date and based on employee service and compensation (if applicable) before that date. The accumulated benefit obligation differs from the projected benefit obligation in that it includes no assumption about future compensation levels. For plans with flat-benefit or nonpay-related pension benefit formulas, the accumulated benefit obligation and the projected benefit obligation are the same.

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-Publisher FASB

-Name Accounting Standards Codification

-Glossary Accumulated Benefit Obligation

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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.

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-Glossary Gain or Loss

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The increase in the fair value of plan assets from contributions made by the employer.

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Amount of effect of a one-percentage-point decrease in the assumed health care cost trend rates on the accumulated postretirement benefit obligation for health care benefits.

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Amount of effect of a one-percentage-point decrease in the assumed health care cost trend rates on the aggregate of the service and interest cost components of net periodic postretirement health care benefit costs.

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The effect of a one-percentage-point increase in the assumed health care cost trend rates on the accumulated postretirement benefit obligation for health care benefits.

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Amount of employer's best estimate of contributions expected to be paid to the plan during the next fiscal year beginning after the date of the latest statement of financial position.

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The amount of the cost recognized during the period for defined contribution plans.

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