Retirement Benefits (Details) (Unaudited) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Employer Contributions (Amounts in paragraphs)
Employer contributions, voluntary			$ 500
Defined Contribution Plans Disclosure (Amounts in paragraphs)
Maximum percentage of employee compensation eligible for cash matching of employee contributions			4.00%
Pension Benefits
Components of Net Periodic Benefit Cost (Table Amounts) [Abstract]
Service cost	130	133	260	266
Interest cost	305	304	610	608
Expected return on plan assets	(423)	(380)	(846)	(760)
Amortization of:
Prior service cost (credit)	6	9	12	18
Net loss from previous years	41	51	82	102
Net periodic benefit cost	59	117	118	234
Employer Contributions (Amounts in paragraphs)
Expected employer contributions	59		59
Employer contributions			550
Defined Contribution Plans Disclosure (Amounts in paragraphs)
Defined contribution plans cost	76	86	161	166
Medical and Life Benefits
Components of Net Periodic Benefit Cost (Table Amounts) [Abstract]
Service cost	8	8	16	16
Interest cost	29	30	58	60
Expected return on plan assets	(16)	(14)	(32)	(28)
Amortization of:
Prior service cost (credit)	(13)	(13)	(26)	(26)
Net loss from previous years	3	5	6	10
Net periodic benefit cost	11	16	22	32
Employer Contributions (Amounts in paragraphs)
Expected employer contributions	124		124
Employer contributions			$ 40

Amortization of Prior Service Cost and Losses.

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Defined benefit plan contributions by employer voluntary.

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The maximum percentage of compensation the employer will contribute in order to match an employee's contribution to the plan.

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The amount of gains or losses recognized in net periodic benefit cost.

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The amount of the prior service cost or credit recognized in net periodic benefit cost relating to benefit changes attributable to plan participants' prior service pursuant to a plan amendment or a plan initiation.

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

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The employer's best estimate, as soon as it can be reasonably determined, 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. Estimated contributions may be presented in the aggregate combining (1) contributions required by funding regulations or laws, (2) discretionary contributions, and (3) noncash contributions.

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An amount calculated as a basis for determining the extent of delayed recognition of the effects of changes in the fair value of assets. The expected return on plan assets is determined based on the expected long-term rate of return on plan assets and the market-related value of plan assets.

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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.

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The total amount of net periodic benefit cost for defined benefit plans for the period. Periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) due to settlements or curtailments.

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

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