Retirement Benefits (Details) (Unaudited) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
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	$ 390	$ 399
Interest cost	305	304	915	912
Expected return on plan assets	(423)	(380)	(1,269)	(1,140)
Amortization of:
Prior service cost (credit)	6	9	18	27
Net loss from previous years	41	51	123	153
Net periodic benefit cost	59	117	177	351
Defined contribution plans cost	64	77	225	243
Employer Contributions (Amounts in paragraphs)
Employer contributions required	59		59
Employer contributions			572
Employer contributions, voluntary			500
Medical and Life Benefits
Components of Net Periodic Benefit Cost (Table Amounts) [Abstract]
Service cost	8	8	24	24
Interest cost	29	30	87	90
Expected return on plan assets	(16)	(14)	(48)	(42)
Amortization of:
Prior service cost (credit)	(13)	(13)	(39)	(39)
Net loss from previous years	3	5	9	15
Net periodic benefit cost	11	16	33	48
Employer Contributions (Amounts in paragraphs)
Employer contributions required	124		124
Employer contributions			$ 73

Amortization of Prior Service Cost and Losses.

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The amount of voluntary contributions made by the employer.

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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 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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