Retirement Plans (Details 3) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2015
Pension [Member]
Net Periodic Pension And OPEB Cost/(Benefit) Abstract
Service cost	$ 70	$ 72	$ 54
Interest cost	158	134	141
Expected return on plan assets	(230)	(202)	(190)
Amortization of prior service cost/(credit)	0	0	1
Amortization of actuarial loss	71	106	83
Net periodic benefit cost / (benefit)	69	110	89
Weighted-Average Actuarial Assumptions Used To Determine Benefit Expense [Abstract]
Discount rate - expense	4.72%	3.78%	4.54%
Expected return on plan assets - expense	7.50%	7.50%	7.50%
Compensation increase - expense	4.00%	3.43%	3.69%
Actual return (loss) on pension plan assets, net of fees	6.00%	17.00%	13.00%
OPEB [Member]
Net Periodic Pension And OPEB Cost/(Benefit) Abstract
Service cost	2	3	3
Interest cost	14	12	15
Expected return on plan assets	0	0	0
Amortization of prior service cost/(credit)	(11)	(16)	(18)
Amortization of actuarial loss	10	15	13
Net periodic benefit cost / (benefit)	15	14	13
Weighted-Average Actuarial Assumptions Used To Determine Benefit Expense [Abstract]
Discount rate - expense	4.47%	3.48%	4.36%
Health care cost trend rate (employees under 65)	6.49%	6.64%	6.91%
Ultimate health care cost trend rate	4.50%	4.50%	4.50%
Year ultimate trend reached	2028	2028	2028
Effects On OPEB Of A One-Percentage Point Change In The Assumed Health Care Cost Trend Rates [Abstract]
Effect on total service and interest cost components - one % pt. increase	1
Effect on total service and interest cost components - one % pt. decrease	(1)
Effect on accumulated benefit obligation - one % pt. increase	19
Effect on accumulated benefit obligation - one % pt. decrease	$ (16)
OPEB [Member] \| 2015 Forecast [Member]
Weighted-Average Actuarial Assumptions Used To Determine Benefit Expense [Abstract]
Health care cost trend rate (employees under 65)				6.49%
Ultimate health care cost trend rate				4.50%
Year ultimate trend reached				2028

The actual return on pension plan assets, net of fees.

No definition available.

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The assumed health care cost trend rate used to measure the expected cost of benefits covered by the plan (gross eligible charges) for employees under age 65. This is based upon the annual rate of change in the cost of health care benefits currently provided by the postretirement benefit plan, due to factors other than changes in the composition of the plan population by age and dependency status.

+ References

No definition available.

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- Definition

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

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- Definition

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.

+ References

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- Definition

The interest rate used to adjust for the time value of money.

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- Definition

An assumption as to the rate of return on plan assets reflecting the average rate of earnings expected on the funds invested or to be invested to provide for the benefits included in the benefit obligation.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 30

-Glossary Expected Long-Term Rate of Return on Plan Assets

-URI http://asc.fasb.org/extlink&oid=6512013

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (k)(3)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

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- Definition

Expected rate of compensation increases (for pay-related plans).

+ References

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- Definition

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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- Definition

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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The effect of a one-percentage-point increase 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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- Definition

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.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 30

-Glossary Expected Return on Plan Assets

-URI http://asc.fasb.org/extlink&oid=6512136

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 60

-Glossary Expected Return on Plan Assets

-URI http://asc.fasb.org/extlink&oid=6512171

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (h)(3)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

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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.

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- Definition

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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- 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.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (h)(1)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Service Cost (Component of Net Periodic Pension Cost)

-URI http://asc.fasb.org/extlink&oid=6525008

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

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The ultimate trend rate for health care costs.

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- Definition

Year the ultimate health care cost trend rate is expected to be reached, in CCYY format.

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