Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure for Single Counter Party

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- Definition

Concentration Risk, Number of Customers Provided Service

+ References

No definition available.

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- Definition

Long-term Contract for Purchase of Electric Power, Term of Contract

+ References

No definition available.

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- Definition

The aggregate fair value of additional assets that would be required to be posted as collateral for derivative instruments with credit-risk-related contingent features if the credit-risk-related contingent features were triggered at the end of the reporting period.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4H

-Subparagraph (e)

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5624258-113959

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- Definition

The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4H

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5624258-113959

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- Definition

Maximum amount of loss due to credit risk that, based on the gross fair value of the financial instrument, the entity would incur if parties to the financial instruments that make up the concentration failed completely to perform according to the terms of the contracts and the collateral or other security, if any, for the amount due proved to be of no value to the entity.

+ References

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- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 21

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=35750535&loc=d3e13537-108611

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 275

-SubTopic 10

-Section 50

-Paragraph 20

-URI http://asc.fasb.org/extlink&oid=6927468&loc=d3e6404-108592

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-Topic 275

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-Paragraph 18

-URI http://asc.fasb.org/extlink&oid=6927468&loc=d3e6351-108592

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- Definition

Fair value, after offset of derivative asset, of financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, elected not to be and before offset against a right to receive collateral under a master netting arrangement. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 50

-Paragraph 3

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=34720828&loc=SL20225862-175312

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 55

-Paragraph 10

-URI http://asc.fasb.org/extlink&oid=36459792&loc=SL20226008-175313

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 55

-Paragraph 9

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-Topic 815

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-Section 50

-Paragraph 8

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=35706170&loc=d3e41678-113959

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- Definition

Revenue related to midstream and downstream gas activities. May include the following: gathering from wells, processing to remove impurities, storage, transmission, and the sale of natural gas and related products.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.1)

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 932

-SubTopic 235

-Section 50

-Paragraph 23

-Subparagraph (a)

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-Topic 932

-SubTopic 235

-Section 50

-Paragraph 24

-URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62246-109447

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Credit Risk (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Concentration Risk [Line Items]
Gross credit exposure	$ 228
Gas transportation and storage	1,543	1,535	1,401
Additional collateral to be posted if the credit-related contingent features were triggered	20	146
Collateral already posted	1	76
Fair value of all derivative instruments not fully collateralized	49	169
Investment Grade Counterparties \| Investment Grade
Concentration Risk [Line Items]
Concentration of credit risk	86.00%
CounterpartyA
Concentration Risk [Line Items]
Amount of exposure	23
Customer Concentration Risk \| DTI \| Sales Revenue, Net
Concentration Risk [Line Items]
Concentration of credit risk	94.00%
Number of customers	260
Customer Concentration Risk \| East Ohio \| Sales Revenue, Net
Concentration Risk [Line Items]
Concentration of credit risk	98.00%
Customer Concentration Risk \| Ten Largest Customers \| DTI \| Sales Revenue, Net
Concentration Risk [Line Items]
Concentration of credit risk	41.00%
Number of customers	10
Customer Concentration Risk \| Thirty Largest Customers \| DTI \| Sales Revenue, Net
Concentration Risk [Line Items]
Concentration of credit risk	74.00%
Number of customers	30
Gas transportation and storage	$ 718
Customer Concentration Risk \| Long Term Capacity Contracts \| DTI \| Sales Revenue, Net
Concentration Risk [Line Items]
Concentration of credit risk	99.00%
Term of long term contract	3 years
Customer Concentration Risk \| Annual Capacity Contracts \| DTI \| Sales Revenue, Net
Concentration Risk [Line Items]
Concentration of credit risk	1.00%
Customer Concentration Risk \| Unsubscribed Firm Transportation Capacity \| DTI \| Sales Revenue, Net
Concentration Risk [Line Items]
Concentration of credit risk	1.00%