XML 81 R63.htm IDEA: XBRL DOCUMENT v2.4.1.9

Risk Management Activities and Derivative Transactions Derivatives Under FTP (Details) (USD $)	6 Months Ended
	Mar. 31, 2015	Sep. 30, 2014
Derivative
FTP transaction limit	130,000,000tve_FtpTransactionLimit
Maximum hedge volume	75.00%tve_MaximumHedgeVolume
Market value limitation of outstanding construction materials hedging transactions	100,000,000tve_MarketValueLimitationOfOutstandingConstructionMaterialsHedgingTransactions
Portfolio value at risk limit for foreign currency transactions	5,000,000tve_PortfolioValueAtRiskLimitForForeignCurrencyTransactions
Swap contracts
Derivative
Remaining terms	3 years
Coal Contract Derivatives
Derivative
Fair value	0us-gaap_DerivativeFairValueOfDerivativeNet / tve_DerivativesUnderFinancialTradingProgramAxis = us-gaap_CoalContractMember	0us-gaap_DerivativeFairValueOfDerivativeNet / tve_DerivativesUnderFinancialTradingProgramAxis = us-gaap_CoalContractMember
Futures Contracts
Derivative
Fair value	0us-gaap_DerivativeFairValueOfDerivativeNet / tve_DerivativesUnderFinancialTradingProgramAxis = us-gaap_FutureMember
Options Contract
Derivative
Fair value	0us-gaap_DerivativeFairValueOfDerivativeNet / tve_DerivativesUnderFinancialTradingProgramAxis = us-gaap_OptionMember

X

- Definition

FTP transaction limit

+ References

No definition available.

+ Details

Name:	tve_FtpTransactionLimit
Namespace Prefix:	tve_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

The market value limitation of outstanding hedging transactions involving construction materials.

+ References

No definition available.

+ Details

Name:	tve_MarketValueLimitationOfOutstandingConstructionMaterialsHedgingTransactions
Namespace Prefix:	tve_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

The maximum hedge volume for construction material transactions.

+ References

No definition available.

+ Details

Name:	tve_MaximumHedgeVolume
Namespace Prefix:	tve_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

X

- Definition

The portfolio value at risk limit for foreign currency transactions.

+ References

No definition available.

+ Details

Name:	tve_PortfolioValueAtRiskLimitForForeignCurrencyTransactions
Namespace Prefix:	tve_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Remaining terms

+ References

No definition available.

+ Details

Name:	tve_Remainingterms
Namespace Prefix:	tve_
Data Type:	us-types:durationStringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Fair value of the assets less the liabilities of a derivative or group of derivatives.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 10

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=35750535&loc=d3e13433-108611



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 45

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 15

-URI http://asc.fasb.org/extlink&oid=35750535&loc=d3e13495-108611



Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 45

-Paragraph 6

-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41271-113958

+ Details

Name:	us-gaap_DerivativeFairValueOfDerivativeNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Details

Name:	us-gaap_DerivativeLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	tve_DerivativesUnderFinancialTradingProgramAxis=us-gaap_CoalContractMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	tve_DerivativesUnderFinancialTradingProgramAxis=us-gaap_FutureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	tve_DerivativesUnderFinancialTradingProgramAxis=us-gaap_OptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DerivativeByNatureAxis=us-gaap_SwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: