Percentage of Purchase Power Obligations

No definition available.

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Namespace Prefix:	tep_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of rent expense incurred for leased assets, including but not limited to, furniture and equipment, that is not directly or indirectly associated with the manufacture, sale or creation of a product or product line.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of the fixed and determinable portion of the unrecorded unconditional purchase obligation maturing in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 440
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=77896938&loc=d3e25336-109308

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of the fixed and determinable portion of the unrecorded unconditional purchase obligation maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of the fixed and determinable portion of the unrecorded unconditional purchase obligation maturing in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of the fixed and determinable portion of the unrecorded unconditional purchase obligation maturing in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of the fixed and determinable portion of the unrecorded unconditional purchase obligation maturing in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

+ Details

Name:	us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnThirdAnniversary
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of the unrecorded obligation to transfer funds in the future for fixed or minimum amounts or quantities of goods or services at fixed or minimum prices (for example, as in take-or-pay contracts or throughput contracts).

+ References

+ Details

Name:	us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceSheetAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of the fixed and determinable portion of the unrecorded unconditional purchase obligation maturing after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

+ Details

Name:	us-gaap_UnrecordedUnconditionalPurchaseObligationDueAfterFiveYears
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Data Type:	xbrli:stringItemType
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Period Type:	duration

- Details

Name:	us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis=us-gaap_FuelMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis=tep_PurchasedPowerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis=tep_TransmissionFacilitiesMember
Namespace Prefix:
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- Details

Name:	us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis=tep_RenewableEnergyPowerPurchaseAgreementMember
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- Details

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Namespace Prefix:
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- Details

Name:	us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis=tep_OperatingLeaseMember
Namespace Prefix:
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- Details

Name:	us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis=us-gaap_ContractualRightsMember
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Data Type:	na
Balance Type:
Period Type:

COMMITMENTS AND CONTINGENCIES (Commitments) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Unrecorded Unconditional Purchase Obligation [Line Items]
2019	$ 198
2020	156
2021	123
2022	101
2023	94
Thereafter	913
Total	1,585
Fuel, Including Transportation
Unrecorded Unconditional Purchase Obligation [Line Items]
2019	85
2020	74
2021	45
2022	26
2023	19
Thereafter	175
Total	424
Purchased Power
Unrecorded Unconditional Purchase Obligation [Line Items]
2019	20
2020	0
2021	0
2022	0
2023	0
Thereafter	0
Total	20
Transmission
Unrecorded Unconditional Purchase Obligation [Line Items]
2019	19
2020	9
2021	5
2022	3
2023	3
Thereafter	9
Total	48
Renewable Power Purchase Agreements
Unrecorded Unconditional Purchase Obligation [Line Items]
2019	64
2020	63
2021	63
2022	63
2023	63
Thereafter	605
Total	$ 921
Percentage of purchase power obligations (in percentage)	100.00%
RES Performance-Based Incentives
Unrecorded Unconditional Purchase Obligation [Line Items]
2019	$ 8
2020	8
2021	7
2022	7
2023	7
Thereafter	39
Total	76
Operating Leases
Unrecorded Unconditional Purchase Obligation [Line Items]
2019	1
2020	1
2021	1
2022	1
2023	1
Thereafter	5
Total	10
Rent expense	1	$ 1	$ 2
Land Easements and Rights-of-Way
Unrecorded Unconditional Purchase Obligation [Line Items]
2019	1
2020	1
2021	2
2022	1
2023	1
Thereafter	80
Total	$ 86