Asset Purchase Agreement, Additional Percentage Share of Cost of Control

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- Definition

Asset Purchase Agreement, Operating and Maintenance Cost Reimbursement Receivable

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- Definition

Asset Purchase Agreement, Option to Purchase, Ownership Interest, Percentage

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- Definition

Asset Purchase Agreement, Proceeds from Operating an Maintenance Cost Reimbursement

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- Definition

Asset Purchase Agreement, Site Contingency, Increase in Loss Exposure Not Accrued, Best Estimate

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Guarantor Obligations, Number of Parental Guarantees

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- Definition

Represents the percentage of share of the cost of control acquired by the entity.

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- Definition

Prepaid Energy Related Inventory, Coal

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- Definition

Supply Agreement [Abstract]

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Surety Bonds Expiring, Amount

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The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

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Amount awarded to other party in judgment or settlement of litigation.

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The value (monetary amount) of the award the plaintiff seeks in the legal matter.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
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-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349

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-Name Accounting Standards Codification
-Topic 450
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-Section 50
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
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-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14435-108349

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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.

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Best estimate of the loss exposure for reasonably possible environmental contingencies at an individual site for which no accrual has been recorded.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 30
-Section 50
-Paragraph 10
-Subparagraph (c),(d)(2)
-URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13237-110859

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Commitments and Contingencies - Environmental Matters and Financial Assurances (Details) $ in Millions			3 Months Ended	12 Months Ended
	Jun. 13, 2017 USD ($)	Jul. 06, 2016 guarantee	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Mar. 12, 2018 USD ($)
Coal Supply Agreement Arbitration \| Four Corners
Four Corners Coal Supply Agreement
Damages sought	$ 30
Settlement amount			$ 45
Arizona Public Service Company \| Coal Supply Agreement Arbitration \| Four Corners
Four Corners Coal Supply Agreement
Damages sought	$ 17
Settlement amount			34
Coal advance purchase					$ 24
Arizona Public Service Company \| Letter of Credit Expiring in 2016 and 2017
Financial Assurances
Outstanding letters of credit			5
Arizona Public Service Company \| Letters of Credit Expiring in 2017
Financial Assurances
Surety bonds expiring, amount			$ 36
4C Acquisition, LLC \| Four Corners Units 4 and 5
Environmental Matters
Percentage of share of cost of control			7.00%
4C Acquisition, LLC \| Four Corners
Environmental Matters
Percentage of share of cost of control		7.00%
4C Acquisition, LLC \| Coal Supply Agreement Arbitration \| Four Corners
Four Corners Coal Supply Agreement
Proceeds from operating and maintenance cost reimbursement				$ 10
Reimbursement payments due to 4CA				$ 20
NTEC \| Four Corners
Four Corners Coal Supply Agreement
Option to purchase ownership interest (as a percent)		7.00%
NTEC \| Coal Supply Agreement Arbitration \| Four Corners
Four Corners Coal Supply Agreement
Option to purchase ownership interest (as a percent)		7.00%
Regional Haze Rules \| Arizona Public Service Company \| Four Corners Units 4 and 5
Environmental Matters
Percentage of share of cost of control			63.00%
Expected environmental cost			$ 400
Regional Haze Rules \| Arizona Public Service Company \| Natural gas tolling contract obligations \| Four Corners Units 4 and 5
Environmental Matters
Additional percentage share of cost of control			7.00%
Regional Haze Rules \| Arizona Public Service Company \| Four Corners \| Four Corners Units 4 and 5
Environmental Matters
Site contingency increase in loss exposure not accrued, best estimate			$ 45
Regional Haze Rules \| Arizona Public Service Company \| Navajo Plant
Environmental Matters
Expected environmental cost			200
Coal combustion waste \| Arizona Public Service Company \| Four Corners
Environmental Matters
Site contingency increase in loss exposure not accrued, best estimate			22
Coal combustion waste \| Arizona Public Service Company \| Navajo Plant
Environmental Matters
Site contingency increase in loss exposure not accrued, best estimate			1
Minimum \| Coal combustion waste \| Arizona Public Service Company \| Cholla
Environmental Matters
Site contingency increase in loss exposure not accrued, best estimate			$ 20
Payment Guarantee
Financial Assurances
Number of parental guarantees \| guarantee		4