SUPPLEMENTAL CASH FLOW (Non-Cash Transactions) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Supplemental Cash Flow Information [Abstract]
Gila River Unit 2, Capital Lease	$ 164	$ 0	$ 0
Accrued Capital Expenditures	31	24	29
Asset Retirement Obligations Increase (Decrease)	20	10	(1)
Renewable Energy Credits	3	2	2
Commitment to Purchase Capital Lease Interests	0	0	36
Net Cost of Removal Increase (Decrease)	$ (4)	$ (88)	$ 8

Commitment to Purchase Capital Lease Interests

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- Definition

Net cost of removal of interim retirements.

+ References

No definition available.

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- Definition

Renewal Energy Credit

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No definition available.

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- Definition

The increase during the period in capital lease obligations due to entering into new capital leases.

+ References

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- Definition

Future cash outflow to pay for construction in progress expenditures that have occurred.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
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- Definition

The increase (decrease) during the reporting period in the carrying amount of asset retirement obligations.

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