NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)

12 Months Ended

Dec. 31, 2016

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Allowance For Doubtful Accounts

The change in the balance of the Allowance for Doubtful Accounts included in Accounts Receivable, Net on the Company's Consolidated Balance Sheets is summarized as follows:

	Years Ended December 31,
(in millions)	2016			2015			2014
Beginning of Period	$	27		$	5		$	5
Additions Charged to Cost and Expense	4			2			2
Write-offs	(3		)	(3		)	(2		)
Provision for Springerville Unit 1, Third-Party Owners	(23		)	23			—
End of Period	$	5		$	27		$	5

AFUDC Rates

The average AFUDC rates on regulated construction expenditures are included in the table below:

	2016		2015		2014
Average AFUDC Rates	7.47	%	6.12	%	7.30	%

Summary Of Average Annual Depreciation Rates For All Utility Plants

Below are the summarized average annual depreciation rates for all utility plant:

	2016		2015		2014
Average Annual Depreciation Rates	2.85	%	2.83	%	2.99	%