FAIR VALUE MEASUREMENTS & DERIVATIVE INSTRUMENTS (Schedule of Fair Value Measurements of Financial Assets and Liabilities) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012
Assets
Cash Equivalent	$ 14	[1]	$ 20	[1]
Restricted Cash	2	[1]	7	[1]
Rabbi Trust Investments to Support the Deferred Compensation and SERP	22	[2]	19	[2]
Energy Contracts	7	[3]	7	[3]
Total Assets	45		53
Liabilities
Liabilities	(15)		(27)
Net Total Assets (Liability)	30		26
Energy Contracts [Member]
Liabilities
Derivative Liability	(7)	[3]	(15)	[3]
Energy Contracts Cash Flow Hedge [Member]
Liabilities
Derivative Liability	(1)	[3]	(2)	[3]
Interest Rate Swap [Member]
Liabilities
Derivative Liability	(7)	[4]	(10)	[4]
TUCSON ELECTRIC POWER COMPANY
Assets
Cash Equivalent	0	[1]	1	[1]
Restricted Cash	2	[1]	7	[1]
Rabbi Trust Investments to Support the Deferred Compensation and SERP	22	[2]	19	[2]
Energy Contracts	2	[3]	3	[3]
Total Assets	26		30
Liabilities
Liabilities	(10)		(15)
Net Total Assets (Liability)	16		15
TUCSON ELECTRIC POWER COMPANY | Energy Contracts [Member]
Liabilities
Derivative Liability	(2)	[3]	(3)	[3]
TUCSON ELECTRIC POWER COMPANY | Energy Contracts Cash Flow Hedge [Member]
Liabilities
Derivative Liability	(1)	[3]	(2)	[3]
TUCSON ELECTRIC POWER COMPANY | Interest Rate Swap [Member]
Liabilities
Derivative Liability	(7)	[4]	(10)	[4]
Level 1 [Member]
Assets
Cash Equivalent	14	[1]	20	[1]
Restricted Cash	2	[1]	7	[1]
Rabbi Trust Investments to Support the Deferred Compensation and SERP	0	[2]	0	[2]
Energy Contracts	0	[3]	0	[3]
Total Assets	16		27
Liabilities
Liabilities	0		0
Net Total Assets (Liability)	16		27
Level 1 [Member] | Energy Contracts [Member]
Liabilities
Derivative Liability	0	[3]	0	[3]
Level 1 [Member] | Energy Contracts Cash Flow Hedge [Member]
Liabilities
Derivative Liability	0	[3]	0	[3]
Level 1 [Member] | Interest Rate Swap [Member]
Liabilities
Derivative Liability	0	[4]	0	[4]
Level 1 [Member] | TUCSON ELECTRIC POWER COMPANY
Assets
Cash Equivalent	0	[1]	1	[1]
Restricted Cash	2	[1]	7	[1]
Rabbi Trust Investments to Support the Deferred Compensation and SERP	0	[2]	0	[2]
Energy Contracts	0	[3]	0	[3]
Total Assets	2		8
Liabilities
Liabilities	0		0
Net Total Assets (Liability)	2		8
Level 1 [Member] | TUCSON ELECTRIC POWER COMPANY | Energy Contracts [Member]
Liabilities
Derivative Liability	0	[3]	0	[3]
Level 1 [Member] | TUCSON ELECTRIC POWER COMPANY | Energy Contracts Cash Flow Hedge [Member]
Liabilities
Derivative Liability	0	[3]	0	[3]
Level 1 [Member] | TUCSON ELECTRIC POWER COMPANY | Interest Rate Swap [Member]
Liabilities
Derivative Liability	0	[4]	0	[4]
Level 2 [Member]
Assets
Cash Equivalent	0	[1]	0	[1]
Restricted Cash	0	[1]	0	[1]
Rabbi Trust Investments to Support the Deferred Compensation and SERP	22	[2]	19	[2]
Energy Contracts	3	[3]	2	[3]
Total Assets	25		21
Liabilities
Liabilities	(9)		(17)
Net Total Assets (Liability)	16		4
Level 2 [Member] | Energy Contracts [Member]
Liabilities
Derivative Liability	(2)	[3]	(7)	[3]
Level 2 [Member] | Energy Contracts Cash Flow Hedge [Member]
Liabilities
Derivative Liability	0	[3]	0	[3]
Level 2 [Member] | Interest Rate Swap [Member]
Liabilities
Derivative Liability	(7)	[4]	(10)	[4]
Level 2 [Member] | TUCSON ELECTRIC POWER COMPANY
Assets
Cash Equivalent	0	[1]	0	[1]
Restricted Cash	0	[1]	0	[1]
Rabbi Trust Investments to Support the Deferred Compensation and SERP	22	[2]	19	[2]
Energy Contracts	1	[3]	1	[3]
Total Assets	23		20
Liabilities
Liabilities	(7)		(13)
Net Total Assets (Liability)	16		7
Level 2 [Member] | TUCSON ELECTRIC POWER COMPANY | Energy Contracts [Member]
Liabilities
Derivative Liability	0	[3]	(3)	[3]
Level 2 [Member] | TUCSON ELECTRIC POWER COMPANY | Energy Contracts Cash Flow Hedge [Member]
Liabilities
Derivative Liability	0	[3]	0	[3]
Level 2 [Member] | TUCSON ELECTRIC POWER COMPANY | Interest Rate Swap [Member]
Liabilities
Derivative Liability	(7)	[4]	(10)	[4]
Level 3 [Member]
Assets
Cash Equivalent	0	[1]	0	[1]
Restricted Cash	0	[1]	0	[1]
Rabbi Trust Investments to Support the Deferred Compensation and SERP	0	[2]	0	[2]
Energy Contracts	4	[3]	5	[3]
Total Assets	4		5
Liabilities
Derivative Liability	6
Liabilities	(6)		(10)
Net Total Assets (Liability)	(2)		(5)
Level 3 [Member] | Energy Contracts [Member]
Liabilities
Derivative Liability	(5)	[3]	(8)	[3]
Level 3 [Member] | Energy Contracts Cash Flow Hedge [Member]
Liabilities
Derivative Liability	(1)	[3]	(2)	[3]
Level 3 [Member] | Interest Rate Swap [Member]
Liabilities
Derivative Liability	0	[4]	0	[4]
Level 3 [Member] | TUCSON ELECTRIC POWER COMPANY
Assets
Cash Equivalent	0	[1]	0	[1]
Restricted Cash	0	[1]	0	[1]
Rabbi Trust Investments to Support the Deferred Compensation and SERP	0	[2]	0	[2]
Energy Contracts	1	[3]	2	[3]
Total Assets	1		2
Liabilities
Liabilities	(3)		(2)
Net Total Assets (Liability)	(2)		0
Level 3 [Member] | TUCSON ELECTRIC POWER COMPANY | Energy Contracts [Member]
Liabilities
Derivative Liability	(2)	[3]	0	[3]
Level 3 [Member] | TUCSON ELECTRIC POWER COMPANY | Energy Contracts Cash Flow Hedge [Member]
Liabilities
Derivative Liability	(1)	[3]	(2)	[3]
Level 3 [Member] | TUCSON ELECTRIC POWER COMPANY | Interest Rate Swap [Member]
Liabilities
Derivative Liability	0	[4]	0	[4]
Netting [Member]
Assets
Cash Equivalent	0	[1],[5]	0	[1],[5]
Restricted Cash	0	[1],[5]	0	[1],[5]
Rabbi Trust Investments to Support the Deferred Compensation and SERP	0	[2],[5]	0	[2],[5]
Energy Contracts	(5)	[3],[5]	(5)	[3],[5]
Total Assets	(5)	[5]	(5)	[5]
Liabilities
Liabilities	5	[5]	5	[5]
Net Total Assets (Liability)	0	[5]	0	[5]
Netting [Member] | Energy Contracts [Member]
Liabilities
Derivative Liability	5	[3],[5]	5	[3],[5]
Netting [Member] | Energy Contracts Cash Flow Hedge [Member]
Liabilities
Derivative Liability	0	[3],[5]	0	[3],[5]
Netting [Member] | Interest Rate Swap [Member]
Liabilities
Derivative Liability	0	[4],[5]	0	[4],[5]
Netting [Member] | TUCSON ELECTRIC POWER COMPANY
Assets
Cash Equivalent	0	[1],[5]	0	[1],[5]
Restricted Cash	0	[1],[5]	0	[1],[5]
Rabbi Trust Investments to Support the Deferred Compensation and SERP	0	[2],[5]	0	[2],[5]
Energy Contracts	(1)	[3],[5]	(1)	[3],[5]
Total Assets	(1)	[5]	(1)	[5]
Liabilities
Liabilities	1	[5]	1	[5]
Net Total Assets (Liability)	0	[5]	0	[5]
Netting [Member] | TUCSON ELECTRIC POWER COMPANY | Energy Contracts [Member]
Liabilities
Derivative Liability	1	[3],[5]	1	[3],[5]
Netting [Member] | TUCSON ELECTRIC POWER COMPANY | Energy Contracts Cash Flow Hedge [Member]
Liabilities
Derivative Liability	0	[3],[5]	0	[3],[5]
Netting [Member] | TUCSON ELECTRIC POWER COMPANY | Interest Rate Swap [Member]
Liabilities
Derivative Liability	0	[4],[5]	0	[4],[5]
Net Fair Value [Member]
Assets
Cash Equivalent	14	[1]	20	[1]
Restricted Cash	2	[1]	7	[1]
Rabbi Trust Investments to Support the Deferred Compensation and SERP	22	[2]	19	[2]
Energy Contracts	2	[3]	2	[3]
Total Assets	40		48
Liabilities
Liabilities	(10)		(22)
Net Total Assets (Liability)	30		26
Net Fair Value [Member] | Energy Contracts [Member]
Liabilities
Derivative Liability	(2)	[3]	(10)	[3]
Net Fair Value [Member] | Energy Contracts Cash Flow Hedge [Member]
Liabilities
Derivative Liability	(1)	[3]	(2)	[3]
Net Fair Value [Member] | Interest Rate Swap [Member]
Liabilities
Derivative Liability	(7)	[4]	(10)	[4]
Net Fair Value [Member] | TUCSON ELECTRIC POWER COMPANY
Assets
Cash Equivalent	0	[1]	1	[1]
Restricted Cash	2	[1]	7	[1]
Rabbi Trust Investments to Support the Deferred Compensation and SERP	22	[2]	19	[2]
Energy Contracts	1	[3]	2	[3]
Total Assets	25		29
Liabilities
Liabilities	(9)		(14)
Net Total Assets (Liability)	16		15
Net Fair Value [Member] | TUCSON ELECTRIC POWER COMPANY | Energy Contracts [Member]
Liabilities
Derivative Liability	(1)	[3]	(2)	[3]
Net Fair Value [Member] | TUCSON ELECTRIC POWER COMPANY | Energy Contracts Cash Flow Hedge [Member]
Liabilities
Derivative Liability	(1)	[3]	(2)	[3]
Net Fair Value [Member] | TUCSON ELECTRIC POWER COMPANY | Interest Rate Swap [Member]
Liabilities
Derivative Liability	$ (7)	[4]	$ (10)	[4]

[1] Cash Equivalents and Restricted Cash represent amounts held in money market funds and certificates of deposit valued at cost, including interest. Cash Equivalents are included in Cash and Cash Equivalents on the balance sheets. Restricted Cash is included in Investments and Other Property – Other on the balance sheets.

[2] Rabbi Trust Investments include amounts related to deferred compensation and Supplement Executive Retirement Plan (SERP) benefits held in mutual and money market funds valued at quoted prices traded in active markets. These investments are included in Investments and Other Property – Other on the balance sheets.

[3] Energy Contracts include gas swap agreements (Level 2), power options (Level 2 or Level 3), gas options (Level 3), forward power purchase and sales contracts (Level 3), and forward power purchase contracts indexed to gas (Level 3), entered into to reduce exposure to energy price risk. These contracts are included in Derivative Instruments on the UNS Energy and TEP balance sheets. The valuation techniques are described below.

[4] Interest Rate Swaps are valued based on the 3-month or 6-month LIBOR index or the Securities Industry and Financial Markets Association municipal swap index. These interest rate swaps are included in Derivative Instruments on the balance sheets.

[5] All energy contracts are subject to legally enforceable master netting arrangements to mitigate credit risk. We have presented the effect of offset by counterparty; however, we present derivatives on a gross basis on the balance sheets.