BUSINESS SEGMENTS (Reconciliation of Income Statement Items from Segments to Consolidation) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended										12 Months Ended
	Dec. 31, 2013		Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012		Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	$ 350,161		$ 437,041	$ 365,217	$ 332,141	$ 348,273		$ 434,108	$ 363,998	$ 315,387	$ 1,484,560		$ 1,461,766		$ 1,478,702
Operating Revenues-Intersegment											0	[1]	0	[1]	0	[1]
Depreciation and Amortization											177,172		177,087		164,815
Interest Income											534		1,106		4,568
Interest Expense											93,375		105,352		112,358
Income Tax Expense											58,427		55,727		66,951
Net Income	13,525		67,990	34,618	11,345	7,506		50,664	26,273	6,476	127,478		90,919		109,975
Capital Expenditures											(325,886)		(307,277)		(374,122)
Assets	4,273,069					4,140,429					4,273,069		4,140,429
Reconciling Adjustments [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues											(2,000)		(1,000)		1,000
Operating Revenues-Intersegment											(39,000)	[1]	(40,000)	[1]	(42,000)	[1]
Depreciation and Amortization											0		0		(1,000)
Interest Income											0		0		0
Interest Expense											0		0		0
Income Tax Expense											0		0		(2,000)
Net Income											0		0		(3,000)
Capital Expenditures											0		0		121,000
Assets	(1,192,000)					(1,122,000)					(1,192,000)		(1,122,000)
TUCSON ELECTRIC POWER COMPANY | Operating Segments [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues											1,180,000		1,145,000		1,141,000
Operating Revenues-Intersegment											17,000	[1]	17,000	[1]	15,000	[1]
Depreciation and Amortization											149,000		150,000		140,000
Interest Income											0		0		4,000
Interest Expense											79,000		88,000		89,000
Income Tax Expense											48,000		39,000		52,000
Net Income											101,000		65,000		85,000
Capital Expenditures											(253,000)		(253,000)		(352,000)
Assets	3,556,000					3,461,000					3,556,000		3,461,000
UNS Electric | Operating Segments [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues											174,000		189,000		188,000
Operating Revenues-Intersegment											2,000	[1]	1,000	[1]	2,000	[1]
Depreciation and Amortization											19,000		18,000		17,000
Interest Income											1,000		0		0
Interest Expense											7,000		8,000		7,000
Income Tax Expense											7,000		11,000		11,000
Net Income											12,000		17,000		18,000
Capital Expenditures											(56,000)		(38,000)		(96,000)
Assets	404,000					370,000					404,000		370,000
UNS Gas | Operating Segments [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues											131,000		129,000		149,000
Operating Revenues-Intersegment											3,000	[1]	4,000	[1]	2,000	[1]
Depreciation and Amortization											9,000		9,000		8,000
Interest Income											0		0		0
Interest Expense											6,000		6,000		7,000
Income Tax Expense											7,000		6,000		7,000
Net Income											11,000		9,000		10,000
Capital Expenditures											(17,000)		(16,000)		(13,000)
Assets	311,000					310,000					311,000		310,000
Other | Operating Segments [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues											2,000	[2]	0	[2]	0	[2]
Operating Revenues-Intersegment											17,000	[1],[2]	18,000	[1],[2]	23,000	[1],[2]
Depreciation and Amortization											0	[2]	0	[2]	1,000	[2]
Interest Income											0	[2]	1,000	[2]	1,000	[2]
Interest Expense											1,000	[2]	3,000	[2]	9,000	[2]
Income Tax Expense											(4,000)	[2]	0	[2]	(1,000)	[2]
Net Income											3,000	[2]	0	[2]	0	[2]
Capital Expenditures											0	[2]	0	[2]	(34,000)	[2]
Assets	$ 1,194,000	[2]				$ 1,121,000	[2]				$ 1,194,000	[2]	$ 1,121,000	[2]

[1] Operating Revenues – Intersegment includes common costs (system, facilities, etc.) allocated to affiliates on a cost-causative basis and recorded as revenue by TEP, sales of power between TEP and UNS Electric at third-party market prices, control area services provided by TEP to UNS Electric based on a FERC-approved tariff, sales of gas by UNS Gas at third-party market prices for use in UNS Electric's generating facilities, and supplemental workforce charges charges (primarily meter reading services) provided to the utilities by an unregulated affiliate.

[2] Other includes the UNS Energy and UES holding companies, Millennium, and UED.