BUSINESS SEGMENTS (Reconciliation of Income Statement Items from Segments to Consolidation) (Detail) (USD $)	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	$ 386,606,000		$ 365,217,000		$ 719,998,000		$ 697,358,000
Operating Revenues-Intersegment	0	[1]	0	[1]	0	[1]	0
Income Before Income Taxes	67,191,000		38,293,000		92,334,000		56,996,000
Net Income	42,354,000		34,618,000		57,829,000		45,963,000
Reconciling Adjustments [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	0		0		0		0
Operating Revenues-Intersegment	(9,000,000)	[1]	(9,000,000)	[1]	(18,000,000)	[1]	(19,000,000)
Income Before Income Taxes	0		0		0		0
Net Income	0		0		0		0
TUCSON ELECTRIC POWER COMPANY | Operating Segments [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	318,000,000		300,000,000		569,000,000		543,000,000
Operating Revenues-Intersegment	4,000,000	[1]	4,000,000	[1]	8,000,000	[1]	9,000,000
Income Before Income Taxes	61,467,000		32,439,000		75,977,000		35,000
Net Income	38,725,000		30,787,000		47,897,000		32,266,000
UNS Electric | Operating Segments [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	47,000,000		44,000,000		87,000,000		80,000,000
Operating Revenues-Intersegment	0	[1]	0	[1]	1,000,000	[1]	1,000,000	[1]
Income Before Income Taxes	6,000,000		6,000,000		9,000,000		9,000,000
Net Income	4,000,000		4,000,000		6,000,000		6,000,000
UNS Gas | Operating Segments [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	22,000,000		21,000,000		64,000,000		73,000,000
Operating Revenues-Intersegment	1,000,000	[1]	1,000,000	[1]	1,000,000	[1]	1,000,000
Income Before Income Taxes	0		0		8,000,000		13,000,000
Net Income	0		0		5,000,000		8,000,000
Other | Operating Segments [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	0		0		0	[2]	1,000,000
Operating Revenues-Intersegment	4,000,000	[1]	4,000,000	[1]	8,000,000	[1],[2]	8,000,000
Income Before Income Taxes	0		0		(1,000,000)		0
Net Income	$ (1,000,000)		$ 0		$ (1,000,000)	[2]	$ 0

[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 (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.