BUSINESS SEGMENTS (Reconciliation of Income Statement Items from Segments to Consolidation) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	$ 333,392		$ 332,141
Operating Revenues-Intersegment	0	[1]	0
Income Before Income Taxes	25,143		18,703
Net Income	15,475		11,345
Reconciling Adjustments [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	0		0
Operating Revenues-Intersegment	(9,000)	[1]	(9,000)
Income Before Income Taxes	0		0
Net Income	0		0
TUCSON ELECTRIC POWER COMPANY | Operating Segments [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	252,000		244,000
Operating Revenues-Intersegment	4,000	[1]	4,000
Income Before Income Taxes	14,510		2,735
Net Income	9,172		1,478
UNS Electric | Operating Segments [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	40,000		36,000
Operating Revenues-Intersegment	1,000	[1]	1,000	[1]
Income Before Income Taxes	3,000		4,000
Net Income	2,000		2,000
UNS Gas | Operating Segments [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	41,000		52,000
Operating Revenues-Intersegment	0	[1]	0
Income Before Income Taxes	8,000		12,000
Net Income	5,000		8,000
Other | Operating Segments [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	0	[2]	0
Operating Revenues-Intersegment	4,000	[1],[2]	4,000
Income Before Income Taxes	(1,000)		0
Net Income	$ (1,000)	[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.