Business Segments (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2009
Reconciling adjustments of Income Statement items in consolidation
Operating Revenues - External	$ 450,947,000	$ 438,830,000	$ 1,165,387,000	$ 1,096,792,000
Operating Revenues - Intersegment	0	0	0	0
Income Before Income Taxes	97,840,000	99,458,000	164,703,000	173,750,000
Net Income	59,712,000	55,665,000	101,787,000	101,732,000
Reconciling adjustments of intersegment revenues in consolidation
Wholesale Sales	41,847,000	36,838,000	121,506,000	102,397,000	2,000,000
Gas Revenue - UNS Gas to UNS Electric	16,831,000	16,140,000	99,041,000	96,598,000
Other Revenues	28,884,000	25,824,000	88,624,000	76,053,000
Total Intersegment Revenue	0	0	0	0
Business Intersegment, Eliminations [Member]
Reconciling adjustments of Income Statement items in consolidation
Operating Revenues - External	0	0	0	0
Operating Revenues - Intersegment	(9,000,000)	(16,000,000)	(34,000,000)	(50,000,000)
Income Before Income Taxes	0	(2,000,000)	(4,000,000)	(6,000,000)
Net Income	0	(2,000,000)	(2,000,000)	(4,000,000)
Reconciling adjustments of intersegment revenues in consolidation
Total Intersegment Revenue	(9,000,000)	(16,000,000)	(34,000,000)	(50,000,000)
Business Intersegment, Eliminations [Member] | TEP Segment [Member] | Corporate Services [Member]
Reconciling adjustments of intersegment revenues in consolidation
Other Revenues	2,000,000	2,000,000	7,000,000	6,000,000
Business Intersegment, Eliminations [Member] | TEP Segment [Member] | Control Area Services [Member]
Reconciling adjustments of intersegment revenues in consolidation
Other Revenues	1,000,000	1,000,000	2,000,000	2,000,000
Business Intersegment, Eliminations [Member] | Other [Member]
Reconciling adjustments of intersegment revenues in consolidation
Wholesale Sales	0	3,000,000	6,000,000	8,000,000
Business Intersegment, Eliminations [Member] | Other [Member] | Supplemental Workforce [Member]
Reconciling adjustments of intersegment revenues in consolidation
Other Revenues	4,000,000	5,000,000	13,000,000	13,000,000
UNS GAS, INC. [Member] | Business Intersegment, Eliminations [Member]
Reconciling adjustments of intersegment revenues in consolidation
Gas Revenue - UNS Gas to UNS Electric	1,000,000	2,000,000	2,000,000	4,000,000
UNS ELECTRIC, INC. [Member] | Business Intersegment, Eliminations [Member]
Reconciling adjustments of intersegment revenues in consolidation
Wholesale Sales		1,000,000	2,000,000	2,000,000
TEP Segment [Member]
Reconciling adjustments of Income Statement items in consolidation
Operating Revenues - External	366,000,000	350,000,000	894,000,000	837,000,000
Operating Revenues - Intersegment	4,000,000	5,000,000	11,000,000	23,000,000
Income Before Income Taxes	88,000,000	97,000,000	136,000,000	157,000,000
Net Income	54,000,000	60,000,000	84,000,000	98,000,000
Reconciling adjustments of intersegment revenues in consolidation
Wholesale Sales	1,000,000	2,000,000	2,000,000	15,000,000
Total Intersegment Revenue	4,000,000	5,000,000	11,000,000	23,000,000
UNS GAS, INC. [Member]
Reconciling adjustments of Income Statement items in consolidation
Operating Revenues - External	17,000,000	17,000,000	101,000,000	99,000,000
Operating Revenues - Intersegment	1,000,000	2,000,000	2,000,000	4,000,000
Income Before Income Taxes	(1,000,000)	(2,000,000)	10,000,000	9,000,000
Net Income	(1,000,000)	(1,000,000)	6,000,000	5,000,000
Reconciling adjustments of intersegment revenues in consolidation
Total Intersegment Revenue	1,000,000	2,000,000	2,000,000	4,000,000
UNS ELECTRIC, INC. [Member]
Reconciling adjustments of Income Statement items in consolidation
Operating Revenues - External	68,000,000	72,000,000	169,000,000	160,000,000
Operating Revenues - Intersegment	0	1,000,000	2,000,000	2,000,000
Income Before Income Taxes	11,000,000	7,000,000	23,000,000	20,000,000
Net Income	7,000,000	5,000,000	14,000,000	12,000,000
Reconciling adjustments of intersegment revenues in consolidation
Total Intersegment Revenue	0	1,000,000	2,000,000	2,000,000
Other [Member]
Reconciling adjustments of Income Statement items in consolidation
Operating Revenues - External	0	0	1,000,000	1,000,000
Operating Revenues - Intersegment	4,000,000	8,000,000	19,000,000	21,000,000
Income Before Income Taxes	0	(1,000,000)	0	(6,000,000)
Net Income	0	(6,000,000)	0	(9,000,000)
Reconciling adjustments of intersegment revenues in consolidation
Total Intersegment Revenue	$ 4,000,000	$ 8,000,000	$ 19,000,000	$ 21,000,000