UTILITY PLANT AND JOINTLY-OWNED FACILITES (Schedule of Asset Retirement Obligations) (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Public Utility, Property, Plant and Equipment [Line Items]
Liabilities Incurred	$ 8,064,000	[1]	$ 789,000	[1]	$ 7,638,000	[1]
UNS Energy
Public Utility, Property, Plant and Equipment [Line Items]
Beginning Balance	14,000,000		13,000,000
Liabilities Incurred	1,000,000		0
Accretion Expense	1,000,000		1,000,000
Revision to Estimated Cash Flows	7,000,000	[2]	0	[2]
Ending Balance	23,000,000		14,000,000
UNS Electric
Public Utility, Property, Plant and Equipment [Line Items]
Ending Balance	$ 1,000,000		$ 1,000,000

[1] The non-cash additions to asset retirement obligations and related capitalized assets represent revision of estimated asset retirement cost due to changes in timing and amount of expected future asset retirement obligations.

[2] Primarily related to changes in expected retirement dates of generating facilities.