SCHEDULE II - Valuation and Qualifying Accounts (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended							12 Months Ended
	Dec. 31, 2013 Allowance for Doubtful Accounts [Member]	Dec. 31, 2012 Allowance for Doubtful Accounts [Member]	Dec. 31, 2011 Allowance for Doubtful Accounts [Member]	Dec. 31, 2013 Other Valuation Allowance [Member]	Dec. 31, 2012 Other Valuation Allowance [Member]	Dec. 31, 2011 Other Valuation Allowance [Member]	Dec. 31, 2010 Other Valuation Allowance [Member]	Dec. 31, 2013 TUCSON ELECTRIC POWER COMPANY Allowance for Doubtful Accounts [Member]		Dec. 31, 2012 TUCSON ELECTRIC POWER COMPANY Allowance for Doubtful Accounts [Member]		Dec. 31, 2011 TUCSON ELECTRIC POWER COMPANY Allowance for Doubtful Accounts [Member]		Dec. 31, 2013 TUCSON ELECTRIC POWER COMPANY Other Valuation Allowance [Member]		Dec. 31, 2012 TUCSON ELECTRIC POWER COMPANY Other Valuation Allowance [Member]		Dec. 31, 2011 TUCSON ELECTRIC POWER COMPANY Other Valuation Allowance [Member]		Dec. 31, 2010 TUCSON ELECTRIC POWER COMPANY Other Valuation Allowance [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	$ 7	$ 16	$ 13	$ 6	$ 9	$ 6	$ 4	$ 5	[1]	$ 14	[1]	$ 11	[1]	$ 4	[2]	$ 8	[2]	$ 4	[2]	$ 3	[2]
Additions-Charged to Income	2	4	5					2	[1]	3	[1]	4	[1]
Deductions	2	13	2					2	[1]	12	[1]	1	[1]
Ending Balance	$ 7	$ 7	$ 16	$ 6	$ 9	$ 6	$ 4	$ 5	[1]	$ 5	[1]	$ 14	[1]	$ 4	[2]	$ 8	[2]	$ 4	[2]	$ 3	[2]

[1] TEP, UNS Electric, and UNS Gas record additions to the Allowance for Doubtful Accounts based on historical experience and any specific customer collection issues identified. Deductions principally reflect amounts charged off as uncollectible, less amounts recovered. Amounts include reserves for trade receivables, wholesales sales, and in-kind transmission imbalances.

[2] As the Other reserves are not individually significant, additions and deductions need not be disclosed. Principally reserves for sales tax audits, litigation matters, and damages billable to third parties.