UNS ENERGY EARNINGS PER SHARE - Number of Stock Options to Purchase Shares of Common Stock Excluded from Computation of Diluted Earning Per Share (Detail) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Anti-Dilutive Shares Excluded from the Diluted EPS Computation	6	50	153
Stock Options [Member]
Anti-Dilutive Shares Excluded from the Diluted EPS Computation	0	50	153
Restricted Stock Units (RSUs) [Member]
Anti-Dilutive Shares Excluded from the Diluted EPS Computation	6	0	0