UTILITY PLANT AND JOINTLY-OWNED FACILITES (Utility Plant in Service by Company and Major Class) (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Public Utility, Property, Plant and Equipment [Line Items]
Capitalized Computer Software, Gross	$ 40	$ 36
Amortization of computer software costs	14	13	10
TUCSON ELECTRIC POWER COMPANY
Public Utility, Property, Plant and Equipment [Line Items]
Capitalized Computer Software, Gross	39	35
Amortization of computer software costs	$ 14	$ 13	$ 10