NATURE OF OPERATIONS AND FINANCIAL STATEMENT PRESENTATION (Additional Information) (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2014
Deferred Income Taxes Current And Noncurrent [Member]
Quantifying Misstatement in Current Year Financial Statements, Amount	$ 7
Deferred Income Taxes Current And Noncurrent [Member] | TUCSON ELECTRIC POWER COMPANY
Quantifying Misstatement in Current Year Financial Statements, Amount	7
Capital Lease Obligation Current And Noncurrent [Member]
Quantifying Misstatement in Current Year Financial Statements, Amount	18
Capital Lease Obligation Current And Noncurrent [Member] | TUCSON ELECTRIC POWER COMPANY
Quantifying Misstatement in Current Year Financial Statements, Amount	$ 18