PENDING MERGER WITH FORTIS (Pending Merger With Fortis) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	Jun. 30, 2014	Dec. 11, 2013 Fortis Inc	Jun. 30, 2014 Total Bill Credit Refunds Over 5 Years [Member]	Jun. 30, 2014 Bill Credit Refunds in Year 1 [Member]	Jun. 30, 2014 Annual Bill Credit Refunds in Years 1Through 5 [Member]	Jun. 30, 2014 May Through September [Member] TUCSON ELECTRIC POWER COMPANY
Business Acquisition [Line Items]
Share price		$ 60.25
Customer Bill Credits Required Per Merger Settlement Agreement Subject to Regulatory Approval			$ 30	$ 10	$ 5
Dividend Restrictions Per Merger Settlement Agreement Pending Regulatory Approval	60.00%
Required Equity Capitalization for Regulated Utilities Prior to Dividend Payment	50.00%
Required Equity Investment By Acquiring Company Per Merger Settlement Agreement Subject to Regulatory Approval	220
Merger-Related Costs Expected Upon Closing of Merger Subject to Regulatory Approval	$ 19					$ 15