PLANNED PURCHASE OF GAS-FIRED GENERATION FACILITY Additional Information (Details) (Entegra, Gila River Generating Station Unit 3, USD $) In Millions, unless otherwise specified	Dec. 23, 2013 MW	Dec. 23, 2013 TUCSON ELECTRIC POWER COMPANY MW	Dec. 23, 2013 UNS ELECTRIC, INC. MW	Jun. 30, 2014 Scenario, Forecast [Member] TUCSON ELECTRIC POWER COMPANY
Unusual or Infrequent Item [Line Items]
Planned Purchase of Gas-Fired Generation Facility	$ 219	$ 164	$ 55
Generating capacity of plant in MW	550	413	137
Percentage of ownership in Generating Unit		75.00%	25.00%
Amount of Potential Letter Of Credit				$ 15

Minimum amount of other commitment not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in the taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions.

No definition available.

Name:	us-gaap_OtherCommitment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant