CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Cash Flows from Operating Activities
Net Income	$ 87,541	$ 96,433
Depreciation	93,857	87,729
Amortization Expense	21,449	24,393
Amortization of Deferred Debt-Related Costs included in Interest Expense	1,959	1,831
Use of Renewable Energy Credits for Compliance	15,129	11,766
Deferred Income Taxes	53,991	53,381
Pension and Retiree Expense	10,236	14,909
Pension and Retiree Funding	(12,989)	(26,118)
Share-Based Compensation Expense	5,010	2,239
Allowance for Equity Funds Used During Construction	(4,983)	(2,923)
LFCR Revenue	(8,350)	0
Increase (Decrease) to Reflect PPFAC Recovery Treatment	(20,167)	(5,079)
Fortis Acquisition Direct Customer Benefit	18,870	0
PPFAC Reduction - 2013 TEP Rate Order	0	3,000
Changes in Assets and Liabilities which Provided (Used) Cash Exclusive of Changes Shown Separately[Abstract]
Accounts Receivable	(45,758)	(41,227)
Materials and Fuel Inventory	(274)	14,955
Accounts Payable	(472)	(8,678)
Income Taxes	(25)	(10,681)
Interest Accrued	(3,849)	1,008
Taxes Other Than Income Taxes	18,745	17,405
Other	(8,652)	19,836
Net Cash Flows – Operating Activities	221,268	254,179
Cash Flows from Investing Activities
Capital Expenditures	(227,153)	(180,451)
Purchase of Intangibles—Renewable Energy Credits	(22,047)	(17,552)
Return of Investments in Springerville Lease Debt	0	9,104
Restricted Cash Released	0	4,500
Other, net	12,883	4,656
Net Cash Flows—Investing Activities	(236,317)	(179,743)
Cash Flows from Financing Activities
Proceeds from Borrowings Under Revolving Credit Facility	190,000	78,000
Repayments of Borrowings Under Revolving Credit Facility	(155,000)	(78,000)
Proceeds from Issuance of Long-Term Debt	149,168	0
Payments of Capital Lease Obligations	(165,145)	(99,621)
Dividends Paid to UNS Energy	0	(20,000)
Payment of Debt Issue/Retirement Costs	(1,652)	(1,022)
Other, net	551	1,250
Net Cash Flows—Financing Activities	17,922	(119,393)
Net Increase (Decrease) in Cash and Cash Equivalents	2,873	(44,957)
Cash and Cash Equivalents, Beginning of Year	25,335	79,743
Cash and Cash Equivalents, End of Period	$ 28,208	$ 34,786