El Paso Electric 10-Q 6 Nov 14 2014 Q3 Quarterly report Financial data

Document_And_Entity_Informatio

Document And Entity Information	9 Months Ended
	Sep. 30, 2014	Oct. 31, 2014
Document and Entity Information [Line Items]	'	'
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	30-Sep-14	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q3	'
Trading Symbol	'ee	'
Entity Registrant Name	'EL PASO ELECTRIC CO /TX/	'
Entity Central Index Key	'0000031978	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Large Accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	40,357,982

Balance_Sheets

Balance Sheets (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Utility plant:	'	'
Electric plant in service	$3,148,820	$3,076,549
Less accumulated depreciation and amortization	-1,250,226	-1,214,088
Net plant in service	1,898,594	1,862,461
Construction work in progress	389,245	282,647
Nuclear fuel; includes fuel in process of $58,086 and $48,492, respectively	195,793	188,185
Less accumulated amortization	-84,649	-75,820
Net nuclear fuel	111,144	112,365
Net utility plant	2,398,983	2,257,473
Current assets:	'	'
Cash and cash equivalents	13,410	25,592
Accounts receivable, principally trade, net of allowance for doubtful accounts of $2,309 and $2,261, respectively	112,681	65,350
Accumulated deferred income taxes	15,553	26,965
Inventories, at cost	46,284	45,942
Undercollection of fuel revenues	10,781	7,248
Prepayments and other	8,678	7,694
Total current assets	207,387	178,791
Deferred charges and other assets:	'	'
Decommissioning trust funds	229,048	214,095
Regulatory assets	98,329	101,050
Other	32,449	34,879
Total deferred charges and other assets	359,826	350,024
Total assets	2,966,196	2,786,288
Capitalization:	'	'
Common stock, stated value $1 per share, 100,000,000 shares authorized, 65,709,570 and 65,639,091 shares issued, and 141,331 and 120,534 restricted shares, respectively	65,851	65,760
Capital in excess of stated value	317,501	314,443
Retained earnings	1,039,591	985,665
Accumulated other comprehensive income, net of tax	17,561	2,612
Total stockholders equity subtotal before treasury stock	1,440,504	1,368,480
Treasury stock, 25,492,919 shares at cost	-424,647	-424,647
Common stock equity	1,015,857	943,833
Long-term debt	984,688	999,620
Total capitalization	2,000,545	1,943,453
Current liabilities:	'	'
Current maturities of long-term debt	15,000	0
Short-term borrowings under the revolving credit facility	89,528	14,352
Accounts payable, principally trade	61,552	61,795
Taxes accrued	33,592	25,206
Interest accrued	14,391	12,189
Overcollection of fuel revenues	3,348	1,048
Other	24,406	22,932
Total current liabilities	241,817	137,522
Deferred Credits and Other Liabilities:	'	'
Accumulated deferred income taxes	483,475	449,925
Accrued pension liability	57,729	84,012
Accrued postretirement benefit liability	54,554	50,655
Asset retirement obligation	69,566	65,214
Regulatory liabilities	27,161	26,416
Other	31,349	29,091
Total deferred credits and other liabilities	723,834	705,313
Commitments and contingencies	'	'
Total capitalization and liabilities	$2,966,196	$2,786,288

Balance_Sheets_Parenthetical

Balance Sheets Parenthetical (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, except Share data, unless otherwise specified
Nuclear fuel; fuel in process	$58,086	$48,492
Allowance for Doubtful Accounts Receivable, Current	$2,309	$2,261
Common Stock, Par or Stated Value Per Share	$1	$1
Common Stock, Shares Authorized	100,000,000	100,000,000
Common Stock, Shares, Issued	65,709,570	65,639,091
Common stock, restricted shares	141,331	120,534
Treasury Stock, Shares	25,492,919	25,492,919

Statements_Of_Operations

Statements Of Operations (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Operating revenues	$283,645	$282,661	$720,962	$700,065	$911,259	$888,867
Energy expenses:	'	'	'	'	'	'
Fuel	70,523	69,268	191,781	175,097	243,452	221,041
Purchased and interchanged power	18,071	17,395	54,114	46,185	70,292	63,132
Cost of services, energy services	88,594	86,663	245,895	221,282	313,744	284,173
Operating revenues net of energy expenses	195,051	195,998	475,067	478,783	597,515	604,694
Other operating expenses:	'	'	'	'	'	'
Other operations	59,514	58,810	175,937	173,810	239,282	236,240
Maintenance	15,392	12,723	45,619	41,260	65,427	57,994
Depreciation and amortization	20,685	20,416	62,336	59,346	82,616	78,573
Taxes other than income taxes	17,964	18,153	48,883	44,782	61,848	58,594
Utilities operating expense	113,555	110,102	332,775	319,198	449,173	431,401
Operating income	81,496	85,896	142,292	159,585	148,342	173,293
Other income (deductions):	'	'	'	'	'	'
Allowance for equity funds used during construction	3,848	2,287	10,215	7,465	12,758	10,303
Investment and interest income, net	2,373	2,086	8,537	5,151	10,419	6,715
Miscellaneous non-operating income	52	12	2,159	14	3,054	46
Miscellaneous non-operating deductions	-1,036	-537	-2,054	-2,641	-3,048	-3,160
Nonoperating income (expense)	5,237	3,848	18,857	9,989	23,183	13,904
Interest charges (credits):	'	'	'	'	'	'
Interest on long-term debt and revolving credit facility	14,617	14,623	43,803	43,829	58,609	57,634
Other interest	438	153	899	456	874	781
Capitalized interest	-1,270	-1,302	-3,797	-3,911	-5,185	-5,231
Allowance for borrowed funds used during construction	-2,190	-1,379	-5,841	-4,520	-7,376	-6,199
Interest expense	11,595	12,095	35,064	35,854	46,922	46,985
Income before income taxes	75,138	77,649	126,085	133,720	124,603	140,212
Income tax expense	22,662	27,084	38,898	46,328	36,225	48,001
Net income	$52,476	$50,565	$87,187	$87,392	$88,378	$92,211
Basic earnings per share	$1.30	$1.26	$2.16	$2.17	$2.19	$2.29
Diluted earnings per share	$1.30	$1.26	$2.16	$2.17	$2.19	$2.29
Dividends declared per share of common stock	$0.28	$0.27	$0.83	$0.78	$1.09	$1.03
Weighted average number of shares outstanding	40,213,741	40,132,250	40,181,367	40,107,555	40,169,801	40,084,525
Weighted average number of shares and dilutive potential shares outstanding	40,264,810	40,132,250	40,209,001	40,123,626	40,190,527	40,114,921

Statements_Of_Comprehensive_Op

Statements Of Comprehensive Operations (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Net income	$52,476	$50,565	$87,187	$87,392	$88,378	$92,211
Unrecognized pension and postretirement benefit costs:	'	'	'	'	'	'
Net gain (loss) arising during period	0	0	19,700	0	102,664	-2,109
Prior service benefit	0	0	0	0	97	0
Reclassification adjustments included in net income for amortization of:	'	'	'	'	'	'
Prior service benefit	-2,065	-1,369	-5,594	-4,169	-6,985	-5,610
Net loss	1,615	2,903	4,567	8,323	6,716	11,316
Net unrealized gains/losses on marketable securities:	'	'	'	'	'	'
Net holding gains arising during period	897	4,300	7,965	8,861	16,803	6,802
Reclassification adjustments for net gains included in net income	-824	-199	-3,791	-287	-4,057	-161
Net losses on cash flow hedges:	'	'	'	'	'	'
Reclassification adjustment for interest expense included in net income	110	104	326	306	431	405
Total other comprehensive income (loss) before income taxes	-267	5,739	23,173	13,034	115,669	10,643
Income tax benefit (expense) related to items of other comprehensive income (loss):	'	'	'	'	'	'
Unrecognized pension and postretirement benefit costs	171	-469	-7,161	-1,550	-39,177	-1,327
Net unrealized gains on marketable securities	-31	-796	-889	-1,433	-2,556	-1,300
Losses on cash flow hedges	-42	-39	-174	-129	-213	-143
Total income tax benefit (expense)	98	-1,304	-8,224	-3,112	-41,946	-2,770
Other comprehensive income (loss), net of tax	-169	4,435	14,949	9,922	73,723	7,873
Comprehensive income	$52,307	$55,000	$102,136	$97,314	$162,101	$100,084

Statements_Of_Cash_Flows

Statements Of Cash Flows (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Cash flows from operating activities:	'	'
Net income	$87,187	$87,392
Adjustments to reconcile net income to net cash provided by operating activities:	'	'
Depreciation and amortization of electric plant in service	62,336	59,346
Amortization of nuclear fuel	33,942	33,621
Deferred income taxes, net	35,990	45,479
Allowance for equity funds used during construction	-10,215	-7,465
Other amortization and accretion	14,470	12,345
Gain on sale of property, plant and equipment	-2,092	0
Other operating activities	-3,843	-484
Change in:	'	'
Accounts receivable	-47,331	-35,097
Inventories	-1,000	-4,772
Net undercollection of fuel revenues	-1,233	-8,362
Prepayments and other	-4,381	-5,471
Accounts payable	3,557	-3,729
Taxes accrued	7,669	6,794
Other current liabilities	3,255	9,654
Deferred charges and credits	-3,674	-4,340
Net cash provided by operating activities	174,637	184,911
Cash flows from investing activities:	'	'
Cash additions to utility property, plant and equipment	-189,273	-165,303
Cash additions to nuclear fuel	-28,772	-19,895
Capitalized interest and AFUDC:	'	'
Utility property, plant and equipment	-16,056	-11,985
Nuclear fuel	-3,797	-3,911
Allowance for equity funds used during construction	10,215	7,465
Decommissioning trust funds:	'	'
Purchases, including funding of $3.4 million	-54,343	-36,413
Sales and maturities	47,355	29,419
Proceeds from sale of property, plant and equipment	2,395	0
Other investing activities	4,438	4,856
Net cash used for investing activities	-227,838	-195,767
Cash flows from financing activities:	'	'
Dividends paid	-33,261	-31,379
Borrowings under the revolving credit facility:	'	'
Proceeds	186,215	34,167
Payments	-111,039	-40,831
Other financing activities	-896	-210
Net cash provided by (used for) financing activities	41,019	-38,253
Net decrease in cash and cash equivalents	-12,182	-49,109
Cash and cash equivalents at beginning of period	25,592	111,057
Cash and cash equivalents at end of period	$13,410	$61,948

Statements_Of_Cash_Flows_Paren

Statements Of Cash Flows Parenthetical (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Payments To Fund Decommissioning Fund	$3.40	$3.40

Principles_Of_Preparation

Principles Of Preparation	9 Months Ended
	Sep. 30, 2014
Accounting Policies [Abstract]	'
Principles Of Preparation	'
	Principles of Preparation
	These condensed financial statements should be read in conjunction with the financial statements and notes thereto in the Annual Report of El Paso Electric Company on Form 10-K for the year ended December 31, 2013 (the "2013 Form 10-K"). Capitalized terms used in this report and not defined herein have the meaning ascribed to such terms in the 2013 Form 10-K. In the opinion of the Company’s management, the accompanying financial statements contain all adjustments necessary to present fairly the financial position of the Company at September 30, 2014 and December 31, 2013; the results of its operations and comprehensive operations for the three, nine and twelve months ended September 30, 2014 and 2013; and its cash flows for the nine months ended September 30, 2014 and 2013. The results of operations and comprehensive operations for the three and nine months ended September 30, 2014 and the cash flows for the nine months ended September 30, 2014 are not necessarily indicative of the results to be expected for the full calendar year.
	Pursuant to the rules and regulations of the Securities and Exchange Commission ("SEC"), certain financial information has been condensed and certain footnote disclosures have been omitted. Such information and disclosures are normally included in financial statements prepared in accordance with generally accepted accounting principles.
	Use of Estimates. The preparation of financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
	Revenues. Revenues related to the sale of electricity are generally recorded when service is rendered or electricity is delivered to customers. The billing of electricity sales to retail customers is based on the reading of their meters, which occurs on a systematic basis throughout the month. Unbilled revenues are estimated based on monthly generation volumes and by applying an average revenue/kWh to the number of estimated kWhs delivered but not billed. Accounts receivable included accrued unbilled revenues of $26.9 million at September 30, 2014 and $19.8 million at December 31, 2013. The Company presents revenues net of sales taxes in its statements of operations.
	Supplemental Cash Flow Disclosures (in thousands)
			Nine Months Ended
			September 30,
			2014		2013
	Cash paid (received) for:
		Interest on long-term debt and borrowing under the revolving credit facility	$	37,689	$	36,975
		Income tax paid (refunded), net	2,969		(36		)
	Non-cash financing activities:
		Grants of restricted shares of common stock	3,025		2,607
		Issuance of performance shares	—		849
	New Accounting Standards. In July 2013, the Financial Accounting Standards Board ("FASB") issued new guidance (Accounting Standards Update ("ASU") 2013-11, Income Taxes (Topic 740)) to eliminate the diversity in the financial statement presentation of an unrecognized tax benefit when a net operating loss carryforward, a similar tax loss, or a tax credit carryforward exists. ASU 2013-11 requires an entity to present an unrecognized tax benefit in the financial statements as a reduction to a deferred tax asset for a net operating loss carryforward, a similar tax loss, or a tax credit carryforward, except in certain circumstances when it would be reflected as a liability. The Company implemented ASU 2013-11 in the first quarter of 2014 on a prospective basis. This ASU did not have a significant impact on the Company's statement of operations or statement of cash flows.
	In May 2014, the FASB issued new guidance (ASU 2014-09, Revenue from Contracts with Customers (Topic 606)) to provide a framework that replaces the existing revenue recognition guidance. ASU 2014-09 is the result of a joint effort by the FASB and the International Accounting Standards Board (IASB) intended to clarify the principles for recognizing revenue and to develop a common revenue standard for U.S. Generally Accepted Accounting Principles ("GAAP") and International Financial Reporting Standards. ASU 2014-09 provides that an entity should recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. ASU 2014-09 is effective for annual periods and interim periods within that reporting period beginning after December 15, 2016, for public business entities. Early adoption of ASU 2014-09 is not permitted. The Company is currently assessing the future impact of this ASU.

Accumulated_Other_Comprehensiv

Accumulated Other Comprehensive Income (Notes)	9 Months Ended
	Sep. 30, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]	'
Comprehensive Income (Loss) Note [Text Block]	'
	Accumulated Other Comprehensive Income (Loss)
	Changes in Accumulated Other Comprehensive Income (Loss) (net of tax) by component are presented below (in thousands):
			Three Months Ended September 30, 2014																Three Months Ended September 30, 2013
			Unrecognized Pension and Postretirement Benefit Costs				Net Unrealized Gains (Losses) on Marketable Securities				Net Losses on Cash Flow Hedges				Accumulated Other Comprehensive Income (Loss)				Unrecognized Pension and Postretirement Benefit Costs				Net Unrealized Gains (Losses) on Marketable Securities				Net Losses on Cash Flow Hedges			Accumulated Other Comprehensive Income (Loss)
	Balance at beginning of period		$	(9,539	)		$	39,483			$	(12,214	)		$	17,730			$	(74,198	)		$	26,030			$	(12,429	)	$	(60,597	)
		Other comprehensive income before reclassifications	—				733				—				733				—				3,463				—			3,463
		Amounts reclassified from accumulated other comprehensive income (loss)	(279		)		(691		)		68				(902		)		1,065				(158		)		65			972
	Balance at end of period		$	(9,818	)		$	39,525			$	(12,146	)		$	17,561			$	(73,133	)		$	29,335			$	(12,364	)	$	(56,162	)
			Nine Months Ended September 30, 2014																Nine Months Ended September 30, 2013
			Unrecognized Pension and Postretirement Benefit Costs				Net Unrealized Gains (Losses) on Marketable Securities				Net Losses on Cash Flow Hedges				Accumulated Other Comprehensive Income (Loss)				Unrecognized Pension and Postretirement Benefit Costs				Net Unrealized Gains (Losses) on Marketable Securities				Net Losses on Cash Flow Hedges			Accumulated Other Comprehensive Income (Loss)
	Balance at beginning of period		$	(21,330	)		$	36,240			$	(12,298	)		$	2,612			$	(75,737	)		$	22,194			$	(12,541	)	$	(66,084	)
		Other comprehensive income before reclassifications	12,147				6,377				—				18,524				—				7,383				—			7,383
		Amounts reclassified from accumulated other comprehensive income (loss)	(635		)		(3,092		)		152				(3,575		)		2,604				(242		)		177			2,539
	Balance at end of period		$	(9,818	)		$	39,525			$	(12,146	)		$	17,561			$	(73,133	)		$	29,335			$	(12,364	)	$	(56,162	)
			Twelve Months Ended September 30, 2014																Twelve Months Ended September 30, 2013
			Unrecognized Pension and Postretirement Benefit Costs				Net Unrealized Gains (Losses) on Marketable Securities				Net Losses on Cash Flow Hedges				Accumulated Other Comprehensive Income (Loss)				Unrecognized Pension and Postretirement Benefit Costs				Net Unrealized Gains (Losses) on Marketable Securities				Net Losses on Cash Flow Hedges			Accumulated Other Comprehensive Income (Loss)
	Balance at beginning of period		$	(73,133	)		$	29,335			$	(12,364	)		$	(56,162	)		$	(75,403	)		$	23,994			$	(12,626	)	$	(64,035	)
		Other comprehensive income (loss) before reclassifications	63,518				13,476				—				76,994				(1,331		)		5,492				—			4,161
		Amounts reclassified from accumulated other comprehensive income (loss)	(203		)		(3,286		)		218				(3,271		)		3,601				(151		)		262			3,712
	Balance at end of period		$	(9,818	)		$	39,525			$	(12,146	)		$	17,561			$	(73,133	)		$	29,335			$	(12,364	)	$	(56,162	)
	Amounts reclassified from accumulated other comprehensive income (loss) for the three, nine and twelve months ended September 30, 2014 and 2013 are as follows ( in thousands):
	Details about Accumulated Other Comprehensive Income (Loss) Components			Three Months Ended September 30,								Nine Months Ended September 30,								Twelve Months Ended September 30,								Affected Line Item in the Statement of Operations
				2014				2013				2014				2013				2014				2013
	Amortization of pension and postretirement benefit costs:
		Prior service benefit		$	2,065			1,369				$	5,594			4,169				$	6,985			$	5,610			(a)
		Net loss		(1,615		)		(2,903		)		(4,567		)		(8,323		)		(6,716		)		(11,316		)		(a)
				450				(1,534		)		1,027				(4,154		)		269				(5,706		)		(a)
		Income tax effect		(171		)		469				(392		)		1,550				(66		)		2,105
				279				(1,065		)		635				(2,604		)		203				(3,601		)		(a)
	Marketable securities:
		Net realized gain on sale of securities		824				199				3,791				287				4,057				474				Investment and interest income, net
		Unrealized losses on available-for-sale securities included in pre-tax income		—				—				—				—				—				(313		)		Investment and interest income, net
				824				199				3,791				287				4,057				161				Income before income taxes
		Income tax effect		(133		)		(41		)		(699		)		(45		)		(771		)		(10		)		Income tax expense
				691				158				3,092				242				3,286				151				Net income
	Loss on cash flow hedge:
		Amortization of loss		(110		)		(104		)		(326		)		(306		)		(431		)		(405		)		Interest on long-term debt and revolving credit facility
				(110		)		(104		)		(326		)		(306		)		(431		)		(405		)		Income before income taxes
		Income tax effect		42				39				174				129				213				143				Income tax expense
				(68		)		(65		)		(152		)		(177		)		(218		)		(262		)		Net income
		Total reclassifications		$	902			$	(972	)		$	3,575			$	(2,539	)		$	3,271			$	(3,712	)
	(a) These items are included in the computation of net periodic benefit cost. See Note I, Employee Benefits, for additional information.

Regulation

Regulation	9 Months Ended
	Sep. 30, 2014
Public Utilities, General Disclosures [Abstract]	'
Regulation	'
	Regulation
	General
	The rates and services of the Company are regulated by incorporated municipalities in Texas, the Public Utility Commission of Texas ("PUCT"), the New Mexico Public Regulation Commission ("NMPRC"), and the Federal Energy Regulatory Commission ("FERC"). The PUCT and the NMPRC have jurisdiction to review municipal orders, ordinances and utility agreements regarding rates and services within their respective states and over certain other activities of the Company. The FERC has jurisdiction over the Company's wholesale (sales for resale) transactions, transmission service and compliance with federally-mandated reliability standards. The decisions of the PUCT, NMPRC and the FERC are subject to judicial review.
	Texas Regulatory Matters
	2012 Texas Retail Rate Settlement. On April 17, 2012, the El Paso City Council approved the settlement of the Company's 2012 Texas retail rate case and fuel reconciliation in PUCT Docket No. 40094. The PUCT issued a final order approving the settlement on May 23, 2012 and the rates were effective as of May 1, 2012. As part of the 2012 Texas retail rate settlement, the Company agreed to submit a future fuel reconciliation request covering the period beginning July 1, 2009 and ending no later than June 30, 2013 by December 31, 2013 or as part of its next rate case, if earlier. The Company filed a fuel reconciliation request covering the period July 1, 2009 through March 31, 2013, as later discussed. The 2012 Texas retail rate settlement also provided for the continuation of the energy efficiency cost recovery factor and the military base discount recovery factor. Both of these surcharges require annual filings to reconcile and revise the recovery factors.
	Energy Efficiency Cost Recovery Factor. The Company made its annual filing to establish its energy efficiency cost recovery factor for 2015 on May 1, 2014. In addition to projected energy efficiency costs for 2015 and true-up to prior year actual costs, the Company requested approval of a $2.0 million bonus for 2013 energy efficiency program results in accordance with PUCT rules. In a proposal for decision issued on October 7, 2014, the Administrative Law Judge ("ALJ") recommended approval of the Company's requested cost recovery including the requested bonus. The PUCT is scheduled to consider a final order at its November 14, 2014 open meeting.
	Fuel and Purchased Power Costs. The Company's actual fuel costs, including purchased power energy costs, are recovered from customers through a fixed fuel factor. The PUCT has adopted a fuel cost recovery rule (the "Texas Fuel Rule") that allows the Company to seek periodic adjustments to its fixed fuel factor. The Company can seek to revise its fixed fuel factor based upon the approved formula at least four months after its last revision except in the month of December. On April 15, 2014, the Company filed a request, which was assigned Docket No. 42384, to increase its fixed fuel factor by $10.7 million or 6.9% annually, pursuant to its approved formula. The revised fixed fuel factor reflects expected increases in prices for natural gas over the twelve month period beginning March 2014. The increase in the fixed fuel factor received final approval on May 28, 2014 and was effective with May 2014 billings. On August 26, 2014, the Company filed a request with the PUCT, which was designated Docket No. 42779, to surcharge under-recovered fuel costs of $19.9 million to customers over a twelve month period to begin in October 2014. However, on October 3, 2014, the Company withdrew its surcharge request as the Company believes that, as a result of declining natural gas prices and the reimbursement by the United States Department of Energy ("DOE") of amounts spent by the Company on spent nuclear fuel storage (see Note D), under-recovered costs, which as of September 30, 2014 have been reduced to $10.7 million, can be recovered through the current fuel factor.
	Fuel Reconciliation Proceeding. Pursuant to the 2012 Texas retail rate settlement discussed above, on September 27, 2013, the Company filed an application with the PUCT, designated as Docket No. 41852, to reconcile $545.3 million of fuel and purchased power expenses incurred during the 45-month period from July 1, 2009 through March 31, 2013. A settlement was reached and a final order was issued by the PUCT on July 11, 2014. The nine months ended September 30, 2014 financial results includes a $2.1 million, pre-tax increase to income reflecting the settlement of the Texas fuel reconciliation proceeding. The settlement included the recognition of $3.4 million of Palo Verde performance rewards associated with the 2009 to 2012 performance periods net of disallowed fuel and purchased power costs of $1.75 million of which $0.5 million had been reserved. Palo Verde performance rewards are not recorded on the Company's books until the PUCT has ordered a final determination in a fuel proceeding or comparable evidence of collectability is obtained. In addition, the Company reimbursed the City of El Paso approximately $0.1 million in incurred expenses. The settlement provided for the current mine reclamation costs related to the Four Corners generating units to continue in the amount of approximately $70 thousand per month. The Company also agreed to file a request in a separate proceeding for a PUCT finding on the reasonableness of its decision to not continue participation in Four Corners Units 4 & 5 after July 2016 after the Company enters into an agreement containing the terms of the disposition. The settlement provides that 100% of margins on non-arbitrage sales (as defined by the settlement) and 50% of margins on arbitrage sales be shared with its Texas customers beginning April 1, 2014. For the period April 1, 2014 through June 30, 2015, the Company's total share of margins assignable to Texas retail jurisdiction, on arbitrage and non-arbitrage off-system sales, may not exceed 10% of the total margins assignable to the Texas retail jurisdiction on all off-system sales. The PUCT's final order completes the regulatory review and reconciliation of the Company's fuel expenses for the period through March 31, 2013.
	Montana Power Station Approvals. As discussed further below, the Company has received a Certificate of Convenience and Necessity ("CCN") from the PUCT to construct all four units of the Montana Power Station ("MPS") in El Paso County, Texas. The Company also obtained air permits from the Texas Commission on Environmental Quality ("TCEQ"), and Environmental Protection Agency ("EPA").
	On June 23, 2014, the U.S. Supreme Court issued an opinion in the Utility Air Regulatory Group vs EPA regarding EPA's authority to require greenhouse gas emissions ("GHG") Prevention of Significant Deterioration ("PSD") permits for stationary sources. The opinion concluded that EPA erred in making applicability of the Clean Air Act ("CAA") permitting requirements based on GHG emissions. As a result, the Company believes its EPA air permit is no longer required and could be rescinded, and it is eligible for a standard air permit to replace the new source review permit issued by the TCEQ. Accordingly, on August 1, 2014, the Company submitted a request to EPA to rescind the EPA air permit which request remains pending. Also, on September 16, 2014, the Company applied for a standard air permit, which TCEQ issued on October 2, 2014.
	On December 13, 2012, in PUCT Docket No. 40301, the Company received CCN approval from the PUCT for MPS Units 1 and 2. On September 6, 2013, the Company filed an application with the PUCT for issuance of a CCN to construct, own and operate two additional 88 MW natural gas-fired generating units designated as the MPS Units 3 and 4. The case was designated PUCT Docket No. 41763. Hearings in this case were held before an ALJ in February 2014. On July 11, 2014, the PUCT approved the CCN to construct MPS Units 3 and 4.
	In 2013 the Company filed three transmission line CCN applications with the PUCT as part of the MPS Project:
	•	MPS to Caliente: a 115-kV transmission line from the MPS to the existing Caliente Substation in east El Paso. (PUCT Docket No. 41360)
	•	MPS In & Out: a 115-kV transmission line from the MPS to intersect with the existing Caliente - Coyote 115-kV transmission line. (PUCT Docket No. 41359)
	•	MPS to Montwood: a 115-kV transmission line from the MPS to the existing Montwood Substation in east El Paso. (PUCT Docket No. 41809)
	The Company is requesting to build these transmission lines to connect the new MPS to the electrical grid in order to meet expected customer growth and electric demand and to improve system reliability. On March 10, 2014, the PUCT issued a final order approving a unanimous settlement in the MPS to Caliente transmission CCN filing. On August 18, 2014, the PUCT issued final orders approving unanimous settlements of the MPS In & Out transmission CCN filing and the MPS to Montwood transmission CCN filing.
	Other Required Approvals. The Company has obtained other required approvals for recovery of fuel costs through fixed fuel factors, other tariffs and approvals as required by the Public Utility Regulatory Act (the "PURA") and the PUCT.
	New Mexico Regulatory Matters
	2009 New Mexico Stipulation. On December 10, 2009, the NMPRC issued a final order conditionally approving the stipulated rates in NMPRC Case No. 09-00171-UT. The stipulated rates went into effect with January 2010 bills. The stipulated rates provide for an Efficient Use of Energy Factor Rate Rider to recover energy efficiency expenditures which requires an annual filing and approval of the related costs and incentives and any necessary adjustments to the recovery factors.
	Fuel and Purchased Power Cost Recovery. Fuel and purchased power costs are recovered through a Fuel and Purchased Power Cost Adjustment Clause (the "FPPCAC"). On January 8, 2014, the NMPRC approved the continuation of the FPPCAC without modification in NMPRC Case No. 13-00380-UT. Fuel and purchased power costs are reconciled to actual costs on a monthly basis and recovered or refunded to customers the second succeeding month. The Company recovers its investment in Palo Verde Unit 3 in New Mexico through the FPPCAC as purchased power using a proxy market price approved in the 2009 New Mexico rate stipulation.
	Montana Power Station Approvals. The Company has received a CCN from the NMPRC to construct all four units of the MPS. The Company obtained air permits from the TCEQ and EPA as explained above. On September 6, 2013, the Company filed an application with the NMPRC for issuance of a CCN to construct, own and operate two additional 88 MW natural gas-fired generating units designated as the MPS Units 3 and 4. The case was designated NMPRC Case No. 13-00297-UT. A final order approving the Company's application was issued on June 11, 2014.
	Revolving Credit Facility, Issuance of Long-Term Debt and Guarantee of Debt. On October 30, 2013, the Company received approval in NMPRC Case No. 13-00317-UT to amend its current $300 million Revolving Credit Facility ("RCF") to include an option, subject to lender's approval, to expand the amount of the potential borrowings available under the facility to $400 million and extend the maturity date by up to four years; issue up to $300 million in new long-term debt; and to guarantee the issuance of up to $50 million of new debt by Rio Grande Resources Trust ("RGRT") to finance future purchases of nuclear fuel and to refinance existing debt obligations related to the financing of purchases of nuclear fuel.
	On January 14, 2014, the Company and RGRT entered into a second amended and restated credit agreement related to the RCF with JP Morgan Chase Bank, N.A., as administrative agent and issuing bank, and Union Bank, N.A., as syndication agent, and various lending banks party thereto. Under the terms of the agreement, the Company has available $300 million and the ability to increase the RCF by up to $100 million (up to a total of $400 million) upon the satisfaction of certain conditions, more fully set forth in the agreement, including obtaining commitments from lenders or third party financial institutions. The RCF has a term ending January 2019. The Company may extend the maturity date up to two times, in each case for an additional one year period upon the satisfaction of certain conditions.
	Other Required Approvals. The Company has obtained other required approvals for other tariffs, securities transactions, long-term resource plans, recovery of energy efficiency costs through a base rate rider and other approvals as required by the NMPRC.
	Federal Regulatory Matters
	Public Service Company of New Mexico's ("PNM") 2010 Transmission Rate Case. On October 27, 2010, PNM filed a Notice of Transmission Rate Change for transmission delivery services provided by PNM. These rates went into effect on June 1, 2011. The Company takes transmission service from PNM. On January 2, 2013, the FERC issued a letter order approving a unanimous stipulation and agreement. Pursuant to the stipulation, on January 31, 2013, PNM refunded $1.9 million, for amounts that PNM collected since June 1, 2011, in excess of settlement rates. This amount was recorded in the fourth quarter of 2012 as a reduction of transmission expense.
	Revolving Credit Facility, Issuance of Long-Term Debt and Guarantee of Debt. On November 15, 2013, the FERC issued an order in Docket No. ES13-59-000 approving the Company's filing to amend its current $300 million RCF to include an option, subject to lender's approval, to expand the amount of the potential borrowings available under the facility to $400 million and extend the maturity date by up to four years; issue up to $300 million in new long-term debt; and to guarantee the issuance of up to $50 million of new debt by RGRT to finance future purchases of nuclear fuel and to refinance existing debt obligations related to the purchase of nuclear fuel. As noted above, on January 14, 2014, the Company and RGRT entered into a second amended and restated credit agreement related to the RCF.
	Other Required Approvals. The Company has obtained required approvals for rates and tariffs, securities transactions and other approvals as required by the FERC.

Palo_Verde

Palo Verde	9 Months Ended
	Sep. 30, 2014
Palo Verde [Abstract]	'
Palo Verde	'
	Palo Verde
	Spent Nuclear Fuel and Waste Disposal
	Pursuant to the Nuclear Waste Policy Act of 1982, as amended in 1987 (the "NWPA"), the DOE is legally obligated to accept and dispose of all spent nuclear fuel and other high-level radioactive waste generated by all domestic power reactors by 1998. The DOE's obligations are reflected in a contract for Disposal of Spent Nuclear Fuel and/or High-Level Radioactive Waste (the "Standard Contract") with each nuclear power plant. The DOE failed to begin accepting spent nuclear fuel by 1998. On May 17, 2012, Arizona Public Service Company ("APS") submitted to the government a claim for damages ("Initial Disclosure") associated with the DOE's partial breach of the Standard Contract with Palo Verde. The Initial Disclosure sought damages for spent nuclear fuel storage and management costs incurred by APS, on behalf of the participant owners of Palo Verde, for the period January 1, 2007 through June 30, 2011. On April 21, 2014, the Department of Justice recommended a payment amount of approximately $57 million for APS' claim, acting on behalf of itself and the participant owners of Palo Verde, for spent nuclear fuel related damages from January 1, 2007 through June 30, 2011, and reimbursement for certain ongoing future spent nuclear fuel storage costs through at least 2016 through an annual claims submission process. On October 8, 2014, the Company received approximately $9.1 million, representing its share of the award, which was recorded as an accounts receivable as of September 30, 2014. The majority of the award was refunded to customers through the applicable fuel adjustment clauses in September 2014. On October 31, 2014, APS acting on behalf of the participant owners of Palo Verde, submitted to the government an additional request for reimbursement of spent nuclear fuel storage costs for the period July 1, 2011 through June 30, 2014. The total submitted claim amount was $42.5 million, of which the Company’s portion is $6.7 million. Any reimbursement is anticipated to be received in the first half of 2015 and the majority will be refunded to customers through the applicable fuel adjustment clauses.
	The One-Mill Fee
	In 2011, the National Association of Regulatory Utility Commissioners and the Nuclear Energy Institute challenged DOE's 2010 determination of the adequacy of the one tenth of a cent per kWh fee (the "one-mill fee") paid by the nation's commercial nuclear power plant owners pursuant to their individual obligations under the Standard Contract. This fee is recovered by the Company through applicable fuel adjustment clauses. In June 2012, the U.S. Court of Appeals for the District of Columbia Circuit (the "D.C. Circuit") held that DOE failed to conduct a sufficient fee analysis in making the 2010 determination. The D.C. Circuit remanded the 2010 determination to the Secretary of the DOE ("Secretary") with instructions to conduct a new fee adequacy determination within six months. In February 2013, upon completion of the DOE's revised one-mill fee adequacy determination, the court reopened the proceedings. On November 19, 2013, the D.C. Circuit ordered the Secretary to notify Congress of his intent to suspend collecting annual fees for nuclear waste disposal from nuclear power plant operators, as he is required to do pursuant to the NWPA and the court's order. On January 3, 2014, the Secretary notified Congress of his intention to suspend collection of the one-mill fee, subject to Congress' disapproval and on May 12, 2014, APS was notified by the DOE that, effective May 16, 2014, the one-mill fee would be suspended. Electricity generated and sold prior to May 16, 2014 remained subject to the one-mill fee.

Common_Stock

Common Stock	9 Months Ended
	Sep. 30, 2014
Class of Stock Disclosures [Abstract]	'
Shareholders' Equity and Share-based Payments, Including Earnings Per Share Information	'
	Common Stock
	Dividend Policy. The Company paid $11.3 million and $10.7 million in quarterly cash dividends during the three months ended September 30, 2014 and 2013, respectively. The Company paid a total of $33.3 million and $43.9 million in quarterly cash dividends during the nine and twelve months ended September 30, 2014, respectively. The Company paid a total of $31.4 million and $41.4 million in quarterly cash dividends during the nine and twelve months ended September 30, 2013, respectively.
	Basic and Diluted Earnings Per Share. The basic and diluted earnings per share are presented below (in thousands except for share data):
		Three Months Ended September 30,
		2014				2013
	Weighted average number of common shares outstanding:
	Basic number of common shares outstanding	40,213,741				40,132,250
	Dilutive effect of unvested performance awards	51,069				—
	Diluted number of common shares outstanding	40,264,810				40,132,250
	Basic net income per common share:
	Net income	$	52,476			$	50,565
	Income allocated to participating restricted stock	(175		)		(150		)
	Net income available to common shareholders	$	52,301			$	50,415
	Diluted net income per common share:
	Net income	$	52,476			$	50,565
	Income reallocated to participating restricted stock	(175		)		(150		)
	Net income available to common shareholders	$	52,301			$	50,415
	Basic net income per common share:
	Distributed earnings	$	0.28			$	0.265
	Undistributed earnings	1.02				0.995
	Basic net income per common share	$	1.3			$	1.26
	Diluted net income per common share:
	Distributed earnings	$	0.28			$	0.265
	Undistributed earnings	1.02				0.995
	Diluted net income per common share	$	1.3			$	1.26
		Nine Months Ended September 30,
		2014				2013
	Weighted average number of common shares outstanding:
	Basic number of common shares outstanding	40,181,367				40,107,555
	Dilutive effect of unvested performance awards	27,634				16,071
	Diluted number of common shares outstanding	40,209,001				40,123,626
	Basic net income per common share:
	Net income	$	87,187			$	87,392
	Income allocated to participating restricted stock	(293		)		(249		)
	Net income available to common shareholders	$	86,894			$	87,143
	Diluted net income per common share:
	Net income	$	87,187			$	87,392
	Income reallocated to participating restricted stock	(293		)		(249		)
	Net income available to common shareholders	$	86,894			$	87,143
	Basic net income per common share:
	Distributed earnings	$	0.825			$	0.78
	Undistributed earnings	1.335				1.39
	Basic net income per common share	$	2.16			$	2.17
	Diluted net income per common share:
	Distributed earnings	$	0.825			$	0.78
	Undistributed earnings	1.335				1.39
	Diluted net income per common share	$	2.16			$	2.17
		Twelve Months Ended September 30,
		2014				2013
	Weighted average number of common shares outstanding:
	Basic number of common shares outstanding	40,169,801				40,084,525
	Dilutive effect of unvested performance awards	20,726				28,122
	Dilutive effect of stock options	—				2,274
	Diluted number of common shares outstanding	40,190,527				40,114,921
	Basic net income per common share:
	Net income	$	88,378			$	92,211
	Income allocated to participating restricted stock	(285		)		(253		)
	Net income available to common shareholders	$	88,093			$	91,958
	Diluted net income per common share:
	Net income	$	88,378			$	92,211
	Income reallocated to participating restricted stock	(285		)		(253		)
	Net income available to common shareholders	$	88,093			$	91,958
	Basic net income per common share:
Distributed earnings	$	1.09			$	1.03
Undistributed earnings	1.1				1.26
Basic net income per common share	$	2.19			$	2.29
Diluted net income per common share:
Distributed earnings	$	1.09			$	1.03
Undistributed earnings	1.1				1.26
Diluted net income per common share	$	2.19			$	2.29
The amount of restricted stock awards and performance shares at 100% performance level excluded from the calculation of the diluted number of common shares outstanding because their effect was antidilutive is presented below:
	Three Months Ended						Nine Months Ended		Twelve Months Ended
	September 30,						September 30,		September 30,
	2014			2013			2014	2013	2014	2013
Restricted stock awards	59,627			54,224			60,264	49,455	59,296	47,636
Performance shares (a)	48,733			124,997			87,784	111,726	88,575	105,090
____________________
(a)	Certain performance shares were excluded from the computation of diluted earnings per share as no payouts would have been required based upon performance at the end of each corresponding period.

Income_Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2014
Components of Income Tax Expense (Benefit), Continuing Operations [Abstract]	'
Income Taxes	'
	Income Taxes
	The Company files income tax returns in the United States ("U.S.") federal jurisdiction and in the states of Texas, New Mexico and Arizona. The Company is no longer subject to tax examination by the taxing authorities in the federal, Arizona and New Mexico jurisdictions for years prior to 2009. The Company is currently under audit in Texas for tax years 2007 through 2011. The Company reached a settlement with the Arizona Department of Revenue ("ADOR") in March 2014 in their audit of income tax returns for the years 1998 through 2007 which did not have a material effect on income tax expense. Additionally, the Company reached a settlement with the ADOR in September 2014 in their audit of income tax returns for 2008 which did not have a material effect on income tax expense.
	For the three months ended September 30, 2014 and 2013, the Company’s effective tax rate was 30.2% and 34.9%, respectively. For the nine months ended September 30, 2014 and 2013, the Company's effective tax rate was 30.9% and 34.6%, respectively. For the twelve months ended September 30, 2014 and 2013, the Company's effective tax rate was 29.1% and 34.2%, respectively. The Company's effective tax rate for all time periods presented differs from the federal statutory tax rate of 35.0% primarily due to the allowance for equity funds used during construction, a domestic production activities deduction earned in 2014 and state income taxes. The Company's effective tax rate for the nine months ended September 30, 2014 also differs from the federal statutory tax rate of 35.0% due to capital gains in the qualified decommissioning trusts realized in the first quarter of 2014, which are taxed at a federal rate of 20.0%.
	FASB guidance prescribes a recognition threshold and measurement attribute for the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. In the three months ended September 30, 2014, a $2.8 million decrease was made to the reserve related to units of property for capitalized assets. In September 2014, the Company received an Issue Resolution Agreement ("IRA") from the Internal Revenue Service ("IRS") regarding the generation repairs deduction for all years. In the IRA, the IRS declared that the method used by the Company to calculate the generation repair deduction was substantially the same as the method outlined in the Revenue Procedure and declared that therefore no adjustment to the deduction taken in previous tax returns by the Company was required. A reconciliation of the September 30, 2014 and 2013 amount of unrecognized tax benefit is as follows (in thousands):
		2014			2013
	Balance at January 1	$	7,200		$	9,800
	Additions for tax positions of prior years	300			800
	Reductions for tax positions of prior years	(2,800		)	(4,100		)
	Balance at September 30	$	4,700		$	6,500

Commitments_Contingencies_And_

Commitments, Contingencies And Uncertainties	9 Months Ended
	Sep. 30, 2014
Commitments and Contingencies Disclosure [Abstract]	'
Commitments, Contingencies And Uncertainties	'
	Commitments, Contingencies and Uncertainties
	For a full discussion of commitments and contingencies, see Note K of Notes to Financial Statements in the 2013 Form 10-K. In addition, see Notes C and D above and Notes C and E of Notes to Financial Statements in the 2013 Form 10-K regarding matters related to wholesale power sales contracts and transmission contracts subject to regulation and Palo Verde, including decommissioning, spent nuclear fuel and waste disposal, and liability and insurance matters.
	Power Purchase and Sale Contracts
	To supplement its own generation and operating reserves, and to meet required renewable portfolio standards, the Company engages in firm power purchase arrangements which may vary in duration and amount based on evaluation of the Company’s resource needs, the economics of the transactions, and specific renewable portfolio requirements. For a full discussion of power purchase and sale contracts that the Company has entered into with various counterparties, see Note K of Notes to Financial Statements in the 2013 Form 10-K. In addition, the 50 MW Macho Springs solar photovoltaic project located in Luna County, New Mexico began commercial operation in May 2014.
	Environmental Matters
	General. The Company is subject to extensive laws, regulations and permit requirements with respect to air and greenhouse gas emissions, water discharges, soil and water quality, waste management and disposal, natural resources and other environmental matters by federal, state, regional, tribal and local authorities. Failure to comply with such laws, regulations and requirements can result in actions by authorities or other third parties that might seek to impose on the Company administrative, civil and/or criminal penalties or other sanctions. In addition, releases of pollutants or contaminants into the environment can result in costly cleanup liabilities. These laws, regulations and requirements are subject to change through modification or reinterpretation, or the introduction of new laws and regulations and, as a result, the Company may face additional capital and operating costs to comply. For a full discussion of certain key environmental issues, laws and regulations facing the Company see Note K of Notes to Financial Statements in the 2013 Form 10-K.
	Clean Air Interstate Rule/Cross State Air Pollution Rule. The EPA promulgated the Cross-State Air Pollution Rule ("CSAPR") in August 2011, which rule involves requirements to limit emissions of nitrogen oxides ("NOx") and sulfur dioxide ("SO2") from certain of the Company's power plants in Texas and/or purchase allowances representing other parties' emissions reductions. CSAPR was intended to replace the EPA's 2005 Clean Air Interstate Rule ("CAIR"). While the U.S. Court of Appeals for the District of Columbia Circuit ("D.C. Circuit") vacated CSAPR in August 2012 and allowed CAIR to stand until the EPA issued a proper replacement, on April 29, 2014, the U.S. Supreme Court reversed and upheld CSAPR, remanding certain portions of CSAPR to the D.C. Circuit for further consideration. On June 26, 2014, the EPA filed a motion asking the D.C. Circuit to lift its stay on CSAPR, which was scheduled to go into effect on January 1, 2012. On October 23, 2014, the D. C. Circuit lifted its stay of CSAPR, and oral arguments to address some provisions not previously addressed in litigation are to take place on March 11, 2015. The Company is evaluating what impact the D.C. Circuit actions may have on its operations.
	Other Laws and Regulations and Risks. The Company intends to cease its participation in Four Corners Generating Station ("Four Corners") at the expiration of the 50-year participation agreement in July 2016. The Company believes that it has better economic and cleaner alternatives for serving the energy needs of its customers than coal-fired generation, which is subject to extensive regulation and litigation. For example, as a result of APS's recent Best Available Retrofit Technology Federal Implementation Plan compliance strategy notification to the EPA, Four Corners is required to install expensive pollution control equipment in order to continue operation in the future. The Company's share of the cost of these controls is currently estimated by APS to be approximately $39 million if the Company were to extend its participation in the plant. In addition, the EPA has entered into a consent decree which would require it to issue its final rulemaking regarding the regulation of coal combustion residuals ("CCR") under the federal Resource, Conservation and Recovery Act by December 19, 2014. Once issued, the Company may be required to incur significant costs to address CCRs either generated in the past and disposed of at or from Four Corners, as well as CCRs generated in connection with the ongoing operations of Four Corners. Further, assured supplies of water are important for the Company's operations and assets, including Four Corners. Four Corners is located in a region that has been experiencing drought conditions which could affect the plant's water supply. Four Corners has accordingly been involved in negotiations and proceedings with third parties relating to water supply issues. The drought conditions and related negotiations and proceedings could adversely affect the amount of power available, or the price thereof, from Four Corners. The Company is negotiating with APS on the disposition of its ownership interest in Four Corners to allow the other participants to pursue a life extension of the Four Corners plant.
	Climate Change. On June 25, 2013, President Obama set forth his plan to address climate change. He reiterated a goal of reducing GHG "in the range of 17 percent" below 2005 levels by 2020. The plan included a variety of executive actions, including regulatory measures to reduce carbon dioxide emissions from power plants. In a White House memorandum of the same date, the President directed the EPA to issue a new proposal for GHG rulemaking addressing new power plants by September 20, 2013, and a rule for existing power plants by June 1, 2014. The formal proposal for new power plants was published in the Federal Register on January 8, 2014. The Company submitted its comments on the proposal to EPA on May 9, 2014. Also, on June 16, 2014, the EPA published the proposed rule, "Carbon Pollution Emission Guidelines for Existing Stationary Sources: Electric Utility Generating Units," also called the "Clean Power Plan" or the Clean Air Act Section 111(d) proposed rule, to limit GHGs from existing power plants. The rule is proposing state-specific rate-based goals for carbon dioxide emissions from the power sector, as well as guidelines for states to follow in developing plans to achieve the state-specific goals. The Company is reviewing the proposed rule and plans to provide comments to EPA in the assigned comment period. EPA is expected to issue a final rule by June 1, 2015. Given the significant remaining uncertainties regarding these rules, the costs of these potential requirements can not be estimated.
	Environmental Litigation and Investigations. Since 2009, the EPA and certain environmental organizations have been scrutinizing, and in some cases, have filed lawsuits, relating to certain air emissions and air permitting matters related to Four Corners. In particular, since July 2011, the U.S. Department of Justice (the "DOJ"), on behalf of the EPA, and APS have been engaged in substantive settlement negotiations in an effort to resolve the pending matters. The allegations being addressed through settlement negotiations are that APS failed to obtain the necessary permits and install the controls necessary under the Clean Air Act ("CAA") to reduce SO2, NOx, and particular matter ("PM"), and that defendants failed to obtain an operating permit under Title V of the CAA that reflects applicable requirements imposed by law. In March 2012, the DOJ provided APS with a draft consent decree to settle the EPA matter, which decree contains specific provisions for the reduction and control of NOx, SO2, and PM, as well as provisions for a civil penalty, and expenditures on environmental mitigation projects with an emphasis on projects that address alleged harm to the Navajo Nation. Settlement discussions are on-going and the Company is unable to predict the outcome of these settlement negotiations. The Company has accrued a total of $0.5 million as a loss contingency related to this matter.
	Earthjustice filed a lawsuit in the United States District Court for New Mexico on October 4, 2011 for alleged violations of the Prevention of Significant Deterioration ("PSD") provisions of the CAA related to Four Corners. On January 6, 2012, Earthjustice filed a First Amended Complaint adding claims for violations of the CAA's New Source Performance Standards ("NSPS") program. Among other things, the plaintiffs seek to have the court enjoin operations at Four Corners until APS applies for and obtains any required PSD permits and complies with the referenced NSPS program. The plaintiffs further request the court to order the payment of civil penalties, including a beneficial mitigation project. On April 2, 2012, APS and the other Four Corners participants filed motions to dismiss with the court. The case is being held in abeyance while the parties seek to negotiate a settlement. On March 30, 2013, upon joint motion of the parties, the court issued an order deeming the motions to dismiss withdrawn without prejudice during pendency of the stay. At such time as the stay is lifted, APS, the Company and the other Four Corners participants may reinstate the motions to dismiss. Settlement discussions are on-going. The Company is unable to predict the outcome of this litigation.
	New Mexico Tax Matter Related to Coal Supplied to Four Corners
	On May 23, 2013, the New Mexico Taxation and Revenue Department issued a notice of assessment for coal severance surtax, penalty, and interest totaling approximately $30 million related to coal supplied under the coal supply agreement for Four Corners (the "Assessment"). The Company's share of the Assessment is approximately $1.5 million. On behalf of the Four Corners participants, the coal supplier made a partial payment of the Assessment and immediately filed a refund claim with respect to that partial payment in August 2013. The New Mexico Taxation and Revenue Department denied the refund claim. On December 19, 2013, the coal supplier and APS, on its own behalf and as operating agent for Four Corners, filed complaints with the New Mexico District Court contesting both the validity of the Assessment and the refund claim denial. APS believes the Assessment and the refund claim denial are without merit. The Company cannot predict the timing, results, or potential impacts of the outcome of this litigation.

Litigation

Litigation	9 Months Ended
	Sep. 30, 2014
Litigation [Abstract]	'
Litigation Matters Disclosure	'
	Litigation
	The Company is a party to various legal actions. In many of these matters, the Company has excess casualty liability insurance that covers the various claims, actions and complaints. Based on a review of these claims and applicable insurance coverage, the Company believes that none of these claims will have a material adverse effect on the financial position, results of operations or cash flows of the Company. See Notes C and G above and Notes C and K of the Notes to Financial Statements in the 2013 Form 10-K for discussion of the effects of government legislation and regulation on the Company.

Employee_Benefits

Employee Benefits	9 Months Ended
	Sep. 30, 2014
General Discussion of Pension and Other Postretirement Benefits [Abstract]	'
Employee Benefits	'
	Employee Benefits
	Retirement Plans
	The net periodic benefit cost recognized for the three, nine and twelve months ended September 30, 2014 and 2013 is made up of the components listed below as determined using the projected unit credit actuarial cost method (in thousands):
		Three Months Ended						Nine Months Ended						Twelve Months Ended
		September 30,						September 30,						September 30,
		2014			2013			2014			2013			2014			2013
	Components of net periodic benefit cost:
	Service cost	$	2,112		$	2,166		$	6,474		$	6,996		$	8,805		$	9,204
	Interest cost	3,691			3,410			11,351			10,210			14,755			13,600
	Expected return on plan assets	(4,681		)	(4,281		)	(14,017		)	(12,831		)	(18,294		)	(16,442		)
	Amortization of:
	Net loss	2,283			2,903			6,571			8,323			9,346			11,162
	Prior service (benefit) cost	(877		)	23			(2,030		)	73			(2,006		)	101
	Net periodic benefit cost	$	2,528		$	4,221		$	8,349		$	12,771		$	12,606		$	17,625
	During the nine months ended September 30, 2014, the Company contributed $10.4 million of its projected $10.9 million 2014 annual contribution to its retirement plans.
	During the quarter ended March 31, 2014, the Company implemented certain amendments to the Retirement Income Plan and Excess Benefit Plan. In the first quarter of 2014, the Company offered a cash balance pension plan as an alternative to its current final average pay pension plan for employees hired prior to January 1, 2014. The cash balance pension plan also included an enhanced employer matching contribution to the employee's respective 401(k) Defined Contribution Plan. The revisions in the benefit plans were effective April 1, 2014. As a result of these actions, the Company remeasured the assets and liabilities of the retirement plans based on actuarially determined estimates, using the end of alternative choice date of February 28, 2014 as the remeasurement date. The discount rate used to remeasure the benefit obligation at February 28, 2014 was 4.6% for the Retirement Income Plan and 4.5% for the Excess Benefit Plan, compared to 4.9% for both plans at December 31, 2013. As a result of the changes described above, the benefit obligation of the affected plans decreased $19.7 million, accumulated other comprehensive income before income taxes increased $19.7 million, estimated future benefit payments from 2014 through 2018 increased $21.7 million compared to the previous estimates. The 2014 net periodic benefit cost is estimated to decrease by $6.2 million compared to the net periodic benefit cost incurred in 2013 due to the changes described above and revisions to actuarial assumptions.
	Other Postretirement Benefits
	The net periodic benefit cost recognized for the three, nine and twelve months ended September 30, 2014 and 2013 is made up of the components listed below (in thousands):
		Three Months Ended						Nine Months Ended						Twelve Months Ended
		September 30,						September 30,						September 30,
		2014			2013			2014			2013			2014			2013
	Components of net periodic benefit cost:
	Service cost	$	712		$	972		$	2,134		$	3,172		$	2,805		$	4,266
	Interest cost	1,115			1,292			3,347			4,042			4,461			5,455
	Expected return on plan assets	(529		)	(485		)	(1,587		)	(1,435		)	(2,103		)	(1,864		)
	Amortization of:
	Prior service benefit	(1,188		)	(1,392		)	(3,564		)	(4,242		)	(4,979		)	(5,711		)
	Net (gain) loss	(668		)	—			(2,004		)	—			(2,630		)	154
	Net periodic benefit cost (benefit)	$	(558	)	$	387		$	(1,674	)	$	1,537		$	(2,446	)	$	2,300
	The Company has not contributed to its other postretirement benefits plan during the nine months ended September 30, 2014 and does not expect to contribute to its other postretirement benefit plan in 2014.

Financial_Instruments_And_Inve

Financial Instruments And Investments (Notes)	9 Months Ended
	Sep. 30, 2014
Fair Value Disclosures [Abstract]	'
Financial Instruments and Investments	'
	Financial Instruments and Investments
	FASB guidance requires the Company to disclose estimated fair values for its financial instruments. The Company has determined that cash and temporary investments, investment in debt securities, accounts receivable, decommissioning trust funds, long-term debt, short-term borrowings under the RCF, accounts payable and customer deposits meet the definition of financial instruments. The carrying amounts of cash and temporary investments, accounts receivable, accounts payable and customer deposits approximate fair value because of the short maturity of these items. Investments in debt securities and decommissioning trust funds are carried at fair value.
	Long-Term Debt and Short-Term Borrowings Under the RCF. The fair values of the Company's long-term debt and short-term borrowings under the RCF are based on estimated market prices for similar issues and are presented below (in thousands):
		September 30, 2014						December 31, 2013
		Carrying			Estimated			Carrying			Estimated
		Amount			Fair			Amount			Fair
					Value						Value
	Pollution Control Bonds	$	193,135		$	209,049		$	193,135		$	193,990
	Senior Notes	696,553			828,958			696,485			734,515
	RGRT Senior Notes (1)	110,000			117,145			110,000			115,850
	RCF (1)	89,528			89,528			14,352			14,352
	Total	$	1,089,216		$	1,244,680		$	1,013,972		$	1,058,707
	_______________
	-1	Nuclear fuel financing as of September 30, 2014 and December 31, 2013 is funded through the $110 million RGRT Senior Notes and $17.5 million and $14.4 million, respectively under the RCF. As of September 30, 2014, $72.0 million was outstanding under the RCF for working capital or general corporate purposes. As of December 31, 2013, no amount was outstanding under the RCF for working capital or general corporate purposes. The interest rate on the Company's borrowings under the RCF is reset throughout the quarter reflecting current market rates. Consequently, the carrying value approximates fair value.
	Marketable Securities. The Company's marketable securities, included in decommissioning trust funds in the balance sheets, are reported at fair value which was $229.0 million and $214.1 million at September 30, 2014 and December 31, 2013, respectively. These securities are classified as available for sale under FASB guidance for certain investments in debt and equity securities and are valued using prices and other relevant information generated by market transactions involving identical or comparable securities. The reported fair values include gross unrealized losses on marketable securities whose impairment the Company has deemed to be temporary. The tables below present the gross unrealized losses and the fair value of these securities, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position (in thousands):
		September 30, 2014
		Less than 12 Months						12 Months or Longer						Total
		Fair			Unrealized			Fair			Unrealized			Fair			Unrealized
		Value			Losses			Value			Losses			Value			Losses
	Description of Securities (1):
	Federal Agency Mortgage Backed Securities	$	874		$	(6	)	$	2,371		$	(113	)	$	3,245		$	(119	)
	U.S. Government Bonds	1,223			(4		)	16,322			(799		)	17,545			(803		)
	Municipal Obligations	4,344			(34		)	11,679			(532		)	16,023			(566		)
	Corporate Obligations	1,415			(15		)	2,061			(86		)	3,476			(101		)
	Total Debt Securities	7,856			(59		)	32,433			(1,530		)	40,289			(1,589		)
	Common Stock	801			(137		)	—			—			801			(137		)
	Common Collective Trust-Equity Funds	16,760			(139		)	—			—			16,760			(139		)
	Total Temporarily Impaired Securities	$	25,417		$	(335	)	$	32,433		$	(1,530	)	$	57,850		$	(1,865	)
	_________________
	-1	Includes approximately 101 securities.
		December 31, 2013
		Less than 12 Months						12 Months or Longer						Total
		Fair			Unrealized			Fair			Unrealized			Fair			Unrealized
		Value			Losses			Value			Losses			Value			Losses
	Description of Securities (2):
	Federal Agency Mortgage Backed Securities	$	6,444		$	(169	)	$	1,421		$	(119	)	$	7,865		$	(288	)
	U.S. Government Bonds	8,114			(245		)	10,866			(840		)	18,980			(1,085		)
	Municipal Obligations	12,286			(335		)	7,782			(479		)	20,068			(814		)
	Corporate Obligations	3,284			(96		)	901			(54		)	4,185			(150		)
	Total Debt Securities	30,128			(845		)	20,970			(1,492		)	51,098			(2,337		)
	Common Stock	2,305			(126		)	—			—			2,305			(126		)
	Total Temporarily Impaired Securities	$	32,433		$	(971	)	$	20,970		$	(1,492	)	$	53,403		$	(2,463	)
	_________________
	-2	Includes approximately 122 securities.
	The Company monitors the length of time the security trades below its cost basis along with the amount and percentage of the unrealized loss in determining if a decline in fair value of marketable securities below recorded cost is considered to be other than temporary. In addition, the Company will research the future prospects of individual securities as necessary. As a result of these factors, as well as the Company's intent and ability to hold these securities until their market price recovers, these securities are considered temporarily impaired. The Company does not anticipate expending monies held in trust before 2044 or a later period when the Company begins to decommission Palo Verde.
	The reported fair values also include gross unrealized gains on marketable securities which have not been recognized in the Company's net income. The table below presents the unrecognized gross unrealized gains and the fair value of these securities, aggregated by investment category (in thousands):
		September 30, 2014						December 31, 2013
		Fair			Unrealized			Fair			Unrealized
		Value			Gains			Value			Gains
	Description of Securities:
	Federal Agency Mortgage Backed Securities	$	12,975		$	586		$	9,929		$	433
	U.S. Government Bonds	12,482			279			6,258			126
	Municipal Obligations	14,748			630			8,783			450
	Corporate Obligations	11,645			729			9,188			506
	Total Debt Securities	51,850			2,224			34,158			1,515
	Common Stock	109,848			49,060			103,808			43,145
	Equity Mutual Funds	—			—			16,802			3,081
	Cash and Cash Equivalents	9,500			—			5,924			—
	Total	$	171,198		$	51,284		$	160,692		$	47,741
	The Company's marketable securities include investments in municipal, corporate and federal debt obligations. Substantially all of the Company's mortgage-backed securities, based on contractual maturity, are due in ten years or more. The mortgage-backed securities have an estimated weighted average maturity which generally range from three years to eight years and reflects anticipated future prepayments. The contractual year for maturity of these available-for-sale securities as of September 30, 2014 is as follows (in thousands):
		Total			2014			2015			2019 through 2023			2024 and Beyond
								through
								2018
Municipal Debt Obligations	$	30,771		$	—		$	11,151		$	15,911		$	3,709
Corporate Debt Obligations	15,121			—			3,267			7,441			4,413
U.S. Government Bonds	30,027			—			15,931			7,236			6,860
The Company recognizes impairment losses on certain of its securities deemed to be other than temporary. In accordance with FASB guidance, these impairment losses are recognized in net income, and a lower cost basis is established for these securities. The Company did not recognize other than temporary impairment losses on its available-for-sale securities in the three, nine and twelve month periods ending September 30, 2014. The Company did not recognize other than temporary impairment losses on its available-for-sale securities in the three and nine month periods ending September 30, 2013, however for the twelve months ended September 30, 2013, $0.3 million of other than temporary impairment losses were recognized.
The Company's marketable securities in its decommissioning trust funds are sold from time to time and the Company uses the specific identification basis to determine the amount to reclassify out of accumulated other comprehensive income and into net income. The proceeds from the sale of these securities and the related effects on pre-tax income are as follows (in thousands):
	Three Months Ended						Nine Months Ended						Twelve Months Ended
	September 30,						September 30,						September 30,
	2014			2013			2014			2013			2014			2013
Proceeds from sales or maturities of available-for-sale securities	$	10,980		$	7,057		$	47,355		$	29,419		$	74,083		$	53,866
Gross realized gains included in pre-tax income	$	1,239		$	212		$	4,502		$	593		$	4,895		$	814
Gross realized losses included in pre-tax income	(415		)	(13		)	(711		)	(306		)	(838		)	(340		)
Gross unrealized losses included in pre-tax income	—			—			—			—			—			(313		)
Net gains in pre-tax income	$	824		$	199		$	3,791		$	287		$	4,057		$	161
Net unrealized holding gains included in accumulated other comprehensive income	$	897		$	4,300		$	7,965		$	8,861		$	16,803		$	6,802
Net gains reclassified out of accumulated other comprehensive income	(824		)	(199		)	(3,791		)	(287		)	(4,057		)	(161		)
Net gains in other comprehensive income	$	73		$	4,101		$	4,174		$	8,574		$	12,746		$	6,641
Fair Value Measurements. FASB guidance requires the Company to provide expanded quantitative disclosures for financial assets and liabilities recorded on the balance sheet at fair value. Financial assets carried at fair value include the Company's decommissioning trust investments and investment in debt securities which are included in deferred charges and other assets on the balance sheets. The Company has no liabilities that are measured at fair value on a recurring basis. The FASB guidance establishes a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value into three levels as follows:
•	Level 1 – Observable inputs that reflect quoted market prices for identical assets and liabilities in active markets. Financial assets utilizing Level 1 inputs include the nuclear decommissioning trust investments in active exchange-traded equity securities, mutual funds and U.S. Treasury securities that are in a highly liquid and active market.
•	Level 2 – Inputs other than quoted market prices included in Level 1 that are observable for the asset or liability either directly or indirectly. Financial assets utilizing Level 2 inputs include the nuclear decommissioning trust investments in fixed income securities. The fair value of these financial instruments is based on evaluated prices that reflect observable market information, such as actual trade information of similar securities, adjusted for observable differences. The Common Collective Trusts are valued using the net asset value ("NAV") provided by the administrator of the fund. The NAV price is quoted on a restrictive market although the underlying investments are traded on active markets.
•	Level 3 – Unobservable inputs using data that is not corroborated by market data and primarily based on internal Company analysis using models and various other analyses. Financial assets utilizing Level 3 inputs are the Company's investment in debt securities.
The securities in the Company's decommissioning trust funds are valued using prices and other relevant information generated by market transactions involving identical or comparable securities. FASB guidance identifies this valuation technique as the "market approach" with observable inputs. The Company analyzes available-for-sale securities to determine if losses are other than temporary.
During the first quarter of 2014, the Company sold its nuclear decommissioning trust investments in equity mutual funds, classified as Level 1, and invested those assets in common collective trusts which are classified as Level 2. The fair value of the Company's decommissioning trust funds and investment in debt securities, at September 30, 2014 and December 31, 2013, and the level within the three levels of the fair value hierarchy defined by FASB guidance are presented in the table below (in thousands):
Description of Securities	Fair Value as of September 30, 2014			Quoted Prices			Significant			Significant
				in Active			Other			Unobservable
				Markets for			Observable			Inputs
				Identical Assets			Inputs			(Level 3)
				(Level 1)			(Level 2)
Trading Securities:
Investments in Debt Securities	$	1,608		$	—		$	—		$	1,608
Available for sale:
U.S. Government Bonds	$	30,027		$	30,027		$	—		$	—
Federal Agency Mortgage Backed Securities	16,220			—			16,220			—
Municipal Obligations	30,771			—			30,771			—
Corporate Obligations	15,121			—			15,121			—
Subtotal, Debt Securities	92,139			30,027			62,112			—
Common Stock	110,649			110,649			—			—
Common Collective Trust-Equity Funds	16,760			—			16,760			—
Cash and Cash Equivalents	9,500			9,500			—			—
Total available for sale	$	229,048		$	150,176		$	78,872		$	—
Description of Securities	Fair Value as of December 31, 2013			Quoted Prices			Significant			Significant
				in Active			Other			Unobservable
				Markets for			Observable			Inputs
				Identical Assets			Inputs			(Level 3)
				(Level 1)			(Level 2)
Trading Securities:
Investments in Debt Securities	$	1,555		$	—		$	—		$	1,555
Available for sale:
U.S. Government Bonds	$	25,238		$	25,238		$	—		$	—
Federal Agency Mortgage Backed Securities	17,794			—			17,794			—
Municipal Obligations	28,851			—			28,851			—
Corporate Obligations	13,373			—			13,373			—
Subtotal, Debt Securities	85,256			25,238			60,018			—
Common Stock	106,113			106,113			—			—
Equity Mutual Funds	16,802			16,802			—			—
Cash and Cash Equivalents	5,924			5,924			—			—
Total available for sale	$	214,095		$	154,077		$	60,018		$	—
There were no transfers in or out of Level 1 and Level 2 fair value measurements categories due to changes in observable inputs during the three, nine and twelve month periods ending September 30, 2014 and 2013. There were no purchases, sales, issuances, and settlements related to the assets in the Level 3 fair value measurement category during the three, nine and twelve months ended September 30, 2014 and 2013.

Principles_Of_Preparation_Poli

Principles Of Preparation (Policy)	9 Months Ended
	Sep. 30, 2014
Accounting Policies [Abstract]	'
Use of Estimates, Policy	'
	Use of Estimates. The preparation of financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Revenue Recognition, Policy	'
	Revenues. Revenues related to the sale of electricity are generally recorded when service is rendered or electricity is delivered to customers. The billing of electricity sales to retail customers is based on the reading of their meters, which occurs on a systematic basis throughout the month. Unbilled revenues are estimated based on monthly generation volumes and by applying an average revenue/kWh to the number of estimated kWhs delivered but not billed. Accounts receivable included accrued unbilled revenues of $26.9 million at September 30, 2014 and $19.8 million at December 31, 2013. The Company presents revenues net of sales taxes in its statements of operations.

Principles_Of_Preparation_Prin

Principles Of Preparation Principles Of Preparation (Tables)	9 Months Ended
	Sep. 30, 2014
Supplemental Cash Flow Information [Abstract]	'
Cash Flow, Supplemental Disclosures	'
	Supplemental Cash Flow Disclosures (in thousands)
			Nine Months Ended
			September 30,
			2014		2013
	Cash paid (received) for:
		Interest on long-term debt and borrowing under the revolving credit facility	$	37,689	$	36,975
		Income tax paid (refunded), net	2,969		(36		)
	Non-cash financing activities:
		Grants of restricted shares of common stock	3,025		2,607
		Issuance of performance shares	—		849

Accumulated_Other_Comprehensiv1

Accumulated Other Comprehensive Income (Tables)	9 Months Ended
	Sep. 30, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]	'
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]	'
	Changes in Accumulated Other Comprehensive Income (Loss) (net of tax) by component are presented below (in thousands):
			Three Months Ended September 30, 2014																Three Months Ended September 30, 2013
			Unrecognized Pension and Postretirement Benefit Costs				Net Unrealized Gains (Losses) on Marketable Securities				Net Losses on Cash Flow Hedges				Accumulated Other Comprehensive Income (Loss)				Unrecognized Pension and Postretirement Benefit Costs				Net Unrealized Gains (Losses) on Marketable Securities				Net Losses on Cash Flow Hedges			Accumulated Other Comprehensive Income (Loss)
	Balance at beginning of period		$	(9,539	)		$	39,483			$	(12,214	)		$	17,730			$	(74,198	)		$	26,030			$	(12,429	)	$	(60,597	)
		Other comprehensive income before reclassifications	—				733				—				733				—				3,463				—			3,463
		Amounts reclassified from accumulated other comprehensive income (loss)	(279		)		(691		)		68				(902		)		1,065				(158		)		65			972
	Balance at end of period		$	(9,818	)		$	39,525			$	(12,146	)		$	17,561			$	(73,133	)		$	29,335			$	(12,364	)	$	(56,162	)
			Nine Months Ended September 30, 2014																Nine Months Ended September 30, 2013
			Unrecognized Pension and Postretirement Benefit Costs				Net Unrealized Gains (Losses) on Marketable Securities				Net Losses on Cash Flow Hedges				Accumulated Other Comprehensive Income (Loss)				Unrecognized Pension and Postretirement Benefit Costs				Net Unrealized Gains (Losses) on Marketable Securities				Net Losses on Cash Flow Hedges			Accumulated Other Comprehensive Income (Loss)
	Balance at beginning of period		$	(21,330	)		$	36,240			$	(12,298	)		$	2,612			$	(75,737	)		$	22,194			$	(12,541	)	$	(66,084	)
		Other comprehensive income before reclassifications	12,147				6,377				—				18,524				—				7,383				—			7,383
		Amounts reclassified from accumulated other comprehensive income (loss)	(635		)		(3,092		)		152				(3,575		)		2,604				(242		)		177			2,539
	Balance at end of period		$	(9,818	)		$	39,525			$	(12,146	)		$	17,561			$	(73,133	)		$	29,335			$	(12,364	)	$	(56,162	)
			Twelve Months Ended September 30, 2014																Twelve Months Ended September 30, 2013
			Unrecognized Pension and Postretirement Benefit Costs				Net Unrealized Gains (Losses) on Marketable Securities				Net Losses on Cash Flow Hedges				Accumulated Other Comprehensive Income (Loss)				Unrecognized Pension and Postretirement Benefit Costs				Net Unrealized Gains (Losses) on Marketable Securities				Net Losses on Cash Flow Hedges			Accumulated Other Comprehensive Income (Loss)
	Balance at beginning of period		$	(73,133	)		$	29,335			$	(12,364	)		$	(56,162	)		$	(75,403	)		$	23,994			$	(12,626	)	$	(64,035	)
		Other comprehensive income (loss) before reclassifications	63,518				13,476				—				76,994				(1,331		)		5,492				—			4,161
		Amounts reclassified from accumulated other comprehensive income (loss)	(203		)		(3,286		)		218				(3,271		)		3,601				(151		)		262			3,712
	Balance at end of period		$	(9,818	)		$	39,525			$	(12,146	)		$	17,561			$	(73,133	)		$	29,335			$	(12,364	)	$	(56,162	)
Reclassification out of Accumulated Other Comprehensive Income [Table Text Block]	'
	Amounts reclassified from accumulated other comprehensive income (loss) for the three, nine and twelve months ended September 30, 2014 and 2013 are as follows ( in thousands):
	Details about Accumulated Other Comprehensive Income (Loss) Components			Three Months Ended September 30,								Nine Months Ended September 30,								Twelve Months Ended September 30,								Affected Line Item in the Statement of Operations
				2014				2013				2014				2013				2014				2013
	Amortization of pension and postretirement benefit costs:
		Prior service benefit		$	2,065			1,369				$	5,594			4,169				$	6,985			$	5,610			(a)
		Net loss		(1,615		)		(2,903		)		(4,567		)		(8,323		)		(6,716		)		(11,316		)		(a)
				450				(1,534		)		1,027				(4,154		)		269				(5,706		)		(a)
		Income tax effect		(171		)		469				(392		)		1,550				(66		)		2,105
				279				(1,065		)		635				(2,604		)		203				(3,601		)		(a)
	Marketable securities:
		Net realized gain on sale of securities		824				199				3,791				287				4,057				474				Investment and interest income, net
		Unrealized losses on available-for-sale securities included in pre-tax income		—				—				—				—				—				(313		)		Investment and interest income, net
				824				199				3,791				287				4,057				161				Income before income taxes
		Income tax effect		(133		)		(41		)		(699		)		(45		)		(771		)		(10		)		Income tax expense
				691				158				3,092				242				3,286				151				Net income
	Loss on cash flow hedge:
		Amortization of loss		(110		)		(104		)		(326		)		(306		)		(431		)		(405		)		Interest on long-term debt and revolving credit facility
				(110		)		(104		)		(326		)		(306		)		(431		)		(405		)		Income before income taxes
		Income tax effect		42				39				174				129				213				143				Income tax expense
				(68		)		(65		)		(152		)		(177		)		(218		)		(262		)		Net income
		Total reclassifications		$	902			$	(972	)		$	3,575			$	(2,539	)		$	3,271			$	(3,712	)
	(a) These items are included in the computation of net periodic benefit cost. See Note I, Employee Benefits, for additional information.

Common_Stock_Tables

Common Stock (Tables)	9 Months Ended
	Sep. 30, 2014
Class of Stock Disclosures [Abstract]	'
Schedule of Earnings Per Share, Basic and Diluted	'
	Basic and Diluted Earnings Per Share. The basic and diluted earnings per share are presented below (in thousands except for share data):
		Three Months Ended September 30,
		2014				2013
	Weighted average number of common shares outstanding:
	Basic number of common shares outstanding	40,213,741				40,132,250
	Dilutive effect of unvested performance awards	51,069				—
	Diluted number of common shares outstanding	40,264,810				40,132,250
	Basic net income per common share:
	Net income	$	52,476			$	50,565
	Income allocated to participating restricted stock	(175		)		(150		)
	Net income available to common shareholders	$	52,301			$	50,415
	Diluted net income per common share:
	Net income	$	52,476			$	50,565
	Income reallocated to participating restricted stock	(175		)		(150		)
	Net income available to common shareholders	$	52,301			$	50,415
	Basic net income per common share:
	Distributed earnings	$	0.28			$	0.265
	Undistributed earnings	1.02				0.995
	Basic net income per common share	$	1.3			$	1.26
	Diluted net income per common share:
	Distributed earnings	$	0.28			$	0.265
	Undistributed earnings	1.02				0.995
	Diluted net income per common share	$	1.3			$	1.26
		Nine Months Ended September 30,
		2014				2013
	Weighted average number of common shares outstanding:
	Basic number of common shares outstanding	40,181,367				40,107,555
	Dilutive effect of unvested performance awards	27,634				16,071
	Diluted number of common shares outstanding	40,209,001				40,123,626
	Basic net income per common share:
	Net income	$	87,187			$	87,392
	Income allocated to participating restricted stock	(293		)		(249		)
	Net income available to common shareholders	$	86,894			$	87,143
	Diluted net income per common share:
	Net income	$	87,187			$	87,392
	Income reallocated to participating restricted stock	(293		)		(249		)
	Net income available to common shareholders	$	86,894			$	87,143
	Basic net income per common share:
	Distributed earnings	$	0.825			$	0.78
	Undistributed earnings	1.335				1.39
	Basic net income per common share	$	2.16			$	2.17
	Diluted net income per common share:
	Distributed earnings	$	0.825			$	0.78
	Undistributed earnings	1.335				1.39
	Diluted net income per common share	$	2.16			$	2.17
		Twelve Months Ended September 30,
		2014				2013
	Weighted average number of common shares outstanding:
	Basic number of common shares outstanding	40,169,801				40,084,525
	Dilutive effect of unvested performance awards	20,726				28,122
	Dilutive effect of stock options	—				2,274
	Diluted number of common shares outstanding	40,190,527				40,114,921
	Basic net income per common share:
	Net income	$	88,378			$	92,211
	Income allocated to participating restricted stock	(285		)		(253		)
	Net income available to common shareholders	$	88,093			$	91,958
	Diluted net income per common share:
	Net income	$	88,378			$	92,211
	Income reallocated to participating restricted stock	(285		)		(253		)
	Net income available to common shareholders	$	88,093			$	91,958
	Basic net income per common share:
	Distributed earnings	$	1.09			$	1.03
	Undistributed earnings	1.1				1.26
Basic net income per common share	$	2.19			$	2.29
Diluted net income per common share:
Distributed earnings	$	1.09			$	1.03
Undistributed earnings	1.1				1.26
Diluted net income per common share	$	2.19			$	2.29
Schedule of Antidilutive Securities Excluded From Computation Of Earnings Per Share	'
	The amount of restricted stock awards and performance shares at 100% performance level excluded from the calculation of the diluted number of common shares outstanding because their effect was antidilutive is presented below:
		Three Months Ended						Nine Months Ended		Twelve Months Ended
		September 30,						September 30,		September 30,
		2014			2013			2014	2013	2014	2013
	Restricted stock awards	59,627			54,224			60,264	49,455	59,296	47,636
	Performance shares (a)	48,733			124,997			87,784	111,726	88,575	105,090
	____________________
	(a)	Certain performance shares were excluded from the computation of diluted earnings per share as no payouts would have been required based upon performance at the end of each corresponding period.

Income_Taxes_Tables

Income Taxes (Tables)	9 Months Ended
	Sep. 30, 2014
Components of Income Tax Expense (Benefit), Continuing Operations [Abstract]	'
Summary of Income Tax Contingencies [Table Text Block]	'
	A reconciliation of the September 30, 2014 and 2013 amount of unrecognized tax benefit is as follows (in thousands):
		2014			2013
	Balance at January 1	$	7,200		$	9,800
	Additions for tax positions of prior years	300			800
	Reductions for tax positions of prior years	(2,800		)	(4,100		)
	Balance at September 30	$	4,700		$	6,500

Employee_Benefits_Tables

Employee Benefits (Tables)	9 Months Ended
	Sep. 30, 2014
Retirement Plans	'
Defined Benefit Plan Disclosure [Line Items]	'
Schedule of Net Benefit Costs	'
	The net periodic benefit cost recognized for the three, nine and twelve months ended September 30, 2014 and 2013 is made up of the components listed below as determined using the projected unit credit actuarial cost method (in thousands):
		Three Months Ended						Nine Months Ended						Twelve Months Ended
		September 30,						September 30,						September 30,
		2014			2013			2014			2013			2014			2013
	Components of net periodic benefit cost:
	Service cost	$	2,112		$	2,166		$	6,474		$	6,996		$	8,805		$	9,204
	Interest cost	3,691			3,410			11,351			10,210			14,755			13,600
	Expected return on plan assets	(4,681		)	(4,281		)	(14,017		)	(12,831		)	(18,294		)	(16,442		)
	Amortization of:
	Net loss	2,283			2,903			6,571			8,323			9,346			11,162
	Prior service (benefit) cost	(877		)	23			(2,030		)	73			(2,006		)	101
	Net periodic benefit cost	$	2,528		$	4,221		$	8,349		$	12,771		$	12,606		$	17,625
Other Postretirement Benefit Plans, Defined Benefit	'
Defined Benefit Plan Disclosure [Line Items]	'
Schedule of Net Benefit Costs	'
	The net periodic benefit cost recognized for the three, nine and twelve months ended September 30, 2014 and 2013 is made up of the components listed below (in thousands):
		Three Months Ended						Nine Months Ended						Twelve Months Ended
		September 30,						September 30,						September 30,
		2014			2013			2014			2013			2014			2013
	Components of net periodic benefit cost:
	Service cost	$	712		$	972		$	2,134		$	3,172		$	2,805		$	4,266
	Interest cost	1,115			1,292			3,347			4,042			4,461			5,455
	Expected return on plan assets	(529		)	(485		)	(1,587		)	(1,435		)	(2,103		)	(1,864		)
	Amortization of:
	Prior service benefit	(1,188		)	(1,392		)	(3,564		)	(4,242		)	(4,979		)	(5,711		)
	Net (gain) loss	(668		)	—			(2,004		)	—			(2,630		)	154
	Net periodic benefit cost (benefit)	$	(558	)	$	387		$	(1,674	)	$	1,537		$	(2,446	)	$	2,300

Financial_Instruments_And_Inve1

Financial Instruments And Investments (Tables)	9 Months Ended
	Sep. 30, 2014
Fair Value Disclosures [Abstract]	'
Fair Values Of Long-Term Debt And Short-Term Borrowings Under the RCF	'
	Long-Term Debt and Short-Term Borrowings Under the RCF. The fair values of the Company's long-term debt and short-term borrowings under the RCF are based on estimated market prices for similar issues and are presented below (in thousands):
		September 30, 2014						December 31, 2013
		Carrying			Estimated			Carrying			Estimated
		Amount			Fair			Amount			Fair
					Value						Value
	Pollution Control Bonds	$	193,135		$	209,049		$	193,135		$	193,990
	Senior Notes	696,553			828,958			696,485			734,515
	RGRT Senior Notes (1)	110,000			117,145			110,000			115,850
	RCF (1)	89,528			89,528			14,352			14,352
	Total	$	1,089,216		$	1,244,680		$	1,013,972		$	1,058,707
	_______________
	-1	Nuclear fuel financing as of September 30, 2014 and December 31, 2013 is funded through the $110 million RGRT Senior Notes and $17.5 million and $14.4 million, respectively under the RCF. As of September 30, 2014, $72.0 million was outstanding under the RCF for working capital or general corporate purposes. As of December 31, 2013, no amount was outstanding under the RCF for working capital or general corporate purposes. The interest rate on the Company's borrowings under the RCF is reset throughout the quarter reflecting current market rates. Consequently, the carrying value approximates fair value.
Unrecognized Gross Unrealized Gains (Losses) And the Fair Value	'
	The tables below present the gross unrealized losses and the fair value of these securities, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position (in thousands):
		September 30, 2014
		Less than 12 Months						12 Months or Longer						Total
		Fair			Unrealized			Fair			Unrealized			Fair			Unrealized
		Value			Losses			Value			Losses			Value			Losses
	Description of Securities (1):
	Federal Agency Mortgage Backed Securities	$	874		$	(6	)	$	2,371		$	(113	)	$	3,245		$	(119	)
	U.S. Government Bonds	1,223			(4		)	16,322			(799		)	17,545			(803		)
	Municipal Obligations	4,344			(34		)	11,679			(532		)	16,023			(566		)
	Corporate Obligations	1,415			(15		)	2,061			(86		)	3,476			(101		)
	Total Debt Securities	7,856			(59		)	32,433			(1,530		)	40,289			(1,589		)
	Common Stock	801			(137		)	—			—			801			(137		)
	Common Collective Trust-Equity Funds	16,760			(139		)	—			—			16,760			(139		)
	Total Temporarily Impaired Securities	$	25,417		$	(335	)	$	32,433		$	(1,530	)	$	57,850		$	(1,865	)
	_________________
	-1	Includes approximately 101 securities.
		December 31, 2013
		Less than 12 Months						12 Months or Longer						Total
		Fair			Unrealized			Fair			Unrealized			Fair			Unrealized
		Value			Losses			Value			Losses			Value			Losses
	Description of Securities (2):
	Federal Agency Mortgage Backed Securities	$	6,444		$	(169	)	$	1,421		$	(119	)	$	7,865		$	(288	)
	U.S. Government Bonds	8,114			(245		)	10,866			(840		)	18,980			(1,085		)
	Municipal Obligations	12,286			(335		)	7,782			(479		)	20,068			(814		)
	Corporate Obligations	3,284			(96		)	901			(54		)	4,185			(150		)
	Total Debt Securities	30,128			(845		)	20,970			(1,492		)	51,098			(2,337		)
	Common Stock	2,305			(126		)	—			—			2,305			(126		)
	Total Temporarily Impaired Securities	$	32,433		$	(971	)	$	20,970		$	(1,492	)	$	53,403		$	(2,463	)
	_________________
	-2	Includes approximately 122 securities.
	The Company monitors the length of time the security trades below its cost basis along with the amount and percentage of the unrealized loss in determining if a decline in fair value of marketable securities below recorded cost is considered to be other than temporary. In addition, the Company will research the future prospects of individual securities as necessary. As a result of these factors, as well as the Company's intent and ability to hold these securities until their market price recovers, these securities are considered temporarily impaired. The Company does not anticipate expending monies held in trust before 2044 or a later period when the Company begins to decommission Palo Verde.
	The reported fair values also include gross unrealized gains on marketable securities which have not been recognized in the Company's net income. The table below presents the unrecognized gross unrealized gains and the fair value of these securities, aggregated by investment category (in thousands):
		September 30, 2014						December 31, 2013
		Fair			Unrealized			Fair			Unrealized
		Value			Gains			Value			Gains
	Description of Securities:
	Federal Agency Mortgage Backed Securities	$	12,975		$	586		$	9,929		$	433
	U.S. Government Bonds	12,482			279			6,258			126
	Municipal Obligations	14,748			630			8,783			450
	Corporate Obligations	11,645			729			9,188			506
	Total Debt Securities	51,850			2,224			34,158			1,515
	Common Stock	109,848			49,060			103,808			43,145
	Equity Mutual Funds	—			—			16,802			3,081
	Cash and Cash Equivalents	9,500			—			5,924			—
	Total	$	171,198		$	51,284		$	160,692		$	47,741
Contractual Year For Maturity Of Available-For-Sale Securities	'
	The contractual year for maturity of these available-for-sale securities as of September 30, 2014 is as follows (in thousands):
		Total			2014			2015			2019 through 2023			2024 and Beyond
								through
								2018
	Municipal Debt Obligations	$	30,771		$	—		$	11,151		$	15,911		$	3,709
	Corporate Debt Obligations	15,121			—			3,267			7,441			4,413
	U.S. Government Bonds	30,027			—			15,931			7,236			6,860
Sale of Securities And The Related Effects On Pre-Tax Income	'
	The proceeds from the sale of these securities and the related effects on pre-tax income are as follows (in thousands):
		Three Months Ended						Nine Months Ended						Twelve Months Ended
		September 30,						September 30,						September 30,
		2014			2013			2014			2013			2014			2013
	Proceeds from sales or maturities of available-for-sale securities	$	10,980		$	7,057		$	47,355		$	29,419		$	74,083		$	53,866
	Gross realized gains included in pre-tax income	$	1,239		$	212		$	4,502		$	593		$	4,895		$	814
	Gross realized losses included in pre-tax income	(415		)	(13		)	(711		)	(306		)	(838		)	(340		)
	Gross unrealized losses included in pre-tax income	—			—			—			—			—			(313		)
	Net gains in pre-tax income	$	824		$	199		$	3,791		$	287		$	4,057		$	161
	Net unrealized holding gains included in accumulated other comprehensive income	$	897		$	4,300		$	7,965		$	8,861		$	16,803		$	6,802
	Net gains reclassified out of accumulated other comprehensive income	(824		)	(199		)	(3,791		)	(287		)	(4,057		)	(161		)
	Net gains in other comprehensive income	$	73		$	4,101		$	4,174		$	8,574		$	12,746		$	6,641
Fair Value, Measurement Inputs, Disclosure	'
	The fair value of the Company's decommissioning trust funds and investment in debt securities, at September 30, 2014 and December 31, 2013, and the level within the three levels of the fair value hierarchy defined by FASB guidance are presented in the table below (in thousands):
	Description of Securities	Fair Value as of September 30, 2014			Quoted Prices			Significant			Significant
					in Active			Other			Unobservable
					Markets for			Observable			Inputs
					Identical Assets			Inputs			(Level 3)
					(Level 1)			(Level 2)
	Trading Securities:
	Investments in Debt Securities	$	1,608		$	—		$	—		$	1,608
	Available for sale:
	U.S. Government Bonds	$	30,027		$	30,027		$	—		$	—
	Federal Agency Mortgage Backed Securities	16,220			—			16,220			—
	Municipal Obligations	30,771			—			30,771			—
	Corporate Obligations	15,121			—			15,121			—
	Subtotal, Debt Securities	92,139			30,027			62,112			—
	Common Stock	110,649			110,649			—			—
	Common Collective Trust-Equity Funds	16,760			—			16,760			—
	Cash and Cash Equivalents	9,500			9,500			—			—
	Total available for sale	$	229,048		$	150,176		$	78,872		$	—
	Description of Securities	Fair Value as of December 31, 2013			Quoted Prices			Significant			Significant
					in Active			Other			Unobservable
					Markets for			Observable			Inputs
					Identical Assets			Inputs			(Level 3)
					(Level 1)			(Level 2)
	Trading Securities:
	Investments in Debt Securities	$	1,555		$	—		$	—		$	1,555
	Available for sale:
	U.S. Government Bonds	$	25,238		$	25,238		$	—		$	—
	Federal Agency Mortgage Backed Securities	17,794			—			17,794			—
	Municipal Obligations	28,851			—			28,851			—
	Corporate Obligations	13,373			—			13,373			—
	Subtotal, Debt Securities	85,256			25,238			60,018			—
	Common Stock	106,113			106,113			—			—
	Equity Mutual Funds	16,802			16,802			—			—
	Cash and Cash Equivalents	5,924			5,924			—			—
	Total available for sale	$	214,095		$	154,077		$	60,018		$	—

Principles_Of_Preparation_Accr

Principles Of Preparation (Accrued Unbilled Revenues) (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Accounting Policies [Abstract]	'	'
Accrued unbilled revenues	$26.90	$19.80

Principles_Of_Preparation_Supp

Principles Of Preparation (Supplemental Cash Flow Disclosures) (Details) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Supplemental Cash Flow Information [Abstract]	'	'
Interest on long-term debt and borrowing under the revolving credit facility	$37,689	$36,975
Income tax paid (refunded), net	2,969	-36
Restricted Stock	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Common stock issued	3,025	2,607
Performance Shares	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Common stock issued	$0	$849

Accumulated_Other_Comprehensiv2

Accumulated Other Comprehensive Income by Component (Details) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'	'	'
Accumulated Other Comprehensive Income (Loss), beginning balance	$17,730	($60,597)	$2,612	($66,084)	($56,162)	($64,035)
Other Comprehensive Income (Loss) before Reclassifications	733	3,463	18,524	7,383	76,994	4,161
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	-902	972	-3,575	2,539	-3,271	3,712
Accumulated Other Comprehensive Income (Loss), ending balance	17,561	-56,162	17,561	-56,162	17,561	-56,162
Accumulated Defined Benefit Plans Adjustment	'	'	'	'	'	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'	'	'
Accumulated Other Comprehensive Income (Loss), beginning balance	-9,539	-74,198	-21,330	-75,737	-73,133	-75,403
Other Comprehensive Income (Loss) before Reclassifications	0	0	12,147	0	63,518	-1,331
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	-279	1,065	-635	2,604	-203	3,601
Accumulated Other Comprehensive Income (Loss), ending balance	-9,818	-73,133	-9,818	-73,133	-9,818	-73,133
Accumulated Net Unrealized Investment Gain (Loss)	'	'	'	'	'	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'	'	'
Accumulated Other Comprehensive Income (Loss), beginning balance	39,483	26,030	36,240	22,194	29,335	23,994
Other Comprehensive Income (Loss) before Reclassifications	733	3,463	6,377	7,383	13,476	5,492
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	-691	-158	-3,092	-242	-3,286	-151
Accumulated Other Comprehensive Income (Loss), ending balance	39,525	29,335	39,525	29,335	39,525	29,335
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges	'	'	'	'	'	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'	'	'
Accumulated Other Comprehensive Income (Loss), beginning balance	-12,214	-12,429	-12,298	-12,541	-12,364	-12,626
Other Comprehensive Income (Loss) before Reclassifications	0	0	0	0	0	0
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	68	65	152	177	218	262
Accumulated Other Comprehensive Income (Loss), ending balance	($12,146)	($12,364)	($12,146)	($12,364)	($12,146)	($12,364)

Accumulated_Other_Comprehensiv3

Accumulated Other Comprehensive Income Amounts Reclassified (Details) (USD $)	3 Months Ended				9 Months Ended				12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]	'		'		'		'		'		'
Prior service benefit	$2,065		$1,369		$5,594		$4,169		$6,985		$5,610
Unrealized Losses on Available-for-Sale Securities included in Pre-Tax Income	0		0		0		0		0		313
Interest on long-term debt and revolving credit facility	-11,595		-12,095		-35,064		-35,854		-46,922		-46,985
Income tax expense	22,662		27,084		38,898		46,328		36,225		48,001
Net income (loss)	52,301		50,415		86,894		87,143		88,093		91,958
Reclassification out of Accumulated Other Comprehensive Income	'		'		'		'		'		'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'		'		'		'		'		'
Net income (loss)	902		-972		3,575		-2,539		3,271		-3,712
Reclassification out of Accumulated Other Comprehensive Income | Accumulated Defined Benefit Plans Adjustment	'		'		'		'		'		'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'		'		'		'		'		'
Prior service benefit	2,065	[1]	1,369	[1]	5,594	[1]	4,169	[1]	6,985	[1]	5,610	[1]
Net Loss	-1,615	[1]	-2,903	[1]	-4,567	[1]	-8,323	[1]	-6,716	[1]	-11,316	[1]
Income (Loss) before income tax	450	[1]	-1,534	[1]	1,027	[1]	-4,154	[1]	269	[1]	-5,706	[1]
Income tax expense	-171		469		-392		1,550		-66		2,105
Net income (loss)	279	[1]	-1,065	[1]	635	[1]	-2,604	[1]	203	[1]	-3,601	[1]
Reclassification out of Accumulated Other Comprehensive Income | Accumulated Net Unrealized Investment Gain (Loss)	'		'		'		'		'		'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'		'		'		'		'		'
Net Realized Gain on Sale of Securities	824		199		3,791		287		4,057		474
Unrealized Losses on Available-for-Sale Securities included in Pre-Tax Income	0		0		0		0		0		-313
Income (Loss) before income tax	824		199		3,791		287		4,057		161
Income tax expense	-133		-41		-699		-45		-771		-10
Net income (loss)	691		158		3,092		242		3,286		151
Reclassification out of Accumulated Other Comprehensive Income | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges	'		'		'		'		'		'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'		'		'		'		'		'
Interest on long-term debt and revolving credit facility	-110		-104		-326		-306		-431		-405
Income (Loss) before income tax	-110		-104		-326		-306		-431		-405
Income tax expense	42		39		174		129		213		143
Net income (loss)	($68)		($65)		($152)		($177)		($218)		($262)
[1]	These items are included in the computation of net periodic benefit cost. See Note I, Employee Benefits, for additional information.

Regulation_Narrative_Details

Regulation (Narrative) (Details) (USD $)

9 Months Ended

0 Months Ended

9 Months Ended

0 Months Ended

0 Months Ended

0 Months Ended

0 Months Ended

9 Months Ended

0 Months Ended

9 Months Ended

0 Months Ended

9 Months Ended

9 Months Ended

12 Months Ended

0 Months Ended

Sep. 30, 2014

Dec. 31, 2013

Aug. 26, 2014

Jul. 11, 2014

Sep. 30, 2014

28-May-14

1-May-14

Sep. 30, 2014

Jan. 14, 2014

Oct. 30, 2013

Jan. 14, 2014

Oct. 30, 2013

Oct. 29, 2013

Nov. 15, 2013

Nov. 15, 2013

Nov. 14, 2013

Jan. 31, 2013

Jul. 11, 2014

Jul. 11, 2014

Mar. 10, 2014

Aug. 18, 2014

Sep. 30, 2014

Aug. 18, 2014

Oct. 30, 2013

Nov. 15, 2013

Sep. 30, 2014

Sep. 30, 2014

Jul. 11, 2014

Jun. 11, 2014

Sep. 30, 2014

Jul. 11, 2014

Sep. 30, 2014

Feb. 28, 2015

Sep. 30, 2015

Apr. 21, 2014

PUCT Docket No. 42779

PUCT Docket No. 41852

PUCT Docket No. 41852

Fixed Fuel Factor

PUCT

PUCT

NMPRC

NMPRC

NMPRC

NMPRC

NMPRC

FERC

FERC

FERC

FERC

Non-Arbitrage Sales

Arbitrage Sales

MPS To Caliente Transmission Line

MPS In & Out Transmission Line

Caliente - Coyote Transmission Line

MPS To Montwood Transmission Line

Nuclear Fuel Financing

Nuclear Fuel Financing

Montana Power Station

Montana Power Station

Montana Power Station

Montana Power Station

Minimum

Maximum

Four Corners Generating Station

Scenario, Forecast

Scenario, Forecast

Suit Against Department of Energy for Spent Fuel

PUCT Docket No. 42384

PUCT Docket No. 41852

PUCT Docket No. 41852

PUCT Docket No. 41360

PUCT Docket No. 41359

kV

PUCT Docket No. 41809

NMPRC

FERC

PUCT

NMPRC

Phase II of Construction

Phase II of Construction

PUCT Docket No. 41852

PUCT Docket No. 42384

PUCT Docket No. 42779

kV

kV

kV

PUCT

NMPRC

MW

MW

Public Utilities Requested Performance Incentive Bonus Related To Energy Efficiency Program

'

'

'

'

'

'

$2,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Fixed Fuel Factor Revision Period, in Months

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'4 months

'

'

'

'

'

Increase (Decrease) In Fixed Fuel Factor

'

'

'

'

'

10,700,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Percent Increase (Decrease) In Fixed Fuel Factor

'

'

'

'

'

6.90%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Period Of Expected Increases In Prices For Natural Gas

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'12 months

'

'

Public Utility Requested Surcharge

'

'

19,900,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Public Utility Requested Surcharge Collecting Period

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'12 months

'

Settlement Agreement, Counterparty's Name

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'United States Department of Energy

Undercollection of fuel revenues

10,781,000

7,248,000

'

'

'

'

'

10,700,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Reconcilable Fuel Expense

'

'

'

545,300,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Fuel Reconciliation Period

'

'

'

'45 months

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Fuel Reconciliation Settlement, Increase (Decrease) in Income Before Tax

'

'

'

'

2,100,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Rewards For Operations Requested

'

'

'

3,400,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Disallowed Reconcilable Fuel Expense

'

'

'

1,750,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Disallowed Reconcilable Fuel Expense, Reserve

'

'

'

500,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Intervenor Reimbursed Expenses

'

'

'

100,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Accrued Reclamation Costs, Allowed

'

'

'

70,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Date participation is ceased

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

6-Jul-16

'

'

'

Customers' Percentage of Off System Sales Margins

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

100.00%

50.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Retained Percentage Of Off System Sales Margins, Period Covered Start Date

'

'

'

1-Apr-14

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Retained Percentage Of Off System Sales Margins, Period Covered End Date

'

'

'

30-Jun-15

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Retained Percentage of Off System Sales Margins

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

10.00%

'

'

'

'

Number of power generation units authorized to be constructed

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

4

4

2

2

'

'

'

'

'

'

Electric Capacity

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

115

115

115

115

'

'

'

'

88

88

'

'

'

'

'

'

Number Of Transmission Lines

3

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Line of Credit Facility, Current Borrowing Capacity

'

'

'

'

'

'

'

'

'

'

300,000,000

400,000,000

300,000,000

'

400,000,000

300,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Line of Credit Facility, Expiration Period

'

'

'

'

'

'

'

'

'

'4 years

'

'

'

'4 years

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Debt Instrument, Face Amount

'

'

'

'

'

'

'

'

'

'

'

300,000,000

'

'

300,000,000

'

'

'

'

'

'

'

'

50,000,000

50,000,000

'

'

'

'

'

'

'

'

'

'

Line of Credit Facility, Increase (Decrease), Net

'

'

'

'

'

'

'

'

100,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Line of Credit Facility, Maximum Borrowing Capacity

'

'

'

'

'

'

'

'

'

'

400,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Line of Credit Facility, Expiration Date

'

'

'

'

'

'

'

'

14-Jan-19

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Line of Credit renewal option, renewal times

'

'

'

'

'

'

'

'

2

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Line of Credit renewal term, year

'

'

'

'

'

'

'

'

'1 year

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Refund Related to Dispute

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$1,900,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Palo_Verde_Narrative_Details

Palo Verde (Narrative) (Details) (USD $)

0 Months Ended

3 Months Ended

0 Months Ended

6 Months Ended

In Millions, unless otherwise specified

16-May-14

Apr. 21, 2014

17-May-12

Sep. 30, 2014

Apr. 21, 2014

17-May-12

Apr. 21, 2014

Oct. 31, 2014

Oct. 08, 2014

Oct. 31, 2014

Oct. 31, 2014

Oct. 31, 2014

Oct. 08, 2014

Jun. 30, 2015

Jun. 30, 2015

Suit Against Department of Energy for Spent Fuel

Suit Against Department of Energy for Spent Fuel

Suit Against Department of Energy for Spent Fuel

Subsequent Event

Subsequent Event

Subsequent Event

Subsequent Event

Subsequent Event

Subsequent Event

Minimum

Maximum

APS and Palo Verde Participants

Suit Against Department of Energy for Spent Fuel

Suit Against Department of Energy for Spent Fuel

Suit Against Department of Energy for Spent Fuel

Suit Against Department of Energy for Spent Fuel

Scenario, Forecast

Scenario, Forecast

APS and Palo Verde Participants

Palo Verde Generating Station

Palo Verde Generating Station

Jointly Owned Utility Plant Interests [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Reimbursement anticipated to be received, date

'

'

'

'

'

'

'

'

'

'

'

'

'

1-Jan-15

30-Jun-15

Settlement Agreement, Counterparty's Name

'

'

'

'

'United States Department of Energy

'

'

'

'

'

'

'

'

'

'

Lawsuit Filing Date

'

'

'May 17, 2012

'

'

'

'

'October 31, 2014

'

'

'

'

'

'

'

Settlement Agreement, Date

'

'

'

'

'April 21, 2014

'

'

'

'

'

'

'

'

'

'

Name of Federal Authority or Agency

'

'Department of Justice

'

'

'

'

'

'

'

'

'

'

'

'

'

Settlement, Amount

'

'

'

'

'

'

$57

'

'

'

'

'

$9.10

'

'

Litigation Covered Period Start Date

'

'

'

'

'

1-Jan-07

'

'

'

1-Jul-11

'

'

'

'

'

Litigation Covered Period End Date

'

'

'

'

'

30-Jun-11

'

'

'

30-Jun-14

'

'

'

'

'

Reimbursement requested, Amount

'

'

'

'

'

'

'

'

'

'

$42.50

$6.70

'

'

'

Settlement Agreement Award Received, Date

'

'

'

'

'

'

'

'

8-Oct-14

'

'

'

'

'

'

DOE award refunded to customers, date

'

'

'

30-Sep-14

'

'

'

'

'

'

'

'

'

'

'

Spent Nuclear Fuel Disposal Fee, per kWh

'

'

'

0.001

'

'

'

'

'

'

'

'

'

'

'

Period to Conduct an Adequacy Assessment Analysis

'

'

'

'6 months

'

'

'

'

'

'

'

'

'

'

'

One-Mill Fee Suspended, Date

16-May-14

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Common_Stock_Narrative_Details

Common Stock (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Dividends, Common Stock, Cash	$11.30	$10.70	$33.30	$31.40	$43.90	$41.40

Common_Stock_Basic_And_Diluted

Common Stock (Basic And Diluted Earnings Per Share) (Details) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Class of Stock Disclosures [Abstract]	'	'	'	'	'	'
Basic number of common shares outstanding	40,213,741	40,132,250	40,181,367	40,107,555	40,169,801	40,084,525
Dilutive effect of unvested performance awards	51,069	0	27,634	16,071	20,726	28,122
Dilutive effect of stock options	'	'	'	'	0	2,274
Diluted number of common shares outstanding	40,264,810	40,132,250	40,209,001	40,123,626	40,190,527	40,114,921
Net income	$52,476	$50,565	$87,187	$87,392	$88,378	$92,211
Income allocated to participating restricted stock	-175	-150	-293	-249	-285	-253
Net income available to common shareholders, basic	52,301	50,415	86,894	87,143	88,093	91,958
Income reallocated to participating restricted stock	-175	-150	-293	-249	-285	-253
Net income available to common shareholders, diluted	$52,301	$50,415	$86,894	$87,143	$88,093	$91,958
Earnings Per Share, Basic, Distributed	$0.28	$0.27	$0.83	$0.78	$1.09	$1.03
Earnings Per Share, Basic, Undistributed	$1.02	$1.00	$1.34	$1.39	$1.10	$1.26
Basic net income per common share	$1.30	$1.26	$2.16	$2.17	$2.19	$2.29
Earnings Per Share, Diluted, Distributed	$0.28	$0.27	$0.83	$0.78	$1.09	$1.03
Earnings Per Sare, Diluted, Undistributed	$1.02	$1.00	$1.34	$1.39	$1.10	$1.26
Diluted net income per common share	$1.30	$1.26	$2.16	$2.17	$2.19	$2.29

Common_Stock_Antidilutive_Secu

Common Stock (Antidilutive Securities Excluded From Computation Of Earnings Per Share) (Details)	3 Months Ended				9 Months Ended				12 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Performance shares payout based upon performance	0		0		0		0		0		0
Performance shares payout level	100.00%		100.00%		100.00%		100.00%		100.00%		100.00%
Restricted Stock	'		'		'		'		'		'
Antidilutive Securities Excluded from the Computation of Diluted Earnings Per Share, Amount	59,627		54,224		60,264		49,455		59,296		47,636
Performance Shares	'		'		'		'		'		'
Antidilutive Securities Excluded from the Computation of Diluted Earnings Per Share, Amount	48,733	[1]	124,997	[1]	87,784	[1]	111,726	[1]	88,575	[1]	105,090	[1]
[1]	Certain performance shares were excluded from the computation of diluted earnings per share as no payouts would have been required based upon performance at the end of each corresponding period.

Income_Taxes_Income_Tax_Rates_

Income Taxes (Income Tax Rates) (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Income Tax [Line Items]	'	'	'	'	'	'
Consolidated effective tax rate	30.20%	34.90%	30.90%	34.60%	29.10%	34.20%
Federal statutory tax rate	35.00%	35.00%	35.00%	35.00%	35.00%	35.00%
Income tax rate capital gains	'	'	20.00%	'	'	'

Income_Taxes_Details

Income Taxes (Details) (USD $)	3 Months Ended	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2014	Sep. 30, 2014	Sep. 30, 2014	Sep. 30, 2014	Sep. 30, 2014	Sep. 30, 2014	Sep. 30, 2014
	Internal Revenue Service (IRS)	Internal Revenue Service (IRS)	NEW MEXICO	TEXAS	TEXAS	Settlement with Taxing Authority	Settlement with Taxing Authority	Settlement with Taxing Authority
		Maximum	Maximum	Earliest Tax Year	Latest Tax Year	ARIZONA	ARIZONA	ARIZONA
						Earliest Tax Year	Latest Tax Year	Maximum
Income Tax [Line Items]	'	'	'	'	'	'	'	'
Tax Year Closed	'	'2008	'2008	'	'	'1998	'2007	'2008
Income Tax Examination, Year under Examination	'	'	'	'2007	'2011	'	'	'
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities	$2.80	'	'	'	'	'	'	'

Income_Taxes_Unrecognized_Tax_

Income Taxes (Unrecognized Tax Benefits) [Roll Forward] (Details) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]	'	'
Balance at beginning of period	$7,200	$9,800
Additions for tax positions of prior years	300	800
Reductions for tax positions of prior years	-2,800	-4,100
Balance at end of period	$4,700	$6,500

Commitments_Contingencies_And_1

Commitments, Contingencies And Uncertainties (Power Purchase and Sale Contracts) (Details) (Macho Springs Solar)	9 Months Ended
	Sep. 30, 2014
	MW
Macho Springs Solar	'
Long-term Contract for Purchase of Electric Power [Line Items]	'
Plant Capacity	50
Plant Commercial Operation Date	23-May-14

Commitments_Contingencies_And_2

Commitments, Contingencies And Uncertainties (Narrative) (Details) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014
Loss Contingencies [Line Items]	'
GHG Emission Level, Percentage	17.00%
Four Corners Coal Plant Participants	'
Loss Contingencies [Line Items]	'
Public Utilities, Assessed Coal Severance Surtax Penalty and Interest	$30
Four Corners Generating Station	'
Loss Contingencies [Line Items]	'
Accrual for Environmental Loss Contingencies	0.5
Public Utilities, Assessed Coal Severance Surtax Penalty and Interest	1.5
Four Corners Generating Station	'
Loss Contingencies [Line Items]	'
Cost of Pollution Control Equipment	$39
Four Corners Generating Station	'
Loss Contingencies [Line Items]	'
Date participation is ceased	6-Jul-16

Employee_Benefits_Retirement_P

Employee Benefits (Retirement Plans And Other Postretirement Benefits) (Details) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Retirement Income Plan	'	'	'	'	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'	'	'	'	'
Service cost	$2,112	$2,166	$6,474	$6,996	$8,805	$9,204
Interest cost	3,691	3,410	11,351	10,210	14,755	13,600
Expected return on plan assets	-4,681	-4,281	-14,017	-12,831	-18,294	-16,442
Amortization of prior service (benefit) cost	-877	23	-2,030	73	-2,006	101
Amortization of net (gain) loss	2,283	2,903	6,571	8,323	9,346	11,162
Net periodic benefit cost (benefit)	2,528	4,221	8,349	12,771	12,606	17,625
Other Postretirement Benefit Plans, Defined Benefit	'	'	'	'	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'	'	'	'	'
Service cost	712	972	2,134	3,172	2,805	4,266
Interest cost	1,115	1,292	3,347	4,042	4,461	5,455
Expected return on plan assets	-529	-485	-1,587	-1,435	-2,103	-1,864
Amortization of prior service (benefit) cost	-1,188	-1,392	-3,564	-4,242	-4,979	-5,711
Amortization of net (gain) loss	-668	0	-2,004	0	-2,630	154
Net periodic benefit cost (benefit)	($558)	$387	($1,674)	$1,537	($2,446)	$2,300

Employee_Benefits_Narrative_De

Employee Benefits (Narrative) (Details) (USD $)	0 Months Ended					0 Months Ended	9 Months Ended
	Feb. 28, 2014	Feb. 28, 2014	Dec. 31, 2013	Feb. 28, 2014	Dec. 31, 2013	Apr. 01, 2014	Sep. 30, 2014	Feb. 28, 2014
		Retirement Income Plan	Retirement Income Plan	Excess Benefit Plan	Excess Benefit Plan	Retirement Plans	Retirement Plans	Retirement Plans
Defined Benefit Plan Disclosure [Line Items]	'	'	'	'	'	'	'	'
Defined Benefit Plan, Employer Contribution	'	'	'	'	'	'	$10,400,000	'
Defined Benefit Plan, Expected Contributions in Current Fiscal Year	'	'	'	'	'	'	10,900,000	'
Defined benefit plans revisions effective date	'	'	'	'	'	1-Apr-14	'	'
Defined Benefit Plan, Remeasurement Date	28-Feb-14	'	'	'	'	'	'	'
Defined Benefit Plan, Discount Rate	'	4.60%	4.90%	4.50%	4.90%	'	'	'
Defined Benefit Plan, Decrease in Accumulated Benefit Obligation due to Plan Amendment	'	'	'	'	'	'	'	19,700,000
Increase in Other Comprehensive Income Arising During Period, before Tax	'	'	'	'	'	'	'	19,700,000
Defined Benefit Plan Increase in Expected Future Benefit Payments due to Plan Amendment	'	'	'	'	'	'	21,700,000	'
Defined Benefit Plan, Decrease in Net Periodic Benefit Cost due to Plan Amendment	'	'	'	'	'	'	$6,200,000	'

Recovered_Sheet1

Financial Instruments and Investments (Carrying Amount and Fair Value Amounts) (Details) (USD $)	Sep. 30, 2014		Dec. 31, 2013
In Thousands, unless otherwise specified
Carrying (Reported) Amount, Fair Value Disclosure	'		'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'
Debt Instrument, Fair Value Disclosure	$1,089,216		$1,013,972
Estimate of Fair Value, Fair Value Disclosure	'		'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'
Debt Instrument, Fair Value Disclosure	1,244,680		1,058,707
Pollution Control Bonds | Carrying (Reported) Amount, Fair Value Disclosure	'		'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'
Debt Instrument, Fair Value Disclosure	193,135		193,135
Pollution Control Bonds | Estimate of Fair Value, Fair Value Disclosure	'		'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'
Debt Instrument, Fair Value Disclosure	209,049		193,990
Senior Notes | Carrying (Reported) Amount, Fair Value Disclosure	'		'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'
Debt Instrument, Fair Value Disclosure	696,553		696,485
Senior Notes | Estimate of Fair Value, Fair Value Disclosure	'		'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'
Debt Instrument, Fair Value Disclosure	828,958		734,515
RGRT Senior Notes | Carrying (Reported) Amount, Fair Value Disclosure	'		'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'
Debt Instrument, Fair Value Disclosure	110,000	[1]	110,000	[1]
RGRT Senior Notes | Estimate of Fair Value, Fair Value Disclosure	'		'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'
Debt Instrument, Fair Value Disclosure	117,145	[1]	115,850	[1]
Revolving Credit Facility | Carrying (Reported) Amount, Fair Value Disclosure	'		'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'
Debt Instrument, Fair Value Disclosure	89,528	[1]	14,352	[1]
Revolving Credit Facility | Estimate of Fair Value, Fair Value Disclosure	'		'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'
Debt Instrument, Fair Value Disclosure	$89,528	[1]	$14,352	[1]
[1]	Nuclear fuel financing as of SeptemberB 30, 2014 and DecemberB 31, 2013 is funded through the $110 million RGRT Senior Notes and $17.5 million and $14.4 million, respectively under the RCF. As of SeptemberB 30, 2014, $72.0 million was outstanding under the RCF for working capital or general corporate purposes. As of DecemberB 31, 2013, no amount was outstanding under the RCF for working capital or general corporate purposes. The interest rate on the Company's borrowings under the RCF is reset throughout the quarter reflecting current market rates. Consequently, the carrying value approximates fair value.

Financial_Instruments_And_Inve2

Financial Instruments And Investments (Long-Term Debt and Short-Term Borrowings - Narratives) (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2014	Dec. 31, 2013	Aug. 18, 2010
In Thousands, unless otherwise specified			Nuclear Fuel Financing	Nuclear Fuel Financing	Working Capital and General Purpose	Working Capital and General Purpose	RGRT Senior Notes
Financial Instruments and Investments [Line Items]	'	'	'	'	'	'	'
Debt Instrument, Face Amount	'	'	'	'	'	'	$110,000
Line of Credit Facility, Amount Outstanding	'	'	17,500	14,400	72,000	0	'
Decommissioning Fund Investments	$229,048	$214,095	'	'	'	'	'

Financial_Instruments_And_Inve3

Financial Instruments And Investments (Marketable Securities Fair Value And Unrealized Losses) (Details) (USD $)	9 Months Ended		12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014		Dec. 31, 2013
	securities		securities
Financial Instruments and Investments [Line Items]	'		'
Marketable Securities Fair Value Less than 12 Months	$25,417	[1]	$32,433	[2]
Marketable Securities Unrealized Losses Less Than 12 Months	-335	[1]	-971	[2]
Marketable Securities Fair Value 12 Months or Longer	32,433	[1]	20,970	[2]
Marketable Securities Unrealized Losses 12 Months or Longer	-1,530	[1]	-1,492	[2]
Marketable Securities Fair Value Total	57,850	[1]	53,403	[2]
Marketable Securities Unrealized Losses Total	-1,865	[1]	-2,463	[2]
Number of securities	101		122
Debt Securities	'		'
Financial Instruments and Investments [Line Items]	'		'
Marketable Securities Fair Value Less than 12 Months	7,856	[1]	30,128	[2]
Marketable Securities Unrealized Losses Less Than 12 Months	-59	[1]	-845	[2]
Marketable Securities Fair Value 12 Months or Longer	32,433	[1]	20,970	[2]
Marketable Securities Unrealized Losses 12 Months or Longer	-1,530	[1]	-1,492	[2]
Marketable Securities Fair Value Total	40,289	[1]	51,098	[2]
Marketable Securities Unrealized Losses Total	-1,589	[1]	-2,337	[2]
Collateralized Mortgage Backed Securities	'		'
Financial Instruments and Investments [Line Items]	'		'
Marketable Securities Fair Value Less than 12 Months	874	[1]	6,444	[2]
Marketable Securities Unrealized Losses Less Than 12 Months	-6	[1]	-169	[2]
Marketable Securities Fair Value 12 Months or Longer	2,371	[1]	1,421	[2]
Marketable Securities Unrealized Losses 12 Months or Longer	-113	[1]	-119	[2]
Marketable Securities Fair Value Total	3,245	[1]	7,865	[2]
Marketable Securities Unrealized Losses Total	-119	[1]	-288	[2]
U.S. Government Bonds	'		'
Financial Instruments and Investments [Line Items]	'		'
Marketable Securities Fair Value Less than 12 Months	1,223	[1]	8,114	[2]
Marketable Securities Unrealized Losses Less Than 12 Months	-4	[1]	-245	[2]
Marketable Securities Fair Value 12 Months or Longer	16,322	[1]	10,866	[2]
Marketable Securities Unrealized Losses 12 Months or Longer	-799	[1]	-840	[2]
Marketable Securities Fair Value Total	17,545	[1]	18,980	[2]
Marketable Securities Unrealized Losses Total	-803	[1]	-1,085	[2]
Municipal Bonds	'		'
Financial Instruments and Investments [Line Items]	'		'
Marketable Securities Fair Value Less than 12 Months	4,344	[1]	12,286	[2]
Marketable Securities Unrealized Losses Less Than 12 Months	-34	[1]	-335	[2]
Marketable Securities Fair Value 12 Months or Longer	11,679	[1]	7,782	[2]
Marketable Securities Unrealized Losses 12 Months or Longer	-532	[1]	-479	[2]
Marketable Securities Fair Value Total	16,023	[1]	20,068	[2]
Marketable Securities Unrealized Losses Total	-566	[1]	-814	[2]
Corporate Debt Securities	'		'
Financial Instruments and Investments [Line Items]	'		'
Marketable Securities Fair Value Less than 12 Months	1,415	[1]	3,284	[2]
Marketable Securities Unrealized Losses Less Than 12 Months	-15	[1]	-96	[2]
Marketable Securities Fair Value 12 Months or Longer	2,061	[1]	901	[2]
Marketable Securities Unrealized Losses 12 Months or Longer	-86	[1]	-54	[2]
Marketable Securities Fair Value Total	3,476	[1]	4,185	[2]
Marketable Securities Unrealized Losses Total	-101	[1]	-150	[2]
Equity Securities	'		'
Financial Instruments and Investments [Line Items]	'		'
Marketable Securities Fair Value Less than 12 Months	801	[1]	2,305	[2]
Marketable Securities Unrealized Losses Less Than 12 Months	-137	[1]	-126	[2]
Marketable Securities Fair Value 12 Months or Longer	0	[1]	0	[2]
Marketable Securities Unrealized Losses 12 Months or Longer	0	[1]	0	[2]
Marketable Securities Fair Value Total	801	[1]	2,305	[2]
Marketable Securities Unrealized Losses Total	-137	[1]	-126	[2]
Common Collective Trust - Equity Funds	'		'
Financial Instruments and Investments [Line Items]	'		'
Marketable Securities Fair Value Less than 12 Months	16,760	[1]	'
Marketable Securities Unrealized Losses Less Than 12 Months	-139	[1]	'
Marketable Securities Fair Value 12 Months or Longer	0	[1]	'
Marketable Securities Unrealized Losses 12 Months or Longer	0	[1]	'
Marketable Securities Fair Value Total	16,760	[1]	'
Marketable Securities Unrealized Losses Total	($139)	[1]	'
[1]	Includes approximately 101 securities.
[2]	Includes approximately 122 securities.

Financial_Instruments_And_Inve4

Financial Instruments And Investments (Unrecognized Gross Unrealized Gains And The Fair Value) (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities, Unrealized Gain Position, Fair Value	$171,198	$160,692
Available-for-sale Securities, Gross Unrealized Gain	51,284	47,741
Debt Securities	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities, Unrealized Gain Position, Fair Value	51,850	34,158
Available-for-sale Securities, Gross Unrealized Gain	2,224	1,515
Collateralized Mortgage Backed Securities	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities, Unrealized Gain Position, Fair Value	12,975	9,929
Available-for-sale Securities, Gross Unrealized Gain	586	433
U.S. Government Bonds	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities, Unrealized Gain Position, Fair Value	12,482	6,258
Available-for-sale Securities, Gross Unrealized Gain	279	126
Municipal Bonds	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities, Unrealized Gain Position, Fair Value	14,748	8,783
Available-for-sale Securities, Gross Unrealized Gain	630	450
Corporate Debt Securities	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities, Unrealized Gain Position, Fair Value	11,645	9,188
Available-for-sale Securities, Gross Unrealized Gain	729	506
Equity Securities	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities, Unrealized Gain Position, Fair Value	109,848	103,808
Available-for-sale Securities, Gross Unrealized Gain	49,060	43,145
Equity Mutual Funds	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities, Unrealized Gain Position, Fair Value	0	16,802
Available-for-sale Securities, Gross Unrealized Gain	0	3,081
Cash and Cash Equivalents	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities, Unrealized Gain Position, Fair Value	9,500	5,924
Available-for-sale Securities, Gross Unrealized Gain	$0	$0

Financial_Instruments_And_Inve5

Financial Instruments And Investments (Contractual Year For Maturity Of Available-For-Sale Securities ) (Details) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014
Schedule of Available-for-sale Securities [Line Items]	'
Contractual Maturity Due For, Mortgaged Backed Securities	'10 years
Municipal Bonds	'
Schedule of Available-for-sale Securities [Line Items]	'
Total	30,771
2014	0
2015 through 2018	11,151
2019 through 2023	15,911
2024 and Beyond	3,709
Corporate Debt Obligations	'
Schedule of Available-for-sale Securities [Line Items]	'
Total	15,121
2014	0
2015 through 2018	3,267
2019 through 2023	7,441
2024 and Beyond	4,413
U.S. Government Bonds	'
Schedule of Available-for-sale Securities [Line Items]	'
Total	30,027
2014	0
2015 through 2018	15,931
2019 through 2023	7,236
2024 and Beyond	6,860
Minimum	'
Schedule of Available-for-sale Securities [Line Items]	'
Debt Instrument, Expected Weighted Average Maturity Year	'3 years
Maximum	'
Schedule of Available-for-sale Securities [Line Items]	'
Debt Instrument, Expected Weighted Average Maturity Year	'8 years

Financial_Instruments_And_Inve6

Financial Instruments And Investments (Unrealized Holding Losses Included In Pre-Tax Income) (Details) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Investments, Debt and Equity Securities [Abstract]	'	'	'	'	'	'
Unrealized losses included in pre-tax income	$0	$0	$0	$0	$0	$313

Financial_Instruments_And_Inve7

Financial Instruments And Investments (Sale Of Securities And The Related Effects On Pre-Tax Income ) (Details) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Investment [Line Items]	'	'	'	'	'	'
Proceeds from sales of available-for-sale securities	$10,980	$7,057	$47,355	$29,419	$74,083	$53,866
Gross realized gains included in pre-tax income	1,239	212	4,502	593	4,895	814
Gross realized losses included in pre-tax income	-415	-13	-711	-306	-838	-340
Other than temporary impairment losses, recognized in earnings before tax	0	0	0	0	0	-313
Net unrealized holding gains (losses) included in accumulated other comprehensive income	897	4,300	7,965	8,861	16,803	6,802
Net gains (losses) in pre-tax income	824	199	3,791	287	4,057	161
Net gains (losses) in other comprehensive income	$73	$4,101	$4,174	$8,574	$12,746	$6,641

Financial_Instruments_And_Inve8

Financial Instruments And Investments (Company's Decommissioning Trust Funds And Investments In Debt Securities) (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Decommissioning Fund Investments	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	$229,048	$214,095
Decommissioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1)	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	150,176	154,077
Decommissioning Fund Investments | Significant Other Observable Inputs (Level 2)	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	78,872	60,018
Decommissioning Fund Investments | Significant Unobservable Inputs (Level 3)	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	0	0
Debt Securities	'	'
Financial Instruments and Investments [Line Items]	'	'
Investments in Debt Securities	1,608	1,555
Debt Securities | Quoted Prices In Active Markets For Identical Assets (Level 1)	'	'
Financial Instruments and Investments [Line Items]	'	'
Investments in Debt Securities	0	0
Debt Securities | Significant Other Observable Inputs (Level 2)	'	'
Financial Instruments and Investments [Line Items]	'	'
Investments in Debt Securities	0	0
Debt Securities | Significant Unobservable Inputs (Level 3)	'	'
Financial Instruments and Investments [Line Items]	'	'
Investments in Debt Securities	1,608	1,555
Debt Securities | Decommissioning Fund Investments	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	92,139	85,256
Debt Securities | Decommissioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1)	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	30,027	25,238
Debt Securities | Decommissioning Fund Investments | Significant Other Observable Inputs (Level 2)	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	62,112	60,018
Debt Securities | Decommissioning Fund Investments | Significant Unobservable Inputs (Level 3)	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	0	0
U.S. Government Bonds | Decommissioning Fund Investments	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	30,027	25,238
U.S. Government Bonds | Decommissioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1)	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	30,027	25,238
U.S. Government Bonds | Decommissioning Fund Investments | Significant Other Observable Inputs (Level 2)	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	0	0
U.S. Government Bonds | Decommissioning Fund Investments | Significant Unobservable Inputs (Level 3)	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	0	0
Collateralized Mortgage Backed Securities | Decommissioning Fund Investments	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	16,220	17,794
Collateralized Mortgage Backed Securities | Decommissioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1)	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	0	0
Collateralized Mortgage Backed Securities | Decommissioning Fund Investments | Significant Other Observable Inputs (Level 2)	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	16,220	17,794
Collateralized Mortgage Backed Securities | Decommissioning Fund Investments | Significant Unobservable Inputs (Level 3)	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	0	0
Municipal Bonds | Decommissioning Fund Investments	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	30,771	28,851
Municipal Bonds | Decommissioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1)	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	0	0
Municipal Bonds | Decommissioning Fund Investments | Significant Other Observable Inputs (Level 2)	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	30,771	28,851
Municipal Bonds | Decommissioning Fund Investments | Significant Unobservable Inputs (Level 3)	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	0	0
Corporate Debt Securities | Decommissioning Fund Investments	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	15,121	13,373
Corporate Debt Securities | Decommissioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1)	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	0	0
Corporate Debt Securities | Decommissioning Fund Investments | Significant Other Observable Inputs (Level 2)	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	15,121	13,373
Corporate Debt Securities | Decommissioning Fund Investments | Significant Unobservable Inputs (Level 3)	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	0	0
Equity Securities | Decommissioning Fund Investments	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	110,649	106,113
Equity Securities | Decommissioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1)	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	110,649	106,113
Equity Securities | Decommissioning Fund Investments | Significant Other Observable Inputs (Level 2)	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	0	0
Equity Securities | Decommissioning Fund Investments | Significant Unobservable Inputs (Level 3)	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	0	0
Common Collective Trust - Equity Funds | Decommissioning Fund Investments	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	16,760	'
Common Collective Trust - Equity Funds | Decommissioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1)	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	0	'
Common Collective Trust - Equity Funds | Decommissioning Fund Investments | Significant Other Observable Inputs (Level 2)	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	16,760	'
Common Collective Trust - Equity Funds | Decommissioning Fund Investments | Significant Unobservable Inputs (Level 3)	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	0	'
Equity Mutual Funds | Decommissioning Fund Investments	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	'	16,802
Equity Mutual Funds | Decommissioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1)	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	'	16,802
Equity Mutual Funds | Decommissioning Fund Investments | Significant Other Observable Inputs (Level 2)	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	'	0
Equity Mutual Funds | Decommissioning Fund Investments | Significant Unobservable Inputs (Level 3)	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	'	0
Cash and Cash Equivalents | Decommissioning Fund Investments	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	9,500	5,924
Cash and Cash Equivalents | Decommissioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1)	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	9,500	5,924
Cash and Cash Equivalents | Decommissioning Fund Investments | Significant Other Observable Inputs (Level 2)	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	0	0
Cash and Cash Equivalents | Decommissioning Fund Investments | Significant Unobservable Inputs (Level 3)	'	'
Financial Instruments and Investments [Line Items]	'	'
Available-for-sale Securities	$0	$0