El Paso Electric 10-Q 6 Nov 15 2015 Q3 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	9 Months Ended
	Sep. 30, 2015	Oct. 31, 2015
Document and Entity Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	Q3
Trading Symbol	ee
Entity Registrant Name	EL PASO ELECTRIC CO /TX/
Entity Central Index Key	31,978
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		40,426,668

Balance Sheets

Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Utility plant:
Electric plant in service	$ 3,571,195	$ 3,229,255
Less accumulated depreciation and amortization	(1,311,260)	(1,266,672)
Net plant in service	2,259,935	1,962,583
Construction work in progress	262,591	414,284
Nuclear fuel; includes fuel in process of $39,810 and $46,996, respectively	198,359	185,185
Less accumulated amortization	(85,532)	(73,701)
Net nuclear fuel	112,827	111,484
Net utility plant	2,635,353	2,488,351
Current assets:
Cash and cash equivalents	12,573	40,504
Accounts receivable, principally trade, net of allowance for doubtful accounts of $2,249 and $2,253, respectively	104,321	71,165
Accumulated deferred income taxes	22,602	13,957
Inventories, at cost	49,115	45,889
Under-collection of fuel revenues	2,429	10,253
Prepayments and other	11,403	12,213
Total current assets	202,443	193,981
Deferred charges and other assets:
Decommissioning trust funds	231,885	234,286
Regulatory assets	110,354	112,086
Other	29,843	30,597
Total deferred charges and other assets	372,082	376,969
Total assets	3,209,878	3,059,301
Capitalization:
Common stock, stated value $1 per share, 100,000,000 shares authorized, 65,705,078 and 65,725,246 shares issued, and 135,888 and 124,297 restricted shares, respectively	65,841	65,850
Capital in excess of stated value	319,846	318,515
Retained earnings	1,078,668	1,032,537
Accumulated other comprehensive loss, net of tax	(20,223)	(8,001)
Total stockholders equity subtotal before treasury stock	1,444,132	1,408,901
Treasury stock, 25,414,298 and 25,492,919 shares, respectively, at cost	(423,337)	(424,647)
Common stock equity	1,020,795	984,254
Long-term debt, net of current portion	1,134,258	1,134,179
Total capitalization	2,155,053	2,118,433
Current liabilities:
Current maturities of long-term debt	0	15,000
Short-term borrowings under the revolving credit facility	118,693	14,532
Accounts payable, principally trade	50,742	78,862
Taxes accrued	33,631	28,210
Interest accrued	16,836	12,758
Over-collection of fuel revenues	4,042	932
Other	26,720	24,715
Total current liabilities	250,664	175,009
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes	512,672	474,154
Accrued pension liability	86,502	94,272
Accrued post-retirement benefit liability	63,406	59,342
Asset retirement obligation	79,905	74,577
Regulatory liabilities	24,615	26,099
Other	37,061	37,415
Total deferred credits and other liabilities	$ 804,161	$ 765,859
Commitments and contingencies
Total capitalization and liabilities	$ 3,209,878	$ 3,059,301

Balance Sheets Parenthetical

Balance Sheets Parenthetical - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Nuclear fuel; fuel in process	$ 39,810	$ 46,996
Allowance for Doubtful Accounts Receivable, Current	$ 2,249	$ 2,253
Common Stock, Par or Stated Value Per Share	$ 1	$ 1
Common Stock, Shares Authorized	100,000,000	100,000,000
Common Stock, Shares, Issued	65,705,078	65,725,246
Common stock, restricted shares	135,888	124,297
Treasury Stock, Shares	25,414,298	25,492,919

Statements Of Operations

Statements Of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Operating revenues	$ 289,713	$ 283,645	$ 672,967	$ 720,962	$ 869,530	$ 911,259
Energy expenses:
Fuel	60,798	70,523	148,340	191,781	207,564	243,452
Purchased and interchanged power	19,520	18,071	42,437	54,114	53,127	70,292
Cost of services, energy services	80,318	88,594	190,777	245,895	260,691	313,744
Operating revenues net of energy expenses	209,395	195,051	482,190	475,067	608,839	597,515
Other operating expenses:
Other operations	65,360	59,514	178,615	175,937	241,510	239,282
Maintenance	14,355	15,392	49,772	45,619	69,782	65,427
Depreciation and amortization	22,380	20,685	67,080	62,336	88,086	82,616
Taxes other than income taxes	19,253	17,964	48,844	48,883	62,711	61,848
Utilities operating expense	121,348	113,555	344,311	332,775	462,089	449,173
Operating income	88,047	81,496	137,879	142,292	146,750	148,342
Other income (deductions):
Allowance for equity funds used during construction	1,874	3,848	8,417	10,215	12,864	12,758
Investment and interest income, net	5,912	2,373	12,564	8,537	17,660	10,419
Miscellaneous non-operating income	850	52	1,537	2,159	3,453	3,054
Miscellaneous non-operating deductions	(1,015)	(1,036)	(2,777)	(2,054)	(4,922)	(3,048)
Nonoperating income (expense)	7,621	5,237	19,741	18,857	29,055	23,183
Interest charges (credits):
Interest on long-term debt and revolving credit facility	16,465	14,617	49,443	43,803	64,668	58,609
Other interest	424	438	941	899	1,292	874
Capitalized interest	(1,208)	(1,270)	(3,758)	(3,797)	(5,053)	(5,185)
Allowance for borrowed funds used during construction	(1,353)	(2,190)	(5,365)	(5,841)	(7,892)	(7,376)
Interest expense	14,328	11,595	41,261	35,064	53,015	46,922
Income before income taxes	81,340	75,138	116,359	126,085	122,790	124,603
Income tax expense	24,600	22,662	35,089	38,898	37,279	36,225
Net income	$ 56,740	$ 52,476	$ 81,270	$ 87,187	$ 85,511	$ 88,378
Basic earnings per share	$ 1.400	$ 1.300	$ 2.010	$ 2.160	$ 2.120	$ 2.190
Diluted earnings per share	1.400	1.300	2.010	2.160	2.120	2.190
Dividends declared per share of common stock	$ 0.295	$ 0.280	$ 0.870	$ 0.825	$ 1.150	$ 1.090
Weighted average number of shares outstanding	40,289,010	40,213,741	40,267,533	40,181,367	40,255,439	40,169,801
Weighted average number of shares and dilutive potential shares outstanding	40,329,529	40,264,810	40,299,801	40,209,001	40,279,640	40,190,527

Statements Of Comprehensive Ope

Statements Of Comprehensive Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Net income	$ 56,740	$ 52,476	$ 81,270	$ 87,187	$ 85,511	$ 88,378
Unrecognized pension and post-retirement benefit costs:
Net gain (loss) arising during period	0	0	0	19,700	(74,028)	102,664
Prior service benefit	0	0	0	0	34,200	97
Reclassification adjustments included in net income for amortization of:
Prior service benefit	(1,606)	(2,065)	(4,931)	(5,594)	(6,996)	(6,985)
Net loss	1,966	1,615	6,466	4,567	8,081	6,716
Net unrealized gains/losses on marketable securities:
Net holding gains (losses) arising during period	(8,092)	897	(8,641)	7,965	(5,779)	16,803
Reclassification adjustments for net gains included in net income	(4,324)	(824)	(7,887)	(3,791)	(11,446)	(4,057)
Net losses on cash flow hedges:
Reclassification adjustment for interest expense included in net income	118	110	348	326	460	431
Total other comprehensive income (loss) before income taxes	(11,938)	(267)	(14,645)	23,173	(55,508)	115,669
Income tax benefit (expense) related to items of other comprehensive income (loss):
Unrecognized pension and post-retirement benefit costs	(134)	171	(756)	(7,161)	14,456	(39,177)
Net unrealized losses (gains) on marketable securities	2,459	(31)	3,340	(889)	3,469	(2,556)
Losses on cash flow hedges	(46)	(42)	(161)	(174)	(201)	(213)
Total income tax benefit (expense)	2,279	98	2,423	(8,224)	17,724	(41,946)
Other comprehensive income (loss), net of tax	(9,659)	(169)	(12,222)	14,949	(37,784)	73,723
Comprehensive income	$ 47,081	$ 52,307	$ 69,048	$ 102,136	$ 47,727	$ 162,101

Statements Of Cash Flows

Statements Of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Cash flows from operating activities:
Net income	$ 81,270	$ 87,187
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of electric plant in service	67,080	62,336
Amortization of nuclear fuel	32,864	33,942
Deferred income taxes, net	32,090	35,990
Allowance for equity funds used during construction	(8,417)	(10,215)
Other amortization and accretion	13,273	14,470
Gain on sale of property, plant and equipment	(587)	(2,092)
Net gains on sale of decommissioning trust funds	(7,887)	(3,791)
Other operating activities	387	(52)
Change in:
Accounts receivable	(33,156)	(47,331)
Inventories	(3,226)	(1,000)
Net over-collection (under-collection) of fuel revenues	10,934	(1,233)
Prepayments and other	(5,401)	(4,381)
Accounts payable	(14,397)	3,557
Taxes accrued	8,747	7,669
Interest accrued	4,078	2,202
Other current liabilities	2,005	1,053
Deferred charges and credits	(3,227)	(3,674)
Net cash provided by operating activities	176,430	174,637
Cash flows from investing activities:
Cash additions to utility property, plant and equipment	(211,516)	(189,273)
Cash additions to nuclear fuel	(30,483)	(28,772)
Capitalized interest and AFUDC:
Utility property, plant and equipment	(13,782)	(16,056)
Nuclear fuel	(3,758)	(3,797)
Allowance for equity funds used during construction	8,417	10,215
Decommissioning trust funds:
Purchases, including funding of $3.4 million	(70,016)	(54,343)
Sales and maturities	63,776	47,355
Proceeds from sale of property, plant and equipment	644	2,395
Other investing activities	(627)	4,438
Net cash used for investing activities	(257,345)	(227,838)
Cash flows from financing activities:
Dividends paid	(35,138)	(33,261)
Borrowings under the revolving credit facility:
Proceeds	266,779	186,215
Payments	(162,618)	(111,039)
Payment on maturing RGRT senior notes	(15,000)	0
Other financing activities	(1,039)	(896)
Net cash provided by financing activities	52,984	41,019
Net decrease in cash and cash equivalents	(27,931)	(12,182)
Cash and cash equivalents at beginning of period	40,504	25,592
Cash and cash equivalents at end of period	$ 12,573	$ 13,410

Statements Of Cash Flows Parent

Statements Of Cash Flows Parenthetical - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Payments To Fund Decommissioning Fund	$ 3.4	$ 3.4

Principles Of Preparation

Principles Of Preparation	9 Months Ended
	Sep. 30, 2015
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, 2014 (the " 2014 Form 10-K"). Capitalized terms used in this report and not defined herein have the meaning ascribed to such terms in the 2014 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, 2015 and December 31, 2014 ; the results of its operations and comprehensive operations for the three, nine and twelve months ended September 30, 2015 and 2014 ; and its cash flows for the nine months ended September 30, 2015 and 2014 . The results of operations and comprehensive operations for the three and nine months ended September 30, 2015 and the cash flows for the nine months ended September 30, 2015 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 (the "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 $30.1 million at September 30, 2015 and $21.2 million at December 31, 2014 . The Company presents revenues net of sales taxes in its statements of operations. Supplemental Cash Flow Disclosures (in thousands) Nine Months Ended September 30, 2015 2014 Cash paid (received) for: Interest on long-term debt and borrowing under the revolving credit facility $ 41,406 $ 37,689 Income tax paid (refunded), net (272 ) 2,969 Non-cash investing and financing activities: Changes in accrued plant additions (13,150 ) (3,762 ) Grants of restricted shares of common stock 1,106 3,025 New Accounting Standards. In May 2014, the Financial Accounting Standards Board ("FASB") issued new guidance (Accounting Standards Update ("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 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 was originally intended to be effective for annual periods and interim periods within that reporting period beginning after December 15, 2016, for public business entities. In August 2015, FASB issued ASU 2015-14 to defer the effective date of ASU 2014-09 for all entities by one year. Public business entities will apply the guidance in ASU 2014-09 to annual reporting periods beginning after December 15, 2017 and interim periods within that reporting period. Early adoption of ASU 2014-09 is permitted after December 15, 2016. The Company is currently assessing the future impact of this ASU . In April 2015, the FASB issued ASU 2015-03, Interest - Imputation of Interest (Topic 715) to simplify the presentation of debt issuance costs. ASU 2015-03 requires that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. The recognition and measurement guidance for debt issuance costs are not affected by this ASU. ASU 2015-03 is effective for financial statements issued for fiscal years beginning after December 15, 2015, and interim periods within those fiscal years. In August 2015, FASB issued ASU 2015-15, Interest - Imputation of Interest (Subtopic 835-30), to provide further clarification to ASU 2015-03 as it relates to the presentation and subsequent measurement of debt issuance costs associated with line of credit arrangements. The Company does not expect ASU 2015-03 and ASU 2015-15 to materially impact the Company's results of operations and cash flows. In May 2015, FASB issued ASU 2015-07, Fair Value Measurement (Topic 820) to eliminate the requirement to categorize investments in the fair value hierarchy if the fair value is measured at net asset value ("NAV") per share (or its equivalent) using the practical expedient in the FASB’s fair value measurement gui dance . Reporting entities must still provide sufficient information to enable users to reconcile total investments in the fair value hierarchy and total investments measured at fair value in the financial statements. Additionally, the scope of current disclosure requirements for investments eligible to be measured at NAV will be limited to investments to which the practical expedient is applied. This ASU is effective in fiscal years beginning after December 15, 2015, and interim periods within those fiscal years. The ASU requires retrospective application. Early adoption is permitted. The Company is currently assessing the future impact of this ASU.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Notes)	9 Months Ended
	Sep. 30, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Comprehensive Income (Loss) Note	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, 2015 Three Months Ended September 30, 2014 Unrecognized Pension and Post-retirement Benefit Costs Net Unrealized Gains (Losses) on Marketable Securities Net Losses on Cash Flow Hedges Accumulated Other Comprehensive Income (Loss) Unrecognized Pension and Post-retirement 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 $ (34,331 ) $ 35,726 $ (11,959 ) $ (10,564 ) $ (9,539 ) $ 39,483 $ (12,214 ) $ 17,730 Other comprehensive income (loss) before reclassifications — (6,485 ) — (6,485 ) — 733 — 733 Amounts reclassified from accumulated other comprehensive income (loss) 226 (3,472 ) 72 (3,174 ) (279 ) (691 ) 68 (902 ) Balance at end of period $ (34,105 ) $ 25,769 $ (11,887 ) $ (20,223 ) $ (9,818 ) $ 39,525 $ (12,146 ) $ 17,561 Nine Months Ended September 30, 2015 Nine Months Ended September 30, 2014 Unrecognized Pension and Post-retirement Benefit Costs Net Unrealized Gains (Losses) on Marketable Securities Net Losses on Cash Flow Hedges Accumulated Other Comprehensive Income (Loss) Unrecognized Pension and Post-retirement 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 $ (34,884 ) $ 38,957 $ (12,074 ) $ (8,001 ) $ (21,330 ) $ 36,240 $ (12,298 ) $ 2,612 Other comprehensive income (loss) before reclassifications — (6,854 ) — (6,854 ) 12,147 6,377 — 18,524 Amounts reclassified from accumulated other comprehensive income (loss) 779 (6,334 ) 187 (5,368 ) (635 ) (3,092 ) 152 (3,575 ) Balance at end of period $ (34,105 ) $ 25,769 $ (11,887 ) $ (20,223 ) $ (9,818 ) $ 39,525 $ (12,146 ) $ 17,561 Twelve Months Ended September 30, 2015 Twelve Months Ended September 30, 2014 Unrecognized Pension and Post-retirement Benefit Costs Net Unrealized Gains (Losses) on Marketable Securities Net Losses on Cash Flow Hedges Accumulated Other Comprehensive Income (Loss) Unrecognized Pension and Post-retirement 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 $ (9,818 ) $ 39,525 $ (12,146 ) $ 17,561 $ (73,133 ) $ 29,335 $ (12,364 ) $ (56,162 ) Other comprehensive income (loss) before reclassifications (24,775 ) (4,537 ) — (29,312 ) 63,518 13,476 — 76,994 Amounts reclassified from accumulated other comprehensive income (loss) 488 (9,219 ) 259 (8,472 ) (203 ) (3,286 ) 218 (3,271 ) Balance at end of period $ (34,105 ) $ 25,769 $ (11,887 ) $ (20,223 ) $ (9,818 ) $ 39,525 $ (12,146 ) $ 17,561 Amounts reclassified from accumulated other comprehensive income (loss) for the three, nine and twelve months ended September 30, 2015 and 2014 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 2015 2014 2015 2014 2015 2014 Amortization of pension and post-retirement benefit costs: Prior service benefit $ 1,606 $ 2,065 $ 4,931 $ 5,594 $ 6,996 $ 6,985 (a) Net loss (1,966 ) (1,615 ) (6,466 ) (4,567 ) (8,081 ) (6,716 ) (a) (360 ) 450 (1,535 ) 1,027 (1,085 ) 269 (a) Income tax effect 134 (171 ) 756 (392 ) 597 (66 ) (226 ) 279 (779 ) 635 (488 ) 203 (a) Marketable securities: Net realized gain on sale of securities 4,324 824 7,887 3,791 11,446 4,057 Investment and interest income, net 4,324 824 7,887 3,791 11,446 4,057 Income before income taxes Income tax effect (852 ) (133 ) (1,553 ) (699 ) (2,227 ) (771 ) Income tax expense 3,472 691 6,334 3,092 9,219 3,286 Net income Loss on cash flow hedge: Amortization of loss (118 ) (110 ) (348 ) (326 ) (460 ) (431 ) Interest on long-term debt and revolving credit facility (118 ) (110 ) (348 ) (326 ) (460 ) (431 ) Income before income taxes Income tax effect 46 42 161 174 201 213 Income tax expense (72 ) (68 ) (187 ) (152 ) (259 ) (218 ) Net income Total reclassifications $ 3,174 $ 902 $ 5,368 $ 3,575 $ 8,472 $ 3,271 (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, 2015
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"). Municipal orders, ordinances and other agreements regarding rates and services adopted by Texas municipalities are subject to review and approval by the PUCT. 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, the NMPRC and the FERC are subject to judicial review. Texas Regulatory Matters 2012 Texas Retail Rate Case . 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 discussed below. 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. 2015 Texas Rate Case Filing. On August 10, 2015, the Company filed with the City of El Paso, other municipalities incorporated in its Texas service territory, and the PUCT in Docket No. 44941, a request for an increase in non-fuel base revenues of approximately $71.5 million . The Company has invoked its statutory right to have its new rates relate back for consumption after the 155 th day after the filing (i.e. January 12, 2016). As such, the difference in rates that would have been collected will be surcharged or refunded to customers beginning after the PUCT's final order in Docket No. 44941 which is expected to be early in the second quarter of 2016. The PUCT has the authority to require the Company to surcharge or refund such difference over a period not to exceed eighteen (18) months. The Company cannot predict the outcome of the case at this time. 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 the 2013 energy efficiency program results in accordance with PUCT rules. The PUCT approved the Company's request at its November 14, 2014 open meeting. The Company recorded the $2.0 million bonus as operating revenue in the fourth quarter of 2014. On May 1, 2015, the Company made its annual filing to establish its energy efficiency cost recovery factor for 2016. In addition to projected energy efficiency costs for 2016 and true-up to prior year actual costs, the Company requested approval of a $1.0 million bonus for the 2014 energy efficiency program results in accordance with PUCT rules. This case was assigned PUCT Docket No. 44677. A stipulation and settlement agreement was filed September 24, 2015 and the PUCT approved the settlement on November 5, 2015. The settlement approved by the PUCT includes a performance bonus of $1.0 million . 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. The Texas Fuel Rule requires the Company to request to refund fuel costs in any month when the over-recovery balance exceeds a threshold material amount and it expects fuel costs to continue to be materially over-recovered. The Texas Fuel Rule also permits the Company to seek to surcharge fuel under-recoveries in any month the balance exceeds a threshold material amount and it expects fuel cost recovery to continue to be materially under-recovered. Fuel over- and under-recoveries are considered material when they exceed 4% of the previous twelve months' fuel costs. All such fuel revenue and expense activities are subject to periodic final review by the PUCT in fuel reconciliation proceedings. On April 15, 2015, the Company filed a request, which was assigned PUCT Docket No. 44633, to reduce its fixed fuel factor by approximately 24% to reflect an expected reduction in fuel expense. The over-recovered balance was below the materiality threshold. The reduction in the fixed fuel factor was effective on an interim basis May 1, 2015 and approved by the PUCT on May 20, 2015 . As of September 30, 2015, the Company had under-recovered fuel costs in the amount of $2.4 million for the Texas jurisdiction. 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 PUCT 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 PUCT's final order completes the regulatory review and reconciliation of the Company's fuel expenses for the period through March 31, 2013. The settlement provides that 100% of margins on non-arbitrage off-system sales (as defined by the settlement) and 50% of margins on arbitrage off-system 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 Company also agreed in the settlement to file with the PUCT a proceeding to address the reasonableness of the Company's decision to not continue to participate in the Four Corners Generating Station ("Four Corners") and to include fuel costs related to final coal mine closing and reclamation costs. On June 10, 2015, the Company filed this application with the PUCT. This case was assigned PUCT Docket No. 44805 and is addressed in more detail below. Montana Power Station Approvals . T he Company has received a Certificate of Convenience and Necessity ("CCN") from the PUCT to construct four natural gas fired generating units at the Montana Power Station (the "MPS") in El Paso County, Texas. The Company also obtained air permits from the Texas Commission on Environmental Quality (the "TCEQ") and the U.S. Environmental Protection Agency (the "EPA"). The PUCT has issued final orders approving CCNs for the MPS to Caliente transmission line, MPS In & Out transmission line and the MPS to Montwood transmission line. These transmission lines will connect MPS to the Company’s transmission system for delivery of electricity throughout its service territory. MPS Units 1 and 2 and the MPS to Caliente and MPS In & Out transmission lines became operational in March 2015 . Solar Generation CCN Filing. On April 20, 2015, the Company filed an application with the PUCT requesting CCN authorization to construct a new 20 MW solar-powered generation facility to be located on Fort Bliss in the Company's service territory in Texas. This case was assigned PUCT Docket No. 44637. The Company was unable to reach an agreement with the United States Army on essential terms of the easement within Fort Bliss on which the facility would be located. Accordingly, on August 19, 2015, the Company filed a notice that it was withdrawing its application, and on the same day the Administrative Law Judge dismissed the case. Community Solar. On June 8, 2015, the Company filed a petition with the PUCT to initiate a community solar program to include construction and ownership of a 3 MW solar photovoltaic system located at the MPS. Participation will be on a voluntary basis, and customers will contract for a set capacity (kW) amount and receive all energy produced. The Company has requested a PUCT final order approving the program so that the project can be completed before December 31, 2016 to maximize potential tax benefits. This case was assigned PUCT Docket No. 44800. A hearing on the merits is currently scheduled for early December 2015. Four Corners Generating Station. On June 10, 2015, the Company filed an application requesting reasonableness and public interest findings and certain rate- and accounting- related findings to sell its ownership interest in Four Corners to Arizona Public Service Company ("APS") pursuant to a Purchase and Sale Agreement executed February 17, 2015 . The anticipated closing date is July 6, 2016 , pending regulatory approval. This case was assigned PUCT Docket No. 44805. The deadline for parties to request hearing is set as November 20, 2015, and the deadline for the PUCT Staff to file a recommendation in the case is November 30, 2015, if no hearing is requested. It is expected that the final coal mine closing and reclamation costs will be addressed in the proceeding as well as other issues related to post-participation events such as the asset retirement obligations. The Company cannot predict the outcome of the case at this time. Other Required Approvals . The Company has obtained other required approvals for 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 are updated annually for adjustment to the recovery factors. 2015 New Mexico Rate Case Filing . On May 11, 2015, the Company filed with the NMPRC (NMPRC Case No. 15-00127-UT) for an annual increase in non-fuel base rates of approximately $8.6 million or 7.1% . The filing also requests an annual reduction of $15.4 million , or 21.5% , for fuel and purchased power costs recovered in base rates. The reduction in fuel and purchased power rates reflects reduced fuel prices and improvements in system heat rates due to new generating unit additions. Based on the standard procedural schedule, the Company expects new rates to go into effect early in the second quarter of 2016. A hearing in the case has been set to begin on November 16, 2015. The Company cannot predict the outcome of the case at this time. Fuel and Purchased Power Costs. Fuel and purchased power costs are recovered through base rates and a Fuel and Purchased Power Cost Adjustment Clause (the "FPPCAC") that accounts for changes in the costs of fuel relative to the amount included in base rates. 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 costs related to Palo Verde Unit 3 capacity and energy in New Mexico through the FPPCAC as purchased power using a proxy market price approved in the 2014 FPPCAC continuation. Montana Power Station Approvals. The Company has received a CCN from the NMPRC to construct four units at the MPS and the associated transmission lines. The Company also obtained all necessary air permits from the TCEQ and the EPA. A final order in NMPRC Case No. 13-00297-UT approving the CCN for MPS Units 3 and 4 was issued on June 11, 2014. MPS Units 1 and 2 and the MPS to Caliente and MPS In & Out transmission lines became operational in March 2015 . Solar Generation CCN Filing. On April 20, 2015, the Company filed a petition with the NMPRC requesting CCN authorization to construct a new 20 MW solar-powered generation facility to be located on Fort Bliss in the Company's service territory in Texas. This case was assigned NMPRC Case No. 15-00099-UT. The Company was unable to reach an agreement with the United States Army on essential terms of the easement within Fort Bliss on which the facility would be located. Accordingly, on August 17, 2015, the Company filed a motion to withdraw the CCN filing. On September 23, 2015, the NMPRC issued a Final Order accepting the Hearing Examiner’s Recommended Decision to grant the Company's motion to withdraw. Four Corners Generating Station. On April 27, 2015, the Company filed an application requesting all necessary regulatory approvals to sell its ownership interest in Four Corners to APS pursuant to a Purchase and Sale Agreement executed February 17, 2015 . The anticipated closing date is July 6, 2016 , pending regulatory approval. This case was assigned NMPRC Case No. 15-00109-UT. Hearings in the case are scheduled for January 2016. The Company cannot predict the outcome of the case at this time. Expedited Approval for CCN (5 MW Holloman Facility) . On June 15, 2015, the Company filed a petition with the NMPRC requesting CCN authorization to construct a 5 MW solar-powered generation facility to be located at Holloman Air Force Base ("HAFB") in the Company's service territory in New Mexico. The new facility will be a dedicated Company-owned resource serving HAFB. The Company has requested approval such that the project can be completed before December 31, 2016 to maximize potential tax benefits. This case was assigned NMPRC Case No. 15-00185-UT. On October 7, 2015, the NMPRC issued a Final Order accepting the Hearing Examiner’s Recommended Decision to approve the CCN, as modified, that the Company shall not seek to recover any revenue requirement associated with the facility from New Mexico jurisdictional customers other than HAFB without prior NMPRC approval. Issuance of Long-Term Debt and Guarantee of Debt. On October 7, 2015 the Company received approval in NMPRC Case No. 15-00280-UT to issue up to $310 million in new long-term debt; and to guarantee the issuance of up to $65 million of new debt by Rio Grande Resources Trust ("RGRT") to finance future purchases of nuclear fuel and to refinance existing nuclear fuel debt obligations. This approval supersedes prior approvals. Other Required Approvals . The Company has obtained other required approvals for other tariffs, securities transactions, recovery of energy efficiency costs through a base rate rider and other approvals as required by the NMPRC. Federal Regulatory Matters Four Corners Generating Station. On June 26, 2015, APS filed an application requesting authorization from FERC to purchase 100% of the Company’s ownership interest in Units 4 and 5 of Four Corners and the associated transmission interconnection facilities and rights. APS has requested authorization by FERC on or before December 24, 2015. The Company cannot predict the outcome of the case at this time. Public Service Company of New Mexico's ( " PNM " ) Transmission Rate Case. On December 31, 2012, PNM filed with FERC to change its method of transmission rate recovery for its transmission delivery services from stated rates to formula rates. The Company takes transmission service from PNM and is among the PNM transmission customers affected by PNM's shift to formula rates. On March 1, 2013, the FERC issued an order rejecting in part PNM's filing, and establishing settlement judge and hearing procedures. On March 20, 2015, PNM filed with FERC a settlement agreement and offer of settlement resolving all issues set for hearing in the proceeding. On March 25, 2015, the Chief Judge issued an order granting PNM's motion to implement the settled rates. However, the Company is still awaiting a final decision from the Commission on whether the settlement will be approved. The Company cannot predict the outcome of the case at this time. Revolving Credit Facility; Issuance of Long-Term Debt and Guarantee of Debt. On October 19, 2015, the FERC issued an order in Docket No. ES15-66-000 approving the Company’s filing to issue short-term debt under its existing revolving credit facility up to $400 million outstanding at any one time, to issue up to $310 million in long-term debt, and to guarantee the issuance of up to $65 million of new long-term debt by RGRT to finance future nuclear fuel purchases. The authorization is effective from November 15, 2015 through November 15, 2017 . This approval supersedes prior approvals. 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, 2015
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 U.S. Department of Energy (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 December 19, 2012 , APS, acting on behalf of itself and the participant owners of Palo Verde, filed a second breach of contract lawsuit against the DOE. This lawsuit sought to recover damages incurred due to the DOE's failure to accept Palo Verde's spent nuclear fuel for the period beginning January 1, 2007 through June 30, 2011 . On August 18, 2014 , APS and the DOE entered into a settlement agreement, stipulating to a dismissal of the lawsuit and payment of $57.4 million by the DOE to the Palo Verde owners for certain specified costs incurred by Palo Verde during the period January 1, 2007 through June 30, 2011 . On October 8, 2014 , the Company received approximately $9.1 million , representing its share of the award. The majority of the award was credited to customers through the applicable fuel adjustment clauses. On October 31, 2014 , APS acting on behalf of itself and 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 accepted claim amount was $42.0 million . On June 1, 2015 , the Company received approximately $6.6 million , representing its share of the award. The majority of the award was credited to customers through the applicable fuel adjustment clauses in March 2015.

Common Stock

Common Stock	9 Months Ended
	Sep. 30, 2015
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Shareholders' Equity and Share-based Payments, Including Earnings Per Share Information	Common Stock Dividends. The Company paid $11.9 million and $11.3 million in quarterly cash dividends during the three months ended September 30, 2015 and 2014 , respectively. The Company paid a total of $35.1 million and $46.4 million in quarterly cash dividends during the nine and twelve months ended September 30, 2015 , 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. 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, 2015 2014 Weighted average number of common shares outstanding: Basic number of common shares outstanding 40,289,010 40,213,741 Dilutive effect of unvested performance awards 40,519 51,069 Diluted number of common shares outstanding 40,329,529 40,264,810 Basic net income per common share: Net income $ 56,740 $ 52,476 Income allocated to participating restricted stock (184 ) (175 ) Net income available to common shareholders $ 56,556 $ 52,301 Diluted net income per common share: Net income $ 56,740 $ 52,476 Income reallocated to participating restricted stock (184 ) (175 ) Net income available to common shareholders $ 56,556 $ 52,301 Basic net income per common share: Distributed earnings $ 0.295 $ 0.280 Undistributed earnings 1.105 1.020 Basic net income per common share $ 1.400 $ 1.300 Diluted net income per common share: Distributed earnings $ 0.295 $ 0.280 Undistributed earnings 1.105 1.020 Diluted net income per common share $ 1.400 $ 1.300 Nine Months Ended September 30, 2015 2014 Weighted average number of common shares outstanding: Basic number of common shares outstanding 40,267,533 40,181,367 Dilutive effect of unvested performance awards 32,268 27,634 Diluted number of common shares outstanding 40,299,801 40,209,001 Basic net income per common share: Net income $ 81,270 $ 87,187 Income allocated to participating restricted stock (253 ) (293 ) Net income available to common shareholders $ 81,017 $ 86,894 Diluted net income per common share: Net income $ 81,270 $ 87,187 Income reallocated to participating restricted stock (253 ) (293 ) Net income available to common shareholders $ 81,017 $ 86,894 Basic net income per common share: Distributed earnings $ 0.870 $ 0.825 Undistributed earnings 1.140 1.335 Basic net income per common share $ 2.010 $ 2.160 Diluted net income per common share: Distributed earnings $ 0.870 $ 0.825 Undistributed earnings 1.140 1.335 Diluted net income per common share $ 2.010 $ 2.160 Twelve Months Ended September 30, 2015 2014 Weighted average number of common shares outstanding: Basic number of common shares outstanding 40,255,439 40,169,801 Dilutive effect of unvested performance awards 24,201 20,726 Diluted number of common shares outstanding 40,279,640 40,190,527 Basic net income per common share: Net income $ 85,511 $ 88,378 Income allocated to participating restricted stock (265 ) (285 ) Net income available to common shareholders $ 85,246 $ 88,093 Diluted net income per common share: Net income $ 85,511 $ 88,378 Income reallocated to participating restricted stock (265 ) (285 ) Net income available to common shareholders $ 85,246 $ 88,093 Basic net income per common share: Distributed earnings $ 1.15 $ 1.09 Undistributed earnings 0.97 1.10 Basic net income per common share $ 2.12 $ 2.19 Diluted net income per common share: Distributed earnings $ 1.15 $ 1.09 Undistributed earnings 0.97 1.10 Diluted net income per common share $ 2.12 $ 2.19 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, 2015 2014 2015 2014 2015 2014 Restricted stock awards 65,076 59,627 60,647 60,264 60,742 59,296 Performance shares (a) 59,898 48,733 59,898 87,784 63,111 88,575 (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, 2015
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 and New Mexico jurisdictions for years prior to 2010 . The Company is currently under audit in Texas for tax years 2007 through 2011 and in Arizona for tax years 2009 through 2012 . For both the three months ended September 30, 2015 and 2014 , the Company’s effective tax rate was 30.2% . For the nine months ended September 30, 2015 and 2014 , the Company’s effective tax rate was 30.2% and 30.9% , respectively. For the twelve months ended September 30, 2015 and 2014 , the Company's effective tax rate was 30.4% and 29.1% , respectively. The Company's effective tax rate for all time periods differs from the federal statutory tax rate of 35.0% primarily due to the allowance for equity funds used during construction and state income taxes. The Company’s effective tax rate for the three and nine months ended September 30, 2015 also differs from the federal statutory tax rate of 35.0% due to a domestic production activities deduction earned in 2015 and capital gains in the qualified decommissioning trust realized in the first and third quarters of 2015, which are taxed at a federal rate of 20% . In June 2015, legislation was approved in Texas which permanently reduced the Texas Franchise Tax rate to 0.75% tax on taxable margins down from an interim rate of 0.95% . The rate reduction is applicable to tax reports originally due on or after January 1, 2016 and is retroactive to January 1, 2015 tax accruals. The implementation of this rate change in June 2015 did not have a material impact on the financial statements of the Company.

Commitments, Contingencies And

Commitments, Contingencies And Uncertainties	9 Months Ended
	Sep. 30, 2015
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 2014 Annual Report on Form 10-K. In addition, see Notes C and D above and Notes C and E of Notes to Financial Statements in the 2014 Annual Report on 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 2014 Form 10-K. In addition to the contracts disclosed in the 2014 Form 10-K, in October 2015, the 25 MW additional energy transaction with Freeport-McMoran Copper and Gold Energy Services, LLC due to expire in December 2015 was extended through December 2016, in accordance with the Power Purchase and Sale Agreement. 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 more detailed discussion of certain key environmental issues, laws and regulations facing the Company see Note K of Notes to Financial Statements in the 2014 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, and on October 23, 2014, the D.C Circuit lifted its stay of CSAPR. On July 28, 2015, the D.C. Circuit ruled that the EPA's emissions budgets for 13 states including Texas are invalid but left the rule in place on remand. While we are unable to determine the full impact of this decision until EPA takes further action, the Company believes it is currently positioned to comply with CSAPR. National Ambient Air Quality Standards. Under the Clean Air Act ("CAA"), the EPA sets National Ambient Air Quality Standards ("NAAQS") for six criteria pollutants considered harmful to public health and the environment, including particulate matter ("PM"), NOx, carbon monoxide ("CO"), ozone and SO2. NAAQS must be reviewed by the EPA at five -year intervals. In 2010, the EPA tightened the NAAQS for both NOx and SO2. The EPA is considering a 1-hour secondary NAAQS for NOx and SO2. In January 2013, the EPA tightened the NAAQS for fine PM. On October 1, 2015, following on its November 2014 proposal, EPA released a final rule tightening the primary and secondary NAAQS for ground-level ozone from its 2008 standard levels of 75 parts per billion ("ppb") to 70 ppb. Ozone is the main component of smog. While not directly emitted into the air, it forms from precursors, including NOx and volatile organic compounds, in combination with sunlight. The EPA is expected to make attainment/nonattainment designations for the revised ozone standards by October 1, 2017. While it is currently unknown how the areas in which we operate will be designated, for nonattainment areas classified as "Moderate" and above, states, and any tribes that choose to do so, are expected to be required to complete development of implementation plans in the 2020-2021 timeframe. Nonattainment areas will have from 2020 to 2037 to meet the primary (health) standard, with the exact attainment date varying based on the ozone level in the area. The Company continues to evaluate what impact these final and proposed NAAQS could have on its operations. If the Company is required to install additional equipment to control emissions at its facilities, the NAAQS, individually or in the aggregate, could have a material impact on its operations and financial results. Utility MACT. The operation of coal-fired power plants, such as the Company's Four Corners plant, results in emissions of mercury and other air toxics. In December 2011, the EPA finalized Mercury and Air Toxics Standards (known as the "Utility MACT", or "MATS Rule") for oil-and coal-fired power plants, which requires significant reductions in emissions of mercury and other air toxics. Several judicial and other challenges were made to this rule, and on June 29, 2015, the U.S. Supreme Court remanded the rule to the D.C. Circuit Court, which rule remains in effect until the D.C. Circuit Court and the EPA take action. The legal status of the MATS Rule notwithstanding, the Four Corners plant operator, APS, believes Units 4 and 5 will require no additional modifications to achieve compliance with the MATS Rule, as currently written. We cannot currently predict, however, what additional modifications or costs may be incurred if the EPA rewrites the MATS Rule on remand. Other Laws and Regulations and Risks. The Company has entered into an agreement to sell its interest in Four Corners to APS 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. By ceasing its participation in Four Corners, the Company expects to avoid the significant cost required to install expensive pollution control equipment in order to continue operation of the plant as well as the risks of water availability that might adversely affect the amount of power available, or the price thereof, from Four Corners in the future. The closing of the transaction is subject to the receipt of regulatory approvals. Coal Combustion Waste. On October 19, 2015 the EPA's final rule regulating the disposal of coal combustion residuals (the “CCR Rule”) from electric utilities as solid waste took effect. The Company has a 7% ownership interest in Units 4 and 5 of Four Corners, the only coal-fired generating facility for which the Company has an ownership interest subject to the CCR Rule. The Company entered into a Purchase and Sale Agreement with APS in February 2015 to sell the Company’s entire ownership interest in Four Corners. For a discussion on the Purchase and Sale Agreement see Note E of the Notes to the Financial Statements in the 2014 Annual Report on Form 10-K. The CCR Rule requires plant owners to treat coal combustion residuals as Subtitle D (as opposed to a more costly Subtitle C) waste. In general, the Company is liable for only 7% of costs to comply with the CCR Rule (consistent with our ownership percentage). The Company, however, believes under the terms of the Four Corners Purchase Agreement and after the pending sale, as a former owner, that the Company is not responsible for a significant portion of the costs under the CCR Rule, such as ongoing operational costs after July 2016. Accordingly, the Company does not expect the CCR Rule to have a significant impact on our financial condition or results of operations. On September 30, 2015, the EPA finalized revisions to the wastewater effluent limitation guidelines for steam electric power generators (the “Revised ELG Rule”). The Revised ELG Rule establishes requirements for wastewater streams from certain processes at affected facilities, including limits on toxic metals in wastewater discharges. Facilities must comply with the Revised ELG Rule between 2018 and 2023. The EPA anticipates that the new requirements in the Revised ELG Rule will only affect certain coal-fired steam electric power plants. Because the Company will no longer have an interest in Four Corners after July 2016, the Company does not expect the Revised ELG Rule to have a significant impact on our financial condition or results of operations. In 2012, several environmental groups filed a lawsuit in federal district court against the Office of Surface Mining Reclamation and Enforcement ("OSM") of the U.S. Department of the Interior challenging OSM’s 2012 approval of a permit revision which allowed for the expansion of mining operations into a new area of the mine that serves Four Corners ("Area IV North"). In April 2015, the court issued an order invalidating the permit revision, thereby prohibiting mining in Area IV North until OSM takes action to cure the defect in its permitting process identified by the court. Navajo Transitional Energy Company, the owner of the mine and supplier of coal to Four Corners, has indicated that it does not anticipate any near-term interruption of coal supply to the plant as a result of the suspension of mining in Area IV North. The Company cannot predict the time period that will be required for OSM’s further permitting process to be completed or whether the outcome of the process will be sufficient to allow the permit to be reinstated. Climate Change. The U.S. federal government has either considered, proposed and/or finalized legislation or regulations limiting greenhouse gas ("GHG") emissions, including carbon dioxide ("CO2"). In particular, the U.S. Congress has considered legislation to restrict or regulate GHG emissions. In the past few years, the EPA began using the CAA to regulate CO2 and other GHG emissions, such as the 2009 GHG Reporting Rule and the EPA's sulfur hexafluoride ("SF6") reporting rule, both of which apply to the Company, as well as the EPA's 2010 actions to impose permitting requirements on new and modified sources of GHG emissions. After announcing his plan to address climate change in 2013, the President directed the EPA to issue proposals for GHG rulemaking addressing power plants. In October 2015, the EPA published a final rule establishing new source performance standards ("NSPS") limiting CO2 emissions from new, modified and reconstructed electric generating units. In October 2015, the EPA also published a rule establishing guidelines for states to regulate CO2 emissions from existing power plants, as well as a proposed "federal plan" to address CO2 emissions from affected units in those states that do not submit an approvable compliance plan. The standards for existing plants are known as the Clean Power Plan ("CPP"), under which rule interim emissions performance rates must be achieved beginning in 2022 and final emissions performance rates by 2030. Legal challenges to the CPP were filed by groups of states and industry members in the Court of Appeals for the D.C. Circuit on October 23, 2015, and more challenges are expected. We are evaluating the CPP, the NSPS and the proposed CPP "federal plan" and, in part because state CPP compliance plans are not due until September 2016, we cannot at this time determine the impact of the CPP on our financial position, results of operations or cash flows. 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. Beginning in July 2011, the U.S. Department of Justice (the "DOJ"), on behalf of the EPA, and APS were engaged in substantive settlement negotiations in an effort to resolve DOJ pre-enforcement action. The allegations being addressed through settlement negotiations are that APS failed to obtain the necessary permits and install the controls necessary under the CAA to reduce SO2, NOx, and PM, and that defendants failed to obtain an operating permit under Title V of the CAA that reflects applicable requirements imposed by law. In November 2014, 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. On June 24, 2015, the parties filed with the U.S. District Court for New Mexico a settlement agreement ("CAA Settlement Agreement") resolving this matter. On August 17, 2015, the U.S. District Court for New Mexico entered the CAA Settlement Agreement. The agreement imposes a total civil penalty payable by the co-owners of Four Corners collectively in the amount of $1.5 million , and it requires the co-owners to pay $6.7 million for environmental mitigation projects. As of September 30, 2015, the Company has a provision for its share of approximately $0.5 million related to this matter. In a related action, on October 4, 2011, Earthjustice filed a lawsuit in the United States District Court for New Mexico alleging violations of the Prevention of Significant Deterioration ("PSD") provisions of the CAA related to Four Corners. Thereafter, on January 6, 2012, Earthjustice filed a First Amended Complaint adding claims for violations of the CAA's NSPS program. The lawsuit addressed allegations similar to those raised in the DOJ pre-enforcement action described in the preceding paragraph. Among other things, the plaintiffs sought 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. Because the allegations in the DOJ pre-enforcement action and this lawsuit were substantially similar, the negotiations between the DOJ and APS regarding the pre-enforcement action also included Earthjustice. Accordingly, in response to the CAA Settlement Agreement, the parties to the case moved to dismiss the proceedings. Accordingly, the proceedings were terminated as of August 17, 2015. The CAA Settlement Agreement represents the final judgment in this case. 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. On June 30, 2015, the court ruled that the Assessment was not valid and further ruled that APS and the other Four Corners co-owners receive a refund of all of the contested amounts previously paid under the applicable tax statute. The New Mexico Taxation and Revenue Department filed a Notice of Appeal on August 31, 2015 with respect to the decision. The Company cannot predict the timing, results, or potential impacts of the outcome of this litigation.

Litigation

Litigation	9 Months Ended
	Sep. 30, 2015
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. The Company expenses legal costs, including expenses related to loss contingencies, as they are incurred. See Notes C and G above and Notes C and K of the Notes to Financial Statements in the 2014 Annual Report on 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, 2015
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, 2015 and 2014 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, 2015 2014 2015 2014 2015 2014 Components of net periodic benefit cost: Service cost $ 2,394 $ 2,112 $ 6,594 $ 6,474 $ 8,707 $ 8,805 Interest cost 3,622 3,691 10,872 11,351 14,563 14,755 Expected return on plan assets (4,951 ) (4,681 ) (14,846 ) (14,017 ) (19,528 ) (18,294 ) Amortization of: Net loss 2,485 2,283 7,985 6,571 10,267 9,346 Prior service benefit (855 ) (877 ) (2,630 ) (2,030 ) (3,506 ) (2,006 ) Net periodic benefit cost $ 2,695 $ 2,528 $ 7,975 $ 8,349 $ 10,503 $ 12,606 During the nine months ended September 30, 2015 , the Company contributed $10.4 million of its projected $11.1 million 2015 annual contribution to its retirement plans. Other Postretirement Benefits The net periodic benefit cost recognized for the three, nine and twelve months ended September 30, 2015 and 2014 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, 2015 2014 2015 2014 2015 2014 Components of net periodic benefit cost: Service cost $ 841 $ 712 $ 2,591 $ 2,134 $ 3,302 $ 2,805 Interest cost 976 1,115 3,026 3,347 4,142 4,461 Expected return on plan assets (503 ) (529 ) (1,553 ) (1,587 ) (2,082 ) (2,103 ) Amortization of: Prior service benefit (751 ) (1,188 ) (2,301 ) (3,564 ) (3,490 ) (4,979 ) Net gain (519 ) (668 ) (1,519 ) (2,004 ) (2,186 ) (2,630 ) Net periodic benefit cost (benefit) $ 44 $ (558 ) $ 244 $ (1,674 ) $ (314 ) $ (2,446 ) The Company has not contributed to its other postretirement benefits plan during the nine months ended September 30, 2015 and does not expect to contribute to its other postretirement benefit plan in 2015 .

Financial Instruments And Inves

Financial Instruments And Investments (Notes)	9 Months Ended
	Sep. 30, 2015
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 Revolving Credit Facility (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, 2015 December 31, 2014 Carrying Amount Estimated Fair Value Carrying Amount Estimated Fair Value Pollution Control Bonds $ 193,135 $ 210,179 $ 193,135 $ 213,083 Senior Notes 846,123 994,040 846,044 968,728 RGRT Senior Notes (1) 95,000 101,745 110,000 117,215 RCF (1) 118,693 118,693 14,532 14,532 Total $ 1,252,951 $ 1,424,657 $ 1,163,711 $ 1,313,558 _______________ (1) Nuclear fuel financing of $95 million at September 30, 2015 and $110 million at December 31, 2014 , is funded through the RGRT Senior Notes and $33.7 million and $14.5 million , respectively under the RCF. As of September 30, 2015 , $85.0 million was outstanding under the RCF for working capital or general corporate purposes. As of December 31, 2014 , 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 $231.9 million and $234.3 million at September 30, 2015 and December 31, 2014 , 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, 2015 Less than 12 Months 12 Months or Longer Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Description of Securities (1) : Federal Agency Mortgage Backed Securities $ 94 $ (1 ) $ 2,197 $ (46 ) $ 2,291 $ (47 ) U.S. Government Bonds 6,375 (58 ) 13,402 (432 ) 19,777 (490 ) Municipal Obligations 10,994 (244 ) 9,019 (493 ) 20,013 (737 ) Corporate Obligations 7,036 (406 ) 1,629 (135 ) 8,665 (541 ) Total Debt Securities 24,499 (709 ) 26,247 (1,106 ) 50,746 (1,815 ) Common Stock 6,958 (908 ) — — 6,958 (908 ) Institutional Funds-International Equity 21,536 (1,725 ) — — 21,536 (1,725 ) Equity Mutual Funds 8,792 (502 ) — — 8,792 (502 ) Total Temporarily Impaired Securities $ 61,785 $ (3,844 ) $ 26,247 $ (1,106 ) $ 88,032 $ (4,950 ) _________________ (1) Includes 141 securities. December 31, 2014 Less than 12 Months 12 Months or Longer Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Description of Securities (2) : Federal Agency Mortgage Backed Securities $ — $ — $ 2,383 $ (57 ) $ 2,383 $ (57 ) U.S. Government Bonds 1,552 (2 ) 20,060 (573 ) 21,612 (575 ) Municipal Obligations 6,433 (65 ) 8,570 (410 ) 15,003 (475 ) Corporate Obligations 2,455 (24 ) 2,461 (111 ) 4,916 (135 ) Total Debt Securities 10,440 (91 ) 33,474 (1,151 ) 43,914 (1,242 ) Common Stock 1,475 (229 ) — — 1,475 (229 ) Institutional Funds-International Equity 22,736 (821 ) — — 22,736 (821 ) Total Temporarily Impaired Securities $ 34,651 $ (1,141 ) $ 33,474 $ (1,151 ) $ 68,125 $ (2,292 ) _________________ (2) Includes 106 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 is expected or is scheduled 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, 2015 December 31, 2014 Fair Value Unrealized Gains Fair Value Unrealized Gains Description of Securities: Federal Agency Mortgage Backed Securities $ 18,780 $ 562 $ 15,388 $ 665 U.S. Government Bonds 25,250 468 20,016 567 Municipal Obligations 10,288 371 11,642 595 Corporate Obligations 11,419 490 13,762 850 Total Debt Securities 65,737 1,891 60,808 2,677 Common Stock 72,309 35,032 99,160 48,253 Cash and Cash Equivalents 5,807 — 6,193 — Total $ 143,853 $ 36,923 $ 166,161 $ 50,930 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 two years to six years and reflects anticipated future prepayments. The contractual year for maturity of these available-for-sale securities as of September 30, 2015 is as follows (in thousands): Total 2015 2016 2020 through 2024 2025 and Beyond Municipal Debt Obligations $ 30,301 $ — $ 10,193 $ 13,526 $ 6,582 Corporate Debt Obligations 20,084 697 5,720 7,594 6,073 U.S. Government Bonds 45,027 3,051 15,666 16,844 9,466 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, 2015 and 2014 , respectively. 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, 2015 2014 2015 2014 2015 2014 Proceeds from sales or maturities of available-for-sale securities $ 26,618 $ 10,980 $ 63,776 $ 47,355 $ 124,732 $ 74,083 Gross realized gains included in pre-tax income $ 4,515 $ 1,239 $ 8,330 $ 4,502 $ 12,467 $ 4,895 Gross realized losses included in pre-tax income (191 ) (415 ) (443 ) (711 ) (1,021 ) (838 ) Net gains in pre-tax income $ 4,324 $ 824 $ 7,887 $ 3,791 $ 11,446 $ 4,057 Net unrealized holding gains (losses) included in accumulated other comprehensive income $ (8,092 ) $ 897 $ (8,641 ) $ 7,965 $ (5,779 ) $ 16,803 Net gains reclassified out of accumulated other comprehensive income (4,324 ) (824 ) (7,887 ) (3,791 ) (11,446 ) (4,057 ) Net gains (losses) in other comprehensive income $ (12,416 ) $ 73 $ (16,528 ) $ 4,174 $ (17,225 ) $ 12,746 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 Institutional Funds are valued using the 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 analysis. 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 institutional funds which are classified as Level 2. The fair value of the Company's decommissioning trust funds and investment in debt securities, at September 30, 2015 and December 31, 2014 , 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, 2015 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Trading Securities: Investments in Debt Securities $ 1,573 $ — $ — $ 1,573 Available for sale: U.S. Government Bonds $ 45,027 $ 45,027 $ — $ — Federal Agency Mortgage Backed Securities 21,071 — 21,071 — Municipal Obligations 30,301 — 30,301 — Corporate Obligations 20,084 — 20,084 — Subtotal, Debt Securities 116,483 45,027 71,456 — Common Stock 79,267 79,267 — — Equity Mutual Funds 8,792 8,792 — — Institutional Funds-International Equity 21,536 — 21,536 — Cash and Cash Equivalents 5,807 5,807 — — Total available for sale $ 231,885 $ 138,893 $ 92,992 $ — Description of Securities Fair Value as of December 31, 2014 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Trading Securities: Investments in Debt Securities $ 1,653 $ — $ — $ 1,653 Available for sale: U.S. Government Bonds $ 41,628 $ 41,628 $ — $ — Federal Agency Mortgage Backed Securities 17,771 — 17,771 — Municipal Obligations 26,645 — 26,645 — Corporate Obligations 18,678 — 18,678 — Subtotal, Debt Securities 104,722 41,628 63,094 — Common Stock 100,635 100,635 — — Institutional Funds-International Equity 22,736 — 22,736 — Cash and Cash Equivalents 6,193 6,193 — — Total available for sale $ 234,286 $ 148,456 $ 85,830 $ — 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, 2015 and 2014 . 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, 2015 and 2014 .

Principles Of Preparation (Poli

Principles Of Preparation (Policy)	9 Months Ended
	Sep. 30, 2015
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 $30.1 million at September 30, 2015 and $21.2 million at December 31, 2014 . The Company presents revenues net of sales taxes in its statements of operations.
New Accounting Standards, Policy	New Accounting Standards. In May 2014, the Financial Accounting Standards Board ("FASB") issued new guidance (Accounting Standards Update ("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 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 was originally intended to be effective for annual periods and interim periods within that reporting period beginning after December 15, 2016, for public business entities. In August 2015, FASB issued ASU 2015-14 to defer the effective date of ASU 2014-09 for all entities by one year. Public business entities will apply the guidance in ASU 2014-09 to annual reporting periods beginning after December 15, 2017 and interim periods within that reporting period. Early adoption of ASU 2014-09 is permitted after December 15, 2016. The Company is currently assessing the future impact of this ASU . In April 2015, the FASB issued ASU 2015-03, Interest - Imputation of Interest (Topic 715) to simplify the presentation of debt issuance costs. ASU 2015-03 requires that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. The recognition and measurement guidance for debt issuance costs are not affected by this ASU. ASU 2015-03 is effective for financial statements issued for fiscal years beginning after December 15, 2015, and interim periods within those fiscal years. In August 2015, FASB issued ASU 2015-15, Interest - Imputation of Interest (Subtopic 835-30), to provide further clarification to ASU 2015-03 as it relates to the presentation and subsequent measurement of debt issuance costs associated with line of credit arrangements. The Company does not expect ASU 2015-03 and ASU 2015-15 to materially impact the Company's results of operations and cash flows. In May 2015, FASB issued ASU 2015-07, Fair Value Measurement (Topic 820) to eliminate the requirement to categorize investments in the fair value hierarchy if the fair value is measured at net asset value ("NAV") per share (or its equivalent) using the practical expedient in the FASB’s fair value measurement gui dance . Reporting entities must still provide sufficient information to enable users to reconcile total investments in the fair value hierarchy and total investments measured at fair value in the financial statements. Additionally, the scope of current disclosure requirements for investments eligible to be measured at NAV will be limited to investments to which the practical expedient is applied. This ASU is effective in fiscal years beginning after December 15, 2015, and interim periods within those fiscal years. The ASU requires retrospective application. Early adoption is permitted. The Company is currently assessing the future impact of this ASU.

Principles Of Preparation (Tabl

Principles Of Preparation (Tables)	9 Months Ended
	Sep. 30, 2015
Supplemental Cash Flow Information [Abstract]
Cash Flow, Supplemental Disclosures	Supplemental Cash Flow Disclosures (in thousands) Nine Months Ended September 30, 2015 2014 Cash paid (received) for: Interest on long-term debt and borrowing under the revolving credit facility $ 41,406 $ 37,689 Income tax paid (refunded), net (272 ) 2,969 Non-cash investing and financing activities: Changes in accrued plant additions (13,150 ) (3,762 ) Grants of restricted shares of common stock 1,106 3,025

Accumulated Other Comprehensi20

Accumulated Other Comprehensive Income (Tables)	9 Months Ended
	Sep. 30, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Schedule of 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, 2015 Three Months Ended September 30, 2014 Unrecognized Pension and Post-retirement Benefit Costs Net Unrealized Gains (Losses) on Marketable Securities Net Losses on Cash Flow Hedges Accumulated Other Comprehensive Income (Loss) Unrecognized Pension and Post-retirement 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 $ (34,331 ) $ 35,726 $ (11,959 ) $ (10,564 ) $ (9,539 ) $ 39,483 $ (12,214 ) $ 17,730 Other comprehensive income (loss) before reclassifications — (6,485 ) — (6,485 ) — 733 — 733 Amounts reclassified from accumulated other comprehensive income (loss) 226 (3,472 ) 72 (3,174 ) (279 ) (691 ) 68 (902 ) Balance at end of period $ (34,105 ) $ 25,769 $ (11,887 ) $ (20,223 ) $ (9,818 ) $ 39,525 $ (12,146 ) $ 17,561 Nine Months Ended September 30, 2015 Nine Months Ended September 30, 2014 Unrecognized Pension and Post-retirement Benefit Costs Net Unrealized Gains (Losses) on Marketable Securities Net Losses on Cash Flow Hedges Accumulated Other Comprehensive Income (Loss) Unrecognized Pension and Post-retirement 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 $ (34,884 ) $ 38,957 $ (12,074 ) $ (8,001 ) $ (21,330 ) $ 36,240 $ (12,298 ) $ 2,612 Other comprehensive income (loss) before reclassifications — (6,854 ) — (6,854 ) 12,147 6,377 — 18,524 Amounts reclassified from accumulated other comprehensive income (loss) 779 (6,334 ) 187 (5,368 ) (635 ) (3,092 ) 152 (3,575 ) Balance at end of period $ (34,105 ) $ 25,769 $ (11,887 ) $ (20,223 ) $ (9,818 ) $ 39,525 $ (12,146 ) $ 17,561 Twelve Months Ended September 30, 2015 Twelve Months Ended September 30, 2014 Unrecognized Pension and Post-retirement Benefit Costs Net Unrealized Gains (Losses) on Marketable Securities Net Losses on Cash Flow Hedges Accumulated Other Comprehensive Income (Loss) Unrecognized Pension and Post-retirement 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 $ (9,818 ) $ 39,525 $ (12,146 ) $ 17,561 $ (73,133 ) $ 29,335 $ (12,364 ) $ (56,162 ) Other comprehensive income (loss) before reclassifications (24,775 ) (4,537 ) — (29,312 ) 63,518 13,476 — 76,994 Amounts reclassified from accumulated other comprehensive income (loss) 488 (9,219 ) 259 (8,472 ) (203 ) (3,286 ) 218 (3,271 ) Balance at end of period $ (34,105 ) $ 25,769 $ (11,887 ) $ (20,223 ) $ (9,818 ) $ 39,525 $ (12,146 ) $ 17,561
Reclassification out of Accumulated Other Comprehensive Income	Amounts reclassified from accumulated other comprehensive income (loss) for the three, nine and twelve months ended September 30, 2015 and 2014 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 2015 2014 2015 2014 2015 2014 Amortization of pension and post-retirement benefit costs: Prior service benefit $ 1,606 $ 2,065 $ 4,931 $ 5,594 $ 6,996 $ 6,985 (a) Net loss (1,966 ) (1,615 ) (6,466 ) (4,567 ) (8,081 ) (6,716 ) (a) (360 ) 450 (1,535 ) 1,027 (1,085 ) 269 (a) Income tax effect 134 (171 ) 756 (392 ) 597 (66 ) (226 ) 279 (779 ) 635 (488 ) 203 (a) Marketable securities: Net realized gain on sale of securities 4,324 824 7,887 3,791 11,446 4,057 Investment and interest income, net 4,324 824 7,887 3,791 11,446 4,057 Income before income taxes Income tax effect (852 ) (133 ) (1,553 ) (699 ) (2,227 ) (771 ) Income tax expense 3,472 691 6,334 3,092 9,219 3,286 Net income Loss on cash flow hedge: Amortization of loss (118 ) (110 ) (348 ) (326 ) (460 ) (431 ) Interest on long-term debt and revolving credit facility (118 ) (110 ) (348 ) (326 ) (460 ) (431 ) Income before income taxes Income tax effect 46 42 161 174 201 213 Income tax expense (72 ) (68 ) (187 ) (152 ) (259 ) (218 ) Net income Total reclassifications $ 3,174 $ 902 $ 5,368 $ 3,575 $ 8,472 $ 3,271 (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, 2015
Common Stock, Number of Shares, Par Value and Other 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, 2015 2014 Weighted average number of common shares outstanding: Basic number of common shares outstanding 40,289,010 40,213,741 Dilutive effect of unvested performance awards 40,519 51,069 Diluted number of common shares outstanding 40,329,529 40,264,810 Basic net income per common share: Net income $ 56,740 $ 52,476 Income allocated to participating restricted stock (184 ) (175 ) Net income available to common shareholders $ 56,556 $ 52,301 Diluted net income per common share: Net income $ 56,740 $ 52,476 Income reallocated to participating restricted stock (184 ) (175 ) Net income available to common shareholders $ 56,556 $ 52,301 Basic net income per common share: Distributed earnings $ 0.295 $ 0.280 Undistributed earnings 1.105 1.020 Basic net income per common share $ 1.400 $ 1.300 Diluted net income per common share: Distributed earnings $ 0.295 $ 0.280 Undistributed earnings 1.105 1.020 Diluted net income per common share $ 1.400 $ 1.300 Nine Months Ended September 30, 2015 2014 Weighted average number of common shares outstanding: Basic number of common shares outstanding 40,267,533 40,181,367 Dilutive effect of unvested performance awards 32,268 27,634 Diluted number of common shares outstanding 40,299,801 40,209,001 Basic net income per common share: Net income $ 81,270 $ 87,187 Income allocated to participating restricted stock (253 ) (293 ) Net income available to common shareholders $ 81,017 $ 86,894 Diluted net income per common share: Net income $ 81,270 $ 87,187 Income reallocated to participating restricted stock (253 ) (293 ) Net income available to common shareholders $ 81,017 $ 86,894 Basic net income per common share: Distributed earnings $ 0.870 $ 0.825 Undistributed earnings 1.140 1.335 Basic net income per common share $ 2.010 $ 2.160 Diluted net income per common share: Distributed earnings $ 0.870 $ 0.825 Undistributed earnings 1.140 1.335 Diluted net income per common share $ 2.010 $ 2.160 Twelve Months Ended September 30, 2015 2014 Weighted average number of common shares outstanding: Basic number of common shares outstanding 40,255,439 40,169,801 Dilutive effect of unvested performance awards 24,201 20,726 Diluted number of common shares outstanding 40,279,640 40,190,527 Basic net income per common share: Net income $ 85,511 $ 88,378 Income allocated to participating restricted stock (265 ) (285 ) Net income available to common shareholders $ 85,246 $ 88,093 Diluted net income per common share: Net income $ 85,511 $ 88,378 Income reallocated to participating restricted stock (265 ) (285 ) Net income available to common shareholders $ 85,246 $ 88,093 Basic net income per common share: Distributed earnings $ 1.15 $ 1.09 Undistributed earnings 0.97 1.10 Basic net income per common share $ 2.12 $ 2.19 Diluted net income per common share: Distributed earnings $ 1.15 $ 1.09 Undistributed earnings 0.97 1.10 Diluted net income per common share $ 2.12 $ 2.19
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, 2015 2014 2015 2014 2015 2014 Restricted stock awards 65,076 59,627 60,647 60,264 60,742 59,296 Performance shares (a) 59,898 48,733 59,898 87,784 63,111 88,575 (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.

Employee Benefits (Tables)

Employee Benefits (Tables)	9 Months Ended
	Sep. 30, 2015
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, 2015 and 2014 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, 2015 2014 2015 2014 2015 2014 Components of net periodic benefit cost: Service cost $ 2,394 $ 2,112 $ 6,594 $ 6,474 $ 8,707 $ 8,805 Interest cost 3,622 3,691 10,872 11,351 14,563 14,755 Expected return on plan assets (4,951 ) (4,681 ) (14,846 ) (14,017 ) (19,528 ) (18,294 ) Amortization of: Net loss 2,485 2,283 7,985 6,571 10,267 9,346 Prior service benefit (855 ) (877 ) (2,630 ) (2,030 ) (3,506 ) (2,006 ) Net periodic benefit cost $ 2,695 $ 2,528 $ 7,975 $ 8,349 $ 10,503 $ 12,606
Other Postretirement Benefit 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, 2015 and 2014 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, 2015 2014 2015 2014 2015 2014 Components of net periodic benefit cost: Service cost $ 841 $ 712 $ 2,591 $ 2,134 $ 3,302 $ 2,805 Interest cost 976 1,115 3,026 3,347 4,142 4,461 Expected return on plan assets (503 ) (529 ) (1,553 ) (1,587 ) (2,082 ) (2,103 ) Amortization of: Prior service benefit (751 ) (1,188 ) (2,301 ) (3,564 ) (3,490 ) (4,979 ) Net gain (519 ) (668 ) (1,519 ) (2,004 ) (2,186 ) (2,630 ) Net periodic benefit cost (benefit) $ 44 $ (558 ) $ 244 $ (1,674 ) $ (314 ) $ (2,446 )

Financial Instruments And Inv23

Financial Instruments And Investments (Tables)	9 Months Ended
	Sep. 30, 2015
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, 2015 December 31, 2014 Carrying Amount Estimated Fair Value Carrying Amount Estimated Fair Value Pollution Control Bonds $ 193,135 $ 210,179 $ 193,135 $ 213,083 Senior Notes 846,123 994,040 846,044 968,728 RGRT Senior Notes (1) 95,000 101,745 110,000 117,215 RCF (1) 118,693 118,693 14,532 14,532 Total $ 1,252,951 $ 1,424,657 $ 1,163,711 $ 1,313,558 _______________ (1) Nuclear fuel financing of $95 million at September 30, 2015 and $110 million at December 31, 2014 , is funded through the RGRT Senior Notes and $33.7 million and $14.5 million , respectively under the RCF. As of September 30, 2015 , $85.0 million was outstanding under the RCF for working capital or general corporate purposes. As of December 31, 2014 , 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, 2015 Less than 12 Months 12 Months or Longer Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Description of Securities (1) : Federal Agency Mortgage Backed Securities $ 94 $ (1 ) $ 2,197 $ (46 ) $ 2,291 $ (47 ) U.S. Government Bonds 6,375 (58 ) 13,402 (432 ) 19,777 (490 ) Municipal Obligations 10,994 (244 ) 9,019 (493 ) 20,013 (737 ) Corporate Obligations 7,036 (406 ) 1,629 (135 ) 8,665 (541 ) Total Debt Securities 24,499 (709 ) 26,247 (1,106 ) 50,746 (1,815 ) Common Stock 6,958 (908 ) — — 6,958 (908 ) Institutional Funds-International Equity 21,536 (1,725 ) — — 21,536 (1,725 ) Equity Mutual Funds 8,792 (502 ) — — 8,792 (502 ) Total Temporarily Impaired Securities $ 61,785 $ (3,844 ) $ 26,247 $ (1,106 ) $ 88,032 $ (4,950 ) _________________ (1) Includes 141 securities. December 31, 2014 Less than 12 Months 12 Months or Longer Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Description of Securities (2) : Federal Agency Mortgage Backed Securities $ — $ — $ 2,383 $ (57 ) $ 2,383 $ (57 ) U.S. Government Bonds 1,552 (2 ) 20,060 (573 ) 21,612 (575 ) Municipal Obligations 6,433 (65 ) 8,570 (410 ) 15,003 (475 ) Corporate Obligations 2,455 (24 ) 2,461 (111 ) 4,916 (135 ) Total Debt Securities 10,440 (91 ) 33,474 (1,151 ) 43,914 (1,242 ) Common Stock 1,475 (229 ) — — 1,475 (229 ) Institutional Funds-International Equity 22,736 (821 ) — — 22,736 (821 ) Total Temporarily Impaired Securities $ 34,651 $ (1,141 ) $ 33,474 $ (1,151 ) $ 68,125 $ (2,292 ) _________________ (2) Includes 106 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 is expected or is scheduled 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, 2015 December 31, 2014 Fair Value Unrealized Gains Fair Value Unrealized Gains Description of Securities: Federal Agency Mortgage Backed Securities $ 18,780 $ 562 $ 15,388 $ 665 U.S. Government Bonds 25,250 468 20,016 567 Municipal Obligations 10,288 371 11,642 595 Corporate Obligations 11,419 490 13,762 850 Total Debt Securities 65,737 1,891 60,808 2,677 Common Stock 72,309 35,032 99,160 48,253 Cash and Cash Equivalents 5,807 — 6,193 — Total $ 143,853 $ 36,923 $ 166,161 $ 50,930
Contractual Year For Maturity Of Available-For-Sale Securities	The contractual year for maturity of these available-for-sale securities as of September 30, 2015 is as follows (in thousands): Total 2015 2016 2020 through 2024 2025 and Beyond Municipal Debt Obligations $ 30,301 $ — $ 10,193 $ 13,526 $ 6,582 Corporate Debt Obligations 20,084 697 5,720 7,594 6,073 U.S. Government Bonds 45,027 3,051 15,666 16,844 9,466
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, 2015 2014 2015 2014 2015 2014 Proceeds from sales or maturities of available-for-sale securities $ 26,618 $ 10,980 $ 63,776 $ 47,355 $ 124,732 $ 74,083 Gross realized gains included in pre-tax income $ 4,515 $ 1,239 $ 8,330 $ 4,502 $ 12,467 $ 4,895 Gross realized losses included in pre-tax income (191 ) (415 ) (443 ) (711 ) (1,021 ) (838 ) Net gains in pre-tax income $ 4,324 $ 824 $ 7,887 $ 3,791 $ 11,446 $ 4,057 Net unrealized holding gains (losses) included in accumulated other comprehensive income $ (8,092 ) $ 897 $ (8,641 ) $ 7,965 $ (5,779 ) $ 16,803 Net gains reclassified out of accumulated other comprehensive income (4,324 ) (824 ) (7,887 ) (3,791 ) (11,446 ) (4,057 ) Net gains (losses) in other comprehensive income $ (12,416 ) $ 73 $ (16,528 ) $ 4,174 $ (17,225 ) $ 12,746
Fair Value, Measurement Inputs, Disclosure	The fair value of the Company's decommissioning trust funds and investment in debt securities, at September 30, 2015 and December 31, 2014 , 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, 2015 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Trading Securities: Investments in Debt Securities $ 1,573 $ — $ — $ 1,573 Available for sale: U.S. Government Bonds $ 45,027 $ 45,027 $ — $ — Federal Agency Mortgage Backed Securities 21,071 — 21,071 — Municipal Obligations 30,301 — 30,301 — Corporate Obligations 20,084 — 20,084 — Subtotal, Debt Securities 116,483 45,027 71,456 — Common Stock 79,267 79,267 — — Equity Mutual Funds 8,792 8,792 — — Institutional Funds-International Equity 21,536 — 21,536 — Cash and Cash Equivalents 5,807 5,807 — — Total available for sale $ 231,885 $ 138,893 $ 92,992 $ — Description of Securities Fair Value as of December 31, 2014 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Trading Securities: Investments in Debt Securities $ 1,653 $ — $ — $ 1,653 Available for sale: U.S. Government Bonds $ 41,628 $ 41,628 $ — $ — Federal Agency Mortgage Backed Securities 17,771 — 17,771 — Municipal Obligations 26,645 — 26,645 — Corporate Obligations 18,678 — 18,678 — Subtotal, Debt Securities 104,722 41,628 63,094 — Common Stock 100,635 100,635 — — Institutional Funds-International Equity 22,736 — 22,736 — Cash and Cash Equivalents 6,193 6,193 — — Total available for sale $ 234,286 $ 148,456 $ 85,830 $ —

Principles Of Preparation (Accr

Principles Of Preparation (Accrued Unbilled Revenues) (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Accounting Policies [Abstract]
Accrued unbilled revenues	$ 30.1	$ 21.2

Principles Of Preparation (Supp

Principles Of Preparation (Supplemental Cash Flow Disclosures) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Supplemental Cash Flow Information [Abstract]
Interest on long-term debt and borrowing under the revolving credit facility	$ 41,406	$ 37,689
Income tax paid (refunded), net	(272)	2,969
Changes in accrued plant additions	(13,150)	(3,762)
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants of restricted shares of common stock	$ 1,106	$ 3,025

Accumulated Other Comprehensi26

Accumulated Other Comprehensive Income by Component (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended		12 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss), beginning balance				$ (8,001)
Accumulated Other Comprehensive Income (Loss), ending balance		$ (20,223)		(20,223)		$ (20,223)
Accumulated Defined Benefit Plans Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss), beginning balance		(34,331)	$ (9,539)	(34,884)	$ (21,330)	(9,818)	$ (73,133)
Other Comprehensive Income (Loss) before Reclassifications		0	0	0	12,147	(24,775)	63,518
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	[1]	226	(279)	779	(635)	488	(203)
Accumulated Other Comprehensive Income (Loss), ending balance		(34,105)	(9,818)	(34,105)	(9,818)	(34,105)	(9,818)
Accumulated Net Unrealized Investment Gain (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss), beginning balance		35,726	39,483	38,957	36,240	39,525	29,335
Other Comprehensive Income (Loss) before Reclassifications		(6,485)	733	(6,854)	6,377	(4,537)	13,476
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)		(3,472)	(691)	(6,334)	(3,092)	(9,219)	(3,286)
Accumulated Other Comprehensive Income (Loss), ending balance		25,769	39,525	25,769	39,525	25,769	39,525
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss), beginning balance		(11,959)	(12,214)	(12,074)	(12,298)	(12,146)	(12,364)
Other Comprehensive Income (Loss) before Reclassifications		0	0	0	0	0	0
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)		72	68	187	152	259	218
Accumulated Other Comprehensive Income (Loss), ending balance		(11,887)	(12,146)	(11,887)	(12,146)	(11,887)	(12,146)
AOCI Attributable to Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss), beginning balance		(10,564)	17,730	(8,001)	2,612	17,561	(56,162)
Other Comprehensive Income (Loss) before Reclassifications		(6,485)	733	(6,854)	18,524	(29,312)	76,994
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)		(3,174)	(902)	(5,368)	(3,575)	(8,472)	(3,271)
Accumulated Other Comprehensive Income (Loss), ending balance		$ (20,223)	$ 17,561	$ (20,223)	$ 17,561	$ (20,223)	$ 17,561
[1]	These items are included in the computation of net periodic benefit cost. See Note I, Employee Benefits, for additional information.

Accumulated Other Comprehensi27

Accumulated Other Comprehensive Income Amounts Reclassified (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended		12 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income (Loss) before income tax		$ 81,340	$ 75,138	$ 116,359	$ 126,085	$ 122,790	$ 124,603
Income tax expense		(24,600)	(22,662)	(35,089)	(38,898)	(37,279)	(36,225)
Net (Income) Loss		56,740	52,476	81,270	87,187	85,511	88,378
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	[1]	1,606	2,065	4,931	5,594	6,996	6,985
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	[1]	(1,966)	(1,615)	(6,466)	(4,567)	(8,081)	(6,716)
Accumulated Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	[1]	(360)	450	(1,535)	1,027	(1,085)	269
Reclassification from AOCI, Current Period, Tax		134	(171)	756	(392)	597	(66)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1]	(226)	279	(779)	635	(488)	203
Accumulated Net Unrealized Investment Gain (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax		3,472	691	6,334	3,092	9,219	3,286
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax		(72)	(68)	(187)	(152)	(259)	(218)
Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax		(3,174)	(902)	(5,368)	(3,575)	(8,472)	(3,271)
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		4,324	824	7,887	3,791	11,446	4,057
Income (Loss) before income tax		4,324	824	7,887	3,791	11,446	4,057
Income tax expense		(852)	(133)	(1,553)	(699)	(2,227)	(771)
Net (Income) Loss		3,472	691	6,334	3,092	9,219	3,286
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]
Income (Loss) before income tax		(118)	(110)	(348)	(326)	(460)	(431)
Income tax expense		46	42	161	174	201	213
Net (Income) Loss		(72)	(68)	(187)	(152)	(259)	(218)
Interest Rate Contract | 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		$ (118)	$ (110)	$ (348)	$ (326)	$ (460)	$ (431)
[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) $ in Thousands

Nov. 05, 2015USD ($)

Aug. 10, 2015USD ($)

May. 20, 2015

May. 11, 2015USD ($)

May. 01, 2015USD ($)

Nov. 14, 2014USD ($)

Jul. 11, 2014USD ($)

May. 01, 2014USD ($)

Sep. 30, 2015USD ($)

Sep. 30, 2015USD ($)MW

Oct. 19, 2015USD ($)

Oct. 07, 2015USD ($)

Dec. 31, 2014USD ($)

Under-collection of fuel revenues

$ 2,429

$ 2,429

$ 10,253

PUCT Docket No. 41852

Reconcilable Fuel Expense

$ 545,300

Fuel Reconciliation Period

45 months

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

Apr. 1, 2014

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

Jun. 30, 2015

Fixed Fuel Factor | PUCT Docket No. 44633

Percent Increase (Decrease) In Fixed Fuel Factor

(24.00%)

Non-Arbitrage Sales | PUCT Docket No. 41852

Customers' Percentage of Off System Sales Margins

100.00%

Arbitrage Sales | PUCT Docket No. 41852

Customers' Percentage of Off System Sales Margins

50.00%

Minimum

Fixed Fuel Factor Revision Period, in Months

4 months

Maximum | PUCT Docket No. 41852

Retained Percentage of Total Off System Sales Margins

10.00%

PUCT

Period To Relate Back New Rates

155 days

Public Utilities Approved Performance Incentive Bonus Related To Energy Efficiency Program

$ 2,000

Public Utilities Requested Performance Incentive Bonus Related To Energy Efficiency Program

$ 1,000

$ 2,000

Fuel Over And Under Materiality Threshold Percentage

4.00%

4.00%

Under-collection of fuel revenues

$ 2,400

$ 2,400

PUCT | Non-Fuel Base Rate

Public Utilities, Requested Rate Increase (Decrease), Amount

$ 71,500

PUCT | Four Corners Generating Station

Purchase and Sale Agreement, Execution Date

Feb. 17, 2015

Disposal Date

Jul. 6, 2016

PUCT | Montana Power Station

Number of power generation units authorized to be constructed

4

Property, Plant and Equipment, Operational Date

Mar. 20, 2015

PUCT | Fort Bliss

Electric Capacity | MW

20

PUCT | Community Solar At Montana Power Station

Electric Capacity | MW

3

PUCT | Maximum

Surcharge Or Refund Period

18 months

PUCT | Subsequent Event

Public Utilities Approved Performance Incentive Bonus Related To Energy Efficiency Program

$ 1,000

NMPRC | Non-Fuel Base Rate

Public Utilities, Requested Rate Increase (Decrease), Amount

$ 8,600

Public Utilities, Requested Rate Increase (Decrease), Percentage

7.10%

NMPRC | Fuel In Base Rate

Public Utilities, Requested Rate Increase (Decrease), Amount

$ (15,400)

Public Utilities, Requested Rate Increase (Decrease), Percentage

(21.50%)

NMPRC | Four Corners Generating Station

Purchase and Sale Agreement, Execution Date

Feb. 17, 2015

Disposal Date

Jul. 6, 2016

NMPRC | Montana Power Station

Number of power generation units authorized to be constructed

4

Property, Plant and Equipment, Operational Date

Mar. 20, 2015

NMPRC | Fort Bliss

Electric Capacity | MW

20

NMPRC | Holloman

Electric Capacity | MW

5

NMPRC | Subsequent Event

Debt Instrument, Face Amount

$ 310,000

FERC

Debt Issuance Authorization Date Range Start

Nov. 15, 2015

Debt Issuance Authorization Date Range End

Nov. 15, 2017

FERC | Four Corners Generating Station

Jointly Owned Utility Plant Entire Ownership Of Proportionate Interest, Percentage

100.00%

100.00%

FERC | Subsequent Event

Debt Instrument, Face Amount

$ 310,000

Line of Credit Facility, Maximum Borrowing Capacity

400,000

RGRT | NMPRC | Subsequent Event

Debt Instrument, Face Amount

$ 65,000

RGRT | FERC | Subsequent Event

Debt Instrument, Face Amount

$ 65,000

Palo Verde (Narrative) (Detail

Palo Verde (Narrative) (Details) - USD ($) $ in Millions	Jun. 01, 2015	Oct. 31, 2014	Oct. 08, 2014	Aug. 18, 2014	Dec. 19, 2012
Jointly Owned Utility Plant Interests [Line Items]
Settlement Agreement, Date				August 18, 2014
Suit Against Department of Energy for Spent Fuel
Jointly Owned Utility Plant Interests [Line Items]
Settlement Agreement, Counterparty's Name					U.S. Department of Energy
Lawsuit Filing Date		October 31, 2014			December 19, 2012
Suit Against Department of Energy for Spent Fuel | Palo Verde Generating Station
Jointly Owned Utility Plant Interests [Line Items]
Settlement, Amount	$ 6.6		$ 9.1
Settlement Agreement Award Received, Date	Jun. 1, 2015		Oct. 8, 2014
Suit Against Department of Energy for Spent Fuel | Palo Verde Participants
Jointly Owned Utility Plant Interests [Line Items]
Settlement, Amount		$ 42		$ 57.4
Minimum | Suit Against Department of Energy for Spent Fuel
Jointly Owned Utility Plant Interests [Line Items]
Litigation, Period Covered		July 1, 2011			January 1, 2007
Maximum | Suit Against Department of Energy for Spent Fuel
Jointly Owned Utility Plant Interests [Line Items]
Litigation, Period Covered		June 30, 2014			June 30, 2011

Common Stock (Narrative) (Detai

Common Stock (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Dividends, Common Stock, Cash	$ 11,900	$ 11,300	$ 35,138	$ 33,261	$ 46,400	$ 43,900

Common Stock (Basic And Diluted

Common Stock (Basic And Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Earnings Per Share [Abstract]
Basic number of common shares outstanding	40,289,010	40,213,741	40,267,533	40,181,367	40,255,439	40,169,801
Dilutive effect of unvested performance awards	40,519	51,069	32,268	27,634	24,201	20,726
Diluted number of common shares outstanding	40,329,529	40,264,810	40,299,801	40,209,001	40,279,640	40,190,527
Net income	$ 56,740	$ 52,476	$ 81,270	$ 87,187	$ 85,511	$ 88,378
Income allocated to participating restricted stock	(184)	(175)	(253)	(293)	(265)	(285)
Net income available to common shareholders, basic	56,556	52,301	81,017	86,894	85,246	88,093
Income reallocated to participating restricted stock	(184)	(175)	(253)	(293)	(265)	(285)
Net income available to common shareholders, diluted	$ 56,556	$ 52,301	$ 81,017	$ 86,894	$ 85,246	$ 88,093
Earnings Per Share, Basic, Distributed	$ 0.295	$ 0.280	$ 0.870	$ 0.825	$ 1.150	$ 1.090
Earnings Per Share, Basic, Undistributed	1.105	1.020	1.140	1.335	0.970	1.100
Basic net income per common share	1.400	1.300	2.010	2.160	2.120	2.190
Earnings Per Share, Diluted, Distributed	0.295	0.280	0.870	0.825	1.150	1.090
Earnings Per Sare, Diluted, Undistributed	1.105	1.020	1.140	1.335	0.970	1.100
Diluted net income per common share	$ 1.400	$ 1.300	$ 2.010	$ 2.160	$ 2.120	$ 2.190

Common Stock (Antidilutive Secu

Common Stock (Antidilutive Securities Excluded From Computation Of Earnings Per Share) (Details) - shares		3 Months Ended		9 Months Ended		12 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
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		65,076	59,627	60,647	60,264	60,742	59,296
Performance Shares
Antidilutive Securities Excluded from the Computation of Diluted Earnings Per Share, Amount	[1]	59,898	48,733	59,898	87,784	63,111	88,575
[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, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Income Tax [Line Items]
Consolidated effective tax rate	30.20%	30.20%	30.20%	30.90%	30.40%	29.10%
Federal statutory tax rate	35.00%		35.00%		35.00%
Income Tax Rate Capital Gains	20.00%		20.00%
Tax Year 2015 | TEXAS
Income Tax [Line Items]
State Franchise Tax Rate			0.75%
Tax Year 2014 | TEXAS
Income Tax [Line Items]
State Franchise Tax Rate			0.95%

Income Taxes (Details)

Income Taxes (Details)	9 Months Ended
	Sep. 30, 2015
Internal Revenue Service (IRS) | Maximum
Income Tax [Line Items]
Tax Year Closed	2,009
NEW MEXICO | Maximum
Income Tax [Line Items]
Tax Year Closed	2,009
TEXAS | Earliest Tax Year
Income Tax [Line Items]
Income Tax Examination, Year under Examination	2,007
TEXAS | Latest Tax Year
Income Tax [Line Items]
Income Tax Examination, Year under Examination	2,011
ARIZONA | Earliest Tax Year
Income Tax [Line Items]
Income Tax Examination, Year under Examination	2,009
ARIZONA | Latest Tax Year
Income Tax [Line Items]
Income Tax Examination, Year under Examination	2,012

Commitments, Contingencies An35

Commitments, Contingencies And Uncertainties (Power Purchase and Sale Contracts) (Details) - Subsequent Event - Freeport Agreement 3 - 25 MW - MW	Oct. 13, 2015	Oct. 12, 2015
Long-term Contract for Purchase of Electric Power [Line Items]
Long-term Purchase Commitment, Date of Contract Expiration	Dec. 31, 2016	Dec. 31, 2015
Long-term Sales Commitment, Date of Contract Expiration	Dec. 31, 2016	Dec. 31, 2015
Maximum
Long-term Contract for Purchase of Electric Power [Line Items]
Long-Term Purchase Commitment, Quantity	25
Long-Term Sale Commitment, Quantity	25

Commitments, Contingencies An36

Commitments, Contingencies And Uncertainties (Narrative) (Details) $ in Millions	Aug. 17, 2015USD ($)	Sep. 30, 2015USD ($)Decimals	Jul. 28, 2015States
Loss Contingencies [Line Items]
Number of States Affected by EPA's Emissions Budgets | States			13
Number of criteria emissions established under the Clear Air Act		6
Frequency of Review by Environmental Protection Agency		5 years
Jointly Owned Utility Plant, Proportionate Ownership Share		7.00%
Accrual for Environmental Loss Contingencies		$ 0.5
Four Corners Coal Plant Participants
Loss Contingencies [Line Items]
Civil Penalty Amount	$ 1.5
Environmental Mitigation Project Cost	$ 6.7
Public Utilities, Assessed Coal Severance Surtax Penalty and Interest		30
Four Corners Generating Station
Loss Contingencies [Line Items]
Public Utilities, Assessed Coal Severance Surtax Penalty and Interest		$ 1.5
Four Corners Generating Station
Loss Contingencies [Line Items]
Date participation is ceased		Jul. 6, 2016
Minimum
Loss Contingencies [Line Items]
Public Utilities, Government Standard Emission Limit | Decimals		70
Maximum
Loss Contingencies [Line Items]
Public Utilities, Government Standard Emission Limit | Decimals		75

Employee Benefits (Retirement P

Employee Benefits (Retirement Plans And Other Postretirement Benefits) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Retirement Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2,394	$ 2,112	$ 6,594	$ 6,474	$ 8,707	$ 8,805
Interest cost	3,622	3,691	10,872	11,351	14,563	14,755
Expected return on plan assets	(4,951)	(4,681)	(14,846)	(14,017)	(19,528)	(18,294)
Amortization of prior service benefit	(855)	(877)	(2,630)	(2,030)	(3,506)	(2,006)
Amortization of net (gain) loss	2,485	2,283	7,985	6,571	10,267	9,346
Net periodic benefit cost (benefit)	2,695	2,528	7,975	8,349	10,503	12,606
Other Postretirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	841	712	2,591	2,134	3,302	2,805
Interest cost	976	1,115	3,026	3,347	4,142	4,461
Expected return on plan assets	(503)	(529)	(1,553)	(1,587)	(2,082)	(2,103)
Amortization of prior service benefit	(751)	(1,188)	(2,301)	(3,564)	(3,490)	(4,979)
Amortization of net (gain) loss	(519)	(668)	(1,519)	(2,004)	(2,186)	(2,630)
Net periodic benefit cost (benefit)	$ 44	$ (558)	$ 244	$ (1,674)	$ (314)	$ (2,446)

Employee Benefits (Narrative) (

Employee Benefits (Narrative) (Details) $ in Millions	9 Months Ended
	Sep. 30, 2015USD ($)
Retirement Plans
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Employer Contribution	$ 10.4
Defined Benefit Plan, Expected Contributions in Current Fiscal Year	11.1
Other Postretirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Employer Contribution	0
Defined Benefit Plan, Expected Contributions in Current Fiscal Year	$ 0

Financial Instruments And Inv39

Financial Instruments And Investments (Carrying Amount and Fair Value Amounts) (Details) - USD ($) $ in Thousands		Sep. 30, 2015	Dec. 31, 2014
Carrying (Reported) Amount, Fair Value Disclosure
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Fair Value Disclosure		$ 1,252,951	$ 1,163,711
Carrying (Reported) Amount, Fair Value Disclosure | Pollution Control Bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Fair Value Disclosure		193,135	193,135
Carrying (Reported) Amount, Fair Value Disclosure | Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Fair Value Disclosure		846,123	846,044
Carrying (Reported) Amount, Fair Value Disclosure | RGRT Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Fair Value Disclosure	[1]	95,000	110,000
Carrying (Reported) Amount, Fair Value Disclosure | Revolving Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Fair Value Disclosure	[1]	118,693	14,532
Estimate of Fair Value Measurement
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Fair Value Disclosure		1,424,657	1,313,558
Estimate of Fair Value Measurement | Pollution Control Bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Fair Value Disclosure		210,179	213,083
Estimate of Fair Value Measurement | Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Fair Value Disclosure		994,040	968,728
Estimate of Fair Value Measurement | RGRT Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Fair Value Disclosure	[1]	101,745	117,215
Estimate of Fair Value Measurement | Revolving Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Fair Value Disclosure	[1]	$ 118,693	$ 14,532
[1]	Nuclear fuel financing of $95 million at September 30, 2015 and $110 million at December 31, 2014, is funded through the RGRT Senior Notes and $33.7 million and $14.5 million, respectively under the RCF. As of September 30, 2015, $85.0 million was outstanding under the RCF for working capital or general corporate purposes. As of December 31, 2014, 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 Inv40

Financial Instruments And Investments (Long-Term Debt and Short-Term Borrowings - Narratives) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Financial Instruments and Investments [Line Items]
Decommissioning Fund Investments	$ 231,885	$ 234,286
Nuclear Fuel Financing
Financial Instruments and Investments [Line Items]
Line of Credit Facility, Amount Outstanding	33,700	14,500
Working Capital and General Purpose
Financial Instruments and Investments [Line Items]
Line of Credit Facility, Amount Outstanding	85,000	0
RGRT Senior Notes
Financial Instruments and Investments [Line Items]
Long-term Debt, Gross	$ 95,000	$ 110,000

Financial Instruments And Inv41

Financial Instruments And Investments (Marketable Securities Fair Value And Unrealized Losses) (Details) $ in Thousands		9 Months Ended		12 Months Ended
		Sep. 30, 2015USD ($)securities		Dec. 31, 2014USD ($)securities
Financial Instruments and Investments [Line Items]
Marketable Securities Fair Value Less than 12 Months		$ 61,785	[1]	$ 34,651	[2]
Marketable Securities Unrealized Losses Less Than 12 Months		(3,844)	[1]	(1,141)	[2]
Marketable Securities Fair Value 12 Months or Longer		26,247	[1]	33,474	[2]
Marketable Securities Unrealized Losses 12 Months or Longer		(1,106)	[1]	(1,151)	[2]
Marketable Securities Fair Value Total		88,032	[1]	68,125	[2]
Marketable Securities Unrealized Losses Total		$ (4,950)	[1]	$ (2,292)	[2]
Number of securities | securities		141		106
Debt Securities
Financial Instruments and Investments [Line Items]
Marketable Securities Fair Value Less than 12 Months		$ 24,499	[1]	$ 10,440	[2]
Marketable Securities Unrealized Losses Less Than 12 Months		(709)	[1]	(91)	[2]
Marketable Securities Fair Value 12 Months or Longer		26,247	[1]	33,474	[2]
Marketable Securities Unrealized Losses 12 Months or Longer		(1,106)	[1]	(1,151)	[2]
Marketable Securities Fair Value Total		50,746	[1]	43,914	[2]
Marketable Securities Unrealized Losses Total		(1,815)	[1]	(1,242)	[2]
Collateralized Mortgage Backed Securities
Financial Instruments and Investments [Line Items]
Marketable Securities Fair Value Less than 12 Months		94	[1]	0	[2]
Marketable Securities Unrealized Losses Less Than 12 Months		(1)	[1]	0	[2]
Marketable Securities Fair Value 12 Months or Longer		2,197	[1]	2,383	[2]
Marketable Securities Unrealized Losses 12 Months or Longer		(46)	[1]	(57)	[2]
Marketable Securities Fair Value Total		2,291	[1]	2,383	[2]
Marketable Securities Unrealized Losses Total		(47)	[1]	(57)	[2]
U.S. Government Bonds
Financial Instruments and Investments [Line Items]
Marketable Securities Fair Value Less than 12 Months		6,375	[1]	1,552	[2]
Marketable Securities Unrealized Losses Less Than 12 Months		(58)	[1]	(2)	[2]
Marketable Securities Fair Value 12 Months or Longer		13,402	[1]	20,060	[2]
Marketable Securities Unrealized Losses 12 Months or Longer		(432)	[1]	(573)	[2]
Marketable Securities Fair Value Total		19,777	[1]	21,612	[2]
Marketable Securities Unrealized Losses Total		(490)	[1]	(575)	[2]
Municipal Bonds
Financial Instruments and Investments [Line Items]
Marketable Securities Fair Value Less than 12 Months		10,994	[1]	6,433	[2]
Marketable Securities Unrealized Losses Less Than 12 Months		(244)	[1]	(65)	[2]
Marketable Securities Fair Value 12 Months or Longer		9,019	[1]	8,570	[2]
Marketable Securities Unrealized Losses 12 Months or Longer		(493)	[1]	(410)	[2]
Marketable Securities Fair Value Total		20,013	[1]	15,003	[2]
Marketable Securities Unrealized Losses Total		(737)	[1]	(475)	[2]
Corporate Debt Securities
Financial Instruments and Investments [Line Items]
Marketable Securities Fair Value Less than 12 Months		7,036	[1]	2,455	[2]
Marketable Securities Unrealized Losses Less Than 12 Months		(406)	[1]	(24)	[2]
Marketable Securities Fair Value 12 Months or Longer		1,629	[1]	2,461	[2]
Marketable Securities Unrealized Losses 12 Months or Longer		(135)	[1]	(111)	[2]
Marketable Securities Fair Value Total		8,665	[1]	4,916	[2]
Marketable Securities Unrealized Losses Total		(541)	[1]	(135)	[2]
Equity Securities
Financial Instruments and Investments [Line Items]
Marketable Securities Fair Value Less than 12 Months		6,958	[1]	1,475	[2]
Marketable Securities Unrealized Losses Less Than 12 Months		(908)	[1]	(229)	[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		6,958	[1]	1,475	[2]
Marketable Securities Unrealized Losses Total		(908)	[1]	(229)	[2]
Institutional Funds-International Equity
Financial Instruments and Investments [Line Items]
Marketable Securities Fair Value Less than 12 Months		21,536	[1]	22,736	[2]
Marketable Securities Unrealized Losses Less Than 12 Months		(1,725)	[1]	(821)	[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		21,536	[1]	22,736	[2]
Marketable Securities Unrealized Losses Total		(1,725)	[1]	$ (821)	[2]
Equity Funds
Financial Instruments and Investments [Line Items]
Marketable Securities Fair Value Less than 12 Months	[1]	8,792
Marketable Securities Unrealized Losses Less Than 12 Months	[1]	(502)
Marketable Securities Fair Value 12 Months or Longer	[1]	0
Marketable Securities Unrealized Losses 12 Months or Longer	[1]	0
Marketable Securities Fair Value Total	[1]	8,792
Marketable Securities Unrealized Losses Total	[1]	$ (502)
[1]	Includes 141 securities.
[2]	Includes 106 securities.

Financial Instruments And Inv42

Financial Instruments And Investments (Unrecognized Gross Unrealized Gains And The Fair Value) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Financial Instruments and Investments [Line Items]
Available-for-sale Securities, Unrealized Gain Position, Fair Value	$ 143,853	$ 166,161
Available-for-sale Securities, Gross Unrealized Gain	36,923	50,930
Debt Securities
Financial Instruments and Investments [Line Items]
Available-for-sale Securities, Unrealized Gain Position, Fair Value	65,737	60,808
Available-for-sale Securities, Gross Unrealized Gain	1,891	2,677
Collateralized Mortgage Backed Securities
Financial Instruments and Investments [Line Items]
Available-for-sale Securities, Unrealized Gain Position, Fair Value	18,780	15,388
Available-for-sale Securities, Gross Unrealized Gain	562	665
U.S. Government Bonds
Financial Instruments and Investments [Line Items]
Available-for-sale Securities, Unrealized Gain Position, Fair Value	25,250	20,016
Available-for-sale Securities, Gross Unrealized Gain	468	567
Municipal Bonds
Financial Instruments and Investments [Line Items]
Available-for-sale Securities, Unrealized Gain Position, Fair Value	10,288	11,642
Available-for-sale Securities, Gross Unrealized Gain	371	595
Corporate Debt Securities
Financial Instruments and Investments [Line Items]
Available-for-sale Securities, Unrealized Gain Position, Fair Value	11,419	13,762
Available-for-sale Securities, Gross Unrealized Gain	490	850
Equity Securities
Financial Instruments and Investments [Line Items]
Available-for-sale Securities, Unrealized Gain Position, Fair Value	72,309	99,160
Available-for-sale Securities, Gross Unrealized Gain	35,032	48,253
Cash and Cash Equivalents
Financial Instruments and Investments [Line Items]
Available-for-sale Securities, Unrealized Gain Position, Fair Value	5,807	6,193
Available-for-sale Securities, Gross Unrealized Gain	$ 0	$ 0

Financial Instruments And Inv43

Financial Instruments And Investments (Contractual Year For Maturity Of Available-For-Sale Securities ) (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2015USD ($)
Collateralized Mortgage Backed Securities
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	$ 30,301
2,015	0
2016 through 2019	10,193
2020 through 2024	13,526
2025 and Beyond	6,582
Corporate Debt Obligations
Schedule of Available-for-sale Securities [Line Items]
Total	20,084
2,015	697
2016 through 2019	5,720
2020 through 2024	7,594
2025 and Beyond	6,073
U.S. Government Bonds
Schedule of Available-for-sale Securities [Line Items]
Total	45,027
2,015	3,051
2016 through 2019	15,666
2020 through 2024	16,844
2025 and Beyond	$ 9,466
Minimum | Collateralized Mortgage Backed Securities
Schedule of Available-for-sale Securities [Line Items]
Debt Instrument, Expected Weighted Average Maturity Year	2 years
Maximum | Collateralized Mortgage Backed Securities
Schedule of Available-for-sale Securities [Line Items]
Debt Instrument, Expected Weighted Average Maturity Year	6 years

Financial Instruments And Inv44

Financial Instruments And Investments (Sale Of Securities And The Related Effects On Pre-Tax Income ) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Investment [Line Items]
Proceeds from sales of available-for-sale securities	$ 26,618	$ 10,980	$ 63,776	$ 47,355	$ 124,732	$ 74,083
Gross realized gains included in pre-tax income	4,515	1,239	8,330	4,502	12,467	4,895
Gross realized losses included in pre-tax income	(191)	(415)	(443)	(711)	(1,021)	(838)
Net gains (losses) in pre-tax income	4,324	824	7,887	3,791	11,446	4,057
Net unrealized holding gains (losses) included in accumulated other comprehensive income	(8,092)	897	(8,641)	7,965	(5,779)	16,803
Net (gains) losses reclassified out of accumulated other comprehensive income	(4,324)	(824)	(7,887)	(3,791)	(11,446)	(4,057)
Net gains (losses) in other comprehensive income	$ (12,416)	$ 73	$ (16,528)	$ 4,174	$ (17,225)	$ 12,746

Financial Instruments And Inv45

Financial Instruments And Investments (Company's Decommissioning Trust Funds And Investments In Debt Securities) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Decommisioning Fund Investments
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	$ 231,885	$ 234,286
Decommisioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	138,893	148,456
Decommisioning Fund Investments | Significant Other Observable Inputs (Level 2)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	92,992	85,830
Decommisioning 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]
Trading Securities	1,573	1,653
Debt Securities | Quoted Prices In Active Markets For Identical Assets (Level 1)
Financial Instruments and Investments [Line Items]
Trading Securities	0	0
Debt Securities | Significant Other Observable Inputs (Level 2)
Financial Instruments and Investments [Line Items]
Trading Securities	0	0
Debt Securities | Significant Unobservable Inputs (Level 3)
Financial Instruments and Investments [Line Items]
Trading Securities	1,573	1,653
Debt Securities | Decommisioning Fund Investments
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	116,483	104,722
Debt Securities | Decommisioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	45,027	41,628
Debt Securities | Decommisioning Fund Investments | Significant Other Observable Inputs (Level 2)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	71,456	63,094
Debt Securities | Decommisioning Fund Investments | Significant Unobservable Inputs (Level 3)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	0	0
U.S. Government Bonds | Decommisioning Fund Investments
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	45,027	41,628
U.S. Government Bonds | Decommisioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	45,027	41,628
U.S. Government Bonds | Decommisioning Fund Investments | Significant Other Observable Inputs (Level 2)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	0	0
U.S. Government Bonds | Decommisioning Fund Investments | Significant Unobservable Inputs (Level 3)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	0	0
Collateralized Mortgage Backed Securities | Decommisioning Fund Investments
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	21,071	17,771
Collateralized Mortgage Backed Securities | Decommisioning 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 | Decommisioning Fund Investments | Significant Other Observable Inputs (Level 2)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	21,071	17,771
Collateralized Mortgage Backed Securities | Decommisioning Fund Investments | Significant Unobservable Inputs (Level 3)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	0	0
Municipal Bonds | Decommisioning Fund Investments
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	30,301	26,645
Municipal Bonds | Decommisioning 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 | Decommisioning Fund Investments | Significant Other Observable Inputs (Level 2)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	30,301	26,645
Municipal Bonds | Decommisioning Fund Investments | Significant Unobservable Inputs (Level 3)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	0	0
Corporate Debt Securities | Decommisioning Fund Investments
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	20,084	18,678
Corporate Debt Securities | Decommisioning 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 | Decommisioning Fund Investments | Significant Other Observable Inputs (Level 2)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	20,084	18,678
Corporate Debt Securities | Decommisioning Fund Investments | Significant Unobservable Inputs (Level 3)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	0	0
Equity Securities | Decommisioning Fund Investments
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	79,267	100,635
Equity Securities | Decommisioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	79,267	100,635
Equity Securities | Decommisioning Fund Investments | Significant Other Observable Inputs (Level 2)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	0	0
Equity Securities | Decommisioning Fund Investments | Significant Unobservable Inputs (Level 3)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	0	0
Equity Funds | Decommisioning Fund Investments
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	8,792
Equity Funds | Decommisioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	8,792
Equity Funds | Decommisioning Fund Investments | Significant Other Observable Inputs (Level 2)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	0
Equity Funds | Decommisioning Fund Investments | Significant Unobservable Inputs (Level 3)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	0
Institutional Funds-International Equity | Decommisioning Fund Investments
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	21,536	22,736
Institutional Funds-International Equity | Decommisioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	0	0
Institutional Funds-International Equity | Decommisioning Fund Investments | Significant Other Observable Inputs (Level 2)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	21,536	22,736
Institutional Funds-International Equity | Decommisioning Fund Investments | Significant Unobservable Inputs (Level 3)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	0	0
Cash and Cash Equivalents | Decommisioning Fund Investments
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	5,807	6,193
Cash and Cash Equivalents | Decommisioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	5,807	6,193
Cash and Cash Equivalents | Decommisioning Fund Investments | Significant Other Observable Inputs (Level 2)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	0	0
Cash and Cash Equivalents | Decommisioning Fund Investments | Significant Unobservable Inputs (Level 3)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	$ 0	$ 0

Financial Instruments And Inv46

Financial Instruments And Investments Transfers Between Levels (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Fair Value Disclosures [Abstract]
Fair Value, Assets, Level 1 to Level 2 Transfers, Description	no	no	no	no	no	no
Fair Value, Assets, Level 2 to Level 1 Transfers, Description	no	no	no	no	no	no
Fair Value, Asset, Level 3 Purchases, (Sales), Issuances, (Settlements)	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0