Old Dominion Electric Cooperative 10-Q 13 Nov 18 2018 Q3 Quarterly report Financial data

Document And Entity Information

Document And Entity Information	9 Months Ended
	Sep. 30, 2018shares
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3
Entity Registrant Name	OLD DOMINION ELECTRIC COOPERATIVE
Entity Central Index Key	885,568
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding	0

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Electric Plant:
Property, plant, and equipment	$ 2,447,398	$ 1,754,236
Less accumulated depreciation	(853,599)	(891,701)
Net Property, plant, and equipment	1,593,799	862,535
Nuclear fuel, at amortized cost	17,911	18,089
Construction work in progress	33,888	822,667
Net Electric Plant	1,645,598	1,703,291
Investments:
Nuclear decommissioning trust	191,223	183,681
Lease deposits	32,653	106,812
Unrestricted investments and other	7,179	7,009
Total Investments	231,055	297,502
Current Assets:
Cash and cash equivalents	71,447	4,084
Restricted cash and cash equivalents	14,200
Accounts receivable	11,660	10,379
Accounts receivable–members	84,180	83,133
Fuel, materials, and supplies	45,423	52,766
Deferred energy	21,755	3,669
Prepayments and other	4,835	5,274
Total Current Assets	253,500	159,305
Deferred Charges:
Regulatory assets	39,331	45,284
Other	4,279	3,780
Total Deferred Charges	43,610	49,064
Total Assets	2,173,763	2,209,162
CAPITALIZATION AND LIABILITIES:
Patronage capital	425,362	415,384
Non-controlling interest	5,756	5,744
Total Patronage capital and Non-controlling interest	431,118	421,128
Long-term debt	1,198,799	1,198,396
Revolving credit facility		43,400
Total Long-term debt and Revolving credit facility	1,198,799	1,241,796
Total Capitalization	1,629,917	1,662,924
Current Liabilities:
Long-term debt due within one year	40,792	40,792
Accounts payable	111,828	92,259
Accounts payable–members	52,175	59,064
Accrued expenses	25,092	6,391
Regulatory liability–revenue deferral	3,750	15,000
Obligations under long-term lease	32,200	103,683
Total Current Liabilities	265,837	317,189
Deferred Credits and Other Liabilities:
Asset retirement obligations	129,162	126,470
Regulatory liabilities	148,414	101,237
Other	433	1,342
Total Deferred Credits and Other Liabilities	278,009	229,049
Commitments and Contingencies
Total Capitalization and Liabilities	$ 2,173,763	$ 2,209,162

Condensed Consolidated Statemen

Condensed Consolidated Statements Of Revenues, Expenses, And Patronage Capital (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Operating Revenues	$ 257,586	$ 193,425	$ 712,247	$ 540,111
Type of Revenue [Extensible List]	us-gaap:ElectricityMember	us-gaap:ElectricityMember	us-gaap:ElectricityMember	us-gaap:ElectricityMember
Operating Expenses:
Fuel	$ 65,134	$ 32,309	$ 147,573	$ 70,490
Purchased power	71,059	90,185	299,645	293,030
Deferred energy	17,482	(2,408)	(18,086)	(28,651)
Operations and maintenance	15,236	12,753	48,236	37,325
Administrative and general	11,593	10,769	34,848	33,208
Depreciation and amortization	17,057	11,357	45,818	34,040
Amortization of regulatory asset/liability, net	(2,816)	1,021	(7,457)	1,001
Accretion of asset retirement obligations	1,330	1,257	3,991	3,769
Taxes, other than income taxes	2,597	2,089	7,315	6,280
Total Operating Expenses	238,588	183,612	667,028	522,493
Operating Margin	18,998	9,813	45,219	17,618
Other expense, net	(689)	(934)	(2,962)	(2,838)
Investment income	1,949	1,731	6,470	10,000
Interest income on North Anna Unit 3 cost recovery		85	141	4,512
Interest charges, net	(16,862)	(7,434)	(38,874)	(20,005)
Income taxes		(1)	(4)	(3)
Net Margin including Non-controlling interest	3,396	3,260	9,990	9,284
Non-controlling interest		(2)	(12)	(11)
Net Margin attributable to ODEC	3,396	3,258	9,978	9,273
Patronage Capital - Beginning of Period	421,966	408,872	415,384	402,857
Patronage Capital - End of Period	425,362	412,130	425,362	412,130
Electric Transmission [Member]
Operating Expenses:
Transmission	$ 39,916	$ 24,280	$ 105,145	$ 72,001

Condensed Consolidated Statem_2

Condensed Consolidated Statements Of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Operating Activities:
Net Margin including Non-controlling interest	$ 9,990	$ 9,284
Adjustments to reconcile net margin to net cash provided by operating activities:
Depreciation and amortization	45,818	34,040
Other non-cash charges	13,820	14,153
Amortization of lease obligations	4,468	5,064
Interest on lease deposits	(1,671)	(2,274)
Change in current assets	4,613	10,752
Change in deferred energy	(18,086)	(28,651)
Change in current liabilities	10,638	23,457
Change in regulatory assets and liabilities	(2,364)	4,973
Change in deferred charges-other and deferred credits and other liabilities-other	(2,285)	262
Net Cash Provided by Operating Activities	64,941	71,060
Investing Activities:
Purchases of held to maturity securities	(362)	(2,763)
Proceeds from sale of held to maturity securities	76,137	3,064
Increase in other investments	(6,116)	(9,822)
Electric plant additions	(48,431)	(120,939)
Proceeds from sale of asset	115,000
Net Cash Provided by/(Used for) Investing Activities	136,228	(130,460)
Financing Activities:
Issuance of long-term debt		250,000
Debt issuance costs	(255)	(1,386)
Payment of obligation under long-term lease	(75,951)
Draws on revolving credit facility	372,950	312,500
Repayments on revolving credit facility	(416,350)	(464,500)
Net Cash (Used for)/Provided by Financing Activities	(119,606)	96,614
Net Change in Cash and Cash Equivalents and Restricted Cash and Cash Equivalents	81,563	37,214
Cash and Cash Equivalents and Restricted Cash and Cash Equivalents - Beginning of Period	4,084	2,946
Cash and Cash Equivalents and Restricted Cash and Cash Equivalents - End of Period	$ 85,647	$ 40,160

General

General	9 Months Ended
	Sep. 30, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
General	1. The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. In the opinion of management, the accompanying unaudited condensed consolidated financial statements contain all adjustments, which include only normal recurring adjustments, necessary for a fair statement of our consolidated financial position as of September 30, 2018, our consolidated results of operations for the three and nine months ended September 30, 2018 and 2017, and cash flows for the nine months ended September 30, 2018 and 2017. The consolidated results of operations for the three and nine months ended September 30, 2018, are not necessarily indicative of the results to be expected for the entire year. These financial statements should be read in conjunction with the financial statements and notes thereto included in our 2017 Annual Report on Form 10-K filed with the Securities and Exchange Commission. The accompanying financial statements reflect the consolidated accounts of Old Dominion Electric Cooperative and TEC. We are a not-for-profit wholesale power supply cooperative, incorporated under the laws of the Commonwealth of Virginia in 1948. We have two classes of members. Our eleven Class A members are customer-owned electric distribution cooperatives engaged in the retail sale of power to member customers located in Virginia, Delaware, and Maryland. Our sole Class B member is TEC, a taxable corporation owned by our member distribution cooperatives. Our board of directors is composed of two representatives from each of the member distribution cooperatives and one representative from TEC. In accordance with Consolidation Accounting, TEC is considered a variable interest entity for which we are the primary beneficiary. We have eliminated all intercompany balances and transactions in consolidation. The assets and liabilities and non-controlling interest of TEC are recorded at carrying value and the consolidated assets were $5.8 million as of September 30, 2018, and $5.7 million as of December 31, 2017. The income taxes reported on our Condensed Consolidated Statement of Revenues, Expenses, and Patronage Capital relate to the tax provision for TEC. As TEC is wholly-owned by our Class A members, its equity is presented as a non-controlling interest in our consolidated financial statements. Our rates are set periodically by a formula that was accepted for filing by FERC, but are not regulated by the public service commissions of the states in which our member distribution cooperatives operate. See Note 5—Other—FERC Proceeding Related to Formula Rate below. We comply with the Uniform System of Accounts as prescribed by FERC. In conformity with GAAP, the accounting policies and practices applied by us in the determination of rates are also employed for financial reporting purposes. The preparation of our condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported therein. Actual results could differ from those estimates. We do not have any other comprehensive income for the periods presented.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	2. The fair value hierarchy gives the highest priority to quoted prices in active markets (Level 1) and the lowest priority to unobservable data (Level 3). In some cases, the inputs used to measure fair value might fall in different levels of the fair value hierarchy. The lowest level input that is significant to a fair value measurement in its entirety determines the applicable level in the fair value hierarchy. Assessing the significance of a particular input to the fair value measurement in its entirety requires judgment, considering factors specific to the asset or liability. The following table summarizes our financial assets and liabilities measured at fair value on a recurring basis as of September 30, 2018 and December 31, 2017: Quoted Prices in Active Significant Markets for Other Significant Identical Observable Unobservable September 30, Assets Inputs Inputs 2018 (Level 1) (Level 2) (Level 3) (in thousands) Nuclear decommissioning trust (1) $ 58,725 $ 58,725 $ — $ — Nuclear decommissioning trust - net asset value (1)(2) 132,498 — — — Unrestricted investments and other (3) 423 — 423 — Derivatives - gas and power (4) 986 168 818 — Total Financial Assets $ 192,632 $ 58,893 $ 1,241 $ — Quoted Prices in Active Significant Markets for Other Significant Identical Observable Unobservable December Assets Inputs Inputs 2017 (Level 1) (Level 2) (Level 3) (in thousands) Nuclear decommissioning trust (1) $ 59,723 $ 59,723 $ — $ — Nuclear decommissioning trust - net asset value (1)(2) 123,958 — — — Unrestricted investments and other (3) 308 — 308 — Total Financial Assets $ 183,989 $ 59,723 $ 308 $ — Derivatives - gas and power (4) $ 1,034 $ 975 $ 59 $ — Total Financial Liabilities $ 1,034 $ 975 $ 59 $ — (1) For additional information about our nuclear decommissioning trust see Note 4—Investments below. (2) Nuclear decommissioning trust includes investments measured at net asset value per share (or its equivalent) as a practical expedient and these investments have not been categorized in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the Condensed Consolidated Balance Sheet. (3) Unrestricted investments and other includes investments that are related to equity securities. (4) Derivatives - gas and power represent natural gas futures contracts. Level 1 are indexed against NYMEX. Level 2 are valued by ACES using observable market inputs for similar transactions. For additional information about our derivative financial instruments, see Note 1 of the Notes to Consolidated Financial Statements in our 2017 Annual Report on Form 10-K. We did not have any financial assets and liabilities measured at fair value on a recurring basis and included in the Level 3 fair value category.

Derivatives And Hedging

Derivatives And Hedging	9 Months Ended
	Sep. 30, 2018
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Derivatives And Hedging	3. We are exposed to market price risk by purchasing power to supply the power requirements of our member distribution cooperatives that are not met by our owned generation. In addition, the purchase of fuel to operate our generating facilities also exposes us to market price risk. To manage this exposure, we utilize derivative instruments. See Note 1 of the Notes to Consolidated Financial Statements in our 2017 Annual Report on Form 10-K. Changes in the fair value of our derivative instruments accounted for at fair value are recorded as a regulatory asset or regulatory liability. The change in these accounts is included in the operating activities section of our Condensed Consolidated Statements of Cash Flows. Outstanding derivative instruments, excluding contracts accounted for as normal purchase/normal sale, were as follows: Quantity As of September 30, As of December 31, Commodity Unit of Measure 2018 2017 Natural gas MMBTU 33,500,000 23,700,000 The fair value of our derivative instruments, excluding contracts accounted for as normal purchase/normal sale, was as follows: Fair Value As of September 30, As of December 31, Balance Sheet Location 2018 2017 (in thousands) Derivatives in an asset position: Natural gas futures contracts Deferred charges-other $ 986 $ — Total derivatives in an asset position $ 986 $ — Derivatives in a liability position: Natural gas futures contracts Deferred credits and other liabilities-other $ — $ 1,034 Total derivatives in a liability position $ — $ 1,034 The Effect of Derivative Instruments on the Condensed Consolidated Statements of Revenues, Expenses, and Patronage Capital for the Three and Nine Months Ended September 30, 2018 and 2017 Amount of Gain Amount of Gain Amount of Gain Location of (Loss) Reclassified (Loss) Reclassified (Loss) Recognized Gain (Loss) from Regulatory from Regulatory in Regulatory Reclassified Asset/Liability Asset/Liability Derivatives Asset/Liability for from Regulatory into Income for into Income for Accounted Derivatives as of Asset/Liability the Three Months the Nine Months Regulatory Accounting September 30, into Income Ended September 30, Ended September 30, 2018 2017 2018 2017 2018 2017 (in thousands) (in thousands) Natural $ 1,032 $ 1,123 Fuel $ 980 $ (129 ) $ (130 ) $ 870 Total $ 1,032 $ 1,123 $ 980 $ (129 ) $ (130 ) $ 870 Our hedging activities expose us to credit-related risks. We use hedging instruments, including forwards, futures, financial transmission rights, and options, to mitigate our power market price risks. Because we rely substantially on the use of hedging instruments, we are exposed to the risk that counterparties will default in performance of their obligations to us. Although we assess the creditworthiness of counterparties and other credit issues related to these hedging instruments, and we may require our counterparties to post collateral with us, defaults may still occur. Defaults may take the form of failure to physically deliver purchased energy or failure to pay. If a default occurs, we may be forced to enter into alternative contractual arrangements or purchase energy in the forward, short-term, or spot markets at then-current market prices that may exceed the prices previously agreed upon with the defaulting counterparty.

Investments

Investments	9 Months Ended
	Sep. 30, 2018
Investments [Abstract]
Investments	4. Investments were as follows as of September 30, 2018 and December 31, 2017: Gross Gross Unrealized Unrealized Fair Carrying Description Cost Gains Losses Value Value (in thousands) September 30, 2018 Nuclear decommissioning trust (1) Debt securities $ 55,607 $ 2,950 $ — $ 58,557 $ 58,557 Equity securities 82,778 51,058 (1,338 ) 132,498 132,498 Cash and other 168 — — 168 168 Total Nuclear Decommissioning Trust $ 138,553 $ 54,008 $ (1,338 ) $ 191,223 $ 191,223 Lease Deposits (2) Government obligations $ 32,653 $ 37 $ — $ 32,690 $ 32,653 Total Lease Deposits $ 32,653 $ 37 $ — $ 32,690 $ 32,653 Unrestricted investments Government obligations $ 2,350 $ — $ (3 ) $ 2,347 $ 2,350 Debt securities 2,272 — (2 ) 2,270 2,272 Total Unrestricted Investments $ 4,622 $ — $ (5 ) $ 4,617 $ 4,622 Other Equity securities $ 318 $ 105 $ — $ 423 $ 423 Non-marketable equity investments 2,134 2,156 — 4,290 2,134 Total Other $ 2,452 $ 2,261 $ — $ 4,713 $ 2,557 $ 231,055 December 31, 2017 Nuclear decommissioning trust (1) Debt securities $ 54,375 $ 5,029 $ — $ 59,404 $ 59,404 Equity securities 77,838 46,474 (354 ) 123,958 123,958 Cash and other 319 — — 319 319 Total Nuclear Decommissioning Trust $ 132,532 $ 51,503 $ (354 ) $ 183,681 $ 183,681 Lease Deposits (2) Government obligations $ 106,812 $ 776 $ — $ 107,588 $ 106,812 Total Lease Deposits $ 106,812 $ 776 $ — $ 107,588 $ 106,812 Unrestricted investments Government obligations $ 2,344 $ — $ (13 ) $ 2,331 $ 2,344 Debt securities 2,217 — (3 ) 2,214 2,217 Total Unrestricted Investments $ 4,561 $ — $ (16 ) $ 4,545 $ 4,561 Other Equity securities $ 223 $ 85 $ — $ 308 $ 308 Non-marketable equity investments 2,140 2,066 — 4,206 2,140 Total Other $ 2,363 $ 2,151 $ — $ 4,514 $ 2,448 $ 297,502 (1) Investments in the nuclear decommissioning trust are restricted for the use of funding our share of the asset retirement obligations of the future decommissioning of North Anna. See Note 3 of the Notes to Consolidated Financial Statements in our 2017 Annual Report on Form 10-K. Unrealized gains and losses on investments held in the nuclear decommissioning trust are deferred as a regulatory liability or regulatory asset, respectively. (2) Investments in lease deposits are restricted for the use of funding our future lease obligations. See Note 8 of the Notes to Consolidated Financial Statements in our 2017 Annual Report on Form 10-K. Contractual maturities of debt securities as of September 30, 2018, were as follows: Description Less than 1 year 1-5 years 5-10 years More than 10 years Total (in thousands) Other (1) $ — $ — $ 58,557 $ — $ 58,557 Held to maturity 37,035 240 — — 37,275 Total $ 37,035 $ 240 $ 58,557 $ — $ 95,832 (1) The contractual maturities of other debt securities are measured using the effective duration of the bond fund within the nuclear decommissioning trust.

Other

Other	9 Months Ended
	Sep. 30, 2018
Other [Abstract]
Other	5. Wildcat Point Generation Facility On April 17, 2018, Wildcat Point, an approximate 1,000 MW natural gas-fueled combined cycle generation facility, achieved commercial operation and was available for dispatch by PJM. The facility originally was scheduled to become operational in mid-2017. WOPC, a joint venture between PCL Industrial Construction Company and Sargent & Lundy, L.L.C., as the EPC contractor, claims the delay was associated with the incurrence of additional work and other matters, including alleged misrepresentation in the EPC contract, for which it will seek recovery, in whole or in part, from its subcontractors and us. On May 24, 2017, WOPC filed a complaint against Alstom and us, in the United States District Court for the District of Maryland. An amended complaint was filed on July 21, 2017. On August 21, 2017, motions were filed by Alstom and us to transfer venue from the United States District Court for the District of Maryland to the United States District Court for the Eastern District of Virginia, and on November 7, 2017, these motions were granted. We have reviewed the asserted claims of WOPC against us and believe they are without merit. We have not recorded any liability related to these claims as we do not believe any liability is estimable or probable. We intend to vigorously defend against these claims. Additionally, on September 29, 2017, we filed a complaint in the United States District Court for the Eastern District of Virginia against WOPC, alleging that WOPC breached the EPC contract. On November 16, 2017, the United States District Court for the Eastern District of Virginia ordered that the WOPC complaint against Alstom and us, our complaint against WOPC, and a separate complaint filed by WOPC against Mitsubishi on May 9, 2017, be consolidated into one case. On June 27, 2018, an order was issued establishing January 9, 2019 as the date to check the status of discovery, set summary judgement deadlines, and set a trial date. If it is ultimately determined that we owe any such amounts to WOPC, the amounts are not expected to have a material impact on our financial position or results of operations due to our ability to collect such amounts through rates to our member distribution cooperatives. Through September 30, 2018, we capitalized construction costs related to Wildcat Point totaling $842.4 million, which includes $88.4 million of capitalized interest and is offset by $53.2 million of liquidated damages. FERC Proceeding Related to Formula Rate On September 30, 2013, we filed with FERC to revise our cost-based formula rate in order to more closely align our cost recovery from our member distribution cooperatives with the methodologies used by PJM to allocate costs to us. On November 8, 2013, Bear Island, a customer of REC, filed a motion to intervene, protest, and request for hearing. On December 2, 2013, FERC issued its order accepting the proposed revisions for filing to become effective January 1, 2014, subject to refund, and establishing hearing and settlement procedures. On April 13, 2015, we received an initial decision from the hearing judge. On January 19, 2017, FERC issued its order on the hearing judge's initial decision. On February 21, 2017, we submitted our compliance filing, revising the formula rate as we previously suggested and FERC directed in the January 19, 2017 order. Additionally, on February 21, 2017, Bear Island filed a request for rehearing. On March 22, 2017, FERC issued an order granting rehearing of its initial order for the limited purpose of FERC's further consideration of the matter. On March 22, 2018, FERC issued an order denying Bear Island's request for rehearing and accepted our February 21, 2017 compliance filing that revised the formula rate as directed by FERC's January 19, 2017 order. We filed a refund report with FERC on April 23, 2018, that calculated the difference between rates charged under our rate schedule since January 1, 2014, and rates that would have been charged under the revised rate schedule submitted in our February 21, 2017 compliance filing. On July 24, 2018, FERC accepted the refund report, which resulted in a reallocation of costs among our member distribution cooperatives and did not result in any change to our total operating revenues. Revolving Credit Facility We maintain a revolving credit facility to cover our short-term and medium-term funding needs that are not met by cash from operations or other available funds. Commitments under this syndicated credit agreement extend until March 3, 2023. Available funding under this facility totals $500 million through March 3, 2022, and $400 million from March 4, 2022 through March 3, 2023. As of September 30, 2018, we had no borrowings outstanding under this facility Limited Exception under Wholesale Power Contracts We have a wholesale power contract with each of our member distribution cooperatives. Each contract obligates us to sell and deliver to the member distribution cooperative, and obligates the member distribution cooperative to purchase and receive from us, all power that it requires for the operation of its system, with limited exceptions. One of the limited exceptions permits each of our member distribution cooperatives, with 180 days prior written notice, to receive up to the greater of 5% of its demand and associated energy or 5 MW and associated energy from its owned generation or from other suppliers. If all of our member distribution cooperatives elected to utilize the 5% or 5 MW exception, we estimate the current impact would be a reduction of approximately 175 MW of demand and associated energy. As of May 1, 2018, there are approximately 66 MW remaining that can be utilized under this exception. The following table summarizes the cumulative removal of load requirements under this exception since January 1, 2016. Date MW January 1, 2016 9 May 1, 2016 60 June 1, 2017 65 May 1, 2018 109 We do not anticipate that either the current or potential full utilization of this exception by our member distribution cooperatives will have a material impact on our financial condition, results of operations, or cash flows. Cash and Cash Equivalents The following table provides a reconciliation of cash and cash equivalents and restricted cash and cash equivalents reported within the Condensed Consolidated Balance Sheet that sum to the total of the same amounts shown in the Condensed Consolidated Statement of Cash Flows: As of September 30, 2018 2017 (in thousands) Cash and cash equivalents $ 71,447 $ 40,160 Restricted cash and cash equivalents 14,200 — $ 85,647 $ 40,160 Restricted cash and cash equivalents relates to funds held in escrow for payments to Mitsubishi for Wildcat Point. Sale of Rock Springs Combustion Turbine Facility On September 14, 2018, we sold our interest in Rock Springs and related assets to EPRS for $115 million. Prior to the sale, w e and EPRS had each individually owned two natural gas-fired combustion turbine units and a 50% undivided interest in related common facilities at Rock Springs. The transaction resulted in a gain of $42.7 million, which our board of directors approved to defer as a regulatory liability to be amortized over future periods.

New Accounting Pronouncements

New Accounting Pronouncements	9 Months Ended
	Sep. 30, 2018
New Accounting Pronouncements And Changes In Accounting Principles [Abstract]
New Accounting Pronouncements	6. In May 2014, the FASB issued Accounting Standards Update 2014-09 Revenue from Contracts with Customers (Topic 606). This update requires entities to recognize revenue when the transfer of promised goods or services to customers occurs in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. We supply power requirements (energy and demand) to our eleven member distribution cooperatives subject to substantially identical wholesale power contracts with each of them. The revenues from these wholesale power contracts constituted at least 95% of our total revenues for the past three years. We bill our member distribution cooperatives monthly and each member distribution cooperative is required to pay us monthly for power furnished under its wholesale power contract. We transfer control of the electricity over time and our member distribution cooperatives simultaneously receive and consume the benefits of the electricity. The amount we invoice our member distribution cooperatives on a monthly basis corresponds directly to the value to the member distribution cooperatives of our performance, which is determined by our formula rate included in the wholesale power contract. We also sell excess energy and renewable energy credits to non-members at prevailing market prices as control is transferred. We have completed our contract review of our wholesale power and other contracts within the scope of Topic 606, and have finalized our analysis. We have not identified any material impact to our recognition of revenue from the sale of power to our member distribution cooperatives or non-members. We adopted this standard effective January 1, 2018, using the modified retrospective approach. There was no material impact to our recognition of revenue from the sale of power to our member distribution cooperatives or non-members, and there has been no cumulative effect adjustment recognized. Our operating revenues for the three and nine months ended September 30, 2018, were as follows: Three Months Ended September 30, Nine Months Ended September 30, 2018 2018 (in thousands) Member distribution cooperatives Sales to member distribution cooperatives, excluding renewable energy credit sales $ 230,408 $ 657,521 Renewable energy credit sales to member distribution cooperatives 2 14 Total sales to member distribution cooperatives $ 230,410 $ 657,535 Non-members Sales to non-members, excluding renewable energy credit sales $ 24,791 $ 51,762 Renewable energy credit sales to non-members 2,385 2,950 Total sales to non-members $ 27,176 $ 54,712 Total operating revenues $ 257,586 $ 712,247 In January 2016, the FASB issued Accounting Standards Update 2016-01 Recognition and Measurement of Financial Assets and Financial Liabilities. This update retained the current framework for accounting for financial instruments in GAAP but made targeted improvements to address certain aspects of recognition, measurement, presentation, and disclosure of financial instruments. We adopted this update during 2018. The update requires us to measure equity investments at fair value and recognize any changes in fair value in net margin. We account for certain revenues and expenses as a rate-regulated entity in accordance with Accounting for Regulated Operations. With approval from our board of directors, changes in fair value of certain equity investments are recognized as a change in our regulatory liability account on our Condensed Consolidated Balance Sheet. See Note 4—Investments above. In February 2016, the FASB issued Accounting Standards Update 2016-02 Leases (Subtopic 835-30). This update revised accounting guidance for the recognition, measurement, presentation and disclosure of leasing arrangements. The update requires the recognition of lease assets and liabilities for those leases currently classified as operating leases while also refining the definition of a lease. In addition, lessees will be required to disclose key information about the amount, timing, and uncertainty of cash flows arising from leasing arrangements. In July 2018, the FASB issued Accounting Standards Update 2018-11 Leases (Topic 842): Targeted Improvements, which provides an adoption method that would allow companies to apply the new guidance to the financial statements in the period of adoption and thereafter, and not apply the new guidance to comparative periods presented. We are in the process of finalizing our review of the impact of the new accounting guidance related to leases on our financial statements and related disclosure, as well as determining which practical expedients we plan to utilize. We plan to adopt this standard for the fiscal year beginning January 1, 2019. In November 2016, the FASB issued Accounting Standards Update 2016-18 Statement of Cash Flows (Topic 230): Restricted Cash. This update revised accounting guidance for the classification and presentation of restricted cash in the statement of cash flows. We adopted this update effective January 1, 2018, and it requires a reconciliation of cash and cash equivalents and restricted cash and cash equivalents within the Condensed Consolidated Balance Sheet and the amounts shown in the Condensed Consolidated Statement of Cash Flows. See “Cash and Cash Equivalents” above.

New Accounting Pronouncements (

New Accounting Pronouncements (Policies)	9 Months Ended
	Sep. 30, 2018
New Accounting Pronouncements And Changes In Accounting Principles [Abstract]
New Accounting Pronouncements	In May 2014, the FASB issued Accounting Standards Update 2014-09 Revenue from Contracts with Customers (Topic 606). This update requires entities to recognize revenue when the transfer of promised goods or services to customers occurs in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. We supply power requirements (energy and demand) to our eleven member distribution cooperatives subject to substantially identical wholesale power contracts with each of them. The revenues from these wholesale power contracts constituted at least 95% of our total revenues for the past three years. We bill our member distribution cooperatives monthly and each member distribution cooperative is required to pay us monthly for power furnished under its wholesale power contract. We transfer control of the electricity over time and our member distribution cooperatives simultaneously receive and consume the benefits of the electricity. The amount we invoice our member distribution cooperatives on a monthly basis corresponds directly to the value to the member distribution cooperatives of our performance, which is determined by our formula rate included in the wholesale power contract. We also sell excess energy and renewable energy credits to non-members at prevailing market prices as control is transferred. We have completed our contract review of our wholesale power and other contracts within the scope of Topic 606, and have finalized our analysis. We have not identified any material impact to our recognition of revenue from the sale of power to our member distribution cooperatives or non-members. We adopted this standard effective January 1, 2018, using the modified retrospective approach. There was no material impact to our recognition of revenue from the sale of power to our member distribution cooperatives or non-members, and there has been no cumulative effect adjustment recognized. Our operating revenues for the three and nine months ended September 30, 2018, were as follows: Three Months Ended September 30, Nine Months Ended September 30, 2018 2018 (in thousands) Member distribution cooperatives Sales to member distribution cooperatives, excluding renewable energy credit sales $ 230,408 $ 657,521 Renewable energy credit sales to member distribution cooperatives 2 14 Total sales to member distribution cooperatives $ 230,410 $ 657,535 Non-members Sales to non-members, excluding renewable energy credit sales $ 24,791 $ 51,762 Renewable energy credit sales to non-members 2,385 2,950 Total sales to non-members $ 27,176 $ 54,712 Total operating revenues $ 257,586 $ 712,247 In January 2016, the FASB issued Accounting Standards Update 2016-01 Recognition and Measurement of Financial Assets and Financial Liabilities. This update retained the current framework for accounting for financial instruments in GAAP but made targeted improvements to address certain aspects of recognition, measurement, presentation, and disclosure of financial instruments. We adopted this update during 2018. The update requires us to measure equity investments at fair value and recognize any changes in fair value in net margin. We account for certain revenues and expenses as a rate-regulated entity in accordance with Accounting for Regulated Operations. With approval from our board of directors, changes in fair value of certain equity investments are recognized as a change in our regulatory liability account on our Condensed Consolidated Balance Sheet. See Note 4—Investments above. In February 2016, the FASB issued Accounting Standards Update 2016-02 Leases (Subtopic 835-30). This update revised accounting guidance for the recognition, measurement, presentation and disclosure of leasing arrangements. The update requires the recognition of lease assets and liabilities for those leases currently classified as operating leases while also refining the definition of a lease. In addition, lessees will be required to disclose key information about the amount, timing, and uncertainty of cash flows arising from leasing arrangements. In July 2018, the FASB issued Accounting Standards Update 2018-11 Leases (Topic 842): Targeted Improvements, which provides an adoption method that would allow companies to apply the new guidance to the financial statements in the period of adoption and thereafter, and not apply the new guidance to comparative periods presented. We are in the process of finalizing our review of the impact of the new accounting guidance related to leases on our financial statements and related disclosure, as well as determining which practical expedients we plan to utilize. We plan to adopt this standard for the fiscal year beginning January 1, 2019. In November 2016, the FASB issued Accounting Standards Update 2016-18 Statement of Cash Flows (Topic 230): Restricted Cash. This update revised accounting guidance for the classification and presentation of restricted cash in the statement of cash flows. We adopted this update effective January 1, 2018, and it requires a reconciliation of cash and cash equivalents and restricted cash and cash equivalents within the Condensed Consolidated Balance Sheet and the amounts shown in the Condensed Consolidated Statement of Cash Flows. See “Cash and Cash Equivalents” above.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Financial Assets And Liabilities Measured At Fair Value On A Recurring Basis	The following table summarizes our financial assets and liabilities measured at fair value on a recurring basis as of September 30, 2018 and December 31, 2017: Quoted Prices in Active Significant Markets for Other Significant Identical Observable Unobservable September 30, Assets Inputs Inputs 2018 (Level 1) (Level 2) (Level 3) (in thousands) Nuclear decommissioning trust (1) $ 58,725 $ 58,725 $ — $ — Nuclear decommissioning trust - net asset value (1)(2) 132,498 — — — Unrestricted investments and other (3) 423 — 423 — Derivatives - gas and power (4) 986 168 818 — Total Financial Assets $ 192,632 $ 58,893 $ 1,241 $ — Quoted Prices in Active Significant Markets for Other Significant Identical Observable Unobservable December Assets Inputs Inputs 2017 (Level 1) (Level 2) (Level 3) (in thousands) Nuclear decommissioning trust (1) $ 59,723 $ 59,723 $ — $ — Nuclear decommissioning trust - net asset value (1)(2) 123,958 — — — Unrestricted investments and other (3) 308 — 308 — Total Financial Assets $ 183,989 $ 59,723 $ 308 $ — Derivatives - gas and power (4) $ 1,034 $ 975 $ 59 $ — Total Financial Liabilities $ 1,034 $ 975 $ 59 $ — (1) For additional information about our nuclear decommissioning trust see Note 4—Investments below. (2) Nuclear decommissioning trust includes investments measured at net asset value per share (or its equivalent) as a practical expedient and these investments have not been categorized in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the Condensed Consolidated Balance Sheet. (3) Unrestricted investments and other includes investments that are related to equity securities. (4) Derivatives - gas and power represent natural gas futures contracts. Level 1 are indexed against NYMEX. Level 2 are valued by ACES using observable market inputs for similar transactions. For additional information about our derivative financial instruments, see Note 1 of the Notes to Consolidated Financial Statements in our 2017 Annual Report on Form 10-K.

Derivatives And Hedging (Tables

Derivatives And Hedging (Tables)	9 Months Ended
	Sep. 30, 2018
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Schedule Of Outstanding Derivative Instruments	Outstanding derivative instruments, excluding contracts accounted for as normal purchase/normal sale, were as follows: Quantity As of September 30, As of December 31, Commodity Unit of Measure 2018 2017 Natural gas MMBTU 33,500,000 23,700,000
Schedule Of Fair Value Of Derivative Instruments	The fair value of our derivative instruments, excluding contracts accounted for as normal purchase/normal sale, was as follows: Fair Value As of September 30, As of December 31, Balance Sheet Location 2018 2017 (in thousands) Derivatives in an asset position: Natural gas futures contracts Deferred charges-other $ 986 $ — Total derivatives in an asset position $ 986 $ — Derivatives in a liability position: Natural gas futures contracts Deferred credits and other liabilities-other $ — $ 1,034 Total derivatives in a liability position $ — $ 1,034
Schedule Of Derivative Instruments On The Statement Of Revenues, Expenses, And Patronage Capital	The Effect of Derivative Instruments on the Condensed Consolidated Statements of Revenues, Expenses, and Patronage Capital for the Three and Nine Months Ended September 30, 2018 and 2017 Amount of Gain Amount of Gain Amount of Gain Location of (Loss) Reclassified (Loss) Reclassified (Loss) Recognized Gain (Loss) from Regulatory from Regulatory in Regulatory Reclassified Asset/Liability Asset/Liability Derivatives Asset/Liability for from Regulatory into Income for into Income for Accounted Derivatives as of Asset/Liability the Three Months the Nine Months Regulatory Accounting September 30, into Income Ended September 30, Ended September 30, 2018 2017 2018 2017 2018 2017 (in thousands) (in thousands) Natural $ 1,032 $ 1,123 Fuel $ 980 $ (129 ) $ (130 ) $ 870 Total $ 1,032 $ 1,123 $ 980 $ (129 ) $ (130 ) $ 870

Investments (Tables)

Investments (Tables)	9 Months Ended
	Sep. 30, 2018
Investments [Abstract]
Schedule Of Investments	Investments were as follows as of September 30, 2018 and December 31, 2017: Gross Gross Unrealized Unrealized Fair Carrying Description Cost Gains Losses Value Value (in thousands) September 30, 2018 Nuclear decommissioning trust (1) Debt securities $ 55,607 $ 2,950 $ — $ 58,557 $ 58,557 Equity securities 82,778 51,058 (1,338 ) 132,498 132,498 Cash and other 168 — — 168 168 Total Nuclear Decommissioning Trust $ 138,553 $ 54,008 $ (1,338 ) $ 191,223 $ 191,223 Lease Deposits (2) Government obligations $ 32,653 $ 37 $ — $ 32,690 $ 32,653 Total Lease Deposits $ 32,653 $ 37 $ — $ 32,690 $ 32,653 Unrestricted investments Government obligations $ 2,350 $ — $ (3 ) $ 2,347 $ 2,350 Debt securities 2,272 — (2 ) 2,270 2,272 Total Unrestricted Investments $ 4,622 $ — $ (5 ) $ 4,617 $ 4,622 Other Equity securities $ 318 $ 105 $ — $ 423 $ 423 Non-marketable equity investments 2,134 2,156 — 4,290 2,134 Total Other $ 2,452 $ 2,261 $ — $ 4,713 $ 2,557 $ 231,055 December 31, 2017 Nuclear decommissioning trust (1) Debt securities $ 54,375 $ 5,029 $ — $ 59,404 $ 59,404 Equity securities 77,838 46,474 (354 ) 123,958 123,958 Cash and other 319 — — 319 319 Total Nuclear Decommissioning Trust $ 132,532 $ 51,503 $ (354 ) $ 183,681 $ 183,681 Lease Deposits (2) Government obligations $ 106,812 $ 776 $ — $ 107,588 $ 106,812 Total Lease Deposits $ 106,812 $ 776 $ — $ 107,588 $ 106,812 Unrestricted investments Government obligations $ 2,344 $ — $ (13 ) $ 2,331 $ 2,344 Debt securities 2,217 — (3 ) 2,214 2,217 Total Unrestricted Investments $ 4,561 $ — $ (16 ) $ 4,545 $ 4,561 Other Equity securities $ 223 $ 85 $ — $ 308 $ 308 Non-marketable equity investments 2,140 2,066 — 4,206 2,140 Total Other $ 2,363 $ 2,151 $ — $ 4,514 $ 2,448 $ 297,502 (1) Investments in the nuclear decommissioning trust are restricted for the use of funding our share of the asset retirement obligations of the future decommissioning of North Anna. See Note 3 of the Notes to Consolidated Financial Statements in our 2017 Annual Report on Form 10-K. Unrealized gains and losses on investments held in the nuclear decommissioning trust are deferred as a regulatory liability or regulatory asset, respectively. (2) Investments in lease deposits are restricted for the use of funding our future lease obligations. See Note 8 of the Notes to Consolidated Financial Statements in our 2017 Annual Report on Form 10-K.
Schedule Of Contractual Maturities Of Debt Securities	Contractual maturities of debt securities as of September 30, 2018, were as follows: Description Less than 1 year 1-5 years 5-10 years More than 10 years Total (in thousands) Other (1) $ — $ — $ 58,557 $ — $ 58,557 Held to maturity 37,035 240 — — 37,275 Total $ 37,035 $ 240 $ 58,557 $ — $ 95,832 (1) The contractual maturities of other debt securities are measured using the effective duration of the bond fund within the nuclear decommissioning trust.

Other (Tables)

Other (Tables)	9 Months Ended
	Sep. 30, 2018
Other [Abstract]
Summary Of Removal Of Load Requirements Under Exception	The following table summarizes the cumulative removal of load requirements under this exception since January 1, 2016. Date MW January 1, 2016 9 May 1, 2016 60 June 1, 2017 65 May 1, 2018 109
Reconciliation of Cash and Cash Equivalents and Restricted Cash and Cash Equivalents Reported Within Condensed Consolidated Balance Sheet and Shown in Condensed Consolidated Statement of Cash Flows	The following table provides a reconciliation of cash and cash equivalents and restricted cash and cash equivalents reported within the Condensed Consolidated Balance Sheet that sum to the total of the same amounts shown in the Condensed Consolidated Statement of Cash Flows: As of September 30, 2018 2017 (in thousands) Cash and cash equivalents $ 71,447 $ 40,160 Restricted cash and cash equivalents 14,200 — $ 85,647 $ 40,160

New Accounting Pronouncements_2

New Accounting Pronouncements (Tables)	9 Months Ended
	Sep. 30, 2018
New Accounting Pronouncements And Changes In Accounting Principles [Abstract]
Schedule of Operating Revenue	Our operating revenues for the three and nine months ended September 30, 2018, were as follows: Three Months Ended September 30, Nine Months Ended September 30, 2018 2018 (in thousands) Member distribution cooperatives Sales to member distribution cooperatives, excluding renewable energy credit sales $ 230,408 $ 657,521 Renewable energy credit sales to member distribution cooperatives 2 14 Total sales to member distribution cooperatives $ 230,410 $ 657,535 Non-members Sales to non-members, excluding renewable energy credit sales $ 24,791 $ 51,762 Renewable energy credit sales to non-members 2,385 2,950 Total sales to non-members $ 27,176 $ 54,712 Total operating revenues $ 257,586 $ 712,247

General - Additional Informatio

General - Additional Information (Details) $ in Millions	Sep. 30, 2018USD ($)member_classmemberrepresentative	Dec. 31, 2017USD ($)
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Number of classes of members | member_class	2
Number of Class A members | member	11
Number of representatives from each Class A member on the board of directors	2
Number of representatives from each Class B member on the board of directors	1
Consolidated assets | $	$ 5.8	$ 5.7

Fair Value Measurements (Financ

Fair Value Measurements (Financial Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Financial Assets	$ 192,632	$ 183,989
Total Financial Liabilities		1,034
Nuclear Decommissioning Trust [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Financial Assets	58,725	59,723
Nuclear Decommissioning Trust - Net Asset Value [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Financial Assets	132,498	123,958
Unrestricted Investment And Other [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Financial Assets	423	308
Derivative
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Financial Assets	986
Total Financial Liabilities		1,034
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Financial Assets	58,893	59,723
Total Financial Liabilities		975
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Nuclear Decommissioning Trust [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Financial Assets	58,725	59,723
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Nuclear Decommissioning Trust - Net Asset Value [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Financial Assets	0	0
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Unrestricted Investment And Other [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Financial Assets	0	0
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Derivative
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Financial Assets	168
Total Financial Liabilities		975
Significant Other Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Financial Assets	1,241	308
Total Financial Liabilities		59
Significant Other Observable Inputs (Level 2) [Member] | Nuclear Decommissioning Trust [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Financial Assets	0	0
Significant Other Observable Inputs (Level 2) [Member] | Nuclear Decommissioning Trust - Net Asset Value [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Financial Assets	0	0
Significant Other Observable Inputs (Level 2) [Member] | Unrestricted Investment And Other [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Financial Assets	423	308
Significant Other Observable Inputs (Level 2) [Member] | Derivative
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Financial Assets	$ 818
Total Financial Liabilities		$ 59

Derivatives And Hedging (Schedu

Derivatives And Hedging (Schedule Of Outstanding Derivative Instruments) (Details) - MMBTU	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Natural Gas [Member]
Derivative [Line Items]
Quantity	33,500,000	23,700,000

Derivatives And Hedging (Sche_2

Derivatives And Hedging (Schedule Of Fair Value Of Derivative Instruments) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Total derivatives in an asset position	$ 986
Total derivatives in a liability position		$ 1,034
Natural Gas Future Contracts [Member] | Deferred Charges - Other [Member]
Derivatives, Fair Value [Line Items]
Total derivatives in an asset position	$ 986
Natural Gas Future Contracts [Member] | Deferred Credits And Other Liabilities - Other [Member]
Derivatives, Fair Value [Line Items]
Total derivatives in a liability position		$ 1,034

Derivatives And Hedging (Sche_3

Derivatives And Hedging (Schedule Of Derivative Instruments On The Statement Of Revenues, Expenses, And Patronage Capital) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Regulatory Asset/Liability for Derivatives	$ 1,032	$ 1,123	$ 1,032	$ 1,123
Amount Of Gain (Loss) Reclassified from Regulatory Asset/Liability into Income	980	(129)	(130)	870
Natural Gas Future Contracts [Member] | Fuel [Member] | Operating Expense Fuel [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Regulatory Asset/Liability for Derivatives	1,032	1,123	1,032	1,123
Amount Of Gain (Loss) Reclassified from Regulatory Asset/Liability into Income	$ 980	$ (129)	$ (130)	$ 870

Investments (Schedule Of Invest

Investments (Schedule Of Investments) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Schedule of Invested Securities [Line Items]
Held to maturity investments, Cost	$ 32,653	$ 106,812
Equity, Cost	2,134	2,140
Equity Method Investment Gross Unrealized Gains	2,156	2,066
Equity, Fair Value	4,290	4,206
Other, Cost	2,452	2,363
Other Gross Unrealized Gains	2,261	2,151
Other, Fair Value	4,713	4,514
Total Other	2,557	2,448
Held to maturity Investments	37,275
Total Investments	231,055	297,502
Total Nuclear Decommissioning Trust	191,223	183,681
Other [Member]
Schedule of Invested Securities [Line Items]
Investments, Equity securities, Cost	318	223
Investments, Equity securities, Gross Unrealized Gains	105	85
Total Investments	423	308
Government Obligations [Member]
Schedule of Invested Securities [Line Items]
Held to maturity investments, Gross Unrealized Losses	(3)	(13)
Held to maturity Investments	2,350	2,344
Held to maturity investments, Fair Value	2,347	2,331
Debt Securities [Member]
Schedule of Invested Securities [Line Items]
Held to maturity investments, Gross Unrealized Losses	(2)	(3)
Held to maturity Investments	2,272	2,217
Held to maturity investments, Fair Value	2,270	2,214
Unrestricted Investments [Member]
Schedule of Invested Securities [Line Items]
Held to maturity investments, Gross Unrealized Losses	(5)	(16)
Held to maturity Investments	4,622	4,561
Held to maturity investments, Fair Value	4,617	4,545
Nuclear Decommissioning Trust [Member]
Schedule of Invested Securities [Line Items]
Investments, Debt securities, Cost	55,607	54,375
Investments, Debt securities, Gross Unrealized Gains	2,950	5,029
Investments, Debt securities	58,557	59,404
Investments, Equity securities, Cost	82,778	77,838
Investments, Equity securities, Gross Unrealized Gains	51,058	46,474
Investments, Equity securities, Gross Unrealized Losses	(1,338)	(354)
Investments, Equity securities	132,498	123,958
Investments, Cash and other	168	319
Investments, Cost	138,553	132,532
Investments, Gross Unrealized Gains	54,008	51,503
Investments, Gross Unrealized Loss	(1,338)	(354)
Total Nuclear Decommissioning Trust	191,223	183,681
Lease Deposits [Member]
Schedule of Invested Securities [Line Items]
Held to maturity investments, Cost	32,653	106,812
Held to maturity investments, Gross Unrealized Gains	37	776
Held to maturity investments, Fair Value	32,690	107,588
Lease Deposits [Member] | Government Obligations [Member]
Schedule of Invested Securities [Line Items]
Held to maturity investments, Cost	32,653	106,812
Held to maturity investments, Gross Unrealized Gains	37	776
Held to maturity investments, Fair Value	$ 32,690	$ 107,588

Investments (Schedule Of Contra

Investments (Schedule Of Contractual Maturities Of Debt Securities) (Details) $ in Thousands	Sep. 30, 2018USD ($)
Investments [Abstract]
Other debt securities, 5-10 years	$ 58,557
Other debt securities, Total	58,557
Held to maturity securities, Less than 1 year	37,035
Held to maturity securities, 1-5 years	240
Held to maturity securities, 5-10 years	0
Held to maturity, carrying value	37,275
Contractual maturities of securities, Less than 1 year	37,035
Contractual maturities of securities, 1-5 years	240
Contractual maturities of securities, 5-10 years	58,557
Contractual maturities of securities, Total	$ 95,832

Other - Additional Information

Other - Additional Information (Details)	Sep. 14, 2018USD ($)turbine	May 01, 2018MW	Jun. 01, 2017MW	May 01, 2016MW	Jan. 01, 2016MW	Sep. 30, 2018USD ($)MW	Dec. 31, 2017USD ($)
Public Utilities General Disclosures [Line Items]
Construction work in progress						$ 33,888,000	$ 822,667,000
Power received under limited exception to wholesale power contract, period of prior written notice of power received from owned generation or other suppliers						180 days
Power received under limited exception to wholesale power contract, percent of power received from owned generation or other suppliers						5.00%
Power received under limited exception to wholesale power contract, amount of power received from owned generation or other suppliers | MW		109	65	60	9	5
Current maximum reduction in demand and associated energy | MW						175
Remaining Demand and Associated Energy Available for Use | MW		66
Proceeds from sale of asset	$ 115,000,000					$ 115,000,000
Number of natural gas fired combustion turbine units | turbine	2
Percentage of undivided interest in related common facilities	0.50
Asset Purchase Agreement [Member]
Public Utilities General Disclosures [Line Items]
Gain loss on sale of asset	$ 42,700,000
Revolving Credit Facility [Member]
Public Utilities General Disclosures [Line Items]
Credit facility, maximum borrowing capacity						500,000,000
Line of credit outstanding						0	43,400,000
Revolving Credit Facility [Member] | March 4, 2022 through March 3, 2023
Public Utilities General Disclosures [Line Items]
Credit facility, maximum borrowing capacity						400,000,000
Letter of Credit [Member]
Public Utilities General Disclosures [Line Items]
Line of credit outstanding						$ 2,500,000	$ 12,000,000
Wildcat Point [Member]
Public Utilities General Disclosures [Line Items]
Power facility output | MW						1,000
Construction work in progress						$ 842,400,000
Interest costs capitalized						88,400,000
Liquidated damages						$ 53,200,000

Other - (Summary of Removal of

Other - (Summary of Removal of Load Requirements Under Exception) (Details) - MW	May 01, 2018	Jun. 01, 2017	May 01, 2016	Jan. 01, 2016	Sep. 30, 2018
Other [Abstract]
Removal of load requirements under exception	109	65	60	9	5

Other - (Reconciliation of Cash

Other - (Reconciliation of Cash and Cash Equivalents and Restricted Cash and Cash Equivalents Reported Within Condensed Consolidated Balance Sheet and Shown in Condensed Consolidated Statement of Cash Flows) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Cash And Cash Equivalents [Abstract]
Cash and cash equivalents	$ 71,447	$ 4,084	$ 40,160
Restricted cash and cash equivalents	14,200
Cash, cash equivalents, restricted cash and cash equivalents	$ 85,647	$ 4,084	$ 40,160	$ 2,946

New Accounting Pronouncements -

New Accounting Pronouncements - Additional Information (Details)	9 Months Ended
	Sep. 30, 2018Cooperative
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Number of member distributions cooperatives	11
Revenue recognition period for wholesale power contracts	3 years
Minimum [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Revenue percentage from wholesale power contracts	95.00%

New Accounting Pronouncements_3

New Accounting Pronouncements - (Schedule of Operating Revenues) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
New Accounting Pronouncements And Changes In Accounting Principles [Abstract]
Sales to member distribution cooperatives, excluding renewable energy credit sales	$ 230,408		$ 657,521
Renewable energy credit sales to member distribution cooperatives	2		14
Total sales to member distribution cooperatives	230,410		657,535
Sales to non-members, excluding renewable energy credit sales	24,791		51,762
Renewable energy credit sales to non-members	2,385		2,950
Total sales to non-members	27,176		54,712
Total operating revenues	$ 257,586	$ 193,425	$ 712,247	$ 540,111
Type of Revenue [Extensible List]	us-gaap:ElectricityMember	us-gaap:ElectricityMember	us-gaap:ElectricityMember	us-gaap:ElectricityMember