Washington Gas Light (WGLCP) 10-Q30 Apr 202020 Q1 Quarterly reportFinancial data

Company Profile

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2020	Apr. 30, 2020
Document and Entity Information [Abstract]
Entity Registrant Name	Washington Gas Light Company
Entity Central Index Key	0000104819
Document Type	10-Q
Document Period End Date	Mar. 31, 2020
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31
Entity Emerging Growth	false
Entity Small Business	false
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Interactive Data Current	Yes
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		46,479,536

Condensed Balance Sheets

Condensed Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment
At original cost	$ 6,046,692	$ 5,962,866
Accumulated depreciation and amortization	(1,603,239)	(1,579,718)
Net property, plant and equipment	4,443,453	4,383,148
Current Assets
Cash and cash equivalents	42,418	17,069
Receivables (net of allowance for doubtful accounts of $18,829 and $18,708, respectively)	340,198	400,891
Gas costs and other regulatory assets	35,217	9,894
Materials and supplies—principally at average cost	19,964	20,184
Storage gas	31,547	87,977
Prepaid taxes	30,865	34,576
Other prepayments	29,695	33,867
Receivables from associated companies	14,042	12,421
Derivatives	11,248	6,553
Other	11,491	19,619
Total current assets	566,685	643,051
Deferred Charges and Other Assets
Gas costs	60,069	98,717
Pension and other post-retirement benefits	36,175	39,435
Other	82,682	84,886
Prepaid post-retirement benefits	368,542	366,508
Right of use asset	39,045	40,004
Derivatives	15,540	10,370
Other	35,825	30,620
Total deferred charges and other assets	637,878	670,540
Total Assets	5,648,016	5,696,739
Capitalization
Common shareholder’s equity	1,798,678	1,572,196
Long-term debt	1,431,093	1,430,949
Total capitalization	3,229,771	3,003,145
Current Liabilities
Notes payable	45,511	299,483
Accounts payable and other accrued liabilities	219,773	267,408
Customer deposits and advance payments	33,103	40,052
Gas costs and other regulatory liabilities	87,109	105,399
Accrued taxes	29,280	23,781
Payables to associated companies	71,193	57,923
Operating lease liability	5,752	5,850
Derivatives	6,166	4,069
Other	29,788	30,032
Total current liabilities	527,675	833,997
Deferred Credits
Deferred income taxes	510,201	462,475
Accrued pensions and benefits	119,461	115,837
Asset retirement obligations	208,946	206,820
Regulatory liabilities
Accrued asset removal costs	254,213	254,429
Other post-retirement benefits	196,545	199,665
Excess deferred taxes and other	401,279	404,700
Operating lease liability	52,593	53,642
Derivatives	91,760	97,695
Other	55,572	64,334
Total deferred credits	1,890,570	1,859,597
Commitments and Contingencies (Note 11)
Total Capitalization and Liabilities	$ 5,648,016	$ 5,696,739

Condensed Balance Sheets (Paren

Condensed Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Allowance for credit losses	$ 18,829	$ 18,708

Condensed Statements of Operati

Condensed Statements of Operations - USD ($) $ in Thousands	3 Months Ended
Condensed Statements of Operations - USD ($) $ in Thousands	Mar. 31, 2020	Mar. 31, 2019
Income Statement [Abstract]
OPERATING REVENUES	$ 501,735	$ 593,653
OPERATING EXPENSES
Utility cost of gas	141,951	242,263
Operation and maintenance	102,678	111,002
Depreciation and amortization	35,870	35,189
General taxes and other assessments	50,069	52,619
Total Operating Expenses	330,568	441,073
OPERATING INCOME	171,167	152,580
Other income (expense) — net	3,070	4,522
Interest expense	16,694	14,876
INCOME BEFORE INCOME TAXES	157,543	142,226
INCOME TAX EXPENSE	31,459	29,230
NET INCOME (LOSS)	126,084	112,996
Dividends on preferred stock	0	330
NET INCOME (LOSS) APPLICABLE TO COMMON STOCK	$ 126,084	$ 112,666

Condensed Statements of Compreh

Condensed Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 126,084	$ 112,996
Pension and other post-retirement benefit plans
Change in prior service cost	(304)	(162)
Change in actuarial net gain (loss)	2,926	4,904
Total pension and other post-retirement benefit plans	2,622	4,742
INCOME TAX EXPENSE RELATED TO OTHER COMPREHENSIVE INCOME (LOSS)	681	477
OTHER COMPREHENSIVE INCOME	1,941	4,265
COMPREHENSIVE INCOME	$ 128,025	$ 117,261

Condensed Statements of Cash Fl

Condensed Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
Condensed Statements of Cash Flows - USD ($) $ in Thousands	Mar. 31, 2020	Mar. 31, 2019
OPERATING ACTIVITIES
Net income	$ 126,084	$ 112,996
ADJUSTMENTS TO RECONCILE NET INCOME TO NET CASH PROVIDED BY OPERATING ACTIVITIES
Depreciation and amortization	35,870	35,189
Amortization of:
Other regulatory assets and liabilities—net	2,225	1,730
Debt related costs	360	373
Deferred income taxes—net	31,609	29,394
Accrued/deferred pension and other post-retirement benefit cost	465	3,885
Compensation expense related to stock-based awards	446	1,185
Provision for doubtful accounts	5,874	7,489
Unrealized (gain) loss on derivative contracts	(6,122)	(7,148)
Amortization of investment tax credits	(150)	(165)
Other non-cash charges (credits)—net	(22)	208
Changes in operating assets and liabilities (Note 16)	49,043	3,632
Net Cash Provided by Operating Activities	245,682	188,768
FINANCING ACTIVITIES
Capital contribution from parent	125,000	0
Debt issuance costs	0	(209)
Notes payable issued (retired)—net	(253,972)	(91,000)
Dividends on common stock and preferred stock	(25,000)	(24,567)
Net Cash Used in Financing Activities	(153,972)	(115,776)
INVESTING ACTIVITIES
Capital expenditures	(70,995)	(92,739)
Net Cash Used in Investing Activities	(70,995)	(92,739)
INCREASE (DECREASE) IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	20,715	(19,747)
Cash, Cash Equivalents, and Restricted Cash at Beginning of the Period	61,148	71,423
Cash, Cash equivalents and Restricted Cash at End of the Period	$ 81,863	$ 51,676

Accounting Policies

Accounting Policies	3 Months Ended
Accounting Policies	Mar. 31, 2020
Accounting Policies [Abstract]
Accounting Policies	ACCOUNTING POLICIES Basis of Presentation Following the 2018 Merger Agreement, Washington Gas became an indirect, majority owned subsidiary of, among other entities, AltaGas and WGL. In connection with the Merger, WGL formed a wholly owned subsidiary, Wrangler SPE LLC (Wrangler SPE), a bankruptcy remote, special purpose entity to own the common stock of Washington Gas. In addition, WGL owns all of the shares of common stock of certain affiliated non-utility subsidiaries, some of which provide services to Washington Gas, and some of which own interests in other entities. On December 20, 2019, Washington Gas redeemed all the outstanding shares of its preferred stock. As a result, Washington Gas is now an indirect, wholly owned subsidiary of AltaGas and WGL. The condensed financial statements of Washington Gas have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (SEC). Therefore, certain financial information and note disclosures accompanying annual financial statements prepared in accordance with generally accepted accounting principles in the United States of America (GAAP) are omitted in this interim report. The interim condensed financial statements and accompanying notes should be read in conjunction with the Financial Statements on Form 10-K for the year ended December 31, 2019. Due to the seasonal nature of our business, the results of operations for the periods presented in this report are not necessarily indicative of actual results for the full years ending December 31, 2020 and 2019. The information presented in this report on Form 10-Q are presented solely for the registrant Washington Gas on a stand-alone basis. The accompanying unaudited condensed financial statements for Washington Gas reflect all normal recurring adjustments that are necessary, in our opinion, to present fairly the results of operations in accordance with GAAP. For a complete description of our significant accounting policies, refer to Note 1- Accounting Policies of the Notes to Financial Statements on Form 10-K for year ended December 31, 2019. We include herein certain updates to those policies. Accounting Standards Adopted in the Calendar Year and Other Newly Issued Accounting Standards The following tables represent accounting standards adopted by Washington Gas during the three months ended March 31, 2020 , and other newly issued accounting standards that will be adopted by Washington Gas in the future. ACCOUNTING STANDARDS ADOPTED IN CALENDAR YEAR 2020 Standard Description Date of adoption Effect on the financial statements or other significant matters ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, including other subsequent ASUs further amending and clarifying the guidance. For credit losses on financial instruments measured at amortized cost, this standard changes the current incurred loss impairment methodology to an expected loss methodology and requires consideration of a broader range of reasonable and supportable information to determine credit loss estimates. In addition, entities may make a one-time irrevocable election on certain eligible financial instruments to elect fair value treatment on an instrument-by-instrument basis. Early adoption is permitted. January 1, 2020 Cash equivalents, accounts receivable, unbilled revenue, and contract assets are within the scope of the new standard. Upon adoption, we recorded an increase to our allowance for credit losses and a reduction to retained earnings of $1.5 million. See Note 2 - Credit Losses for further information and the new required disclosures. ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement This update modifies the disclosure requirements on fair value measurements. Early adoption is permitted. January 1, 2020 The adoption of this standard did not have a material effect on our financial statements. ASU 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction between Topic 808 and Topic 606 Topic 808 does not provide comprehensive recognition or measurement guidance for collaborative arrangements. This update clarifies the interaction between Topic 606, Revenue from Contracts with Customers and Topic 808. January 1, 2020 The adoption of this standard did not have a material effect on our financial statements. ASU 2019-01, Leases (Topic 842) Codification Improvements This update addresses the determination of the fair value of the underlying asset by lessors that are not manufacturers or dealers, provides guidance for the presentation of the statement of cash flows for sales-type and direct financing leases, and clarifies transition disclosures related to the adoption of ASC 842. January 1, 2020 The adoption of this standard did not have a material effect on our financial statements. Standard Description Date of adoption Effect on the financial statements or other significant matters ASU 2019-04, Codification Improvements to Topic 326, Financial Instruments—Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments The amendments in this ASU provide clarification and improve the codification in recently issued accounting standards. January 1, 2020 The adoption of this standard did not have a material effect on our financial statements. ASU 2020-03, Codification Improvements to Financial Instruments This Update makes technical corrections and minor improvements to the guidance on financial instruments. January 1, 2020 The adoption of this standard did not have a material effect on our financial statements. OTHER NEWLY ISSUED ACCOUNTING STANDARDS Standard Description Required date of adoption Effect on the financial statements or other significant matters ASU 2018-14, Compensation—Retirement Benefits—Defined Benefit Plans—General (Subtopic 715-20): Disclosure Framework—Changes to the Disclosure Requirements for Defined Benefit Plans This standard modifies the disclosure requirements related to defined benefit pension and other postretirement plans. Early adoption is permitted. December 31, 2020 It is not expected that the adoption of this standard will have a material effect on our financial statements. ASU 2019-12, Income Taxes (Topic 740) Simplifying the Accounting for Income Taxes As part of FASB's Simplification Initiative, this standard amends ASC Topic 740 by removing certain exceptions to the general principles and clarifying and amending other current guidance. Early adoption is permitted. January 1, 2021 We are in the process of evaluating the impact the adoption of this standard will have on our financial statements. ASU 2020-04, Reference Rate Reform (Topic 848) Facilitation of the Effects of Reference Rate Reform on Financial Reporting This standard provides optional expedients and exceptions to ease the potential accounting burden associated with transitioning away from reference rates that are expected to be discontinued. The amendments may be elected prospectively to contract modifications made and to hedging relationships existing as of or entered into on or after the date of adoption and through December 31, 2022. December 31, 2022 We are in the process of evaluating the impact the adoption of this standard will have on our financial statements.

Credit Losses

Credit Losses	3 Months Ended
Credit Losses	Mar. 31, 2020
Credit Loss [Abstract]
Credit Losses	CREDIT LOSSES On January 1, 2020, the Company adopted ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , which replaces the incurred loss methodology with an expected loss methodology that is referred to as the current expected credit loss (CECL) model. The measurement of expected credit losses under the CECL model is applicable to financial assets measured at amortized cost and off-balance sheet credit exposures. The CECL model requires the expected credit losses to consider past events, including historical experience, current conditions and reasonable and supportable forecasts. When measuring credit losses, financial assets with similar risk characteristics should be pooled, and credit losses should be recognized over the contractual term of the financial asset. In addition, entities may make a one-time irrevocable election on certain eligible financial instruments to elect fair-value treatment on an instrument-by-instrument basis. Our assessment concluded that our cash equivalents, accounts receivables, unbilled revenue, contract assets, and a long term receivable from one of our trading partners that is part of a collaborative arrangement are within scope of the new standard. We adopted the standard using a modified-retrospective approach through a cumulative-effect adjustment to retained earnings at January 1, 2020. Prior periods presented for comparative purposes are not adjusted. Upon implementation of ASU 2016-13, we recorded a $1.5 million increase to the Company's allowance for doubtful accounts and a decrease to retained earnings. Washington Gas also elected to account for its cash equivalents at fair value. Utility Customer Receivables: Washington Gas is exposed to risk through the non-payment of utility bills by customers. To manage this customer credit risk, Washington Gas customers are offered budget billing options or higher risk customers may be required to provide a cash deposit until the requirement for deposit refunds are met. Washington Gas can recover a portion of non-payments from customers in future periods through the rate-setting process. For accounts receivable and unbilled revenue generated by the utility business, an allowance for doubtful accounts is recognized using a historical loss-rate based on historical payment and collection experience. This rate may be adjusted based on management’s expectations of unusual macroeconomic conditions and other factors . Washington Gas regularly evaluates the reasonableness of the allowance based on a combination of factors, such as: the length of time receivables are past due, historical expected payment, collection experience, financial condition of customers, and other circumstances that could impact customers' ability or desire to make payments. Upon implementation of the new standard, Washington Gas increased the allowance for doubtful accounts by $1.4 million . Based on previous collection experience, Washington Gas did not record an allowance for doubtful accounts for its contract assets associated with our energy management services projects with the federal government. Refer to Note 14 - Related Party Transactions for further information. Washington Gas Asset Optimization : The Utility operates under an existing wholesale counterparty credit policy that is designed to mitigate credit risk. Credit limits are established for each counterparty and credit enhancements such as letters of credits, parent guarantees and cash collateral maybe required. The creditworthiness of all counterparties is continuously monitored. The allowance for doubtful accounts is estimated by applying 30-year historical default rates for one-year receivables sourced from external credit rating agencies to the accounts receivable and unbilled revenue balances associated with counterparties the Utility has determined to be below investment grade. In the event that a counterparty no longer exhibits similar risk characteristics, the associated receivable is evaluated individually. Upon implementation of ASU 2016-13, Washington Gas did not record an amount to the allowance for doubtful accounts. Washington Gas also has a long term receivable from a trading partner totaling $1.4 million in “Deferred charges and other assets-Other”, of which no portion of the balance is past due. The trading partner was eval uated and assigned an internal credit rating in accordance with our credit policy. An allowance for doubtful accounts is recorded based on historical default rates published by external credit rating agencies and a rate commensurate with the period in which the receivable is expected to be collected. With implementation of the new standard, Washington Gas recorded an estimated credit loss reserve of $0.1 million reported as a reduction to “Deferred charges and other assets-Other” . The following table presents the activity of allowance for doubtful accounts by types for the reporting periods. Three Months Ended March 31, 2020 (In millions) Account receivables and Unbilled Revenue Asset Optimization Balance, beginning of period $ 18.7 $ — Provision 5.9 — Write offs charged against the allowance (7.5 ) — Recoveries 0.3 — Adjustment upon adoption of ASC 326 1.4 0.1 Balance, end of period $ 18.8 $ 0.1 On March 11, 2020, the World Health Organization declared the outbreak of a strain of novel coronavirus disease, COVID-19, a global pandemic. Governments in affected areas in which we operate have imposed a number of measures designed to contain the outbreak, including non-essential business closures, travel restrictions, quarantines and cancellations of gatherings and events. These measures have resulted in widespread challenges to businesses and the job market resulting in increased unemployment rates, which could impact the ability of the Company’s customers to pay for services. Washington Gas has temporarily suspended shut-off, collection activities, and assessment of late fees as a result of public service commission orders in the jurisdictions in which the Company operates. In addition, we have received orders from our public service commissions to establish a regulatory asset for incremental collection and other costs related to COVID-19. Due to the speed with which the situation is developing and the uncertainty of its magnitude, outcome and duration, it is currently not possible to reasonably estimate the impact of the pandemic on our customer collections at this time.

Revenue from Contracts With Cus

Revenue from Contracts With Customers	3 Months Ended
Revenue from Contracts With Customers	Mar. 31, 2020
Revenue from Contract with Customer [Abstract]
Revenue from Contracts with Customers	REVENUE FROM CONTRACTS WITH CUSTOMERS The Company recognizes revenue from contracts with customers to depict the transfer of goods or services to customers at an amount it expects to be entitled to in exchange for those goods or services. Washington Gas sells natural gas and distribution services to residential, commercial, industrial and governmental customers through regulated tariff rates approved by regulatory commissions in the jurisdictions where it operates. Customers are billed monthly based on regular meter readings. Customer billings are based on two main components: (i) a fixed service fee and (ii) a variable fee based on usage. For customers who choose to purchase their natural gas from Washington Gas, the bill will include a usage based charge for the cost of the commodity. Revenue is recognized over time as natural gas is delivered or as service is performed. Since meter readings are performed on a cycle basis, Washington Gas recognizes accrued revenue for any services rendered to its customers but not billed at month-end. The tariff sales are generally considered daily or “at-will” contracts as customers may cancel their service at any time (subject to notification requirements in the tariff), and revenue generally represents the amount Washington Gas is entitled to invoice. There are certain contracts that have terms of one year or longer. For these contracts, revenue is recognized based on the amount Washington Gas is entitled to bill the customer. Customers have the choice to purchase natural gas from competitive service providers. Washington Gas charges the competitive service providers balancing fees to manage the natural gas transportation imbalances. Where regulations require, Washington Gas issues customers a consolidated bill to include the natural gas supplied by the competitive service providers and distribution of natural gas. Washington Gas recognizes revenue only for distribution services that it has provided to the customer, and the balancing fees for the services provided to the competitive service provider. We disaggregate revenue by type of service. The following table disaggregates revenue for the three months ended March 31, 2020 and 2019: Disaggregated Revenue by Type of Service Three Months Ended March 31, (In millions) 2020 2019 Revenue from contracts with customers Gas and transportation sales Gas sold and delivered $ 346.3 $ 462.1 Gas delivered for others 97.6 109.4 Other 13.7 13.6 Other revenues 0.7 1.1 Total revenue from contracts with customers $ 458.3 $ 586.2 Other sources of revenue Revenue from alternative revenue programs (a) $ 40.6 $ 4.0 Leasing revenue 0.2 0.2 Other (b) 2.6 3.3 Total revenue from other sources $ 43.4 $ 7.5 Total Operating Revenue $ 501.7 $ 593.7 (a) Washington Gas has determined that its Revenue Normalization Adjustment (RNA), Weather Normalization Adjustment (WNA), and Conservation and Ratemaking Efficiency (CARE) Ratemaking Adjustment (CRA) billing adjustment mechanisms and accelerated pipe replacement programs are alternative revenue programs and accounted for under ASC Topic 980. (b) The amount includes late fees billed. Washington Gas accrues unbilled revenues for gas delivered, but not yet billed at the end of each accounting period due to our customer billing cycles. Unbilled revenues of $74.0 million and $116.3 million are included within "Receivables" on Washington Gas' balance sheets at March 31, 2020 and December 31, 2019 , respectively. Unbilled revenues represent performance obligations that have been satisfied and to which Washington Gas has an unconditional right to payment, except for contract assets related to Washington Gas’ area-wide contract, which requires project acceptance by federal government for the right to payment to occur. The Company does not have transaction price amounts allocated to future performance obligations. The Company applies the practical expedient available under ASC Topic 606 and does not disclose information about the remaining performance obligations for (i) contracts with an original expected length of one year or less, (ii) contracts for which revenue is recognized at the amount to which the Company has the right to invoice for performance completed, and (iii) contracts with variable consideration that is allocated entirely to a wholly unsatisfied performance obligation or to a wholly unsatisfied promise to transfer a distinct good or service that forms part of a single performance obligation. The following table shows the opening and closing balances of contract assets from contracts with customers for the reporting periods, which were included within "Receivables" on Washington Gas' balance sheets. (In millions) 2020 2019 Contract assets at January 1 $ 44.2 $ 85.3 Contract assets at March 31 $ 46.1 $ 34.6 Increase (decrease) in contract assets $ 1.9 $ (50.7 )

Leases

Leases	3 Months Ended
Leases	Mar. 31, 2020
Leases [Abstract]
Leases	LEASES Washington Gas has operating leases as a lessee for our corporate headquarters and other offices, communication tower space, and certain office equipment. The Company also has lessor leases for land, office space and communication tower space that are classified as operating leases. Washington Gas has elected not to separate the lease and non-lease components for its building leases. The leases generally have options to terminate the leases with notice prior to the end of the lease term based on the contract terms. The lease agreements do not contain material residual value guarantees. For information on the lease income recognized during the period, see the Disaggregated Revenue by Type of Service table in Note 3 — Revenue from Contracts with Customers. There were no other significant changes for our operating leases during the three months ended March 31, 2020 .
Leases	LEASES Washington Gas has operating leases as a lessee for our corporate headquarters and other offices, communication tower space, and certain office equipment. The Company also has lessor leases for land, office space and communication tower space that are classified as operating leases. Washington Gas has elected not to separate the lease and non-lease components for its building leases. The leases generally have options to terminate the leases with notice prior to the end of the lease term based on the contract terms. The lease agreements do not contain material residual value guarantees. For information on the lease income recognized during the period, see the Disaggregated Revenue by Type of Service table in Note 3 — Revenue from Contracts with Customers. There were no other significant changes for our operating leases during the three months ended March 31, 2020 .

Accounts Payable and Other Accr

Accounts Payable and Other Accrued Liabilities	3 Months Ended
Accounts Payable and Other Accrued Liabilities	Mar. 31, 2020
Accounts Payable and Accrued Liabilities [Abstract]
Accounts Payable and Other Accrued Liabilities	ACCOUNTS PAYABLE AND OTHER ACCRUED LIABILITIES The table below provides details for the amounts included in “Accounts payable and other accrued liabilities” on the balance sheets. (In millions) March 31, 2020 December 31, 2019 Accounts payable—trade $ 135.9 $ 154.3 Employee benefits and payroll accruals 20.6 39.2 Wages payable 24.1 22.2 Accrued interest 3.1 17.3 Other accrued liabilities (a) 36.1 34.4 Total $ 219.8 $ 267.4 (a) Amount includes $11.9 million and $11.7 million estimated liability associated with Antero judgment at March 31, 2020 and December 31, 2019, respectively, Refer to Note 11 -Commitments and Contingencies for further information.

Short-Term Debt

Short-Term Debt	3 Months Ended
Short-Term Debt	Mar. 31, 2020
Short-term Debt [Abstract]
Short-Term Debt	SHORT-TERM DEBT Washington Gas satisfies the short-term financing requirements through the sale of commercial paper, or through bank borrowings. Due to the seasonal nature of our operations, short-term financing requirements can vary significantly during the year. Revolving credit agreements are maintained to support outstanding commercial paper and to permit short-term borrowing flexibility. The policy of Washington Gas is to maintain bank credit facilities in amounts equal to or greater than the expected maximum commercial paper position. Credit Facility The following is a summary of committed credit available at March 31, 2020 and December 31, 2019 . (In millions) March 31, 2020 December 31, 2019 Committed credit agreements Unsecured revolving credit facility, expires July 19, 2024 (a) $450.0 $450.0 Less: Commercial Paper outstanding (b) (145.6) (400.0) Net committed credit available $304.4 $50.0 Weighted average interest rate 1.91% 2.04% (a) Washington Gas has the right to request extensions with the bank group 's approval. Washington Gas’ revolving credit facility permits it to borrow an additional $100.0 million , with the bank groups' approval, for a total potential maximum borrowing of $550.0 million . (b) The amount presents principal amount of commercial paper. At March 31, 2020 and December 31, 2019 , there were no outstanding bank loans from Washington Gas’ revolving credit facilities. Under the terms of the credit facility, the ratio of financial indebtedness to total capitalization may not exceed 0.65 to 1.0 ( 65.0% ). At March 31, 2020 and December 31, 2019 , Washington Gas' ratios of consolidated financial indebtedness to consolidated total capitalization was 45% and 52% , respectively. In addition, Washington Gas is required to inform lenders of changes in corporate existence, financial conditions, litigation and environmental warranties that might have a material adverse effect. Failure to inform the lenders’ agent of these material changes might constitute default under the agreements. Should Washington Gas fail to pay principal or interest when due on any other indebtedness, such failure may be deemed to constitute a default. Such defaults, if not remedied, could lead to suspension of further loans and/or acceleration in which obligations become immediately due and payable. At March 31, 2020 and December 31, 2019 , Washington Gas was in compliance with all of the covenants under its credit facility. Commercial Paper The total commercial paper carrying value was $ 145.5 million and $ 399.5 million at March 31, 2020 and December 31, 2019 , respectively. At both March 31, 2020 and December 31, 2019 , Washington Gas classified $ 100.0 million of our commercial paper balance as "Long-term debt" on Washington Gas' balance sheets due to its ability and intent to refinance these balances on a long-term basis. Accordingly, $ 45.5 million and $ 299.5 million of commercial paper remained in “Notes payable” at March 31, 2020 and December 31, 2019 , respectively.

Long-Term Debt

Long-Term Debt	3 Months Ended
Long-Term Debt	Mar. 31, 2020
Debt Disclosure [Abstract]
Long-Term Debt	LONG-TERM DEBT Washington Gas issues unsecured long-term debt in the form of medium-term notes (MTNs) and private placement notes with individual terms regarding interest rates, maturities and call or put options. Washington Gas classified certain commercial paper balance as "Long-term debt" due to its ability and intent to refinance these balances on a long-term basis. The following table shows the long-term debt outstanding at March 31, 2020 and December 31, 2019 . Long Term Debt Outstanding (In millions) March 31, 2020 December 31, 2019 Washington Gas Unsecured Notes (a) $ 1,346.0 $ 1,346.0 Commercial Paper 100.0 100.0 Total Long-Term Debt $ 1,446.0 $ 1,446.0 Unamortized discount (4.3 ) (4.3 ) Unamortized debt expense (10.6 ) (10.8 ) Less—current maturities — — Total Long-Term Debt (carrying value) $ 1,431.1 $ 1,430.9 Weighted average interest rate (b) 4.52 % 4.52 % (a) Includes MTNs and private placement notes. The amount represents face value of Washington Gas' unsecured notes including current maturities. (b) Weighted average interest rate is for the Washington Gas unsecured notes including current maturities. There were no issuances or retirements of long term debt for the three months ended March 31, 2020 and 2019 .

Components of Total Equity Comp

Components of Total Equity Components of Total Equity	3 Months Ended
Components of Total Equity Components of Total Equity	Mar. 31, 2020
Stockholders' Equity Note [Abstract]
Components of Total Equity	COMPONENTS OF TOTAL EQUITY Common Stock Paid-In Capital Retained Earnings Accumulated Other Income/(Loss), Net of Taxes (In thousands, except shares) Shares Amount Total Balance at December 31, 2019 46,479,536 $ 46,479 $ 979,273 $ 541,535 $ 4,909 $ 1,572,196 Net income — — — 126,084 — 126,084 Other comprehensive income — — — — 1,941 1,941 Capital contribution from parent — — 125,000 — — 125,000 ASU 2016-13 implementation (a) — — — (1,543 ) — (1,543 ) Dividends declared: Common stock — — — (25,000 ) — (25,000 ) Balance at March 31, 2020 46,479,536 46,479 1,104,273 641,076 6,850 1,798,678 Balance at December 31, 2018 46,479,539 46,479 979,273 543,448 (6,627 ) 1,562,573 Net income — — — 112,996 — 112,996 Other comprehensive income — — — — 4,265 4,265 Dividends declared: Common stock — — — (25,000 ) — (25,000 ) Preferred stock — — — (330 ) — (330 ) Balance at March 31, 2019 46,479,539 46,479 979,273 631,114 (2,362 ) 1,654,504 (a) Due to implementation of ASU 2016-13 Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, see Note 2 — Credit Losses for further information.

Income Taxes

Income Taxes	3 Months Ended
Income Taxes	Mar. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	INCOME TAXES WGL and its wholly owned subsidiaries are included in AltaGas' consolidated income tax returns. We have established a new tax sharing policy with AltaGas Services (US) Inc. (ASUS), an indirect, wholly owned subsidiary of AltaGas, that allocates consolidated tax liabilities and benefits using a ratio determined by the separate taxable income for each member applied to the consolidated return tax liability of the group. State income tax returns are filed on a separate company basis in most states and on a unitary basis as required, where we or the consolidated ASUS group have operations and/or a requirement to file. At March 31, 2020 and December 31, 2019 , Washington Gas recorded a $5.5 million receivable in "Receivables from associated companies" and a $0.6 million payable in "Payables to associated companies" under the ASUS tax sharing policy on Washington Gas' balance sheets, respectively. The Coronavirus Aid, Relief and Economic Security Act ("CARES Act") was signed into law on March 27, 2020. The CARES Act includes various income and payroll tax provisions. While we are still assessing the impact of the legislation, we do not expect there to be a material impact to our financial statements at this time. Amounts of Interest and Penalties Recognized Washington Gas recognizes any accrued interest associated with uncertain tax positions in interest expense and recognizes any accrued penalties associated with uncertain tax positions in other expenses in the statements of income. During the three months ended March 31, 2020 and 2019 , there were no accrued interest expense or penalties associated with uncertain tax positions.

Pension and Other Post-Retireme

Pension and Other Post-Retirement Benefit Plans	3 Months Ended
Pension and Other Post-Retirement Benefit Plans	Mar. 31, 2020
Retirement Benefits [Abstract]
Pension and Other Post-Retirement Benefit Plans	PENSION AND OTHER POST-RETIREMENT BENEFIT PLANS The following table shows the components of the net periodic benefit costs (income) recognized in our financial statements during the three months ended March 31, 2020 and 2019: Components of Net Periodic Benefit Costs (Income) Three Months Ended March 31, 2020 2019 (In millions) Pension Benefits Health and Life Benefits Pension Benefits Health and Life Benefits Service cost $ 3.2 $ 1.3 $ 3.0 $ 1.3 Interest cost 8.9 2.3 10.2 3.0 Expected return on plan assets (10.1 ) (5.6 ) (10.7 ) (6.1 ) Recognized prior service cost (credit) 0.1 (3.4 ) 0.1 (3.9 ) Recognized actuarial loss (gain) 3.3 (0.1 ) 1.3 — Settlement charge (a) 1.1 — 4.3 — Net periodic benefit cost (income) 6.5 (5.5 ) 8.2 (5.7 ) Allocation to affiliates (0.3 ) 0.4 (0.4 ) 0.7 Adjusted net periodic benefit cost (income) 6.2 (5.1 ) 7.8 (5.0 ) Amount allocated to construction projects (0.4 ) (0.2 ) (0.4 ) (0.2 ) Amount deferred as regulatory asset (liability)-net allocations (b) — — 0.7 — Amount charged (credited) to expense $ 5.8 $ (5.3 ) $ 8.1 $ (5.2 ) (a) Amounts relate to partial settlement charges associated with lump sum payments from the Washington Gas’ defined benefit supplemental executive retirement plan (DB SERP) that were paid in the first quarter of 2020 and 2019. (b) Amount represents the amortization of previously unrecovered costs of the applicable pension benefits or the health and life benefits as approved in the District of Columbia through 2019. At March 31, 2020 and December 31, 2019 , the rabbi trust balance associated with the DB SERP and non-funded defined benefit restoration plan (DB restoration) plans were $35.4 million and $40.0 million , respectively. $11.3 million and $24.0 million were recorded in “Current Assets-Other” and “Deferred Charges and Other Assets - Other” on Washington Gas' balance sheets at March 31, 2020 ; $19.5 million and $20.5 million were recorded in “Current Assets-Other” and “Deferred Charges and Other Assets - Other” at December 31, 2019 , respectively, along with other rabbi trust balances.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
Commitments and Contingencies	Mar. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	COMMITMENTS AND CONTINGENCIES Commitments Washington Gas has certain natural gas contracts incurred in the normal course of business that require fixed and determinable payments in the future, including unconditional purchase obligations for pipeline capacity, transportation and storage services. Refer to Note 13- Commitments and Contingencies to the Financial Statements in Form 10-K for the calendar year ended December 31, 2019 for future payments. There were no significant changes to contractual obligations that are out of the normal course of business during the three months ended March 31, 2020 . Merger Commitments In connection with the Merger, Washington Gas and AltaGas have made commitments related to the terms of settlement agreement with the Public Service Commission of the District of Columbia (PSC of DC) and the conditions of approval from the Public Service Commission of Maryland (PSC of MD) and the Virginia State Corporation Commission (SCC of VA). Among other things, these commitments included rate credits distributable to both residential and non-residential customers, gas expansion and other programs, various public interest commitments, and safety programs. As of March 31, 2020 , the cumulative amount of merger commitments expensed was $136.6 million , of which, $16.6 million has not been paid. In addition, there are certain additional regulatory commitments that were and will be expensed as the costs are incurred, including the hiring of damage prevention trainers in each jurisdiction for a total of $2.4 million over 5 years ; investing up to $70.0 million over a 10 -year period to further extend natural gas service; and spending $8.0 million for leak mitigation within 3 years after the Merger close. Additionally, there are a number of operational commitments that will have an impact on the ongoing business of Washington Gas, including reductions of leak backlogs, conducting a root cause analysis related to customer service, increasing supplier diversity, achieving synergy savings benefits, developing protocols for moving meters from inside to outside customers’ premises, as well as reporting and tracking related to all the commitments. Contingencies We account for contingent liabilities utilizing ASC Topic 450, Contingencies. By their nature, the amount of the contingency and the timing of a contingent event and any resulting accounting recognition are subject to our judgment of such events and our estimates of the amounts. Actual results related to contingencies may be difficult to predict and could differ significantly from the estimates included in reported earnings. Antero Contract In June 2019, a jury trial was held in the County Court for Denver, Colorado to consider a contractual dispute relating to gas pricing between Washington Gas and WGL Midstream (together, the Companies) and Antero Resources Corporation (Antero). Following the trial, the jury returned a verdict in favor of Antero for $95.9 million , of which $11.2 million was against Washington Gas, and $84.7 million against WGL Midstream. Following the official entry of the judgment, the Company filed an appeal on August 16, 2019. As a result of this verdict, it was determined that a loss contingency is probable and Washington Gas recorded an estimated liability and recognized a loss in June 2019. In addition, Washington Gas recorded a receivable from our trading partner, and a receivable related to sharing with our customers as the contract relates to asset optimization. Washington Gas has been accruing interest expense on a monthly basis associated with the liability since June 2019. At March 31, 2020 , the estimated liability with court fees and accrued interest was $11.9 million recorded in “Accounts payable and accrued liabilities” on Washington Gas' balance sheets. The receivable from our trading partner was $1.3 million in “Deferred charges and other assets-Other” , and sharing with customers was $4.8 million in “Regulatory assets - Gas costs” on the balance sheets. The interest expense associated with the legal liability was minimal for the three months ended March 31, 2020 . Regulatory Contingencies Certain legal and administrative proceedings incidental to our business, including regulatory contingencies, involve Washington Gas. In our opinion, we have recorded an adequate provision for probable losses or refunds to customers for regulatory contingencies related to these proceedings. Mary land Jurisdiction Maryland Show-Cause Order . On April 23, 2019, the National Transportation and Safety Board (NTSB) held a hearing during which it found, among other things, that the probable cause of the August 10, 2016, explosion and fire at an apartment complex on Arliss Street in Silver Spring, Maryland “was the failure of an indoor mercury service regulator with an unconnected vent line that allowed natural gas into the meter room where it accumulated and ignited from an unknown ignition source. Contributing to the accident was the location of the mercury service regulators where leak detection by odor was not readily available.” Washington Gas disagrees with the NTSB’s probable cause findings. Following this hearing, on June 10, 2019, the NTSB issued an accident report. Following the NTSB hearing on September 5, 2019, the PSC of MD ordered the Company, within 30 days, to (i) provide a detailed response to the NTSB’s probable cause findings, and (ii) provide evidence regarding the status of a 2003 mercury regulator replacement program, and if the program was not completed, to show cause why the Commission should not impose a civil penalty on the Company. The Company timely responded to the PSC of MD’s Show-Cause Order, providing a detailed response to the NTSB’s probable cause findings, providing evidence regarding the status of its 2003 mercury regulator replacement program and demonstrating cause why the PSC of MD should not impose a civil penalty on the Company. Following the Company’s response, certain intervenors filed written comments and a public hearing was held on the matter, with some intervenors and members of the public advocating for penalties against the Company. The Company filed its rejoinder comments and the Show-Cause Order is working its way through the regulatory proceeding process with the PSC of MD. A hearing is expected to occur later this year. Management believes that the likelihood of a civil penalty is probable and has accrued $330,000 to reflect the minimum liability expected to result from the proceeding. Though the Company is unable to estimate the maximum possible penalty, other parties recommended penalties ranging from $32.0 million (Apartment and Office Building Association of Metropolitan Washington argued the Company should absorb all costs of removal and relocation of mercury service regulators) to $123.3 million (Office of People's Counsel argued the Company should absorb all costs of removal and relocation of mercury service regulators and pay a fine of $25,000 per day for each day mercury service regulators remain on the Company’s system). Environmental Matters We are subject to federal, state and local laws and regulations related to environmental matters. These laws and regulations may require expenditures over a long time frame to control environmental effects. Almost all of the environmental liabilities we have recorded are for costs expected to be incurred to remediate sites where we or a predecessor affiliate operated manufactured gas plants (MGPs). Washington Gas has identified up to ten sites where it or its predecessors may have operated MGPs. Washington Gas last used any such plant in 1984. In connection with these operations, we are aware that coal tar and certain other by-products of the gas manufacturing process are present at or near some former sites and may be present at others. At March 31, 2020 and December 31, 2019 , Washington Gas reported a liability of $11.0 million and $10.7 million , respectively, on an undiscounted basis related to future environmental response costs. These estimates principally include the minimum liabilities associated with a range of environmental response costs expected to be incurred. At March 31, 2020 and December 31, 2019 Washington Gas estimated the maximum liability associated with all of its sites to be approximately $30.9 million and $30.7 million , respectively. The estimates were determined by Washington Gas’ environmental experts, based on experience in remediating MGP sites and advice from legal counsel and environmental consultants. The variation between the recorded and estimated maximum liability primarily results from differences in the number of years that will be required to perform environmental response processes and the extent of remediation that may be required. Washington Gas is currently remediating its East Station property, located adjacent to the Anacostia River in Washington D.C., including ground water pump and treat, tar recovery, soil encapsulation and other treatment. Under a 2012 consent decree with the District of Columbia and the federal government, Washington Gas is also conducting a remedial investigation and feasibility study on an adjacent property owned by the District of Columbia. Additional remediation may be required at this property. In addition, at another adjoining property known as the “Boat Club Property,” located to the east of the property owned by the District of Columbia, Washington Gas agreed to perform a site investigation and report the findings pursuant to oversight by the District of Columbia Department of Energy and Environment (DOEE). This property was subject to a July 12, 2019, Administrative Order from the DOEE. This Administrative Order has been withdrawn and a consent order was negotiated and the Company is awaiting its issuance by the DOEE. Washington Gas received a letter in February 2016 from the DOEE and National Park Service regarding the Anacostia River Sediment Project, indicating that the District of Columbia is conducting a separate remedial investigation and feasibility study of the river to determine if and what cleanup measures may be required and to prepare a natural resource damage assessment. On December 27, 2019, DOEE issued an Anacostia River Sediment Project Proposed Plan, a River-wide Feasibility Study, and supporting documents for public comment. Although the Proposed Plan identifies East Station as one of fifteen potential environmental cleanup sites, DOEE is proposing to continue the remediation of East Station under Washington Gas’ existing Consent Decree rather than as part of the Anacostia River Sediment Project. DOEE is proposing to issue an Interim Record of Decision for remediation of “Early Action Areas” (that do not include East Station) in the Anacostia River by September 30, 2020. We are not able to estimate the total amount of potential costs or timing associated with the District of Columbia’s environmental investigation on the Anacostia River at this time. While an allocation method has not been established, Washington Gas has accrued an amount for estimated study costs based on a potential range of estimates. Regulatory orders issued by the PSC of MD allow Washington Gas to recover the costs associated with the sites applicable to Maryland over the period ending in 2025. Regulatory orders issued by the PSC of DC allow Washington Gas a three-year recovery of prudently incurred environmental response costs and allow Washington Gas to defer additional costs incurred between rate cases. Regulatory orders from the SCC of VA have generally allowed the recovery of prudent environmental remediation costs to the extent they were included in the underlying financial data supporting an application for rate change. At both March 31, 2020 and December 31, 2019 , Washington Gas reported a regulatory asset of $7.0 million for the portion of environmental response costs that are expected to be recoverable in future rates.

Derivatives

Derivatives	3 Months Ended
Derivatives	Mar. 31, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives	DERIVATIVES Derivative Instruments Washington Gas enters into contracts that qualify as derivative instruments and are accounted for under ASC Topic 815. These derivative instruments are recorded at fair value on our balance sheets and Washington Gas does not currently designate any derivatives as hedges under ASC Topic 815. Washington Gas’ derivative instruments relate to: (i) Washington Gas’ asset optimization program; (ii) managing price risk associated with the purchase of gas to serve utility customers and (iii) managing interest rate risk. Asset Optimization. Washington Gas optimizes the value of its long-term natural gas transportation and storage capacity resources during periods when these resources are not being used to physically serve utility customers. Specifically, Washington Gas utilizes its transportation capacity assets to benefit from favorable natural gas prices between different geographic locations and utilizes its storage capacity assets to benefit from favorable natural gas prices between different time periods. As part of this asset optimization program, Washington Gas enters into physical and financial derivative transactions in the form of forward, futures and option contracts with the primary objective of securing operating margins that Washington Gas will ultimately realize. The derivative transactions entered into under this program are subject to mark-to-market accounting treatment under ASC Topic 820. Regulatory sharing mechanisms provide for the annual realized profit from these transactions to be shared between Washington Gas’ shareholders and customers; therefore, changes in fair value are recorded through earnings, or as regulatory assets or liabilities to the extent that it is probable that realized gains and losses associated with these derivative transactions will be included in the rates charged to customers when they are realized. Unrealized gains and losses recorded to earnings may cause significant period-to-period volatility; this volatility does not change the operating margins that Washington Gas expects to ultimately realize from these transactions through the use of its storage and transportation capacity resources. Washington Gas has a collaborative arrangement with a third party to facilitate the asset optimization program. The collaborative arrangement allocates a tiered percentage of profits or losses to the third party as compensation for its participation. The costs recorded by Washington Gas related to the collaborative arrangement totaled $1.0 million and $0.7 million for the three months ended March 31, 2020 and 2019, respectively. These amounts were recorded in “Utility cost of gas” on Washington Gas’ statements of operations. Either party may terminate the collaborative arrangement through the delivery of a termination notice. In such an event, Washington Gas may make a payment upon termination. All physically and financially settled contracts under our asset optimization program are reported on a net basis in the statements of operations in “Utility cost of gas”. Total net margins recorded to “Utility cost of gas” after sharing and management fees associated with all asset optimization transactions for the three months ended March 31, 2020 was a net gain of $8.4 million including an unrealized gain of $6.1 million . During the three months ended March 31, 2019 , we recorded a net gain of $8.2 million including an unrealized gain of $7.2 million . Managing Price Risk. To manage price risk associated with acquiring natural gas supply for utility customers, Washington Gas enters into physical and financial derivative transactions in the form of forward, option and other contracts, as authorized by its regulators. Any gains and losses associated with these derivatives are recorded as regulatory liabilities or assets, respectively, to reflect the rate treatment for these economic hedging activities. Operations The following table presents the balance sheet classification for all derivative instruments at March 31, 2020 and December 31, 2019 . Absolute Notional Amounts of Open Positions on Derivative Instruments March 31, 2020 December 31, 2019 Natural Gas (In millions of therms) Asset optimization & trading 11,442.0 11,671.0 Other risk-management activities 887.0 976.0 The following table presents the balance sheet classification for all derivative instruments at March 31, 2020 and December 31, 2019 . Balance Sheet Classification of Derivative Instruments (In millions) March 31, 2020 Gross Gross Netting of Total (a) Current Assets—Derivatives $ 2.9 $ 8.3 $ — $ 11.2 Deferred Charges and Other Assets—Derivatives 15.5 — — $ 15.5 Current Liabilities—Derivatives (0.2 ) (6.0 ) — $ (6.2 ) Deferred Credits—Derivatives — (91.8 ) — $ (91.8 ) Total $ 18.2 $ (89.5 ) $ — $ (71.3 ) December 31, 2019 Current Assets—Derivatives $ 2.9 $ 3.7 $ — $ 6.6 Deferred Charges and Other Assets—Derivatives 9.9 0.5 — 10.4 Current Liabilities—Derivatives 0.7 (11.0 ) 6.2 (4.1 ) Deferred Credits—Derivatives (0.5 ) (97.2 ) — (97.7 ) Total $ 13.0 $ (104.0 ) $ 6.2 $ (84.8 ) (a) Washington Gas has elected to offset the fair value of recognized derivative instruments against the right to reclaim or the obligation to return collateral for derivative instruments executed under the same master netting arrangement in accordance with ASC Topic 815. All recognized derivative contracts and associated financial collateral subject to a master netting arrangement or similar that is eligible for offset under ASC Topic 815 have been presented net in the balance sheets. The following tables present all gains and losses associated with derivative instruments for the three months ended March 31, 2020 and 2019. Washington Gas Light Company Gains and (Losses) on Derivative Instruments (In millions) Three Months Ended March 31, 2020 2019 Recorded to income Utility cost of gas 3.1 4.0 Recorded to regulatory assets Gas costs 8.9 11.9 Total $ 12.0 $ 15.9 Collateral Washington Gas utilizes standardized master netting agreements, which facilitate the netting of cash flows into a single net exposure for a given counterparty. As part of these master netting agreements, cash, letters of credit and parent company guarantees may be required to be posted or obtained from counterparties in order to mitigate credit risk related to both derivatives and non-derivative positions. Under Washington Gas’ offsetting policy, collateral balances are offset against the related counterparties’ derivative positions to the extent the application would not result in the over-collateralization of those derivative positions on the balance sheets. Any collateral posted that is not offset against derivative assets and liabilities is included in “Other prepayments” on the balance sheets. Collateral received and not offset against derivative assets and liabilities is included in “Customer deposits and advance payments” on the accompanying balance sheets. At March 31, 2020 and December 31, 2019 , Washington Gas had $4.8 million and $5.2 million , respectively, in collateral deposits posted with counterparties that are not offset against derivative asset and liabilities. At March 31, 2020 and December 31, 2019 , Washington Gas had $0.1 million and $0.1 million , respectively, cash collateral held representing an obligation, and are not offset against derivative asset and liabilities. Certain derivative instruments of Washington Gas contain contract provisions that require collateral to be posted if the credit rating of Washington Gas falls below certain levels or if counterparty exposure to Washington Gas exceeds a certain level (credit-related contingent features) . At March 31, 2020 and December 31, 2019 , Washington Gas was not required to post collateral related to a derivative liability that contained a credit-related contingent feature. The following table shows the aggregate fair value of all derivative instruments with credit-related contingent features that are in a liability position, as well as the maximum amount of collateral that would be required if the most intrusive credit-risk-related contingent features underlying these agreements were triggered on March 31, 2020 and December 31, 2019 , respectively. Potential Collateral Requirements for Derivative Liabilities (In millions) March 31, 2020 December 31, 2019 Derivative liabilities with credit-risk-contingent features $ 0.1 $ 0.4 Maximum potential collateral requirements 0.1 0.4 We do not enter into derivative contracts for speculative purposes. Concentration of Credit Risk We are exposed to credit risk from derivative instruments with wholesale counterparties, which is represented by the fair value of these instruments at the reporting date. We actively monitor and work to minimize counterparty concentration risk through various practices. At March 31, 2020 , one counterparty represented over 10% of Washington Gas’ credit exposure to wholesale derivative counterparties for a total credit risk of $16.5 million .

Fair Value Measurements

Fair Value Measurements	3 Months Ended
Fair Value Measurements	Mar. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	FAIR VALUE MEASUREMENTS Recurring Basis We measure the fair value of our financial assets and liabilities using a combination of the income and market approaches in accordance with ASC Topic 820. These financial assets and liabilities primarily consist of derivatives recorded on our balance sheets under ASC Topic 815 and short-term investments, commercial paper and long-term debt outstanding required to be disclosed at fair value. Under ASC Topic 820, fair value is defined as the exit price, representing the amount that would be received in the sale of an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. To value our financial instruments, we use market data or assumptions that market participants would use, including assumptions about credit risk (both our own credit risk and the counterparty’s credit risk) and the risks inherent in the inputs to valuation. We enter into derivative contracts in the futures and over-the-counter (OTC) wholesale and retail markets. These markets are the principal markets for the respective wholesale and retail contracts. Our relevant market participants are our existing counterparties and others who have participated in energy transactions at our delivery points. These participants have access to the same market data as Washington Gas. Valuations are generally based on pricing service data or indicative broker quotes depending on the market location. We measure the net credit exposure at the counterparty level where the right to set-off exists. The net exposure is determined using the mark-to-market exposure adjusted for collateral, letters of credit and parent guarantees. We use published default rates from Standard & Poor’s Ratings Services and Moody’s Investors Service as inputs for determining credit adjustments. ASC Topic 820 establishes a fair value hierarchy that prioritizes the inputs used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities and the lowest priority to unobservable inputs. The three levels of the fair value hierarchy under ASC Topic 820 are described below: Level 1. Level 1 of the fair value hierarchy consists of assets or liabilities that are valued using observable inputs based upon unadjusted quoted prices in active markets for identical assets or liabilities at the reporting date. Washington Gas did not have any Level 1 derivatives at March 31, 2020 or December 31, 2019 . Level 2. Level 2 of the fair value hierarchy consists of assets or liabilities that are valued using directly or indirectly observable inputs either corroborated with market data or based on exchange traded market data. Level 2 includes fair values based on industry-standard valuation techniques that consider various assumptions: (i) quoted forward prices, including the use of mid-market pricing within a bid/ask spread; (ii) discount rates; (iii) implied volatility and (iv) other economic factors. Substantially all of these assumptions are observable throughout the full term of the instrument, can be derived from observable data or are supported by observable levels at which transactions are executed in the relevant market. At March 31, 2020 and December 31, 2019 , Level 2 financial assets and liabilities included energy-related physical and financial derivative transactions such as forward, option and other contracts for deliveries at active market locations. Level 3. Level 3 of the fair value hierarchy consists of assets or liabilities that are valued using significant unobservable inputs at the reporting date. These unobservable assumptions reflect our assumptions about estimates that market participants would use in pricing the asset or liability, including natural gas basis prices and annualized volatilities of natural gas prices. A significant change to any one of these inputs in isolation could result in a significant upward or downward fluctuation in the fair value measurement. These inputs may be used with industry standard valuation methodologies that result in our best estimate of fair value for the assets or liabilities at the reporting date. At March 31, 2020 and December 31, 2019 , Level 3 derivative assets and liabilities included: (i) physical contracts valued at illiquid market locations with no observable market data; (ii) long-dated positions where observable pricing is not available over the majority of the life of the contract; (iii) contracts valued using historical spot price volatility assumptions and (iv) valuations using indicative broker quotes for inactive market locations. The following table sets forth financial instruments recorded at fair value at March 31, 2020 and December 31, 2019 , respectively. A financial instrument’s classification within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. Our assessment of the significance of a particular input to the fair value measurement requires judgment and may affect the valuation of fair value assets and liabilities and their placement within the fair value hierarchy. Fair Value Measurements Under the Fair Value Hierarchy (In millions) Level 1 Level 2 Level 3 Total At March 31, 2020 Assets $ — $ 0.7 $ 17.5 $ 18.2 Liabilities $ — $ (0.8 ) $ (88.7 ) $ (89.5 ) At December 31, 2019 Assets $ — $ 0.8 $ 12.2 $ 13.0 Liabilities $ — $ (7.0 ) $ (97.0 ) $ (104.0 ) The following table includes quantitative information about the significant unobservable inputs used in the fair value measurement of our Level 3 financial instruments and the respective fair values of the net derivative asset and liability positions, by contract type, at March 31, 2020 and December 31, 2019 . Quantitative Information about Level 3 Fair Value Measurements (In millions) Net Fair Value Valuation Techniques Unobservable Inputs Weighted Average (a) Range March 31, 2020 ($71.2) Discounted Cash Flow Natural Gas Basis Price (per dekatherm) ($0.34) ($0.878)-$2.133 December 31, 2019 ($84.8) Discounted Cash Flow Natural Gas Basis Price (per dekatherm) — ($0.905)-$2.523 (a) ASU 2018-13 has been applied prospectively, beginning with the interim period ending March 31, 2020. The average level 3 price was weighted by transaction volume. The following table is a summary of the changes in the fair value of our natural gas related derivative instruments that are measured at net fair value on a recurring basis in accordance with ASC Topic 820 using significant Level 3 inputs during the three months ended March 31, 2020 and 2019 , respectively. . Reconciliation of Fair Value Measurements Using Significant Level 3 Inputs Three Months Ended March 31, (In millions) 2020 2019 Balance at beginning of period $ (84.8 ) $ (106.6 ) Realized and unrealized gains (losses) Recorded to income 3.1 3.6 Recorded to regulatory assets—gas costs 9.1 12.5 Transfers into Level 3 — (3.8 ) Transfers out of Level 3 — 5.0 Settlements 1.4 3.2 Balance at end of period $ (71.2 ) $ (86.1 ) Transfers between different levels of the fair value hierarchy may occur based on fluctuations in the valuation inputs and on the level of observable inputs used to value the instruments from period to period. Transfers out of Level 3 were due to valuations that experienced an increase in observable market inputs. Transfers into Level 3 were due to an increase in unobservable market inputs, primarily pricing points. All amounts recorded to income are from the utility cost of gas. Unrealized gains (losses) attributable to derivative assets and liabilities measured using significant Level 3 inputs were recorded as follows for the three months ended March 31, 2020 and 2019, respectively: Unrealized Gains (Losses) Recorded for Level 3 Measurements Three Months Ended March 31, (In millions) 2020 2019 Recorded to income Utility cost of gas $2.3 $2.5 Recorded to regulatory assets Gas costs 7.6 10.5 Total $9.9 $13.0 The following table presents the carrying amounts on Washington Gas' balance sheets and estimated fair values of our financial instruments at March 31, 2020 and December 31, 2019 . Fair Value of Financial Instruments March 31, 2020 December 31, 2019 (In millions) Carrying Amount Fair Value Carrying Amount Fair Value Money market funds (a) $ 78.0 $ 78.0 $ 55.1 $ 55.1 Other long-term receivable (b) $ 1.3 $ 1.3 $ 1.3 $ 1.3 Commercial paper (c) $ 145.5 $ 145.5 $ 399.5 $ 399.5 Washington Gas Unsecured notes (d) $ 1,331.1 $ 1,486.5 $ 1,330.9 $ 1,480.8 (a) The balance at March 31, 2020 includes $38.6 million money market funds located in "Cash and cash equivalents", $11.3 million rabbi trust investment located in "Current Assets-Other", and $28.1 million rabbi trust investments located in "Deferred Charges and Other Assets-Other" of the accompanying balance sheets; The balance at December 31, 2019 includes $11.0 million money market funds located in "Cash and cash equivalents", $ 19.5 million rabbi trust investment located in "Current Assets-Other" and $24.6 million rabbi trust investments located in "Deferred Charges and Other Assets-Other". (b) Amount represents a long-term receivable from one of our trading partners related to Antero contract discussed in Note 11-Commitments and Contingencies. (c) The balance at March 31, 2020 includes $45.5 million located in "Notes payable", and $100.0 million located in “Long-term debt” on the accompanying balance sheets. The balance at December 31, 2019 includes $299.5 million located in "Notes payable", and $100.0 million located in “Long-term debt” on the accompanying balance sheets. (d) Includes adjustments for current maturities and unamortized discounts, as applicable. The amount was included in "Long-term debt" on the accompanying balance sheets. Our money market funds are Level 1 valuations and their carrying amount is equal to fair value. The other long-term receivable is from one of our trading partners related to the Antero contract. The fair value for our other long term receivable approximates its carrying value using Level 2 input to estimate the credit loss associated with the receivable. The carrying cost of our commercial paper approximates fair value using Level 2 inputs. The fair value of Washington Gas unsecured notes was estimated based on valuation techniques using indirectly observable inputs corroborated with market data and therefore is classified as Level 2.

Related Party Transactions

Related Party Transactions	3 Months Ended
Related Party Transactions	Mar. 31, 2020
Related Party Transactions [Abstract]
Related Party Transactions	RELATED PARTY TRANSACTIONS Corporate Service Allocation As a subsidiary of AltaGas and effective with the close of the Merger on July 6, 2018, Washington Gas is charged a proportionate share of corporate governance and other shared services costs from AltaGas, primarily related to human resources, employee benefits, finance, legal, accounting, tax, information technology services, and office services. AltaGas charges Washington Gas for the total shared service costs and Washington Gas in turn allocates a portion of the costs to WGL’s other subsidiaries at the lower of cost or market. Washington Gas records a payable of the total shared service costs allocated to all of WGL's subsidiaries in "Payable to associated companies" and a receivable of the shared service costs allocated to WGL’s other subsidiaries in “Receivables from associated companies” on the balance sheets. Additionally, effective upon the approval by the SCC of Virginia in March 2020, Washington Gas began receiving certain corporate services from SEMCO Energy, Inc., (SEMCO), a subsidiary of A ltaGas. Washington Gas records in "Payable to associated companies" on its balance sheets for the services provided by SEMCO. The expenses associated with services provided by AltaGas and SEMCO are recorded to “Operation and maintenance” on Washington Gas' statements of operations. The net expenses of $5.0 million and $4.5 million were included in “Operation and maintenance” on the statements of operations for the three month ended March 31, 2020 and 2019, respectively, reflecting the corporate service cost allocated to Washington Gas. In addition, Washington Gas provides accounting, treasury, legal and other administrative and general support to WGL’s subsidiaries, and files consolidated tax returns that include affiliated taxable transactions. Effective upon the approvals by the SCC of Virginia, Washington Gas began providing accounting, legal, tax and other administrative and general support to various AltaGas U.S. entities. Washington Gas bills affiliates to which it provides services in accordance with regulatory requirements for the actual cost of providing these services, which approximates their market value. To the extent such billings are outstanding, they are reflected in “Receivables from associated companies” on Washington Gas’ balance sheets. Washington Gas assigns or allocates these costs directly to its affiliates and, therefore, does not recognize revenues or expenses associated with providing these services. Washington Gas believes that allocations based on broad measures of business activity are appropriate for allocating expenses resulting from common services. Affiliate entities are allocated a portion of common services based on a formula driven by appropriate indicators of activity, as approved by management. Project Financing WGL Energy Systems, Inc. (WGL Energy Systems), an indirect, wholly-owned subsidiary of WGL, obtains third-party project financing for energy management services projects with the federal government under Washington Gas’s area-wide contract. As work is performed, Washington Gas establishes a contract asset in “Receivables” representing the government’s obligation to remit principal and interest and records a “Payable to associated company” to WGL Energy Systems for the construction work performed for the same amount. At March 31, 2020 , Washington Gas recorded $46.1 million of contract assets in “Receivables” and a $46.1 million payable to WGL Energy Systems in “Payables to associated companies,” respectively, for energy management services projects financed by WGL Energy Systems that were not complete. At December 31, 2019 , Washington Gas recorded $44.2 million of contract assets in “Receivables” and a $44.2 million payable to WGL Energy Systems in “Payables to associated companies,” respectively, for energy management services projects financed by WGL Energy Systems that were not complete. In October 2018, WGL Energy Systems repaid $53.0 million historically drawn by Washington Gas from a third-party lender for Washington Gas' area-wide contract that the lender demanded repayment for due to delays in achieving final acceptance from the federal government agency customer. The $53.0 million was included in "Payables to associated companies" on Washington Gas' balance sheets at December 31, 2018. In February 2019, WGL sold the receivables, and accordingly, Washington Gas reversed the associated amount in “Payables to associated companies” and “Receivables” on its balance sheets during the three months ended March 31. 2019. Related Party Transactions with Hampshire Hampshire Gas Company (Hampshire), a wholly-owned subsidiary of WGL, owns full and partial interests in underground natural gas storage facilities, including pipeline delivery facilities located in and around Hampshire County, West Virginia, and operates those facilities to serve Washington Gas, which purchases all of the storage services of Hampshire. Washington Gas includes the cost of these services in the bills sent to its customers and records the cost of the services in "Operation and maintenance" in its statements of operations. Hampshire operates under a “pass-through” cost of service-based tariff approved by the FERC and adjusts its billing rates to Washington Gas on a periodic basis to account for changes in its investment in utility plant and associated expenses. The arrangement between Hampshire and Washington Gas is classified as an operating lease. A right-of-use (ROU) asset and lease liability was not recognized upon the adoption of ASC 842 because all the costs associated with the arrangement are variable. Washington Gas recorded $2.0 million and $2.1 million of the expenses related to the cost of services provided by Hampshire in "Operation and maintenance " on Washington Gas' statements of operations for the three months ended March 31, 2020 and 2019, respectively. The outstanding balance not cleared between Washington Gas and Hampshire at the end of the reporting period was recorded in "Payable to associated companies" of Washington Gas' balance sheets. Refer to Note 4 - Leases for further discussion of ASC 842. Other Related Party Transactions I n connection with billing for unregulated third-party marketers, including WGL Energy Services , Inc., (WGL Energy Services), an indirect, wholly-owned subsidiary of WGL, and with other miscellaneous billing processes, Washington Gas collects cash on behalf of affiliates and transfers the cash in a reasonable time period. Cash collected by Washington Gas on behalf of its affiliates but not yet transferred is recorded in “Payables to associated companies” on Washington Gas’ balance sheets. Washington Gas provides gas balancing services related to storage, injections, withdrawals and deliveries to all energy marketers participating in the sale of natural gas on an unregulated basis through the customer choice programs that operate in its service territory, These balancing services include the sale of natural gas supply commodities related to various peaking arrangements contractually supplied to Washington Gas and then partially allocated and assigned by Washington Gas to the energy marketers, including WGL Energy Services. Washington Gas records revenues in " Operating revenue" of its statements of operations for these balancing services pursuant to tariffs approved by the appropriate regulatory bodies. The following table shows the amounts Washington Gas charged WGL Energy Services for balancing services. Washington Gas - Gas Balancing Service Charges Three Month Ended March 31, (In millions) 2020 2019 Gas balancing service charge $ 6.6 $ 8.9 As a result of these balancing services, an imbalance is created for volumes of natural gas received by Washington Gas that are not equal to the volumes of natural gas delivered to customers of the energy marketers. Washington Gas recorded $2.6 million and $2.1 million payable to WGL Energy Services at March 31, 2020 and December 31, 2019 , respectively , related to an imbalance in gas volumes. The payables were recorded in "Accounts payable and other accrued liabilities" on Washington Gas' balance sheets. Washington Gas participates in a purchase of receivables (POR) program as approved by the PSC of MD and separate program approved by the PSC of DC, whereby it purchases receivables from participating energy marketers at approved discount rates. WGL Energy Services is one of the energy marketers that participates in these POR programs whereby it sells its receivables to various utilities, including Washington Gas, at approved discount rates. The receivables purchased by Washington Gas are included in “Accounts receivable” in the accompanying balance sheets. At March 31, 2020 and December 31, 2019 , Washington Gas had balances of $7.0 million and $7.9 million , respectively, of purchased receivables from WGL Energy Services.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	3 Months Ended
Accumulated Other Comprehensive Income (Loss)	Mar. 31, 2020
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss)	ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) The following table shows the changes in accumulated other comprehensive income (loss) for Washington Gas by component for the three months ended March 31, 2020 and 2019 . Changes in Accumulated Other Comprehensive Income (Loss) by Component Three Months Ended March 31, (In thousands) 2020 2019 Beginning Balance $ 4,909 $ (6,627 ) Amortization of prior service credit (a)(b) (304 ) (162 ) Amortization of actuarial loss (a)(b) 1,016 415 Actuarial gain (loss) arising during the period (a) 1,910 4,489 Current-period other comprehensive income 2,622 4,742 Income tax expense related to pension and other post-retirement benefit plans 681 477 Ending Balance $ 6,850 $ (2,362 ) (a) These accumulated other comprehensive income (loss) components are included in the computation of net periodic benefit cost. (b) Amortization of prior service cost and amortization of actuarial gain (loss) represent the amounts reclassified out of AOCI to “Other income (expense)” of statements of operations for the reporting periods.

Supplemental Cash Flow Informat

Supplemental Cash Flow Information	3 Months Ended
Supplemental Cash Flow Information	Mar. 31, 2020
Supplemental Cash Flow Information [Abstract]
Supplemental Cash Flow Information	SUPPLEMENTAL CASH FLOW INFORMATION The following table details the changes in operating assets and liabilities from operating activities, cash payments that have been included in the determination of earnings and non-cash investing and financing activities: Three Months Ended March 31, (In thousands) 2020 2019 CHANGES IN OPERATING ASSETS AND LIABILITIES Receivables $ 53,278 $ (27,774 ) Receivables from associated companies (1,621 ) 249 Gas costs and other regulatory assets/liabilities—net (43,613 ) 6,683 Storage gas 56,430 65,885 Prepaid taxes 3,711 2,037 Accounts payable and other accrued liabilities (59,144 ) (77,797 ) Payables to associated companies 13,270 (2,656 ) Customer deposits and advance payments (6,949 ) (15,521 ) Accrued taxes 5,499 3,232 Other current assets 10,273 2,215 Other current liabilities (243 ) (243 ) Deferred gas costs—net 24,874 50,086 Deferred assets—other (1,014 ) 14,027 Deferred liabilities—other (1,463 ) (2,297 ) Pension and other post-retirement benefits (4,245 ) (14,494 ) Changes in operating assets and liabilities $ 49,043 $ 3,632 SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION Income taxes paid (refunded)—net $ (3,880 ) $ (1,683 ) Interest paid $ 30,965 $ 25,398 SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING AND FINANCING ACTIVITIES: Capital expenditure accruals included in accounts payable and other accrued liabilities $ 45,817 32,738 The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within Washington Gas’ balance sheets that sums to the total of such amounts shown on the statements of cash flo ws March 31, (in thousands) 2020 2019 Cash and cash equivalents $ 42,418 $ 2,142 Restricted cash included in Current assets-Other $ 11,332 $ 4,094 Restricted cash included in Deferred charges and other assets-Other $ 28,113 $ 45,440 Total cash, cash equivalents and restricted cash shown in the statement of cash flows $ 81,863 $ 51,676 Restricted cash included in "Current assets—Other" and "Deferred charges and other assets—Other" on the balance sheets represents amount of investment in rabbi trusts to fund deferred compensation, pension and other post-retirement benefits for certain management personnel and directors. The funds in the rabbi trusts can only be used to pay for plan participant benefits and other plan expenses such as investment fees or trustee fees. The funds are invested in money market funds at end of March 31, 2020 and 2019. Refer to Note 10 — Pension and Other Post-Retirement Benefit Plans for further discussion of rabbi trusts.

Accounting Policies (Policies)

Accounting Policies (Policies)	3 Months Ended
Accounting Policies (Policies)	Mar. 31, 2020
Accounting Policies [Abstract]
Consolidation	Following the 2018 Merger Agreement, Washington Gas became an indirect, majority owned subsidiary of, among other entities, AltaGas and WGL. In connection with the Merger, WGL formed a wholly owned subsidiary, Wrangler SPE LLC (Wrangler SPE), a bankruptcy remote, special purpose entity to own the common stock of Washington Gas. In addition, WGL owns all of the shares of common stock of certain affiliated non-utility subsidiaries, some of which provide services to Washington Gas, and some of which own interests in other entities. On December 20, 2019, Washington Gas redeemed all the outstanding shares of its preferred stock. As a result, Washington Gas is now an indirect, wholly owned subsidiary of AltaGas and WGL.
Basis of Accounting	The condensed financial statements of Washington Gas have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (SEC). Therefore, certain financial information and note disclosures accompanying annual financial statements prepared in accordance with generally accepted accounting principles in the United States of America (GAAP) are omitted in this interim report. The interim condensed financial statements and accompanying notes should be read in conjunction with the Financial Statements on Form 10-K for the year ended December 31, 2019. Due to the seasonal nature of our business, the results of operations for the periods presented in this report are not necessarily indicative of actual results for the full years ending December 31, 2020 and 2019. The information presented in this report on Form 10-Q are presented solely for the registrant Washington Gas on a stand-alone basis. The accompanying unaudited condensed financial statements for Washington Gas reflect all normal recurring adjustments that are necessary, in our opinion, to present fairly the results of operations in accordance with GAAP.
New Accounting Pronouncements	The following tables represent accounting standards adopted by Washington Gas during the three months ended March 31, 2020 , and other newly issued accounting standards that will be adopted by Washington Gas in the future. ACCOUNTING STANDARDS ADOPTED IN CALENDAR YEAR 2020 Standard Description Date of adoption Effect on the financial statements or other significant matters ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, including other subsequent ASUs further amending and clarifying the guidance. For credit losses on financial instruments measured at amortized cost, this standard changes the current incurred loss impairment methodology to an expected loss methodology and requires consideration of a broader range of reasonable and supportable information to determine credit loss estimates. In addition, entities may make a one-time irrevocable election on certain eligible financial instruments to elect fair value treatment on an instrument-by-instrument basis. Early adoption is permitted. January 1, 2020 Cash equivalents, accounts receivable, unbilled revenue, and contract assets are within the scope of the new standard. Upon adoption, we recorded an increase to our allowance for credit losses and a reduction to retained earnings of $1.5 million. See Note 2 - Credit Losses for further information and the new required disclosures. ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement This update modifies the disclosure requirements on fair value measurements. Early adoption is permitted. January 1, 2020 The adoption of this standard did not have a material effect on our financial statements. ASU 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction between Topic 808 and Topic 606 Topic 808 does not provide comprehensive recognition or measurement guidance for collaborative arrangements. This update clarifies the interaction between Topic 606, Revenue from Contracts with Customers and Topic 808. January 1, 2020 The adoption of this standard did not have a material effect on our financial statements. ASU 2019-01, Leases (Topic 842) Codification Improvements This update addresses the determination of the fair value of the underlying asset by lessors that are not manufacturers or dealers, provides guidance for the presentation of the statement of cash flows for sales-type and direct financing leases, and clarifies transition disclosures related to the adoption of ASC 842. January 1, 2020 The adoption of this standard did not have a material effect on our financial statements. Standard Description Date of adoption Effect on the financial statements or other significant matters ASU 2019-04, Codification Improvements to Topic 326, Financial Instruments—Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments The amendments in this ASU provide clarification and improve the codification in recently issued accounting standards. January 1, 2020 The adoption of this standard did not have a material effect on our financial statements. ASU 2020-03, Codification Improvements to Financial Instruments This Update makes technical corrections and minor improvements to the guidance on financial instruments. January 1, 2020 The adoption of this standard did not have a material effect on our financial statements. OTHER NEWLY ISSUED ACCOUNTING STANDARDS Standard Description Required date of adoption Effect on the financial statements or other significant matters ASU 2018-14, Compensation—Retirement Benefits—Defined Benefit Plans—General (Subtopic 715-20): Disclosure Framework—Changes to the Disclosure Requirements for Defined Benefit Plans This standard modifies the disclosure requirements related to defined benefit pension and other postretirement plans. Early adoption is permitted. December 31, 2020 It is not expected that the adoption of this standard will have a material effect on our financial statements. ASU 2019-12, Income Taxes (Topic 740) Simplifying the Accounting for Income Taxes As part of FASB's Simplification Initiative, this standard amends ASC Topic 740 by removing certain exceptions to the general principles and clarifying and amending other current guidance. Early adoption is permitted. January 1, 2021 We are in the process of evaluating the impact the adoption of this standard will have on our financial statements. ASU 2020-04, Reference Rate Reform (Topic 848) Facilitation of the Effects of Reference Rate Reform on Financial Reporting This standard provides optional expedients and exceptions to ease the potential accounting burden associated with transitioning away from reference rates that are expected to be discontinued. The amendments may be elected prospectively to contract modifications made and to hedging relationships existing as of or entered into on or after the date of adoption and through December 31, 2022. December 31, 2022 We are in the process of evaluating the impact the adoption of this standard will have on our financial statements.
Revenue from Contract with Customer	The Company recognizes revenue from contracts with customers to depict the transfer of goods or services to customers at an amount it expects to be entitled to in exchange for those goods or services. Washington Gas sells natural gas and distribution services to residential, commercial, industrial and governmental customers through regulated tariff rates approved by regulatory commissions in the jurisdictions where it operates. Customers are billed monthly based on regular meter readings. Customer billings are based on two main components: (i) a fixed service fee and (ii) a variable fee based on usage. For customers who choose to purchase their natural gas from Washington Gas, the bill will include a usage based charge for the cost of the commodity. Revenue is recognized over time as natural gas is delivered or as service is performed. Since meter readings are performed on a cycle basis, Washington Gas recognizes accrued revenue for any services rendered to its customers but not billed at month-end. The tariff sales are generally considered daily or “at-will” contracts as customers may cancel their service at any time (subject to notification requirements in the tariff), and revenue generally represents the amount Washington Gas is entitled to invoice. There are certain contracts that have terms of one year or longer. For these contracts, revenue is recognized based on the amount Washington Gas is entitled to bill the customer. Customers have the choice to purchase natural gas from competitive service providers. Washington Gas charges the competitive service providers balancing fees to manage the natural gas transportation imbalances. Where regulations require, Washington Gas issues customers a consolidated bill to include the natural gas supplied by the competitive service providers and distribution of natural gas. Washington Gas recognizes revenue only for distribution services that it has provided to the customer, and the balancing fees for the services provided to the competitive service provider.
Debt	Washington Gas satisfies the short-term financing requirements through the sale of commercial paper, or through bank borrowings. Due to the seasonal nature of our operations, short-term financing requirements can vary significantly during the year. Revolving credit agreements are maintained to support outstanding commercial paper and to permit short-term borrowing flexibility. The policy of Washington Gas is to maintain bank credit facilities in amounts equal to or greater than the expected maximum commercial paper position.
Managing Price Risk	Managing Price Risk. To manage price risk associated with acquiring natural gas supply for utility customers, Washington Gas enters into physical and financial derivative transactions in the form of forward, option and other contracts, as authorized by its regulators. Any gains and losses associated with these derivatives are recorded as regulatory liabilities or assets, respectively, to reflect the rate treatment for these economic hedging activities.
Income Taxes	WGL and its wholly owned subsidiaries are included in AltaGas' consolidated income tax returns. We have established a new tax sharing policy with AltaGas Services (US) Inc. (ASUS), an indirect, wholly owned subsidiary of AltaGas, that allocates consolidated tax liabilities and benefits using a ratio determined by the separate taxable income for each member applied to the consolidated return tax liability of the group. State income tax returns are filed on a separate company basis in most states and on a unitary basis as required, where we or the consolidated ASUS group have operations and/or a requirement to file.
Derivatives, Offsetting	We are exposed to credit risk from derivative instruments with wholesale counterparties, which is represented by the fair value of these instruments at the reporting date. We actively monitor and work to minimize counterparty concentration risk through various practices.
Derivatives	Washington Gas enters into contracts that qualify as derivative instruments and are accounted for under ASC Topic 815. These derivative instruments are recorded at fair value on our balance sheets and Washington Gas does not currently designate any derivatives as hedges under ASC Topic 815. Washington Gas’ derivative instruments relate to: (i) Washington Gas’ asset optimization program; (ii) managing price risk associated with the purchase of gas to serve utility customers and (iii) managing interest rate risk. Asset Optimization. Washington Gas optimizes the value of its long-term natural gas transportation and storage capacity resources during periods when these resources are not being used to physically serve utility customers. Specifically, Washington Gas utilizes its transportation capacity assets to benefit from favorable natural gas prices between different geographic locations and utilizes its storage capacity assets to benefit from favorable natural gas prices between different time periods. As part of this asset optimization program, Washington Gas enters into physical and financial derivative transactions in the form of forward, futures and option contracts with the primary objective of securing operating margins that Washington Gas will ultimately realize. The derivative transactions entered into under this program are subject to mark-to-market accounting treatment under ASC Topic 820. Regulatory sharing mechanisms provide for the annual realized profit from these transactions to be shared between Washington Gas’ shareholders and customers; therefore, changes in fair value are recorded through earnings, or as regulatory assets or liabilities to the extent that it is probable that realized gains and losses associated with these derivative transactions will be included in the rates charged to customers when they are realized. Unrealized gains and losses recorded to earnings may cause significant period-to-period volatility; this volatility does not change the operating margins that Washington Gas expects to ultimately realize from these transactions through the use of its storage and transportation capacity resources. Washington Gas has a collaborative arrangement with a third party to facilitate the asset optimization program. The collaborative arrangement allocates a tiered percentage of profits or losses to the third party as compensation for its participation. The costs recorded by Washington Gas related to the collaborative arrangement totaled $1.0 million and $0.7 million for the three months ended March 31, 2020 and 2019, respectively. These amounts were recorded in “Utility cost of gas” on Washington Gas’ statements of operations. Either party may terminate the collaborative arrangement through the delivery of a termination notice. In such an event, Washington Gas may make a payment upon termination. All physically and financially settled contracts under our asset optimization program are reported on a net basis in the statements of operations in “Utility cost of gas”.
Fair Value Measurement	We measure the fair value of our financial assets and liabilities using a combination of the income and market approaches in accordance with ASC Topic 820. These financial assets and liabilities primarily consist of derivatives recorded on our balance sheets under ASC Topic 815 and short-term investments, commercial paper and long-term debt outstanding required to be disclosed at fair value. Under ASC Topic 820, fair value is defined as the exit price, representing the amount that would be received in the sale of an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. To value our financial instruments, we use market data or assumptions that market participants would use, including assumptions about credit risk (both our own credit risk and the counterparty’s credit risk) and the risks inherent in the inputs to valuation. We enter into derivative contracts in the futures and over-the-counter (OTC) wholesale and retail markets. These markets are the principal markets for the respective wholesale and retail contracts. Our relevant market participants are our existing counterparties and others who have participated in energy transactions at our delivery points. These participants have access to the same market data as Washington Gas. Valuations are generally based on pricing service data or indicative broker quotes depending on the market location. We measure the net credit exposure at the counterparty level where the right to set-off exists. The net exposure is determined using the mark-to-market exposure adjusted for collateral, letters of credit and parent guarantees. We use published default rates from Standard & Poor’s Ratings Services and Moody’s Investors Service as inputs for determining credit adjustments. ASC Topic 820 establishes a fair value hierarchy that prioritizes the inputs used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities and the lowest priority to unobservable inputs. The three levels of the fair value hierarchy under ASC Topic 820 are described below: Level 1. Level 1 of the fair value hierarchy consists of assets or liabilities that are valued using observable inputs based upon unadjusted quoted prices in active markets for identical assets or liabilities at the reporting date. Washington Gas did not have any Level 1 derivatives at March 31, 2020 or December 31, 2019 . Level 2. Level 2 of the fair value hierarchy consists of assets or liabilities that are valued using directly or indirectly observable inputs either corroborated with market data or based on exchange traded market data. Level 2 includes fair values based on industry-standard valuation techniques that consider various assumptions: (i) quoted forward prices, including the use of mid-market pricing within a bid/ask spread; (ii) discount rates; (iii) implied volatility and (iv) other economic factors. Substantially all of these assumptions are observable throughout the full term of the instrument, can be derived from observable data or are supported by observable levels at which transactions are executed in the relevant market. At March 31, 2020 and December 31, 2019 , Level 2 financial assets and liabilities included energy-related physical and financial derivative transactions such as forward, option and other contracts for deliveries at active market locations. Level 3. Level 3 of the fair value hierarchy consists of assets or liabilities that are valued using significant unobservable inputs at the reporting date. These unobservable assumptions reflect our assumptions about estimates that market participants would use in pricing the asset or liability, including natural gas basis prices and annualized volatilities of natural gas prices. A significant change to any one of these inputs in isolation could result in a significant upward or downward fluctuation in the fair value measurement. These inputs may be used with industry standard valuation methodologies that result in our best estimate of fair value for the assets or liabilities at the reporting date.

Accounting Policies (Tables)

Accounting Policies (Tables)	3 Months Ended
Accounting Policies (Tables)	Mar. 31, 2020
Accounting Policies [Abstract]
Accounting standards adopted in the current fiscal year	The following tables represent accounting standards adopted by Washington Gas during the three months ended March 31, 2020 , and other newly issued accounting standards that will be adopted by Washington Gas in the future. ACCOUNTING STANDARDS ADOPTED IN CALENDAR YEAR 2020 Standard Description Date of adoption Effect on the financial statements or other significant matters ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, including other subsequent ASUs further amending and clarifying the guidance. For credit losses on financial instruments measured at amortized cost, this standard changes the current incurred loss impairment methodology to an expected loss methodology and requires consideration of a broader range of reasonable and supportable information to determine credit loss estimates. In addition, entities may make a one-time irrevocable election on certain eligible financial instruments to elect fair value treatment on an instrument-by-instrument basis. Early adoption is permitted. January 1, 2020 Cash equivalents, accounts receivable, unbilled revenue, and contract assets are within the scope of the new standard. Upon adoption, we recorded an increase to our allowance for credit losses and a reduction to retained earnings of $1.5 million. See Note 2 - Credit Losses for further information and the new required disclosures. ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement This update modifies the disclosure requirements on fair value measurements. Early adoption is permitted. January 1, 2020 The adoption of this standard did not have a material effect on our financial statements. ASU 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction between Topic 808 and Topic 606 Topic 808 does not provide comprehensive recognition or measurement guidance for collaborative arrangements. This update clarifies the interaction between Topic 606, Revenue from Contracts with Customers and Topic 808. January 1, 2020 The adoption of this standard did not have a material effect on our financial statements. ASU 2019-01, Leases (Topic 842) Codification Improvements This update addresses the determination of the fair value of the underlying asset by lessors that are not manufacturers or dealers, provides guidance for the presentation of the statement of cash flows for sales-type and direct financing leases, and clarifies transition disclosures related to the adoption of ASC 842. January 1, 2020 The adoption of this standard did not have a material effect on our financial statements. Standard Description Date of adoption Effect on the financial statements or other significant matters ASU 2019-04, Codification Improvements to Topic 326, Financial Instruments—Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments The amendments in this ASU provide clarification and improve the codification in recently issued accounting standards. January 1, 2020 The adoption of this standard did not have a material effect on our financial statements. ASU 2020-03, Codification Improvements to Financial Instruments This Update makes technical corrections and minor improvements to the guidance on financial instruments. January 1, 2020 The adoption of this standard did not have a material effect on our financial statements. OTHER NEWLY ISSUED ACCOUNTING STANDARDS Standard Description Required date of adoption Effect on the financial statements or other significant matters ASU 2018-14, Compensation—Retirement Benefits—Defined Benefit Plans—General (Subtopic 715-20): Disclosure Framework—Changes to the Disclosure Requirements for Defined Benefit Plans This standard modifies the disclosure requirements related to defined benefit pension and other postretirement plans. Early adoption is permitted. December 31, 2020 It is not expected that the adoption of this standard will have a material effect on our financial statements. ASU 2019-12, Income Taxes (Topic 740) Simplifying the Accounting for Income Taxes As part of FASB's Simplification Initiative, this standard amends ASC Topic 740 by removing certain exceptions to the general principles and clarifying and amending other current guidance. Early adoption is permitted. January 1, 2021 We are in the process of evaluating the impact the adoption of this standard will have on our financial statements. ASU 2020-04, Reference Rate Reform (Topic 848) Facilitation of the Effects of Reference Rate Reform on Financial Reporting This standard provides optional expedients and exceptions to ease the potential accounting burden associated with transitioning away from reference rates that are expected to be discontinued. The amendments may be elected prospectively to contract modifications made and to hedging relationships existing as of or entered into on or after the date of adoption and through December 31, 2022. December 31, 2022 We are in the process of evaluating the impact the adoption of this standard will have on our financial statements.
Other newly issued accounting standards	OTHER NEWLY ISSUED ACCOUNTING STANDARDS Standard Description Required date of adoption Effect on the financial statements or other significant matters ASU 2018-14, Compensation—Retirement Benefits—Defined Benefit Plans—General (Subtopic 715-20): Disclosure Framework—Changes to the Disclosure Requirements for Defined Benefit Plans This standard modifies the disclosure requirements related to defined benefit pension and other postretirement plans. Early adoption is permitted. December 31, 2020 It is not expected that the adoption of this standard will have a material effect on our financial statements. ASU 2019-12, Income Taxes (Topic 740) Simplifying the Accounting for Income Taxes As part of FASB's Simplification Initiative, this standard amends ASC Topic 740 by removing certain exceptions to the general principles and clarifying and amending other current guidance. Early adoption is permitted. January 1, 2021 We are in the process of evaluating the impact the adoption of this standard will have on our financial statements. ASU 2020-04, Reference Rate Reform (Topic 848) Facilitation of the Effects of Reference Rate Reform on Financial Reporting This standard provides optional expedients and exceptions to ease the potential accounting burden associated with transitioning away from reference rates that are expected to be discontinued. The amendments may be elected prospectively to contract modifications made and to hedging relationships existing as of or entered into on or after the date of adoption and through December 31, 2022. December 31, 2022 We are in the process of evaluating the impact the adoption of this standard will have on our financial statements.

Credit Losses (Tables)

Credit Losses (Tables)	3 Months Ended
Credit Losses (Tables)	Mar. 31, 2020
Credit Loss [Abstract]
Asset Optimization, Allowance for Credit Loss	The following table presents the activity of allowance for doubtful accounts by types for the reporting periods. Three Months Ended March 31, 2020 (In millions) Account receivables and Unbilled Revenue Asset Optimization Balance, beginning of period $ 18.7 $ — Provision 5.9 — Write offs charged against the allowance (7.5 ) — Recoveries 0.3 — Adjustment upon adoption of ASC 326 1.4 0.1 Balance, end of period $ 18.8 $ 0.1
Account Receivables and Unbilled Revenue, Allowance for Credit Loss	The following table presents the activity of allowance for doubtful accounts by types for the reporting periods. Three Months Ended March 31, 2020 (In millions) Account receivables and Unbilled Revenue Asset Optimization Balance, beginning of period $ 18.7 $ — Provision 5.9 — Write offs charged against the allowance (7.5 ) — Recoveries 0.3 — Adjustment upon adoption of ASC 326 1.4 0.1 Balance, end of period $ 18.8 $ 0.1

Revenue from Contracts With C_2

Revenue from Contracts With Customers (Tables)	3 Months Ended
Revenue from Contracts With Customers (Tables)	Mar. 31, 2020
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The following table disaggregates revenue for the three months ended March 31, 2020 and 2019: Disaggregated Revenue by Type of Service Three Months Ended March 31, (In millions) 2020 2019 Revenue from contracts with customers Gas and transportation sales Gas sold and delivered $ 346.3 $ 462.1 Gas delivered for others 97.6 109.4 Other 13.7 13.6 Other revenues 0.7 1.1 Total revenue from contracts with customers $ 458.3 $ 586.2 Other sources of revenue Revenue from alternative revenue programs (a) $ 40.6 $ 4.0 Leasing revenue 0.2 0.2 Other (b) 2.6 3.3 Total revenue from other sources $ 43.4 $ 7.5 Total Operating Revenue $ 501.7 $ 593.7 (a) Washington Gas has determined that its Revenue Normalization Adjustment (RNA), Weather Normalization Adjustment (WNA), and Conservation and Ratemaking Efficiency (CARE) Ratemaking Adjustment (CRA) billing adjustment mechanisms and accelerated pipe replacement programs are alternative revenue programs and accounted for under ASC Topic 980. (b) The amount includes late fees billed.
Contract Assets from Contracts with Customers	he following table shows the opening and closing balances of contract assets from contracts with customers for the reporting periods, which were included within "Receivables" on Washington Gas' balance sheets. (In millions) 2020 2019 Contract assets at January 1 $ 44.2 $ 85.3 Contract assets at March 31 $ 46.1 $ 34.6 Increase (decrease) in contract assets $ 1.9 $ (50.7 )

Accounts Payable and Other Ac_2

Accounts Payable and Other Accrued Liabilities (Tables)	3 Months Ended
Accounts Payable and Other Accrued Liabilities (Tables)	Mar. 31, 2020
Accounts Payable and Accrued Liabilities [Abstract]
Accounts Payable and Other Accrued Liabilities	The table below provides details for the amounts included in “Accounts payable and other accrued liabilities” on the balance sheets. (In millions) March 31, 2020 December 31, 2019 Accounts payable—trade $ 135.9 $ 154.3 Employee benefits and payroll accruals 20.6 39.2 Wages payable 24.1 22.2 Accrued interest 3.1 17.3 Other accrued liabilities (a) 36.1 34.4 Total $ 219.8 $ 267.4 (a) Amount includes $11.9 million and $11.7 million estimated liability associated with Antero judgment at March 31, 2020 and December 31, 2019, respectively, Refer to Note 11 -Commitments and Contingencies for further information.

Short-Term Debt (Tables)

Short-Term Debt (Tables)	3 Months Ended
Short-Term Debt (Tables)	Mar. 31, 2020
Short-term Debt [Abstract]
Commited Credit Available	The following is a summary of committed credit available at March 31, 2020 and December 31, 2019 . (In millions) March 31, 2020 December 31, 2019 Committed credit agreements Unsecured revolving credit facility, expires July 19, 2024 (a) $450.0 $450.0 Less: Commercial Paper outstanding (b) (145.6) (400.0) Net committed credit available $304.4 $50.0 Weighted average interest rate 1.91% 2.04% (a) Washington Gas has the right to request extensions with the bank group 's approval. Washington Gas’ revolving credit facility permits it to borrow an additional $100.0 million , with the bank groups' approval, for a total potential maximum borrowing of $550.0 million . (b) The amount presents principal amount of commercial paper.

Long Term Debt (Tables)

Long Term Debt (Tables)	3 Months Ended
Long Term Debt (Tables)	Mar. 31, 2020
Debt Disclosure [Abstract]
Schedule of Long-term Debt Instruments	The following table shows the long-term debt outstanding at March 31, 2020 and December 31, 2019 . Long Term Debt Outstanding (In millions) March 31, 2020 December 31, 2019 Washington Gas Unsecured Notes (a) $ 1,346.0 $ 1,346.0 Commercial Paper 100.0 100.0 Total Long-Term Debt $ 1,446.0 $ 1,446.0 Unamortized discount (4.3 ) (4.3 ) Unamortized debt expense (10.6 ) (10.8 ) Less—current maturities — — Total Long-Term Debt (carrying value) $ 1,431.1 $ 1,430.9 Weighted average interest rate (b) 4.52 % 4.52 % (a) Includes MTNs and private placement notes. The amount represents face value of Washington Gas' unsecured notes including current maturities. (b) Weighted average interest rate is for the Washington Gas unsecured notes including current maturities.

Components of Total Equity (Tab

Components of Total Equity (Tables)	3 Months Ended
Components of Total Equity (Tables)	Mar. 31, 2020
Stockholders' Equity Note [Abstract]
Schedule of Stockholders Equity	Common Stock Paid-In Capital Retained Earnings Accumulated Other Income/(Loss), Net of Taxes (In thousands, except shares) Shares Amount Total Balance at December 31, 2019 46,479,536 $ 46,479 $ 979,273 $ 541,535 $ 4,909 $ 1,572,196 Net income — — — 126,084 — 126,084 Other comprehensive income — — — — 1,941 1,941 Capital contribution from parent — — 125,000 — — 125,000 ASU 2016-13 implementation (a) — — — (1,543 ) — (1,543 ) Dividends declared: Common stock — — — (25,000 ) — (25,000 ) Balance at March 31, 2020 46,479,536 46,479 1,104,273 641,076 6,850 1,798,678 Balance at December 31, 2018 46,479,539 46,479 979,273 543,448 (6,627 ) 1,562,573 Net income — — — 112,996 — 112,996 Other comprehensive income — — — — 4,265 4,265 Dividends declared: Common stock — — — (25,000 ) — (25,000 ) Preferred stock — — — (330 ) — (330 ) Balance at March 31, 2019 46,479,539 46,479 979,273 631,114 (2,362 ) 1,654,504 (a) Due to implementation of ASU 2016-13 Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, see Note 2 — Credit Losses for further information.

Pension and Other Post-Retire_2

Pension and Other Post-Retirement Benefit Plans (Tables)	3 Months Ended
Pension and Other Post-Retirement Benefit Plans (Tables)	Mar. 31, 2020
Retirement Benefits [Abstract]
Components of Net Periodic Benefit Costs (Income)	The following table shows the components of the net periodic benefit costs (income) recognized in our financial statements during the three months ended March 31, 2020 and 2019: Components of Net Periodic Benefit Costs (Income) Three Months Ended March 31, 2020 2019 (In millions) Pension Benefits Health and Life Benefits Pension Benefits Health and Life Benefits Service cost $ 3.2 $ 1.3 $ 3.0 $ 1.3 Interest cost 8.9 2.3 10.2 3.0 Expected return on plan assets (10.1 ) (5.6 ) (10.7 ) (6.1 ) Recognized prior service cost (credit) 0.1 (3.4 ) 0.1 (3.9 ) Recognized actuarial loss (gain) 3.3 (0.1 ) 1.3 — Settlement charge (a) 1.1 — 4.3 — Net periodic benefit cost (income) 6.5 (5.5 ) 8.2 (5.7 ) Allocation to affiliates (0.3 ) 0.4 (0.4 ) 0.7 Adjusted net periodic benefit cost (income) 6.2 (5.1 ) 7.8 (5.0 ) Amount allocated to construction projects (0.4 ) (0.2 ) (0.4 ) (0.2 ) Amount deferred as regulatory asset (liability)-net allocations (b) — — 0.7 — Amount charged (credited) to expense $ 5.8 $ (5.3 ) $ 8.1 $ (5.2 ) (a) Amounts relate to partial settlement charges associated with lump sum payments from the Washington Gas’ defined benefit supplemental executive retirement plan (DB SERP) that were paid in the first quarter of 2020 and 2019. (b) Amount represents the amortization of previously unrecovered costs of the applicable pension benefits or the health and life benefits as approved in the District of Columbia through 2019.

Derivatives (Tables)

Derivatives (Tables)	3 Months Ended
Derivatives (Tables)	Mar. 31, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Absolute Notional Amounts of Open Positions on Derivative Instruments	The following table presents the balance sheet classification for all derivative instruments at March 31, 2020 and December 31, 2019 . Absolute Notional Amounts of Open Positions on Derivative Instruments March 31, 2020 December 31, 2019 Natural Gas (In millions of therms) Asset optimization & trading 11,442.0 11,671.0 Other risk-management activities 887.0 976.0
Balance Sheet Classification of Derivative Instruments	The following table presents the balance sheet classification for all derivative instruments at March 31, 2020 and December 31, 2019 . Balance Sheet Classification of Derivative Instruments (In millions) March 31, 2020 Gross Gross Netting of Total (a) Current Assets—Derivatives $ 2.9 $ 8.3 $ — $ 11.2 Deferred Charges and Other Assets—Derivatives 15.5 — — $ 15.5 Current Liabilities—Derivatives (0.2 ) (6.0 ) — $ (6.2 ) Deferred Credits—Derivatives — (91.8 ) — $ (91.8 ) Total $ 18.2 $ (89.5 ) $ — $ (71.3 ) December 31, 2019 Current Assets—Derivatives $ 2.9 $ 3.7 $ — $ 6.6 Deferred Charges and Other Assets—Derivatives 9.9 0.5 — 10.4 Current Liabilities—Derivatives 0.7 (11.0 ) 6.2 (4.1 ) Deferred Credits—Derivatives (0.5 ) (97.2 ) — (97.7 ) Total $ 13.0 $ (104.0 ) $ 6.2 $ (84.8 ) (a) Washington Gas has elected to offset the fair value of recognized derivative instruments against the right to reclaim or the obligation to return collateral for derivative instruments executed under the same master netting arrangement in accordance with ASC Topic 815. All recognized derivative contracts and associated financial collateral subject to a master netting arrangement or similar that is eligible for offset under ASC Topic 815 have been presented net in the balance sheets.
Gains and (Losses) on Derivative Instruments	The following tables present all gains and losses associated with derivative instruments for the three months ended March 31, 2020 and 2019. Washington Gas Light Company Gains and (Losses) on Derivative Instruments (In millions) Three Months Ended March 31, 2020 2019 Recorded to income Utility cost of gas 3.1 4.0 Recorded to regulatory assets Gas costs 8.9 11.9 Total $ 12.0 $ 15.9
Potential Collateral Requirements for Derivative Liabilities with Credit-Risk-Contingent Features	The following table shows the aggregate fair value of all derivative instruments with credit-related contingent features that are in a liability position, as well as the maximum amount of collateral that would be required if the most intrusive credit-risk-related contingent features underlying these agreements were triggered on March 31, 2020 and December 31, 2019 , respectively. Potential Collateral Requirements for Derivative Liabilities (In millions) March 31, 2020 December 31, 2019 Derivative liabilities with credit-risk-contingent features $ 0.1 $ 0.4 Maximum potential collateral requirements 0.1 0.4

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
Fair Value Measurements (Tables)	Mar. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements Under the Fair Value Hierarchy	The following table sets forth financial instruments recorded at fair value at March 31, 2020 and December 31, 2019 , respectively. A financial instrument’s classification within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. Our assessment of the significance of a particular input to the fair value measurement requires judgment and may affect the valuation of fair value assets and liabilities and their placement within the fair value hierarchy. Fair Value Measurements Under the Fair Value Hierarchy (In millions) Level 1 Level 2 Level 3 Total At March 31, 2020 Assets $ — $ 0.7 $ 17.5 $ 18.2 Liabilities $ — $ (0.8 ) $ (88.7 ) $ (89.5 ) At December 31, 2019 Assets $ — $ 0.8 $ 12.2 $ 13.0 Liabilities $ — $ (7.0 ) $ (97.0 ) $ (104.0 )
Quantitative Information about Level 3 Fair Value Measurements	The following table includes quantitative information about the significant unobservable inputs used in the fair value measurement of our Level 3 financial instruments and the respective fair values of the net derivative asset and liability positions, by contract type, at March 31, 2020 and December 31, 2019 . Quantitative Information about Level 3 Fair Value Measurements (In millions) Net Fair Value Valuation Techniques Unobservable Inputs Weighted Average (a) Range March 31, 2020 ($71.2) Discounted Cash Flow Natural Gas Basis Price (per dekatherm) ($0.34) ($0.878)-$2.133 December 31, 2019 ($84.8) Discounted Cash Flow Natural Gas Basis Price (per dekatherm) — ($0.905)-$2.523 (a) ASU 2018-13 has been applied prospectively, beginning with the interim period ending March 31, 2020. The average level 3 price was weighted by transaction volume.
Reconciliation of Fair Value Measurements Using Significant Level 3 Inputs	The following table is a summary of the changes in the fair value of our natural gas related derivative instruments that are measured at net fair value on a recurring basis in accordance with ASC Topic 820 using significant Level 3 inputs during the three months ended March 31, 2020 and 2019 , respectively. . Reconciliation of Fair Value Measurements Using Significant Level 3 Inputs Three Months Ended March 31, (In millions) 2020 2019 Balance at beginning of period $ (84.8 ) $ (106.6 ) Realized and unrealized gains (losses) Recorded to income 3.1 3.6 Recorded to regulatory assets—gas costs 9.1 12.5 Transfers into Level 3 — (3.8 ) Transfers out of Level 3 — 5.0 Settlements 1.4 3.2 Balance at end of period $ (71.2 ) $ (86.1 )
Unrealized Gains (Losses) Recorded for Level 3 Measurements	Unrealized gains (losses) attributable to derivative assets and liabilities measured using significant Level 3 inputs were recorded as follows for the three months ended March 31, 2020 and 2019, respectively: Unrealized Gains (Losses) Recorded for Level 3 Measurements Three Months Ended March 31, (In millions) 2020 2019 Recorded to income Utility cost of gas $2.3 $2.5 Recorded to regulatory assets Gas costs 7.6 10.5 Total $9.9 $13.0
Fair Value of Financial Instruments	The following table presents the carrying amounts on Washington Gas' balance sheets and estimated fair values of our financial instruments at March 31, 2020 and December 31, 2019 . Fair Value of Financial Instruments March 31, 2020 December 31, 2019 (In millions) Carrying Amount Fair Value Carrying Amount Fair Value Money market funds (a) $ 78.0 $ 78.0 $ 55.1 $ 55.1 Other long-term receivable (b) $ 1.3 $ 1.3 $ 1.3 $ 1.3 Commercial paper (c) $ 145.5 $ 145.5 $ 399.5 $ 399.5 Washington Gas Unsecured notes (d) $ 1,331.1 $ 1,486.5 $ 1,330.9 $ 1,480.8 (a) The balance at March 31, 2020 includes $38.6 million money market funds located in "Cash and cash equivalents", $11.3 million rabbi trust investment located in "Current Assets-Other", and $28.1 million rabbi trust investments located in "Deferred Charges and Other Assets-Other" of the accompanying balance sheets; The balance at December 31, 2019 includes $11.0 million money market funds located in "Cash and cash equivalents", $ 19.5 million rabbi trust investment located in "Current Assets-Other" and $24.6 million rabbi trust investments located in "Deferred Charges and Other Assets-Other". (b) Amount represents a long-term receivable from one of our trading partners related to Antero contract discussed in Note 11-Commitments and Contingencies. (c) The balance at March 31, 2020 includes $45.5 million located in "Notes payable", and $100.0 million located in “Long-term debt” on the accompanying balance sheets. The balance at December 31, 2019 includes $299.5 million located in "Notes payable", and $100.0 million located in “Long-term debt” on the accompanying balance sheets. (d) Includes adjustments for current maturities and unamortized discounts, as applicable. The amount was included in "Long-term debt" on the accompanying balance sheets.

Related Party Transactions (Tab

Related Party Transactions (Tables)	3 Months Ended
Related Party Transactions (Tables)	Mar. 31, 2020
Related Party Transactions [Abstract]
Gas Balancing Service Charges	The following table shows the amounts Washington Gas charged WGL Energy Services for balancing services. Washington Gas - Gas Balancing Service Charges Three Month Ended March 31, (In millions) 2020 2019 Gas balancing service charge $ 6.6 $ 8.9

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Loss) (Tables)	3 Months Ended
Accumulated Other Comprehensive Income (Loss) (Tables)	Mar. 31, 2020
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	The following table shows the changes in accumulated other comprehensive income (loss) for Washington Gas by component for the three months ended March 31, 2020 and 2019 . Changes in Accumulated Other Comprehensive Income (Loss) by Component Three Months Ended March 31, (In thousands) 2020 2019 Beginning Balance $ 4,909 $ (6,627 ) Amortization of prior service credit (a)(b) (304 ) (162 ) Amortization of actuarial loss (a)(b) 1,016 415 Actuarial gain (loss) arising during the period (a) 1,910 4,489 Current-period other comprehensive income 2,622 4,742 Income tax expense related to pension and other post-retirement benefit plans 681 477 Ending Balance $ 6,850 $ (2,362 ) (a) These accumulated other comprehensive income (loss) components are included in the computation of net periodic benefit cost. (b) Amortization of prior service cost and amortization of actuarial gain (loss) represent the amounts reclassified out of AOCI to “Other income (expense)” of statements of operations for the reporting periods.

Supplemental Cash Flow Inform_2

Supplemental Cash Flow Information (Tables)	3 Months Ended
Supplemental Cash Flow Information (Tables)	Mar. 31, 2020
Supplemental Cash Flow Information [Abstract]
Supplemental Cash Flow Information	The following table details the changes in operating assets and liabilities from operating activities, cash payments that have been included in the determination of earnings and non-cash investing and financing activities: Three Months Ended March 31, (In thousands) 2020 2019 CHANGES IN OPERATING ASSETS AND LIABILITIES Receivables $ 53,278 $ (27,774 ) Receivables from associated companies (1,621 ) 249 Gas costs and other regulatory assets/liabilities—net (43,613 ) 6,683 Storage gas 56,430 65,885 Prepaid taxes 3,711 2,037 Accounts payable and other accrued liabilities (59,144 ) (77,797 ) Payables to associated companies 13,270 (2,656 ) Customer deposits and advance payments (6,949 ) (15,521 ) Accrued taxes 5,499 3,232 Other current assets 10,273 2,215 Other current liabilities (243 ) (243 ) Deferred gas costs—net 24,874 50,086 Deferred assets—other (1,014 ) 14,027 Deferred liabilities—other (1,463 ) (2,297 ) Pension and other post-retirement benefits (4,245 ) (14,494 ) Changes in operating assets and liabilities $ 49,043 $ 3,632 SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION Income taxes paid (refunded)—net $ (3,880 ) $ (1,683 ) Interest paid $ 30,965 $ 25,398 SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING AND FINANCING ACTIVITIES: Capital expenditure accruals included in accounts payable and other accrued liabilities $ 45,817 32,738
Reconciliation of cash, cash equivalents and restricted cash	The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within Washington Gas’ balance sheets that sums to the total of such amounts shown on the statements of cash flo ws March 31, (in thousands) 2020 2019 Cash and cash equivalents $ 42,418 $ 2,142 Restricted cash included in Current assets-Other $ 11,332 $ 4,094 Restricted cash included in Deferred charges and other assets-Other $ 28,113 $ 45,440 Total cash, cash equivalents and restricted cash shown in the statement of cash flows $ 81,863 $ 51,676

Accounting Policies (Details)

Accounting Policies (Details) $ in Millions	Jan. 01, 2020USD ($)
Cumulative effect of adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses	$ 1.5

Credit Losses - Narrative (Deta

Credit Losses - Narrative (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Jan. 01, 2020	Dec. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses	$ 18,829		$ 18,708
Long term receivable from trading partner	18,800		$ 18,700
Cumulative effect of adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses		$ 1,500
Allowance for credit losses		1,400
Long term receivable from trading partner	$ 1,400	1,400
Credit loss reserve for long term trading receivable		$ 100

Credit Losses - Rollforward of

Credit Losses - Rollforward of Allowance Accounts (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Account receivables and Unbilled Revenue
Balance at the beginning of period	$ 18,700
Provision	5,874	$ 7,489
Write offs charged against the allowance	(7,500)
Recoveries	300
Balance at end of the period	18,800
Cumulative effect of adoption
Account receivables and Unbilled Revenue
Balance at end of the period	1,400
Asset Optimization
Account receivables and Unbilled Revenue
Balance at the beginning of period	0
Provision	0
Write offs charged against the allowance	0
Recoveries	0
Balance at end of the period	$ 100

Revenue from Contracts With C_3

Revenue from Contracts With Customers - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 458,300	$ 586,200
Revenue from alternative revenue programs	40,600	4,000
Leasing revenue	200	200
Other	2,600	3,300
Other sources of revenue	43,400	7,500
Total Operating Revenue	501,735	593,653
Gas and transportation sales \| Gas sold and delivered
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	346,300	462,100
Gas and transportation sales \| Gas delivered for others
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	97,600	109,400
Gas and transportation sales \| Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	13,700	13,600
Other revenues
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 700	$ 1,100

Revenue From Contracts With C_4

Revenue From Contracts With Customers - Contract Assets (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Unbilled revenues	$ 74		$ 116.3
Contract assets at January 1	44.2	$ 85.3
Contract assets at March 31	46.1	34.6
Increase (decrease) in contract assets	$ 1.9	$ (50.7)

Accounts Payable and Other Ac_3

Accounts Payable and Other Accrued Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Accounts Payable and Accrued Liabilities [Abstract]
Accounts payable—trade	$ 135.9	$ 154.3
Employee benefits and payroll accruals	20.6	39.2
Wages payable	24.1	22.2
Accrued interest	3.1	17.3
Other accrued liabilities	36.1	34.4
Total	219.8	267.4
Washington Gas \| Antero contract
Loss Contingencies [Line Items]
Loss contingency accrual	$ 11.9	$ 11.7

Short-Term Debt (Details)

Short-Term Debt (Details) - USD ($)	Mar. 31, 2020	Dec. 31, 2019
Short-term Debt [Line Items]
Less: Commercial Paper outstanding	$ (145,500,000)	$ (399,500,000)
Credit facility
Short-term Debt [Line Items]
Unsecured revolving credit facility	450,000,000	450,000,000
Less: Commercial Paper outstanding	(145,600,000)	(400,000,000)
Net committed credit available	$ 304,400,000	$ 50,000,000
Weighted average interest rate	1.91%	2.04%
Revolving credit facility additional borrowings	$ 100,000,000
Revolving credit facility maximum borrowing capacity	$ 550,000,000

Short-Term Debt - Additional In

Short-Term Debt - Additional Information (Details)	Mar. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Short-term Debt [Line Items]
Ratio of indebtedness to net capital percentage	45.00%	52.00%
Commercial paper	$ 145,500,000	$ 399,500,000
Maximum
Short-term Debt [Line Items]
Ratio of indebtedness to net capital	0.65
Ratio of indebtedness to net capital percentage	65.00%
Long-term debt
Short-term Debt [Line Items]
Commercial paper	$ 100,000,000	100,000,000
Note payable and project financing
Short-term Debt [Line Items]
Commercial paper	45,500,000	299,500,000
Credit facility
Short-term Debt [Line Items]
Outstanding bank loans	0	0
Commercial paper	$ 145,600,000	$ 400,000,000

Long Term Debt (Details)

Long Term Debt (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Long Term Debt [LIne Items]
Total Long-Term Debt	$ 1,446	$ 1,446
Unamortized discount	(4.3)	(4.3)
Unamortized debt expense	(10.6)	(10.8)
Less—current maturities	0	0
Total Long-Term Debt (carrying value)	$ 1,431.1	$ 1,430.9
Weighted average interest rate	4.52%	4.52%
Unsecured Notes
Long Term Debt [LIne Items]
Total Long-Term Debt	$ 1,346	$ 1,346
Commercial Paper
Long Term Debt [LIne Items]
Total Long-Term Debt	$ 100	$ 100

Components of Total Equity (Det

Components of Total Equity (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Jan. 01, 2020
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	$ 1,572,196	$ 1,562,573
Net income	126,084	112,996
Other comprehensive income	1,941	4,265
Capital contribution from parent	125,000
Dividends Abstract
Common Stock	(25,000)	(25,000)
Preferred Stock		(330)
Ending Balance	$ 1,798,678	$ 1,654,504
ASU 2016-13
Increase (Decrease) in Stockholders' Equity [Roll Forward]
ASU 2016-13 implementation			$ (1,543)
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance (in shares)	46,479,536	46,479,539
Beginning Balance	$ 46,479	$ 46,479
Dividends Abstract
Ending Balance (in shares)	46,479,536	46,479,539
Ending Balance	$ 46,479	$ 46,479
Paid-In Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	979,273	979,273
Capital contribution from parent	125,000
Dividends Abstract
Ending Balance	1,104,273	979,273
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	541,535	543,448
Net income	126,084	112,996
Dividends Abstract
Common Stock	(25,000)	(25,000)
Preferred Stock		(330)
Ending Balance	641,076	631,114
Retained Earnings \| ASU 2016-13
Increase (Decrease) in Stockholders' Equity [Roll Forward]
ASU 2016-13 implementation			$ (1,543)
Accumulated Other Comprehensive Income/(Loss), Net of Taxes
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	4,909	(6,627)
Other comprehensive income	1,941	4,265
Dividends Abstract
Ending Balance	$ 6,850	$ (2,362)

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Receivables from associated companies	$ 5.5	$ 5.5
Payables to associated companies	$ 0.6	$ 0.6

Pension and Other Post-Retire_3

Pension and Other Post-Retirement Benefit Plans - Narrative (Details) - Rabbi Trusts - DB SERP - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	$ 35.4	$ 40
Other assets, current
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	11.3	19.5
Other noncurrent assets
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets	$ 24	$ 20.5

Pension and Other Post-retire_4

Pension and Other Post-retirement Benefit Plans - Components of Net Periodic Benefit Cost Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 3.2	$ 3
Interest cost	8.9	10.2
Expected return on plan assets	(10.1)	(10.7)
Recognized prior service cost (credit)	0.1	0.1
Recognized actuarial loss (gain)	3.3	1.3
Settlement charge	1.1	4.3
Net periodic benefit cost (income)	6.5	8.2
Allocation to affiliates	(0.3)	(0.4)
Adjusted net periodic benefit cost (income)	6.2	7.8
Amount allocated to construction projects	(0.4)	(0.4)
Amount deferred as regulatory asset (liability)-net allocations	0	0.7
Amount charged (credited) to expense	5.8	8.1
Health and Life Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	1.3	1.3
Interest cost	2.3	3
Expected return on plan assets	(5.6)	(6.1)
Recognized prior service cost (credit)	(3.4)	(3.9)
Recognized actuarial loss (gain)	(0.1)	0
Settlement charge	0	0
Net periodic benefit cost (income)	(5.5)	(5.7)
Allocation to affiliates	0.4	0.7
Adjusted net periodic benefit cost (income)	(5.1)	(5)
Amount allocated to construction projects	(0.2)	(0.2)
Amount deferred as regulatory asset (liability)-net allocations	0	0
Amount charged (credited) to expense	$ (5.3)	$ (5.2)

Commitments and Contingencies (

Commitments and Contingencies (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended
	Jun. 30, 2019	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Commitments and Contingencies [Line Items]
Operation and maintenance expenses		$ 102,678		$ 111,002
Deferred gas cost		60,069	$ 98,717
Regulatory assets, noncurrent		82,682	84,886
Accrued minimum liability expected amount		330
Statutory amount available for dividend payments with regulatory approval		25
Environmental response costs
Commitments and Contingencies [Line Items]
Regulatory assets, noncurrent		7,000	7,000
Environmental response costs \| Reserve for Environmental Costs
Commitments and Contingencies [Line Items]
Accrual for environmental loss contingencies		11,000	10,700
Estimated maximum liability		30,900	30,700
Antero contract
Commitments and Contingencies [Line Items]
Loss contingency, damages awarded, value	$ 95,900
Antero contract \| Washington Gas
Commitments and Contingencies [Line Items]
Loss contingency, damages awarded, value	11,200
Loss contingency accrual		11,900	$ 11,700
Loss contingency, receivable		1,300
Deferred gas cost		4,800
Antero contract \| WGL Midstream
Commitments and Contingencies [Line Items]
Loss contingency, damages awarded, value	$ 84,700
Minimum \| Virginia
Commitments and Contingencies [Line Items]
Estimate of possible loss		32,000
Maximum \| Virginia
Commitments and Contingencies [Line Items]
Estimate of possible loss		123,300
Merger agreement, circumstance 2
Commitments and Contingencies [Line Items]
Operation and maintenance expenses		136,600
Other commitments payable		16,600
Merger agreement, circumstance 2 \| Future hiring
Commitments and Contingencies [Line Items]
Operation and maintenance expenses		$ 2,400
Regulatory commitments, term		5 years
Merger agreement, circumstance 2 \| Extend natural gas service
Commitments and Contingencies [Line Items]
Operation and maintenance expenses		$ 70,000
Regulatory commitments, term		10 years
Merger agreement, circumstance 2 \| Future leak mitigation
Commitments and Contingencies [Line Items]
Operation and maintenance expenses		$ 8,000
Regulatory commitments, term		3 years

Derivatives - Narrative (Detail

Derivatives - Narrative (Details) $ in Millions	3 Months Ended
Derivatives - Narrative (Details) $ in Millions	Mar. 31, 2020USD ($)counter_party	Mar. 31, 2019USD ($)	Dec. 31, 2019USD ($)
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Collaborative arrangement expenses	$ 1	$ 0.7
Gain (loss) on asset optimization transactions net pretax	8.4	8.2
Unrealized gains (loss) on asset optimization derivative instruments net pretax	6.1	$ 7.2
Right to reclaim cash	4.8		$ 5.2
Derivative, collateral, obligation to return cash	$ 0.1		$ 0.1
Number of counterparties \| counter_party	1
Percentage of credit exposure	10.00%
Concentration risk credit risk financial instrument exposure	$ 16.5

Derivatives Derivatives - Open

Derivatives Derivatives - Open Positions on Derivative Instruments (Details) - BTU BTU in Millions	Mar. 31, 2020	Dec. 31, 2019
Asset optimization & trading
Derivative [Line Items]
Natural gas derivative transaction, volume	11,442	11,671
Other risk-management activities
Derivative [Line Items]
Natural gas derivative transaction, volume	887	976

Derivatives Derivatives - Balan

Derivatives Derivatives - Balance Sheet Classification of Derivative Instruments (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Gross Derivative Assets	$ 18.2	$ 13
Gross Derivative Liabilities	(89.5)	(104)
Netting of Collateral	0	6.2
Total	(71.3)	(84.8)
Current Assets—Derivatives
Derivative [Line Items]
Gross Derivative Assets	2.9	2.9
Gross Derivative Liabilities	8.3	3.7
Netting of Collateral	0	0
Total	11.2	6.6
Deferred Charges and Other Assets—Derivatives
Derivative [Line Items]
Gross Derivative Assets	15.5	9.9
Gross Derivative Liabilities	0	0.5
Netting of Collateral	0	0
Total	15.5	10.4
Current Liabilities—Derivatives
Derivative [Line Items]
Gross Derivative Assets	(0.2)	0.7
Gross Derivative Liabilities	(6)	(11)
Netting of Collateral	0	6.2
Total	(6.2)	(4.1)
Deferred Credits—Derivatives
Derivative [Line Items]
Gross Derivative Assets	0	(0.5)
Gross Derivative Liabilities	(91.8)	(97.2)
Netting of Collateral	0	0
Total	$ (91.8)	$ (97.7)

Derivatives - Gains and Losses

Derivatives - Gains and Losses (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Gains and (Losses) on Derivative Instruments
Total	$ 12	$ 15.9
Utility cost of gas
Gains and (Losses) on Derivative Instruments
Recorded to income	3.1	4
Gas costs
Gains and (Losses) on Derivative Instruments
Recorded to regulatory assets	$ 8.9	$ 11.9

Derivatives Derivatives - Credi

Derivatives Derivatives - Credit Risk Contingent Features (Details) - Credit Risk Contract - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Derivative liabilities with credit-risk-contingent features	$ 0.1	$ 0.4
Maximum potential collateral requirements	$ 0.1	$ 0.4

Fair Value Measurements - Under

Fair Value Measurements - Under the Fair Value Hierarchy (Details) - Natural Gas Related Derivatives - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Assets	$ 18.2	$ 13
Liabilities	(89.5)	(104)
Level 1
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Assets	0	0
Liabilities	0	0
Level 2
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Assets	0.7	0.8
Liabilities	(0.8)	(7)
Level 3
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Assets	17.5	12.2
Liabilities	$ (88.7)	$ (97)

Fair Value Measurements - Quant

Fair Value Measurements - Quantitative information (Details) - Natural Gas Related Derivatives $ in Millions	Mar. 31, 2020USD ($)$ / dekatherm	Dec. 31, 2019USD ($)$ / dekatherm	Mar. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Fair Value Measurements Details [Line Items]
Net Fair Value \| $	$ (71.2)	$ (84.8)	$ (86.1)	$ (106.6)
Discounted Cash Flow
Fair Value Measurements Details [Line Items]
Net Fair Value \| $	$ (71.2)	$ (84.8)
Discounted Cash Flow \| Weighted Average \| Natural Gas Basis Price
Fair Value Measurements Details [Line Items]
Input price	(0.34)	0
Discounted Cash Flow \| Maximum \| Natural Gas Basis Price
Fair Value Measurements Details [Line Items]
Input price	2.133	2.523
Discounted Cash Flow \| Minimum \| Natural Gas Basis Price
Fair Value Measurements Details [Line Items]
Input price	(0.878)	(0.905)

Fair Value Measurements - Recon

Fair Value Measurements - Reconciliation with Level 3 Inputs (Details) - Natural Gas Related Derivatives - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Reconciliation of Fair Value Measurements Using Significant Level 3 Inputs
Beginning of period	$ (84.8)	$ (106.6)
Recorded to income	3.1	3.6
Recorded to regulatory assets—gas costs	9.1	12.5
Transfers into Level 3	0	(3.8)
Transfers out of Level 3	0	5
Settlements	1.4	3.2
End of period	$ (71.2)	$ (86.1)

Fair Value Measurements - Unrea

Fair Value Measurements - Unrealized Gains and Losses Recorded for Level 3 Measurements (Details) - Natural Gas Related Derivatives - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Unrealized Gains (Losses) Recorded for Level 3 Measurements
Recorded to regulatory assets	$ 9.1	$ 12.5
Total unrealized gains (losses)	9.9	13
Utility cost of gas
Unrealized Gains (Losses) Recorded for Level 3 Measurements
Recorded to income	2.3	2.5
Regulatory asset-gas costs member
Unrealized Gains (Losses) Recorded for Level 3 Measurements
Recorded to regulatory assets	$ 7.6	$ 10.5

Fair Value Measurements - Fair

Fair Value Measurements - Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Commercial paper	$ 145,500	$ 399,500
Restricted cash included in Current assets-Other	11,332		$ 4,094
Restricted cash included in Deferred charges and other assets-Other	28,113		$ 45,440
Long-term debt	1,446,000	1,446,000
Carrying Amount
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Money market funds	78,000	55,100
Other long-term receivable	1,300	1,300
Commercial paper	145,500	399,500
Long-term debt, fair value	1,331,100	1,330,900
Fair Value
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Money market funds	78,000	55,100
Other long-term receivable	1,300	1,300
Commercial paper	145,500	399,500
Long-term debt, fair value	1,486,500	1,480,800
Cash and cash equivalents
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Money market funds	38,600	11,000
Other assets, current
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Restricted cash included in Current assets-Other		19,500
Deferred charges and other assets
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Restricted cash included in Deferred charges and other assets-Other	28,100	24,600
Commercial Paper
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Notes payable and project financing	45,500	299,500
Long-term debt	$ 100,000	$ 100,000

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended
	Oct. 31, 2018	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Related Party Transaction [Line Items]
Payables to associated companies		$ 71,193		$ 57,923
Contract with Customer, Asset, before Allowance for Credit Loss		46,100	$ 34,600	44,200	$ 85,300
Unbilled revenues		74,000		116,300
Receivables from associated companies		14,042		12,421
Operation and maintenance		102,678	111,002
WGL Energy Services
Related Party Transaction [Line Items]
Gas balancing service charge		6,600	8,900
Related party purchased receivables		7,000		7,900
Hampshire Gas Company
Related Party Transaction [Line Items]
Operation and maintenance		2,000	2,100
WGL Energy Services
Related Party Transaction [Line Items]
Payables to associated companies		2,600		2,100
Shared service costs \| Parent Company
Related Party Transaction [Line Items]
Operation and maintenance		5,000	$ 4,500
Energy management services projects not complete \| WGL Energy Systems
Related Party Transaction [Line Items]
Payables to associated companies		$ 46,100		$ 44,200	$ 53,000
Repayments of debt	$ 53,000

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
AOCI, Net of Tax [Roll Forward]
Beginning Balance	$ 1,572,196	$ 1,562,573
Ending Balance	1,798,678	1,654,504
Accumulated other comprehensive income (loss)
AOCI, Net of Tax [Roll Forward]
Beginning Balance	4,909	(6,627)
Current-period other comprehensive income	2,622	4,742
Income tax expense related to pension and other post-retirement benefit plans	681	477
Ending Balance	6,850	(2,362)
Amortization of prior service cost
AOCI, Net of Tax [Roll Forward]
Reclassification	(304)	(162)
Amortization of actuarial gain (loss)
AOCI, Net of Tax [Roll Forward]
Reclassification	1,016	415
Actuarial gain (loss) arising during the period
AOCI, Net of Tax [Roll Forward]
Current-period other comprehensive income	$ 1,910	$ 4,489

Supplemental Cash Flow Inform_3

Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Increase (Decrease) in Operating Capital [Abstract]
Receivables	$ 53,278	$ (27,774)
Receivables from associated companies	(1,621)	249
Gas costs and other regulatory assets/liabilities—net	(43,613)	6,683
Storage gas	56,430	65,885
Prepaid taxes	3,711	2,037
Accounts payable and other accrued liabilities	(59,144)	(77,797)
Payables to associated companies	13,270	(2,656)
Customer deposits and advance payments	(6,949)	(15,521)
Accrued taxes	5,499	3,232
Other current assets	10,273	2,215
Other current liabilities	(243)	(243)
Deferred gas costs—net	24,874	50,086
Deferred assets—other	(1,014)	14,027
Deferred liabilities—other	(1,463)	(2,297)
Pension and other post-retirement benefits	(4,245)	(14,494)
Changes in operating assets and liabilities	49,043	3,632
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION
Income taxes paid (refunded)—net	(3,880)	(1,683)
Interest paid	30,965	25,398
SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING AND FINANCING ACTIVITIES:
Capital expenditure accruals included in accounts payable and other accrued liabilities	45,817	32,738
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	42,418	2,142	$ 17,069
Restricted cash included in Current assets-Other	11,332	4,094
Restricted cash included in Deferred charges and other assets-Other	28,113	45,440
Total cash, cash equivalents and restricted cash shown in the statement of cash flows	$ 81,863	$ 51,676	$ 61,148	$ 71,423

Uncategorized Items - wgl-20200

Label	Element	Value
Cumulative Effect, Period Of Adoption, Adjustment [Member] \| Asset Optimization [Member]
Accounts Receivable, Allowance for Credit Loss	us-gaap_AllowanceForDoubtfulAccountsReceivable	$ 100,000