Washington Gas Light (WGLCP) 10-Q 6 Feb 14 2014 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	3 Months Ended
	Dec. 31, 2013	Jan. 31, 2014
Document and Entity Information [Abstract]	'	'
Entity Registrant Name	'WGL Holdings Inc.	'
Entity Central Index Key	'0001103601	'
Document Type	'10-Q	'
Document Period End Date	31-Dec-13	'
Amendment Flag	'false	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q1	'
Current Fiscal Year End Date	'--09-30	'
Entity Well-known Seasoned Issuer	'Yes	'
Entity Voluntary Filers	'No	'
Entity Current Reporting Status	'Yes	'
Entity Filer Category	'Large Accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	51,860,763

Consolidated_Balance_Sheets_Un

Consolidated Balance Sheets (Unaudited) (USD $)	Dec. 31, 2013	Sep. 30, 2013
In Thousands, unless otherwise specified
Deferred charges and other assets	'	'
Investment in direct financing leases, capital leases	$19,800	'
WGL Holdings, Inc.	'	'
Property, Plant and Equipment	'	'
At original cost	4,169,718	4,118,149
Accumulated depreciation and amortization	-1,222,359	-1,210,686
Net property, plant and equipment	2,947,359	2,907,463
Current Assets	'	'
Cash and cash equivalents	4,810	3,478
Receivables	'	'
Accounts receivable	399,577	229,544
Gas costs and other regulatory assets	10,328	10,825
Unbilled revenues	207,618	98,598
Allowance for doubtful accounts	-18,518	-20,433
Net receivables	599,005	318,534
Materials and supplies-principally at average cost	24,825	24,904
Storage gas	241,868	347,291
Deferred income taxes	25,714	24,522
Prepaid taxes	62,432	24,450
Other prepayments	38,202	29,922
Derivatives	23,461	35,315
Other	19,970	11,595
Total current assets	1,040,287	820,011
Deferred charges and other assets	'	'
Gas costs	204,655	93,963
Pension and other post-retirement benefits	242,401	240,634
Other	65,917	66,010
Derivatives	9,160	26,306
Investment in direct financing leases, capital leases	23,042	23,390
Investment in unconsolidated affiliates	83,402	67,522
Other	15,303	14,761
Total deferred charges and other assets	643,880	532,586
Total Assets	4,631,526	4,260,060
Capitalization	'	'
Common shareholders' equity	1,272,861	1,274,545
Washington Gas Light Company preferred stock	28,173	28,173
Long-term debt	599,223	524,067
Total capitalization	1,900,257	1,826,785
Current Liabilities	'	'
Current maturities of long-term debt	30,000	67,000
Notes payable	443,300	373,100
Accounts payable and other accrued liabilities	313,955	270,658
Wages payable	17,005	18,645
Accrued interest	10,462	3,399
Dividends declared	22,111	22,075
Customer deposits and advance payments	69,235	67,154
Gas costs and other regulatory liabilities	78,641	27,013
Accrued taxes	29,868	16,056
Derivatives	41,398	48,413
Other	34,396	36,564
Total current liabilities	1,090,371	950,077
Deferred Credits	'	'
Unamortized investment tax credits	74,868	46,378
Deferred income taxes	641,699	629,807
Accrued pensions and benefits	150,294	148,890
Asset retirement obligations	102,412	101,321
Regulatory liabilities	'	'
Accrued asset removal costs	320,134	321,266
Other	15,016	13,459
Derivatives	245,609	141,334
Other	90,866	80,743
Total deferred credits	1,640,898	1,483,198
Commitments and Contingencies (Note 13)	'	'
Total Capitalization and Liabilities	4,631,526	4,260,060
Washington Gas Light Company	'	'
Property, Plant and Equipment	'	'
At original cost	3,939,507	3,903,482
Accumulated depreciation and amortization	-1,188,730	-1,178,600
Net property, plant and equipment	2,750,777	2,724,882
Current Assets	'	'
Cash and cash equivalents	2	0
Receivables	'	'
Accounts receivable	220,522	91,405
Gas costs and other regulatory assets	10,328	10,825
Unbilled revenues	111,412	19,418
Allowance for doubtful accounts	-16,014	-17,498
Net receivables	326,248	104,150
Materials and supplies-principally at average cost	24,778	24,857
Storage gas	124,148	132,226
Deferred income taxes	26,180	27,000
Other prepayments	30,803	22,794
Receivables from associated companies	4,847	7,173
Derivatives	6,249	4,278
Other	2	0
Total current assets	543,257	322,478
Deferred charges and other assets	'	'
Gas costs	204,655	93,963
Pension and other post-retirement benefits	241,230	239,434
Other	65,883	65,984
Derivatives	0	16,051
Other	12,403	11,597
Total deferred charges and other assets	524,171	427,029
Total Assets	3,818,205	3,474,389
Capitalization	'	'
Common shareholders' equity	1,043,918	1,024,583
Washington Gas Light Company preferred stock	28,173	28,173
Long-term debt	599,223	524,067
Total capitalization	1,671,314	1,576,823
Current Liabilities	'	'
Current maturities of long-term debt	30,000	67,000
Notes payable	188,000	124,500
Accounts payable and other accrued liabilities	171,579	132,814
Wages payable	15,560	17,057
Accrued interest	10,462	3,399
Dividends declared	19,391	19,359
Customer deposits and advance payments	69,235	67,154
Gas costs and other regulatory liabilities	78,641	27,013
Accrued taxes	34,996	25,380
Payables to associated companies	35,952	20,557
Derivatives	26,678	24,749
Other	7,281	9,047
Total current liabilities	687,775	538,029
Deferred Credits	'	'
Unamortized investment tax credits	7,133	7,354
Deferred income taxes	627,652	611,453
Accrued pensions and benefits	148,882	147,479
Asset retirement obligations	101,044	99,972
Regulatory liabilities	'	'
Accrued asset removal costs	320,134	321,266
Other	15,016	13,459
Derivatives	188,639	106,144
Other	50,616	52,410
Total deferred credits	1,459,116	1,359,537
Commitments and Contingencies (Note 13)	'	'
Total Capitalization and Liabilities	$3,818,205	$3,474,389

Consolidated_Statement_of_Inco

Consolidated Statement of Income (Unaudited) (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012
OPERATING EXPENSES	'		'
NET INCOME (LOSS) APPLICABLE TO COMMON STOCK	$18,629		$52,388
AVERAGE COMMON SHARES OUTSTANDING	'		'
Basic	51,816		51,631
Diluted	51,827		51,688
EARNINGS (LOSS) PER AVERAGE COMMON SHARE	'		'
Basic	$0.36		$1.01
Diluted	$0.36		$1.01
WGL Holdings, Inc.	'		'
OPERATING REVENUES	'		'
Utility	386,541		347,933
Non-utility	293,756		338,803
Total Operating Revenues	680,297	[1]	686,736	[1]
OPERATING EXPENSES	'		'
Utility cost of gas	186,881		142,970
Non-utility cost of energy-related sales	305,351		299,149
Operation and maintenance	88,142		83,630
Depreciation and amortization	26,590		27,304
General taxes and other assessments	40,621		39,067
Total Operating Expenses	647,585		592,120
OPERATING INCOME (LOSS)	32,712		94,616
Equity in earnings of unconsolidated affiliates	490		245
Other income (expense) - net	219		429
Total interest expense	8,992		9,193
INCOME (LOSS) BEFORE INCOME TAXES	24,429		86,097
INCOME TAX EXPENSE (BENEFIT)	5,470		33,379
Net income (loss)	18,959		52,718
Dividends on Washington Gas preferred stock	330		330
NET INCOME (LOSS) APPLICABLE TO COMMON STOCK	18,629		52,388
AVERAGE COMMON SHARES OUTSTANDING	'		'
Basic	51,816		51,631
Diluted	51,827		51,688
EARNINGS (LOSS) PER AVERAGE COMMON SHARE	'		'
Basic	$0.36		$1.01
Diluted	$0.36		$1.01
DIVIDENDS DECLARED PER COMMON SHARE	$0.42		$0.40
Washington Gas Light Company	'		'
OPERATING REVENUES	'		'
Utility	390,415		355,817
OPERATING EXPENSES	'		'
Utility cost of gas	190,695		150,448
Operation and maintenance	72,072		70,393
Depreciation and amortization	25,041		26,488
General taxes and other assessments	37,378		36,451
Total Operating Expenses	325,186		283,780
OPERATING INCOME (LOSS)	65,229		72,037
Other income (expense) - net	-180		139
Total interest expense	8,879		9,095
INCOME (LOSS) BEFORE INCOME TAXES	56,170		63,081
INCOME TAX EXPENSE (BENEFIT)	17,363		24,364
Net income (loss)	38,807		38,717
Dividends on Washington Gas preferred stock	330		330
NET INCOME (LOSS) APPLICABLE TO COMMON STOCK	$38,477		$38,387
[1]	B Operating revenues are reported gross of revenue taxes. Revenue taxes of both the regulated utility and the retail energy-marketing segments include gross receipt taxes. Revenue taxes of the regulated utility segment also include PSC fees, franchise fees and energy taxes. Operating revenue amounts in the "Eliminations" column represent total intersegment revenues associated with sales from the regulated utility segment to the retail energy-marketing segment. Midstream Energy Services' cost of energy related sales is netted with its gross revenues.

Consolidated_Statement_of_Comp

Consolidated Statement of Comprehensive Income (Unaudited) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
WGL Holdings, Inc.	'	'
Net Income (Loss)	$18,959	$52,718
Pension and other postretirement benefit plans	'	'
Change in prior service cost (credit)	-35	-12
Change in actuarial net loss	364	462
Change in transition obligation	0	9
Total pension and other postretirement benefit plans/Current-period other comprehensive income	329	459
INCOME TAX EXPENSE RELATED TO OTHER COMPREHENSIVE INCOME	130	182
OTHER COMPREHENSIVE INCOME	199	277
Comprehensive Income	19,158	52,995
Washington Gas Light Company	'	'
Net Income (Loss)	38,807	38,717
Pension and other postretirement benefit plans	'	'
Change in prior service cost (credit)	-35	-12
Change in actuarial net loss	364	462
Change in transition obligation	0	9
Total pension and other postretirement benefit plans/Current-period other comprehensive income	329	459
INCOME TAX EXPENSE RELATED TO OTHER COMPREHENSIVE INCOME	130	182
OTHER COMPREHENSIVE INCOME	199	277
Comprehensive Income	$39,006	$38,994

Consolidated_Statement_of_Cash

Consolidated Statement of Cash Flows (Unaudited) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
WGL Holdings, Inc.	'	'
OPERATING ACTIVITIES	'	'
Net income (loss)	$18,959	$52,718
ADJUSTMENTS TO RECONCILE NET INCOME TO NET CASH PROVIDED BY (USED IN) OPERATING ACTIVITIES	'	'
Depreciation and amortization	26,590	27,304
Amortization of:	'	'
Other regulatory assets and liabilities-net	360	238
Debt related costs	26	216
Deferred income taxes-net	4,953	26,486
Accrued/deferred pension cost	7,796	7,965
Compensation expense related to equity awards	691	1,214
Provision for doubtful accounts	1,920	4,010
Impairment loss on Springfield Operations Center	770	0
Other non-cash charges (credits)-net	1,165	1,569
CHANGES IN ASSETS AND LIABILITIES	'	'
Accounts receivable and unbilled revenues-net	-282,888	-197,868
Gas costs and other regulatory assets/liabilities-net	52,125	54,297
Storage gas	105,423	2,646
Prepaid taxes	-37,982	-1,220
Other prepayments	-8,280	-10,293
Accounts payable and other accrued liabilities	44,217	42,496
Wages payable	-1,640	-2,012
Customer deposits and advance payments	2,081	-9,765
Unamortized Investment Tax Credits	28,490	6,518
Accrued taxes	13,812	9,092
Accrued interest	7,063	7,374
Other current assets	3,558	-4,114
Other current liabilities	-9,183	-3,455
Deferred gas costs-net	-110,692	-50,159
Deferred assets-other	-7,789	14,939
Deferred liabilities-other	13,322	1,017
Derivatives-deferred	121,421	1,165
Other-net	-8,897	655
Net Cash Provided by (Used in) Operating Activities	-12,609	-16,967
FINANCING ACTIVITIES	'	'
Common stock issued	0	281
Long-term debt issued	75,252	1,491
Long-term debt retired	-37,000	0
Notes payable issued (retired)-net	70,200	113,700
Dividends on common stock and preferred stock	-22,089	-19,688
Other financing activities-net	1,415	-1,129
Net Cash Provided by (Used in) Financing Activities	87,778	94,655
INVESTING ACTIVITIES	'	'
Capital expenditures (excluding AFUDC)	-58,305	-75,917
Investments in non-utility interests	-15,532	-8,116
Distributions from non-utility interests	0	666
Net Cash Used in Investing Activities	-73,837	-83,367
INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	1,332	-5,679
Cash and Cash Equivalents at Beginning of Year	3,478	10,263
Cash and Cash Equivalents at End of Period	4,810	4,584
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION	'	'
Income taxes paid (refunded)- net	7,376	200
Interest paid	1,789	1,559
SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING AND FINANCING ACTIVITIES	'	'
Project debt financing activities - net	253	1,491
Capital expenditure accruals included in accounts payable and other accrued liabilities	16,058	18,781
Dividends paid in common stock	1,312	1,287
Washington Gas Light Company	'	'
OPERATING ACTIVITIES	'	'
Net income (loss)	38,807	38,717
ADJUSTMENTS TO RECONCILE NET INCOME TO NET CASH PROVIDED BY (USED IN) OPERATING ACTIVITIES	'	'
Depreciation and amortization	25,041	26,488
Amortization of:	'	'
Other regulatory assets and liabilities-net	137	710
Debt related costs	187	487
Deferred income taxes-net	10,170	25,954
Accrued/deferred pension cost	7,682	7,899
Compensation expense related to equity awards	1,574	1,152
Provision for doubtful accounts	1,815	3,208
Impairment loss on Springfield Operations Center	770	0
Other non-cash charges (credits)-net	1,284	1,610
CHANGES IN ASSETS AND LIABILITIES	'	'
Accounts receivable and unbilled revenues-net	-222,084	-152,234
Gas costs and other regulatory assets/liabilities-net	52,125	54,297
Storage gas	8,078	9,500
Other prepayments	-8,009	-6,924
Accounts payable and other accrued liabilities	59,119	6,982
Wages payable	-1,497	-1,463
Customer deposits and advance payments	2,081	-12,915
Accrued taxes	9,616	8,087
Accrued interest	7,063	7,374
Other current assets	-1,894	1,798
Other current liabilities	-1,766	-2,728
Deferred gas costs-net	-110,692	-33,620
Deferred assets-other	8,344	15,096
Deferred liabilities-other	1,866	-5,764
Derivatives-deferred	84,424	-11,720
Other-net	-1,635	-30
Net Cash Provided by (Used in) Operating Activities	-27,394	-18,039
FINANCING ACTIVITIES	'	'
Long-term debt issued	75,252	1,491
Long-term debt retired	-37,000	0
Notes payable issued (retired)-net	63,500	96,200
Dividends on common stock and preferred stock	-19,373	-18,912
Other financing activities-net	-595	-677
Net Cash Provided by (Used in) Financing Activities	81,784	78,102
INVESTING ACTIVITIES	'	'
Capital expenditures (excluding AFUDC)	-54,388	-60,063
Net Cash Used in Investing Activities	-54,388	-60,063
INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	2	0
Cash and Cash Equivalents at Beginning of Year	0	1
Cash and Cash Equivalents at End of Period	2	1
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION	'	'
Income taxes paid (refunded)- net	7,200	0
Interest paid	1,676	1,461
SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING AND FINANCING ACTIVITIES	'	'
Project debt financing activities - net	253	1,491
Capital expenditure accruals included in accounts payable and other accrued liabilities	$11,471	$17,935

Accounting_Policies

Accounting Policies	3 Months Ended
	Dec. 31, 2013
Accounting Policies [Abstract]	'
Organization Consolidation And Presentation Of Financial Statements Disclosure Text Block	'
	NOTE 1. ACCOUNTING POLICIES
	Basis of Presentation
	WGL Holdings, Inc. (WGL) is a holding company that owns all of the shares of common stock of Washington Gas Light Company (Washington Gas), a regulated natural gas utility, and all of the shares of common stock of Washington Gas Resources Corporation (Washington Gas Resources), Hampshire Gas Company (Hampshire) and Crab Run Gas Company. Washington Gas Resources owns all of the shares of common stock of four non-utility subsidiaries that include Washington Gas Energy Services, Inc. (WGEServices), Washington Gas Energy Systems, Inc. (WGESystems), WGL Midstream, Inc. (WGL Midstream) and WGSW, Inc. (WGSW). Except where the content clearly indicates otherwise, “WGL,” “we,” “us” or “our” refers to the holding company or the consolidated entity of WGL Holdings, Inc. and all of its subsidiaries. Unless otherwise noted, these notes apply equally to WGL and Washington Gas.
	The interim consolidated financial statements 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 consolidated financial statements and accompanying notes should be read in conjunction with the combined Annual Report on Form 10-K for WGL and Washington Gas for the fiscal year ended September 30, 2013. Due to the seasonal nature of our businesses, the results of operations for the periods presented in this report are not necessarily indicative of actual results for the full fiscal years ending September 30, 2014 and 2013 of either WGL or Washington Gas.
	The accompanying unaudited financial statements for WGL and Washington Gas reflect all normal recurring adjustments that are necessary, in our opinion, to present fairly the results of operations in accordance with GAAP. Certain reclassifications have been recast to conform to current year presentation.
	For a complete description of our accounting policies, refer to Note 1 of the Notes to Consolidated Financial Statements of the combined Annual Report on Form 10-K for WGL and Washington Gas for the fiscal year ended September 30, 2013.
	Storage Gas Valuations
	For Washington Gas and WGEServices, storage gas inventory is stated at the lower-of-cost or market as determined using the first-in, first-out method. For WGL Midstream, storage gas inventory is stated at the lower-of-cost or market using the weighted average cost method. For the three months ended December 31, 2013, WGL Midstream recorded a minimal reduction to net income for lower of cost or market adjustments. For the three months ended December 31, 2012, WGL Midstream recorded a reduction to net income of $8.4 million for lower-of cost or market adjustments.
	In conjunction with optimizing Washington Gas' storage capacity, storage gas inventory may be subject to lower-of-cost or market adjustments. For the three months ended December 31, 2013 and 2012, Washington Gas did not record any lower-of-cost or market adjustments related to its storage gas inventory.
	Accounting Standards Adopted in the Current Fiscal Year
	Balance Sheet Offsetting. In December 2011, the FASB issued ASU 2011-11, Disclosures about Offsetting Assets and Liabilities. This standard amends the disclosure requirements on offsetting in ASC Topic 210 by requiring enhanced disclosures about financial instruments and derivative instruments that are either: (i) offset in accordance with existing guidance or (ii) subject to an enforceable master netting arrangement or similar agreement, irrespective of whether they are offset on the balance sheet. In January 2013, the FASB issued ASU 2013-01, Clarifying the Scope of the Disclosures about Offsetting Assets and Liabilities. ASU 2013-01 limits the scope of the required disclosures to derivatives, repurchase agreements and securities borrowing and securities lending transactions. The disclosures are required irrespective of whether the transactions are offset in the statement of financial position. ASU 2011-11 and ASU 2013-01 were effective for us on October 1, 2013. As a result of the standard, additional disclosures regarding master netting arrangements were added to Note 8 - Derivatives and Weather-Related Instruments. The adoption of these standards did not otherwise affect our financial statements.
	Comprehensive Income. In February 2013, the FASB issued ASU 2013-02, Comprehensive Income (Topic 220): Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income. This standard requires entities to (i) present information about reclassification adjustments from accumulated other comprehensive income (AOCI) to net income in their entirety – the effect on the reclassification on each affected net income line item and (ii) for AOCI reclassification items that are not reclassified in their entirety into net income – a cross-reference to other required US GAAP disclosures. The reclassification information may be presented in a single note or on the face of the financial statements. ASU 2013-02 was effective for us on October 1, 2013. As a result of this standard, we have presented information about reclassification adjustments out of accumulated other comprehensive income in a new footnote to the financial statements. Refer to Note 15 – Changes in Accumulated Other Comprehensive Income for the details of this disclosure. The adoption of this standard did not otherwise affect our financial statements.
	Other Newly Issued Accounting Standards
	Income Taxes. In July 2013, the FASB issued ASU 2013-11, Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists. This standard amends the disclosure requirement of ASC Topic 740 by requiring an unrecognized tax benefit, or a portion of an unrecognized tax benefit be presented in the financial statements as a reduction to a deferred tax asset in most circumstances. ASU 2013-11 will be effective for us on October 1, 2014. We do not expect the adoption of this standard to have a material effect on our financial statements.

Accounts_Payable_and_Other_Acc

Accounts Payable and Other Accrued Liabilities	3 Months Ended
	Dec. 31, 2013
Accounts Payable and Other Accrued Liabilities [Abstract]	'
Accounts Payable and Other Accrued Liabilities	'
	NOTE 2. ACCOUNTS PAYABLE AND OTHER ACCRUED LIABILITIES
	The tables below provide details for the amounts included in “Accounts payable and other accrued liabilities” on the balance sheets for both WGL and Washington Gas.
		WGL Holdings, Inc.
		(In millions)		31-Dec-13		30-Sep-13
		Accounts payable—trade	$	277	$	216.3
		Employee benefits and payroll accruals		14.2		23.4
		Embedded derivatives and other accrued liabilities		22.7		30.9
		Total	$	313.9	$	270.6
		Washington Gas Light Company
		(In millions)		31-Dec-13		30-Sep-13
		Accounts payable—trade	$	142.7	$	99.7
		Employee benefits and payroll accruals		13.5		21.4
		Embedded derivatives and other accrued liabilities		15.3		11.7
		Total	$	171.5	$	132.8

ShortTerm_Debt

Short-Term Debt	3 Months Ended
	Dec. 31, 2013
Short-Term Debt [Abstract]	'
Short-Term Debt	'
	NOTE 3. SHORT-TERM DEBT
	WGL and Washington Gas satisfy their short-term financing requirements through the sale of commercial paper or through bank borrowings. Due to the seasonal nature of the regulated utility and retail energy-marketing segments, 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. WGL's policy is to maintain bank credit facilities in amounts equal to or greater than the expected maximum commercial paper position. The following is a summary of committed credit available at December 31, 2013 and September 30, 2013.
	Committed Credit Available (In millions)
	As of December 31, 2013		WGL Holdings, Inc. (b)		Washington Gas		Total Consolidated
	Committed credit agreements
	Unsecured revolving credit facility, expires April 3, 2017(a)	$	450	$	350	$	800
	Less: Commercial Paper		-255.3		-188		-443.3
	Net committed credit available	$	194.7	$	162	$	356.7
	As of September 30, 2013		WGL Holdings, Inc. (b)		Washington Gas		Total Consolidated
	Committed credit agreements
	Unsecured revolving credit facility, expires April 3, 2017(a)	$	450	$	350	$	800
	Less: Commercial Paper		-248.6		-124.5		-373.1
	Net committed credit available	$	201.4	$	225.5	$	426.9
	(a)Both WGL and Washington Gas have the right to request extensions with the banks’ approval. WGL's revolving credit facility permits it to borrow an additional $100 million, with the banks’ approval, for a total of $550 million. Washington Gas’ revolving credit facility permits it to borrow an additional $100 million, with the banks’ approval, for a total of $450 million.
	(b)WGL Holdings, Inc. includes all subsidiaries other than Washington Gas Light Company.
	At December 31, 2013 and September 30, 2013, WGL and its subsidiaries had outstanding notes payable in the form of commercial paper from revolving credit facilities of $443.3 million and $373.1 million, respectively, at a weighted average interest rate of 0.18% and 0.19%, respectively. At December 31, 2013 and September 30, 2013, there were no outstanding bank loans from WGL's or Washington Gas' revolving credit facilities.

LongTerm_Debt

Long-Term Debt	3 Months Ended
	Dec. 31, 2013
Long-Term Debt [Abstract]	'
Long-Term Debt	'
	Washington Gas issues unsecured Medium-Term Notes (MTNs) and private placement notes with individual terms regarding interest rates, maturities and call or put options. These notes can have maturity dates of one or more years from the date of issuance.
	At December 31, 2013 and September 30, 2013, Washington Gas had the capacity under a shelf registration to issue up to $375.0 million and $450.0 million, respectively, of additional MTNs. At December 31, 2013 and September 30, 2013, outstanding MTNs and private placement notes were $621.0 million and $583.0 million at a weighted average interest rate of 5.86% and 5.91%, respectively.
	The following table shows MTN and private placement issuances and retirements for the quarter ended December 31, 2013.
	MTN and Private Placement Issuances and Retirements
	($ In millions)	Principal		Interest Rate	Nominal Maturity Date
	Quarter Ended December 31, 2013
	Issuances:
	12/5/13	$	75	5.00%(a)	12/15/43
	Total	$	75
	Retirements:
	11/7/13	$	37	4.88%	11/7/13
	Total	$	37
	(a)The estimated effective cost of the issued notes, including consideration of issuance fees and hedge costs, is 4.95%.
	There were no MTN or private placement issuances or retirements for the year ended September 30, 2013.

Common_Shareholders_Equity

Common Shareholders' Equity	3 Months Ended
	Dec. 31, 2013
Common Shareholders' Equity [Abstract]	'
Common Shareholders' Equity	'
	NOTE 5. COMMON SHAREHOLDERS' EQUITY
	The tables below reflect the components of “Common shareholders' equity” for WGL and “Common shareholder's equity” for Washington Gas for the three months ended December 31, 2013.
	WGL Holdings, Inc.
	Components of Common Shareholders’ Equity
	(In thousands)	Common Stock Amount		Paid-In Capital		Retained Earnings			Accumulated Other Comprehensive Loss, Net of Taxes		Total
	Balance at September 30, 2013	$	574,461	$	10,710	$	700,422		$	-11,048	$	1,274,545
	Net income		-		-		18,959			-		18,959
	Other comprehensive income		-		-		-			199		199
	Dividends reinvestment		1,503		-		-			-		1,503
	Stock-based compensation		1,524		-1,744		-			-		-220
	Dividends declared:
	Common stock		-		-		-21,795			-		-21,795
	Preferred stock		-		-		-330			-		-330
	Balance at December 31, 2013	$	577,488	$	8,966	$	697,256		$	-10,849	$	1,272,861
	Washington Gas Light Company
	Components of Common Shareholder's Equity
	(In thousands)	Common Stock Amount		Paid-In Capital			Retained Earnings		Accumulated Other Comprehensive Loss, Net of Taxes		Total
	Balance at September 30, 2013	$	46,479	$	477,968		$	511,184	$	-11,048	$	1,024,583
	Net income		-		-			38,807		-		38,807
	Other comprehensive income		-		-			-		199		199
	Stock-based compensation		-		-266			-		-		-266
	Dividends declared:
	Common stock		-		-			-19,075		-		-19,075
	Preferred stock		-		-			-330		-		-330
	Balance at December 31, 2013	$	46,479	$	477,702		$	530,586	$	-10,849	$	1,043,918
	WGL had 51,841,665 and 51,774,204 shares issued of common stock at December 31, 2013 and September 30, 2013, respectively. Washington Gas had 46,479,536 shares issued of common stock at both December 31, 2013 and September 30, 2013.

Earnings_Per_Share

Earnings Per Share	3 Months Ended
	Dec. 31, 2013
Earnings Per Share [Abstract]	'
Earnings Per Share	'
	NOTE 6. EARNINGS PER SHARE
	Basic EPS is computed by dividing net income by the weighted average number of common shares outstanding during the reported period. Diluted EPS assumes the issuance of common shares pursuant to stock-based compensation plans at the beginning of the applicable period unless the effect of such issuance would be anti-dilutive. The following table reflects the computation of our basic and diluted EPS for the three months ended December 31, 2013 and 2012.
		Basic and Diluted EPS
		(in thousands, except per share data)		Net Income Applicable to Common Stock	Shares		Per Share Amount
		Three Months Ended December 31, 2013
		Basic EPS	$	18,629	51,816	$	0.36
		Stock-based compensation plans		-	11
		Diluted EPS	$	18,629	51,827	$	0.36
		Three Months Ended December 31, 2012
		Basic EPS	$	52,388	51,631	$	1.01
		Stock-based compensation plans		-	57
		Diluted EPS	$	52,388	51,688	$	1.01
	There were no anti-dilutive shares for the three months ended December 31, 2013 and December 31, 2012.

Income_Taxes

Income Taxes	3 Months Ended
	Dec. 31, 2013
Income Taxes [Abstract]	'
Income Taxes	'
	NOTE 7. INCOME TAXES
	As of December 31, 2013 and September 30, 2013, our uncertain tax positions were approximately $25.6 million and $25.1 million, respectively, primarily due to the change in tax accounting for repairs. If the amounts of unrecognized tax benefits are eventually realized, it would not materially impact the effective tax rate. It is reasonably possible that the amount of the unrecognized tax benefit with respect to some of WGL's and Washington Gas' uncertain tax positions will significantly increase or decrease in the next 12 months, however at this time an estimate of the range of reasonably possible outcomes cannot be determined.
	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 December 31, 2013 and 2012, we accrued no expense for interest on uncertain tax positions. At both December 31, 2013 and September 30, 2013, we had a total accrual of $0.1 million of interest expense related to uncertain tax positions included in other deferred credits in the accompanying balance sheets.
	Washington Gas charged the Maryland portion of the Medicare Part D (Med D) regulatory asset to tax expense during the fiscal year ended September 30, 2012 based on positions taken by the Maryland Public Service Commission (PSC of MD) in Washington Gas' rate case during that fiscal year that did not permit recovery. Washington Gas received an order during the three months ended December 31, 2013 in its recent rate case from the PSC of MD that will allow recovery of the Med D Regulatory Asset. Therefore, the tax benefit has been recognized to reinstate the regulatory asset which results in a decrease in the effective rate for the fiscal year ended September 30, 2014. Under ASC 740 – Income Taxes, the full impact of this item is being recognized and makes a significant change to WGL's and Washington Gas' effective tax rate for the three months ended December 31, 2013. The Med D adjustment results in an effective tax rate at December 31, 2013 of 22.4%, although WGL currently expects to have an effective tax rate of approximately 34.9%for the entire fiscal year ended September 30, 2014. The Med D adjustment results in an effective tax rate for Washington Gas of 30.9% at December 31, 2013, although Washington Gas currently expects to have an effective tax rate of approximately 35.0% for the entire fiscal year ended September 30, 2014.

Derivative_and_Weather_Related

Derivative and Weather Related Instruments	3 Months Ended
	Dec. 31, 2013
Derivative and Weather-Related Instruments [Abstract]	'
Derivative and Weather-Related Instruments	'
	NOTE 8. DERIVATIVE AND WEATHER-RELATED INSTRUMENTS
	DERIVATIVE INSTRUMENTS
	Regulated Utility Operations
	Washington Gas enters into contracts related to the sale and purchase of natural gas that qualify as derivative instruments and are accounted for under ASC Topic 815. These derivative instruments are recorded at fair value on our balance sheet and Washington Gas does not 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 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 locking in operating margins that Washington Gas will ultimately realize. The derivatives used under this program are subject to mark-to-market accounting treatment while the capacity and transportation resources are not.
	Regulatory sharing mechanisms allow the profit from these transactions to be shared between Washington Gas' shareholders and customers; therefore, any changes in fair value are recorded through earnings, or as regulatory assets or liabilities to the extent that gains and losses associated with these derivative instruments will be included in the rates charged to customers when they are realized. Valuation changes for the portion of net profits to be retained for shareholders may cause significant period-to-period volatility in earnings from unrealized gains and losses. This volatility does not change the locked-in operating margins that Washington Gas expects to ultimately realize from these transactions through the use of its storage and transportation capacity resources.
	All physically and financially settled contracts under our asset optimization program are reported on a net basis in the statements of income 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 December 31, 2013 was a loss of $19.8 million including an unrealized loss of $26.2 million. During the three months ended December 31, 2012 we recorded a loss of $5.0 million including an unrealized loss of $8.7 million.
	Managing Price Risk. To manage price risk associated with acquiring natural gas supply for utility customers, Washington Gas enters into forward contracts, option contracts, financial contracts and other contracts, as authorized by its regulators. These instruments are accounted for as derivative instruments. 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.
	Managing Interest-Rate Risk. Washington Gas utilizes derivative instruments that are designed to minimize the risk of interest-rate volatility associated with planned issuances of debt securities. Any gains and losses associated with these types of derivatives are recorded as regulatory liabilities or assets, respectively, and amortized in accordance with regulatory requirements, typically over the life of the newly issued debt.
	Non-Utility Operations
	WGEServices enters into certain derivative contracts as part of managing the price risk associated with the sale and purchase of natural gas and electricity. WGL Midstream enters into derivative contracts for the purpose of optimizing its storage and transportation capacity as well as managing the transportation and storage assets on behalf of third parties. Washington Gas Resources has warrants to purchase stock from ASD Holdings, Inc., that are accounted for as derivative instruments. Derivative instruments are recorded at fair value on our consolidated balance sheets. As the storage and transportation capacity utilized by WGL Midstream are not considered to be derivative instruments, they are not recorded at fair value on our consolidated balance sheets. WGEServices, WGL Midstream and Washington Gas Resources do not designate these derivatives as hedges under ASC Topic 815; therefore, changes in the fair value of these derivative instruments are reflected in the earnings of our non-utility operations and may cause significant period-to-period volatility in earnings.
	Consolidated Operations
	Reflected in the tables below is information for WGL as well as Washington Gas. The information for WGL includes derivative instruments for both utility and non-utility operations.
	At December 31, 2013 and September 30, 2013, respectively, the absolute notional amounts of our derivatives are as follows:
		Absolute Notional Amounts
		of Open Positions on Derivative Instruments
		As of December 31, 2013	Notional Amounts
		Derivative transactions	WGL Holdings, Inc.			Washington Gas Light Company
		Natural Gas (In millions of therms)
		Asset optimization		12,771.70			11,010.00
		Retail sales		83			-
		Other risk-management activities		1,763.50			1,442.50
		Electricity (In millions of kWhs)
		Retail sales		4,684.00			-
		Other risk-management activities		19,151.00			-
		Warrants (In millions of shares)		4.6			-
	Absolute Notional Amounts
	of Open Positions on Derivative Instruments
	As of September 30, 2013		Notional Amounts
	Derivative transactions	WGL Holdings, Inc.			Washington Gas Light Company
	Natural Gas (In millions of therms)
	Asset optimization		13,289.60			11,115.80
	Retail sales		98.9			-
	Other risk-management activities		1,803.60			1,455.70
	Electricity (In millions of kWhs)
	Retail sales		4,790.20			-
	Other risk-management activities		17,647.90			-
	Warrants (In millions of shares)		4.6			-
	Interest Rate Swaps (In millions of dollars)(a)		75			75
	(a) The fair value of our interest rate swaps was minimal at 9/30/13.
	The following tables present the balance sheet classification for all derivative instruments as of December 31, 2013 and September 30, 2013.
	WGL Holdings, Inc.
	Balance Sheet Classification of Derivative Instruments
	(In millions)
	As of December 31, 2013	Gross Derivative Assets		Gross Derivative Liabilities		Netting of Collateral		Total(a)
	Current Assets—Derivatives	$	35.6	$	-12.1	$	-	$	23.5
	Deferred Charges and Other Assets—Derivatives		9.2		-		-		9.2
	Accounts Payable and Other Accrued Liabilities		0.4		-		-		0.4
	Current Liabilities—Derivatives		10.3		-54.2		2.5		-41.4
	Deferred Credits—Derivatives		27.5		-275.7		2.6		-245.6
	Total	$	83	$	-342	$	5.1	$	-253.9
	As of September 30, 2013
	Current Assets—Derivatives	$	57.3	$	-19.3	$	-2.7	$	35.3
	Deferred Charges and Other Assets—Derivatives		57.4		-31.1		-		26.3
	Accounts Payable and Other Accrued Liabilities		1.5		-		-		1.5
	Current Liabilities—Derivatives		4.1		-53.4		0.9		-48.4
	Deferred Credits—Derivatives		-		-144		2.7		-141.3
	Total	$	120.3	$	-247.8	$	0.9	$	-126.6
	Washington Gas Light Company
	Balance Sheet Classification of Derivative Instruments
	(In millions)
	As of December 31, 2013	Gross Derivative Assets		Gross Derivative Liabilities		Netting of Collateral		Total(a)
	Current Assets—Derivatives	$	10.9	$	-4.7	$	-	$	6.2
Deferred Charges and Other Assets—Derivatives		-		-		-		-
Current Liabilities—Derivatives		7.4		-34.1		-		-26.7
Deferred Credits—Derivatives		27.2		-215.8		-		-188.6
Total	$	45.5	$	-254.6	$	-	$	-209.1
As of September 30, 2013
Current Assets—Derivatives	$	19.3	$	-12.3	$	-2.7	$	4.3
Deferred Charges and Other Assets—Derivatives		47.2		-31.1		-		16.1
Current Liabilities—Derivatives		1.5		-26.2		-		-24.7
Deferred Credits—Derivatives		-		-106.1		-		-106.1
Total	$	68	$	-175.7	$	-2.7	$	-110.4
(a)WGL 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 815. All recognized derivative contracts and associated financial collateral subject to a master netting arrangement or similar that is eligible for offset under ASC 815 have been presented net in the balance sheet.
The following table presents all gains and losses associated with derivative instruments for the three months ended December 31, 2013 and 2012.
	Gains and Losses on Derivative Instruments
			WGL Holdings, Inc.				Washington Gas Light Company
	(In millions)
	Three Months Ended December 31,		2013		2012		2013		2012
	Recorded to income
	Operating revenues—non-utility	$	-48.5	$	12.2	$	-	$	-
	Utility cost of gas		-27.3		-7.2		-27.3		-7.2
	Non-utility cost of energy-related sales		16.3		-7.5		-		-
	Other income-net		0.1		0.1		-		-
	Recorded to regulatory assets
	Gas costs		-78.3		-11.9		-78.3		-11.9
	Total	$	-137.7	$	-14.3	$	-105.6	$	-19.1
Collateral
WGL 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 parental guarantees may be required to be posted to or obtained from counterparties in order to mitigate credit risk related to both derivatives and non-derivative positions.  Under WGL's 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 sheet. At December 31, 2013, Washington Gas, WGEServices and WGL Midstream posted $3.8 million, $12.6 million and $9.6 million, respectively, of collateral deposits with counterparties that were not offset against open and settled derivative contracts. At September 30, 2013, Washington Gas, WGEServices and WGL Midstream posted $3.0 million, $12.1 million and $8.1 million, respectively, of collateral deposits with counterparties that were not offset against open and settled derivative contracts. In addition, at December 31, 2013 and September 30, 2013, Washington Gas held $10.2 million and $4.6 million, respectively of cash collateral representing an obligation to counterparties that was not offset against open and settled derivative contracts. Any collateral posted that is not offset against open and settled derivative contracts is included in “Other prepayments” in the accompanying balance sheet. Collateral received and not offset against open and settled derivative contracts is included in “Customer deposits and advance payments” in the accompanying balance sheet.
Certain derivative instruments of Washington Gas, WGEServices and WGL Midstream contain contract provisions that require collateral to be posted if the credit rating of WGL falls below certain levels or if counterparty exposure to WGEServices or WGL Midstream exceeds a certain level. Due to counterparty exposure levels, at December 31, 2013, WGEServices posted $5.1 million of collateral related to its derivative liabilities that contained credit-related contingent features. At September 30, 2013, WGEServices posted $3.6 million of collateral related to these aforementioned derivative liabilities. Washington Gas and WGL Midstream were not required to post any collateral related to its derivative liabilities that contained credit-related contingent features at December 31, 2013 or September 30, 2013. 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 December 31, 2013 and September 30, 2013, respectively.
Potential Collateral Requirements for Derivative Liabilities
with Credit-risk-Contingent Features
(In millions)	WGL Holdings, Inc.			Washington Gas Light Company
31-Dec-13
Derivative liabilities with credit-risk-contingent features	$	63.5		$	38
Maximum potential collateral requirements		27			3.9
30-Sep-13
Derivative liabilities with credit-risk-contingent features	$	77		$	44.7
Maximum potential collateral requirements		33.6			1.7
Washington Gas, WGEServices and WGL Midstream do not enter into derivative contracts for speculative purposes.
Concentration of Credit Risk
We are exposed to credit risk from derivative instruments that reflect certain agreements with wholesale counterparties. Our credit policies are designed to mitigate this credit risk by requiring credit enhancements including, but not limited to, letters of credit, parent guarantees and cash collateral when deemed necessary. For certain counterparties or their guarantors that meet our specified creditworthiness criteria, Washington Gas, WGEServices and WGL Midstream grant unsecured credit, which we continuously monitor. Additionally, Washington Gas, WGEServices and WGL Midstream have separate agreements with wholesale counterparties that contain netting provisions to allow offsetting of the receivable and payable exposure related to each counterparty. At December 31, 2013, two counterparties represented over 10% of Washington Gas' credit exposure to wholesale derivative counterparties for a total credit risk of $4.4 million; four counterparties represented over 10% of WGEServices' credit exposure to wholesale counterparties for a total credit risk of $0.7 million; and two counterparties represented over 10% of WGL Midstream's credit exposure to wholesale counterparties for a total credit risk of $11.0 million.
WEATHER-RELATED INSTRUMENTS
Washington Gas did not use any weather-related instruments during the three months ended December 31, 2013. During the three months ended December 31, 2012, Washington Gas used Heating Degree Day (HDD) weather-related instruments to manage its financial exposure to variations from normal weather in the District of Columbia. Under these contracts, Washington Gas purchased protection against net revenue shortfalls due to warmer-than-normal weather and sold to its counterparty the right to receive the benefit when weather is colder than normal. Washington Gas elected to value all weather-related instruments at fair value.
Gains and losses associated with Washington Gas' weather-related instruments are recorded to “Operation and maintenance” expense. During the three months ended December 31, 2012, Washington Gas recorded a pre-tax net gain of $ 0.6 million related to weather instruments.
WGEServices utilizes weather-related instruments for managing the financial effects of weather risks. These instruments cover a portion of WGEServices' estimated revenue or energy-related cost exposure to variations in heating or cooling degree days. These contracts provide for payment to WGEServices of a fixed-dollar amount for every degree day over or under specific levels during the calculation period depending upon the type of contract executed. For the three months ended December 31, 2013 and December 31, 2012, WGEServices recorded a pre-tax loss of $1.1 million and a pre-tax gain of $0.4 million, respectively, related to these contracts.

Fair_Value_Measurements

Fair Value Measurements	3 Months Ended
	Dec. 31, 2013
Fair Value Measurements [Abstract]	'
Fair Value Measurements	'
	NOTE 9. FAIR VALUE MEASUREMENTS
	Recurring Basis
	We measure the fair value of our financial assets and liabilities using a combination of the income and market approach in accordance with ASC Topic 820. These financial assets and liabilities primarily consist of (i) derivatives recorded on our balance sheet under ASC Topic 815, (ii) weather-related instruments and (iii) 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 WGL. We value our derivative contracts based on an “in-exchange” premise, and 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. Level 1 assets and liabilities primarily include exchange traded derivatives and securities.
	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 December 31, 2013 and September 30, 2013, Level 2 financial assets and liabilities included energy-related derivatives such as financial contracts, options and physical forward 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, annualized volatilities of natural gas prices, and electricity congestion 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.
	Our Risk Analysis and Mitigation (RA&M) Group determines the valuation policies and procedures.  The RA&M Group reports to WGL's Chief Financial Officer. In accordance with WGL's valuation policy, we may utilize a variety of valuation methodologies to fair value Level 3 derivative contracts including internally developed valuation inputs and pricing models.  The prices used in our valuations are corroborated using multiple pricing sources, and we periodically conduct assessments to determine whether each valuation model is appropriate for its intended purpose. The RA&M Group also evaluates changes in fair value measurements on a daily basis.
	At December 31, 2013 and September 30, 2013, Level 3 derivative assets and liabilities included: (i) physical contracts valued with significant basis adjustments to observable market data when delivery is to inactive market locations; (ii) long-dated positions where observable pricing is not available over the life of the contract; (iii) contracts valued using historical volatility assumptions; (iv) valuations using indicative broker quotes for inactive market locations and (v) non-publicly traded stock warrants.
	The following tables set forth financial instruments recorded at fair value as of December 31, 2013 and September 30, 2013, 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.
	WGL Holdings, Inc.
	Fair Value Measurements Under the Fair Value Hierarchy
	(In millions)		Level 1		Level 2		Level 3		Total
	At December 31, 2013
	Assets
	Natural gas related derivatives	$	-	$	44.2	$	17.7	$	61.9
	Electricity related derivatives		-		0.1		19.8		19.9
	Warrants		-		-		1.2		1.2
	Total Assets	$	-	$	44.3	$	38.7	$	83
	Liabilities
	Natural gas related derivatives	$	-	$	-34.2	$	-282.2	$	-316.4
	Electricity related derivatives		-		-4.1		-21.5		-25.6
	Total Liabilities	$	-	$	-38.3	$	-303.7	$	-342
	At September 30, 2013
	Assets
	Natural gas related derivatives	$	-	$	72.3	$	21.5	$	93.8
	Electricity related derivatives		-		-		25.4		25.4
	Warrants		-		-		1.1		1.1
	Total Assets	$	-	$	72.3	$	48	$	120.3
	Liabilities
	Natural gas related derivatives	$	-	$	-41.1	$	-176.7	$	-217.8
	Electricity related derivatives		-		-7		-23		-30
	Total Liabilities	$	-	$	-48.1	$	-199.7	$	-247.8
	Washington Gas Light Company
	Fair Value Measurements Under the Fair Value Hierarchy
	(In millions)		Level 1		Level 2		Level 3		Total
	At December 31, 2013
	Assets
	Natural gas related derivatives	$	-	$	30.6	$	14.9	$	45.5
	Total Assets	$	-	$	30.6	$	14.9	$	45.5
	Liabilities
	Natural gas related derivatives	$	-	$	-19.7	$	-234.9	$	-254.6
	Total Liabilities	$	-	$	-19.7	$	-234.9	$	-254.6
	At September 30, 2013
	Assets
	Natural gas related derivatives	$	-	$	51	$	17	$	68
	Total Assets	$	-	$	51	$	17	$	68
	Liabilities
	Natural gas related derivatives	$	-	$	-25.1	$	-150.6	$	-175.7
	Total Liabilities	$	-	$	-25.1	$	-150.6	$	-175.7
	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, as of December 31, 2013 and September 30, 2013.
	Quantitative Information about Level 3 Fair Value Measurements
		Net Fair Value December 31, 2013	Valuation Techniques	Unobservable Inputs	Range
	WGL Holdings, Inc.	(In millions)
	Natural gas related derivatives	($264.50)	Discounted Cash Flow	Natural Gas Basis Price (per dekatherm)	($1.594) -	$3.21
			Option Model	Natural Gas Basis Price (per dekatherm)	($0.372) -	$1.54
				Annualized Volatility of Spot Market Natural Gas	34.6% -	276.60%
	Electricity related derivatives	($1.70)	Discounted Cash Flow	Electricity Congestion Price (per megawatt hour)	($1.888) -	$66.20
			Load-Shaping Option Model	Electricity Congestion Price (per megawatt hour)	$31.965 -	$71.19
	Washington Gas Light Company
	Natural gas related derivatives	($220.00)	Discounted Cash Flow	Natural Gas Basis Price (per dekatherm)	($1.594) -	$3.21
			Option Model	Natural Gas Basis Price (per dekatherm)	$0.027 -	$1.54
Annualized Volatility of Spot Market Natural Gas				46.8% -	276.60%
Quantitative Information about Level 3 Fair Value Measurements
	Net Fair Value September 30, 2013	Valuation Techniques	Unobservable Inputs	Range
WGL Holdings, Inc.	(In millions)
Natural gas related derivatives	($155.20)	Discounted Cash Flow	Natural Gas Basis Price (per dekatherm)	($1.780) -	$2.21
		Option Model	Natural Gas Basis Price (per dekatherm)	($0.181) -	$0.63
			Annualized Volatility of Spot Market Natural Gas	34.6% -	276.60%
Electricity related derivatives	$2.40	Discounted Cash Flow	Electricity Congestion Price (per megawatt hour)	($1.995) -	$64.15
		Washington Gas Light Company
Natural gas related derivatives	($133.60)	Discounted Cash Flow	Natural Gas Basis Price (per dekatherm)	($1.780) -	$2.21
		Option Model	Natural Gas Basis Price (per dekatherm)	$0.024 -	$0.63
			Annualized Volatility of Spot Market Natural Gas	46.8% -	276.60%
The following tables are a summary of the changes in the fair value of our 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 December 31, 2013 and 2012, respectively.
WGL Holdings, Inc. Reconciliation of Fair Value Measurements Using Significant Level 3 Inputs
(In millions)		Natural Gas Related Derivatives		Electricity Related Derivatives		Weather Related Instruments		Warrants		Total
Three Months Ended December 31, 2013
Balance at October 1, 2013	$	-155.2	$	2.4	$	-	$	1.1	$	-151.7
Realized and unrealized gains (losses)
Recorded to income		-46.7		-7.9		-		0.1		-54.5
Recorded to regulatory assets - gas costs		-72		-		-		-		-72
Purchases		-		1.4		-		-		1.4
Settlements		9.4		2.4		-		-		11.8
Balance at December 31, 2013	$	-264.5	$	-1.7	$	-	$	1.2	$	-265
WGL Holdings, Inc. Reconciliation of Fair Value Measurements Using Significant Level 3 Inputs
(In millions)		Natural Gas Related Derivatives		Electricity Related Derivatives		Weather Related Instruments		Warrants		Total
Three Months Ended December 31, 2012
Balance at October 1, 2012	$	39.6	$	2.8	$	-0.5	$	0.9	$	42.8
Realized and unrealized gains (losses)
Recorded to income		-8.6		-10.9		0.6		0.1		-18.8
Recorded to regulatory assets - gas costs		-12.1		-		-		-		-12.1
Purchases		-		2.5		-		-		2.5
Settlements		2.6		10.2		-		-		12.8
Balance at December 31, 2012	$	21.5	$	4.6	$	0.1	$	1	$	27.2
Washington Gas Light Company Reconciliation of Fair Value Measurements Using Significant Level 3 Inputs
(In millions)		Natural Gas Related Derivatives		Electricity Related Derivatives		Weather Related Instruments		Warrants		Total
Three Months Ended December 31, 2013
Balance at October 1, 2013	$	-133.6	$	-	$	-	$	-	$	-133.6
Realized and unrealized gains (losses)
Recorded to income		-23.4		-		-		-		-23.4
Recorded to regulatory assets - gas costs		-72		-		-		-		-72
Settlements		9		-		-		-		9
Balance at December 31, 2013	$	-220	$	-	$	-	$	-	$	-220
Washington Gas Light Company Reconciliation of Fair Value Measurements Using Significant Level 3 Inputs
(In millions)		Natural Gas Related Derivatives		Electricity Related Derivatives		Weather Related Instruments		Warrants		Total
Three Months Ended December 31, 2012
Balance at October 1, 2012	$	35.6	$	-	$	-0.5	$	-	$	35.1
Realized and unrealized gains (losses)
Recorded to income		-7.7		-		0.6		-		-7.1
Recorded to regulatory assets - gas costs		-12.1		-		-		-		-12.1
Settlements		2		-		-		-		2
Balance at December 31, 2012	$	17.8	$	-	$	0.1	$	-	$	17.9
Transfers between different levels of the fair value hierarchy may occur based on the level of observable inputs used to value the instruments from period to period. It is our policy to show both transfers into and out of the different levels of the fair value hierarchy at the fair value as of the beginning of the reporting period. There were no transfers in or out of Level 3 for the three months ended December 31, 2013 or 2012 for WGL or Washington Gas.
The table below sets forth the line items on the statements of income to which amounts are recorded for the three months ended December 31, 2013 and 2012, respectively, related to fair value measurements using significant Level 3 inputs.
WGL Holdings, Inc. Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements
Three Months Ended December 31, 2013
(In millions)	Natural Gas Related Derivatives		Electricity Related Derivatives		Weather Related Instruments		Warrants		Total
Operating revenues—non-utility	$	-25.8	$	-10	$	-	$	-	$	-35.8
Utility cost of gas		-23.4		-		-		-		-23.4
Other income-net		-		-		-		0.1		0.1
Non-utility cost of energy-related sales		2.5		2.1		-		-		4.6
Total	$	-46.7	$	-7.9	$	-	$	0.1	$	-54.5
WGL Holdings, Inc. Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements
Three Months Ended December 31, 2012
(In millions)	Natural Gas Related Derivatives		Electricity Related Derivatives		Weather Related Instruments		Warrants		Total
Operating revenues—non-utility	$	-0.5	$	-1.1	$	-	$	-	$	-1.6
Utility cost of gas		-7.7		-		-		-		-7.7
Other income-net		-		-		-		0.1		0.1
Non-utility cost of energy-related sales		-0.4		-9.8		-		-		-10.2
Operation and maintenance expense		-		-		0.6		-		0.6
Total	$	-8.6	$	-10.9	$	0.6	$	0.1	$	-18.8
Washington Gas Light Company Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements
Three Months Ended December 31, 2013
(In millions)	Natural Gas Related Derivatives		Electricity Related Derivatives		Weather Related Instruments		Warrants		Total
Utility cost of gas	$	-23.4	$	-	$	-	$	-	$	-23.4
Total	$	-23.4	$	-	$	-	$	-	$	-23.4
Washington Gas Light Company Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements
Three Months Ended December 31, 2012
(In millions)	Natural Gas Related Derivatives		Electricity Related Derivatives		Weather Related Instruments		Warrants		Total
Utility cost of gas	$	-7.7	$	-	$	-	$	-	$	-7.7
Operation and maintenance expense		-		-		0.6		-		0.6
Total	$	-7.7	$	-	$	0.6	$	-	$	-7.1
Unrealized gains (losses) attributable to derivative assets and liabilities measured using significant Level 3 inputs were recorded as follows, for the three months ended December 31, 2013 and 2012, respectively.
WGL Holdings, Inc. Unrealized Gains (Losses) Recorded for Level 3 Measurements
Three Months Ended December 31, 2013
(In millions)	Natural Gas Related Derivatives		Electricity Related Derivatives		Weather Related Instruments		Warrants		Total
Recorded to income
Operating revenues—non-utility	$	-25.2	$	-5	$	-	$	-	$	-30.2
Utility cost of gas		-22.9		-		-		-		-22.9
Non-utility cost of energy-related sales		2.3		1		-		-		3.3
Other income—net		-		-		-		0.1		0.1
Recorded to regulatory assets—gas costs		-71.1		-		-		-		-71.1
Total	$	-116.9	$	-4	$	-	$	0.1	$	-120.8
WGL Holdings, Inc. Unrealized Gains (Losses) Recorded for Level 3 Measurements
Three Months Ended December 31, 2012
(In millions)	Natural Gas Related Derivatives		Electricity Related Derivatives		Weather Related Instruments		Warrants		Total
Recorded to income
Operating revenues—non-utility	$	0.3	$	4.3	$	-	$	-	$	4.6
Utility cost of gas		-7.5		-		-		-		-7.5
Non-utility cost of energy-related sales		0.6		9.2		-		-		9.8
Other income-net		-		-		-		0.1		0.1
Operation and maintenance expense		-		-		0.6		-		0.6
Recorded to regulatory assets—gas costs		-11.9		-		-		-		-11.9
Total	$	-18.5	$	13.5	$	0.6	$	0.1	$	-4.3
Washington Gas Light Company Unrealized Gains (Losses) Recorded for Level 3 Measurements
Three Months Ended December 31, 2013
(In millions)	Natural Gas Related Derivatives		Electricity Related Derivatives		Weather Related Instruments		Warrants		Total
Recorded to income
Utility cost of gas	$	-22.9	$	-	$	-	$	-	$	-22.9
Recorded to regulatory assets—gas costs		-71.1		-		-		-		-71.1
Total	$	-94	$	-	$	-	$	-	$	-94
Washington Gas Light Company Unrealized Gains (Losses) Recorded for Level 3 Measurements
Three Months Ended December 31, 2012
(In millions)	Natural Gas Related Derivatives		Electricity Related Derivatives		Weather Related Instruments		Warrants		Total
Recorded to income
Utility cost of gas	$	-7.5	$	-	$	-	$	-	$	-7.5
Operation and maintenance expense		-		-		0.6		-		0.6
Recorded to regulatory assets—gas costs		-11.9		-		-		-		-11.9
Total	$	-19.4	$	-	$	0.6	$	-	$	-18.8
The following table presents the carrying amounts and estimated fair values of our financial instruments at December 31, 2013 and September 30, 2013.
WGL Holdings, Inc. Fair Value of Financial Instruments
	31-Dec-13				30-Sep-13
(In millions)	Carrying Amount		Fair Value		Carrying Amount		Fair Value
Money market funds(a)	$	6.8	$	6.8	$	6.5	$	6.5
Other short-term investments(a)	$	0.2	$	0.2	$	0.1	$	0.1
Commercial paper (b)	$	443.3	$	443.3	$	373.1	$	373.1
Long-term debt(c)	$	599.3	$	688.7	$	524.1	$	630.2
Washington Gas Light Company Fair Value of Financial Instruments
	31-Dec-13				30-Sep-13
(In millions)	Carrying Amount		Fair Value		Carrying Amount		Fair Value
Money market funds(a)	$	3.2	$	3.2	$	3.1	$	3.1
Other short-term investments(a)	$	0.2	$	0.2	$	0.1	$	0.1
Commercial paper (b)	$	188	$	188	$	124.5	$	124.5
Long-term debt(c)	$	599.3	$	688.7	$	524.1	$	630.2
(a)Balance is located in cash and cash equivalents in the accompanying balance sheets. These amounts may be offset by outstanding checks.
(b)Balance is located in notes payable in the accompanying balance sheets.
(c)Excludes current maturities and unamortized discounts.
Our money market funds are Level 1 valuations and their carrying amount approximates fair value. Other short-term investments are primarily overnight investment accounts; therefore, their carrying amount approximates fair value based on Level 2 inputs. The maturity of our commercial paper outstanding at both December 31, 2013 and September 30, 2013 is under 30 days. Due to the short term nature of these notes, the carrying cost of our commercial paper approximates fair value using Level 2 inputs. Washington Gas' long-term debt is not actively traded. The fair value of long-term debt was estimated based on the quoted market prices of the U.S. Treasury issues having a similar term to maturity, adjusted for Washington Gas' credit quality. Our long-term debt fair value measurement is classified as Level 3.
Non Recurring Basis
During the three months ended December 31, 2013, Washington Gas impaired its previous operation facility by reducing the carrying amount of $22.3 million down to its fair value of $21.5 million, resulting in an impairment charge of $0.8 million based on the progress made towards selling the facility. During the fiscal year ended September 30, 2013, Washington Gas impaired this facility by reducing the carrying amount of $24.9 million down to its fair value of $22.3 million, resulting in an impairment charge of $2.6 million. The fair value of this facility is a Level 3 measurement. At September 30, 2013, the facility was valued using the discounted cash value model that incorporated the anticipated sale proceeds indicated through a comparable analysis, incorporating expected market trends, prepared by an independent consultant and the estimated costs to carry the asset until a sale is completed. The December 31, 2013 valuation is based on the progress in the efforts to sell the property.

Operating_Segment_Reporting

Operating Segment Reporting	3 Months Ended
	Dec. 31, 2013
Operating Segment Reporting [Abstract]	'
Operating Segment Reporting	'
	NOTE 10. OPERATING SEGMENT REPORTING
	We have four reportable operating segments: regulated utility, retail energy-marketing, commercial energy systems and midstream energy services. The division of these segments into separate revenue generating components is based upon regulation, products and services. Our chief operating decision maker is our Chief Executive Officer. Our four segments are summarized below.
	Regulated Utility – The regulated utility segment is our core business. It consists of Washington Gas and Hampshire. Washington Gas provides regulated gas distribution services (including the sale and delivery of natural gas) to customers and natural gas transportation services to an unaffiliated natural gas distribution company in West Virginia under a Federal Energy Regulatory Commission (FERC) approved interstate transportation service operating agreement. Hampshire provides regulated interstate natural gas storage services to Washington Gas under a FERC approved interstate storage service tariff.
	Retail Energy-Marketing – The retail energy-marketing segment consists of WGEServices, which sells natural gas and electricity directly to retail customers in competition with regulated utilities and unregulated gas and electricity marketers.
	Commercial Energy Systems – The commercial energy systems segment consists of WGESystems and WGSW. WGES provides design-build energy efficient and sustainable solutions including commercial solar, energy efficiency and combined heat and power projects to government and commercial clients. WGSW is a holding company formed to invest in alternative energy assets.
	Midstream Energy Services – The midstream energy services segment consists of WGL Midstream, which engages in acquiring, managing and optimizing natural gas storage and transportation assets.
	Activities and transactions that are not significant enough on a stand-alone basis to warrant treatment as an operating segment, and that do not fit into one of our four operating segments, are aggregated as “Other Activities” and included as part of non-utility operations in the Operating Segment Financial Information presented below. Administrative and business development activity costs associated with WGL and Washington Gas Resources are included in this segment.
	While net income or loss applicable to common stock is the primary criterion for measuring a segment's performance, we also evaluate our operating segments based on other relevant factors, such as penetration into their respective markets and return on equity.
	The following tables present operating segment information for the three months ended December 31, 2013 and 2012.
	Operating Segment Financial Information
							Non-Utility Operations
	(In thousands)				Regulated Utility	Retail Energy-Marketing		Commercial Energy Systems		Midstream Energy Services		Other Activities		Eliminations(b)		Consolidated
	Three Months Ended December 31, 2013
	Operating revenues (a)			$	390,415	$	322,938	$	4,717	$	-33,173	$	-	$	-4,600	$	680,297
	Operating expenses:
		Cost of energy-related sales			190,695		303,268		3,145		-		-		-4,876		492,232
		Operation			57,430		11,251		1,474		1,124		3,004		17		74,300
		Maintenance			13,842		-		-		-		-		-		13,842
		Depreciation and amortization			25,369		174		1,093		31		-		-77		26,590
		General taxes and other assessments:
			Revenue taxes		24,671		1,947		1		-		-		-		26,619
			Other		12,775		1,068		52		87		21		-1		14,002
			Total operating expenses	$	324,782	$	317,708	$	5,765	$	1,242	$	3,025	$	-4,937	$	647,585
	Operating income (loss)				65,633		5,230		-1,048		-34,415		-3,025		337		32,712
	Equity in earnings of unconsolidated affiliates				-		-		284		206		-		-		490
	Other income (expense) — net				-180		61		65		-83		356		-		219
	Interest expense				8,879		-		-		-		113		-		8,992
	Dividends on Washington Gas preferred stock				330		-		-		-		-		-		330
	Income tax expense (benefit)				17,523		1,976		-562		-12,504		-1,099		136		5,470
	Net income (loss) applicable to common stock			$	38,721	$	3,315	$	-137	$	-21,788	$	-1,683	$	201	$	18,629
	Total assets at December 31, 2013			$	3,828,709	$	418,633	$	380,241	$	171,420	$	299,769	$	-467,246	$	4,631,526
	Capital expenditures			$	55,092	$	75	$	3,138	$	-	$	-	$	-	$	58,305
	Equity method investments at December 31, 2013			$	-	$	-	$	66,526	$	10,813	$	413	$	-	$	77,752
	Three Months Ended December 31, 2012
	Operating revenues (a)			$	355,817	$	324,059	$	11,985	$	2,854	$	-	$	-7,979	$	686,736
	Operating expenses:
		Cost of energy-related sales			150,448		290,133		9,111		-		-		-7,573		442,119
		Operation			58,208		11,359		1,232		844		791		-254		72,180
		Maintenance			11,450		-		-		-		-		-		11,450
		Depreciation and amortization			26,792		175		459		31		-		-153		27,304
		General taxes and other assessments:
			Revenue taxes		24,221		1,431		1		-		-		-		25,653
			Other		12,287		871		79		166		10		1		13,414
			Total operating expenses	$	283,406	$	303,969	$	10,882	$	1,041	$	801	$	-7,979	$	592,120
	Operating income (loss)				72,411		20,090		1,103		1,813		-801		-		94,616
	Equity in earnings of unconsolidated affiliates				-		-		245		-		-		-		245
	Other income (expenses) — net				133		50		80		-		218		-52		429
	Interest expense				9,095		3		43		-		104		-52		9,193
	Dividends on Washington Gas preferred stock				330		-		-		-		-		-		330
	Income tax expense				24,453		7,116		347		537		926		-		33,379
	Net income (loss) applicable to common stock			$	38,666	$	13,021	$	1,038	$	1,276	$	-1,613	$	-	$	52,388
	Total assets at December 31, 2012			$	3,673,308	$	400,951	$	168,761	$	201,111	$	226,221	$	-329,415	$	4,340,937
	Capital expenditures			$	60,615	$	201	$	15,101	$	-	$	-	$	-	$	75,917
	Equity method investments at December 31, 2012			$	-	$	-	$	29,005	$	-	$	285	$	-	$	29,290
	(a) Operating revenues are reported gross of revenue taxes. Revenue taxes of both the regulated utility and the retail energy-marketing segments include gross receipt taxes. Revenue taxes of the regulated utility segment also include PSC fees, franchise fees and energy taxes. Operating revenue amounts in the "Eliminations" column represent total intersegment revenues associated with sales from the regulated utility segment to the retail energy-marketing segment. Midstream Energy Services' cost of energy related sales is netted with its gross revenues.
	(b)Intersegment eliminations net income represents a timing difference between Commercial Energy Systems’ recognition of revenue for the sale of Solar Renewable Energy Credits (SRECs) to Retail Energy-Marketing and Retail Energy-Marketing’s recognition of the associated expense. Retail Energy-Marketing has recorded a portion of the SREC’s purchased as inventory to be used in future periods and will expense them at that time.

Other_Investments

Other Investments	3 Months Ended
	Dec. 31, 2013
Other Investments [Abstract]	'
InvestmentTextBlock	'
	NOTE 11.  OTHER INVESTMENTS
	Variable Interest Entities
	WGL assesses its contractual arrangements to determine control, and, by extension, correct classification of its investments. In most cases, control can be determined based on majority ownership or voting interests. However, there are certain entities known as variable interest entities (VIEs) for which control is difficult to discern based on ownership or voting interests alone. WGL and its subsidiaries first determine if an entity is a VIE. A VIE is an entity that does not have sufficient equity at risk to finance its activities without additional subordinated financial support from other parties, or whose equity investors, as a group, lack the characteristics of a controlling financial interest.
	At December 31, 2013, WGSW is party to three agreements to fund residential and commercial retail solar energy installations with three separate, privately held companies. WGSW has a master purchase agreement and master lease agreement with EchoFirst Finance Company LLC (EchoFirst) and Skyline Innovations, Inc (Skyline) for sale/leaseback arrangements for residential and commercial solar systems. WGSW is also a limited partner in ASD Solar LP, a partnership formed to own and operate a portfolio of residential solar projects, primarily rooftop photovoltaic power generation systems. As a limited partner, WGSW provides funding to the partnership but is excluded from involvement in the partnership's operations.
	At December 31, 2013, Washington Gas Resources owned all of the shares of common stock of Crab Run Gas Company. Crab Run Gas Company is an exploration and production company who is the limited partner in the Western/Crab Run Limited Partnership (Crab Run). The partnership was formed to manage oil and gas properties and perform oil and gas leasing, marketing and production activities.
	We have determined that we have a variable interest in four investments that qualify as VIEs. The four investments are:
	EchoFirst,
	Skyline,
	ASD Solar LP, and
	Crab Run.
	An enterprise that has a controlling financial interest in a VIE is known as the VIE's primary beneficiary and is required to consolidate the VIE. A primary beneficiary has the obligation to absorb expected losses or the right to receive expected gains that could potentially be significant to the VIE and has decision-making rights associated with the activities that are most significant to the VIE's economic performance, including the power to design the VIE.
	In determining whether the Company is the primary beneficiary of a VIE, we assess which variable interest holder has control over the VIE's significant economic activities, such as the design of the companies, vendor selection, operation activities, construction, customer selection, and re-marketing activities after the termination of customer leases. For each of the VIEs identified above, it was determined that another entity controlled the economic activities and had the obligation to absorb expected losses or the right to receive expected gains that could be significant to the VIE. Our maximum financial exposure from agreements is limited to its lease payment receivables and investment contributions made to these companies. All additional future committed contributions are contingent on the projects meeting required criteria. Our exposure is offset by the owned physical assets received as part of the transaction and the quick economic return for the investment through the investment tax credit/treasury grant proceeds and accelerated depreciation. At December 31, 2013, we have determined that WGL and its subsidiaries are not the primary beneficiary for any of the above VIEs, therefore we have not consolidated any of the VIE entities.
	Skyline/Echofirst
	Our agreements with Skyline and EchoFirst are accounted for as direct financing leases. WGSW records lease receipts and associated interest in the "Other Income" line in the accompanying Consolidated Statement of Income. WGSW held a $25.5 million and $29.2 million combined investment in direct financing leases at December 31, 2013 and September 30, 2013, respectively, of which $2.2 million and $5.8 million are current receivables recorded in "Other Current Assets" in the accompanying Consolidated Balance Sheets at December 31, 2013 and September 30, 2013, respectively.
	Minimum future lease payments receivable under direct financing leases over the next five years and thereafter are as follows:
		Minimum Payments Receivable for Direct Financing Leases
		(In millions)
		2014	$	2.2
		2015		1.2
		2016		1.2
		2017		1.2
		2018		1.2
		Thereafter		12.8
		Total	$	19.8
		Minimum payments receivable include $45,000 of unearned income recognized as interest, exclude $4.4 million of residual values and $1.3 million in taxes. The initial direct costs (incurred in FY 2012) associated with these investments was $0.7 million.
	ASD Solar, LP
	Our investment in ASD Solar, LP is accounted for under the equity method of accounting referred to as the hypothetical liquidation at book value method (HLBV) for allocating profits and losses; any profits and losses are included in “Earnings from Equity Method Investments” in the accompanying Consolidated Statement of Income and are added to or subtracted from the carrying amount of WGSW's investment balance.
	ASD Solar, LP is consolidated by the general partner, Solar Direct LLC. Solar Direct LLC is a wholly owned subsidiary of American Solar Direct Inc. (ASDI). The carrying amount of WGSW's investment in ASD Solar, LP exceeds the amount of the underlying equity in net assets by $35.6 million due to WGSW recording additions to its investment in ASD Solar, LP's net assets at fair value of contributions in accordance with GAAP. This basis difference is being amortized over the life of the assets.
	Crab Run
	Crab Run is accounted for under the equity method of accounting; any profits and losses are included in “Earnings from Equity Method Investments” in the accompanying Consolidated Statement of Income and are added to or subtracted from the carrying amount of WGL's investment balance.
	Non-VIE Investments
	ASDHI
	Washington Gas Resources held a $5.6 million investment in American Solar Direct Holdings Inc. (ASDHI), at both December 31, 2013 and September 30, 2013. This investment is recorded at cost. The profits and losses are included in "Other Income" in the accompanying Consolidated Statement of Income. No identified events or changes in circumstances that may have a significant effect on the carrying value of this investment have occurred. At both December 31, 2013 and September 30, 2013, Washington Gas Resources also held $1.1 million in warrants of ASDHI accounted for as derivatives and recorded at fair value.
	Constitution
	In May of 2013, WGL Midstream invested in Constitution Pipeline Company, LLC (Constitution). WGL Midstream will invest an estimated $68.0 million in the project for a 10% share in the pipeline venture. WGL Midstream joins Williams Partners L.P. (41% share), Cabot Oil and Gas Corporation (25% share) and Piedmont Natural Gas (24% share) in the project. This natural gas pipeline venture will transport natural gas from the Marcellus region in northern Pennsylvania to major northeastern markets. Constitution is accounted for under the equity method of accounting; any profits and losses are included in “Earnings from Equity Method Investments” in the accompanying Consolidated Statement of Income and are added to or subtracted from the carrying amount of WGL's investment balance. The equity method is considered appropriate because Constitution is an LLC with specific ownership accounts and ownership between five and fifty percent resulting in WGL Midstream maintaining a more than minor influence over the partnership operating and financing policies.
	The balance sheet location of the investments discussed in this footnote at December 31, 2013 and September 30, 2013 are as follows:
	WGL Holdings, Inc.
	Balance Sheet Location of Other Investments
	As of December 31, 2013 (in millions)	VIEs		Non-VIEs		Total
	Assets
	Investments in unconsolidated affiliates	$	67	$	16.4	$	83.4
	Investments in direct financing leases receivable		23		-		23
	Derivatives		-		1.1		1.1
	Other		2.6		-		2.6
	Total assets	$	92.6	$	17.5	$	110.1
	Liabilities
	Other	$	8.3	$	-	$	8.3
	Total liabilities	$	8.3	$	-	$	8.3
	WGL Holdings, Inc.
	Balance Sheet Location of Other Investments
	As of September 30, 2013 (in millions)	VIEs		Non-VIEs		Total
	Assets
	Investments in unconsolidated affiliates	$	55.4	$	12.1	$	67.5
	Investment in direct financing leases receivable		23.4		-		23.4
	Derivatives		-		1.1		1.1
	Other		5.8		-		5.8
	Total assets	$	84.6	$	13.2	$	97.8
	Liabilities
	Other	$	8.5	$	-	$	8.5
	Total liabilities	$	8.5	$	-	$	8.5
	The income statement location of the investments discussed in this footnote for the three months ended December 31, 2013 and 2012 are as follows:
	WGL Holdings, Inc.
	Income Statement Location of Other Investments
Three Months Ended December 31, 2013 (in millions)	VIEs		Non-VIEs		Total
Equity in earnings of unconsolidated affiliates	$	0.3	$	0.2	$	0.5
Depreciation and amortization		0.1		-		0.1
Other income		0.5		0.2		0.7
Net income	$	0.7	$	0.4	$	1.1
WGL Holdings, Inc.
Income Statement Location of Other Investments
Three Months Ended December 31, 2012 (in millions)	VIEs		Non-VIEs		Total
Equity in earnings of unconsolidated affiliates	$	0.2	$	-	$	0.2
Other income		0.2		0.1		0.3
Net income	$	0.4	$	0.1	$	0.5

Related_Party_Transactions

Related Party Transactions	3 Months Ended
	Dec. 31, 2013
Related Party Transactions [Abstract]	'
Related Party Transactions	'
	NOTE 12. RELATED PARTY TRANSACTIONS
	WGL and its subsidiaries engage in transactions during the ordinary course of business. Inter-company transactions and balances have been eliminated from the consolidated financial statements of WGL, except as described below. Washington Gas provides accounting, treasury, legal and other administrative and general support to affiliates, and files consolidated tax returns with WGL that include affiliated taxable transactions. Washington Gas bills its affiliates in accordance with regulatory requirements for the actual cost of providing these services, which approximates their market value. To the extent such billings are not yet paid, 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.
	In connection with billing for unregulated third party marketers 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. The following table presents the receivables and payables from associated companies on Washington Gas' balance sheets as of December 31, 2013 and September 30, 2013
	Washington Gas Receivables / Payables from Associated Companies
	(In millions)	31-Dec-13			30-Sep-13
	Receivables from Associated Companies	$	4.8		$	7.2
	Payables to Associated Companies	$	36		$	20.6
	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 WGEServices. Washington Gas records revenues for these balancing services pursuant to tariffs approved by the appropriate regulatory bodies. These related party amounts have been eliminated in the consolidated financial statements of WGL. The following table shows the amounts Washington Gas charged WGEServices for balancing services.
	Washington Gas-Gas Balancing Service Charges
			Three Months Ended
			December 31,
	(In millions)		2013		2012
	Gas balancing service charge	$	3.8	$	7.6
	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. WGEServices recognized an accounts receivable from Washington Gas in the amount of $0.3 million and $1.0 million at December 31, 2013 and September 30, 2013, respectively, related to an imbalance in gas volumes. Due to regulatory treatment, these payables and receivables are not eliminated in the consolidated financial statements of WGL. Refer to Note 1—Accounting Policies of the Notes to Consolidated Financial Statements of the combined Annual Report on Form 10-K for the fiscal year ended September 30, 2013 for further discussion of these imbalance transactions.
	Washington Gas participates in a Purchase of Receivables (POR) program as approved by the PSC of MD, whereby it purchases receivables from participating energy marketers at approved discount rates. In addition, WGEServices participates in POR programs with certain Maryland and Pennsylvania utilities, 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 sheet. Any activity between Washington Gas and WGEServices related to the POR program has been eliminated in the accompanying financial statements for WGL. During the three months ended December 31, 2013 and during the fiscal year ended September 30, 2013,Washington Gas purchased $19.9 million and $106.6 million, respectively, of receivables from WGEServices.

Commitments_and_Contingencies

Commitments and Contingencies	3 Months Ended
	Dec. 31, 2013
Commitments and Contingencies [Abstract]	'
Commitments and Contingencies	'
	NOTE 13. COMMITMENTS AND CONTINGENCIES
	RATES AND REGULATORY MATTERS
	Washington Gas makes its requests to modify existing rates based on its determination of the level of net investment in plant and equipment, operating expenses, and a level of return on invested capital that is just and reasonable. The following is an update of significant current regulatory matters in each of Washington Gas' jurisdictions. For a more detailed discussion of the matters below, refer to our combined Annual Report on Form 10-K for WGL and Washington Gas for the fiscal year ended September 30, 2013.
	District of Columbia Jurisdiction
	On August 15, 2013, Washington Gas filed a request for approval with the Public Service Commission of the District of Columbia (PSC of DC) of a revised accelerated pipe replacement plan (“Plan”) and surcharge mechanism to recover the associated costs for the first five years of the Plan. Washington Gas proposes to replace bare and/or unprotected steel services, bare and targeted unprotected steel main, and cast iron main in its distribution system in the District of Columbia at an estimated five-year cost of $110.0 million. Comments and replies were filed by interested parties. A PSC of DC order in this matter is pending.
	Weather Normalization Adjustment (WNA). On November 8, 2013, Washington Gas filed an application for approval of a WNA, which is a rate design mechanism that eliminates the variability of weather from the calculation of actual billed revenues and offers customers more stability in their bills during colder-than-normal winter heating seasons. Washington Gas' application in this matter is pending.
	Maryland Jurisdiction
	On November 22, 2013, the PSC of MD issued an order granting an overall increase of $8.9 million, based on the capital structure recommended by the Staff of the PSC. The order approved a return on equity of 9.50% resulting in an overall rate of return of 7.70%.  The order also clarified that Washington Gas was authorized to establish a regulatory asset and amortize the costs related to the change in tax treatment of Med D.  Finally, the PSC of MD denied Washington Gas' appeal on recovery of the costs to initiate the outsourcing agreement with Accenture, LLP.  As a result of this order, Washington Gas has established a Med D regulatory asset in the first quarter of fiscal year 2014 and has begun amortizing the balance.  On December 20, 2013, Washington Gas filed a request for rehearing and an appeal with the Baltimore City Circuit Court appealing the PSC of MD's rulings on capital structure, return on equity, and recovery of the costs to initiate the outsourcing agreement. The case is pending further commission action.
	Virginia Jurisdiction
	Affiliate Transactions. On October 2, 2012, Washington Gas filed an application with the Commonwealth of Virginia State Corporation Commission (SCC of VA) for approval of revised service agreements between Washington Gas and two affiliates—WGEServices and WGESystems. The revised service agreements incorporate recommendations from the Staff of the SCC of VA that Washington Gas agreed to include as part of the stipulation approved in Washington Gas' Virginia base rate case, revisions to the descriptions of services provided to the affiliates, and revisions to permit the two affiliates to participate in some health and welfare plans sponsored by Washington Gas. On December 21, 2012, the SCC of VA approved the revised services agreements with only minor modifications. On January 18, 2013, Washington Gas filed a separate application requesting approval of revised service agreements between Washington Gas and each of the remaining five affiliates receiving services.
	On April 2, 2013, Washington Gas filed a second amendment to provide additional services to two of its affiliates, and to further revise the proposed service agreements that were included in the January 18, 2013 application. On May 24, 2013, the SCC of VA approved revised service agreements for WGL Holdings Inc., Washington Gas Resources Corp., Hampshire Gas Company, Crab Run Gas Company and WGL Midstream, Inc. On October 10, 2013, the SCC of VA approved a service agreement for Washington Gas to provide services to WGL Midstream CP, LLC a subsidiary of WGL Midstream, Inc.
	On June 16, 2011, Washington Gas submitted an application to the SCC of VA requesting approval of three affiliate transactions with WGL Midstream: (i)  the transfer to WGL Midstream of the remainder of the term of two agreements for natural gas storage service at the Washington Gas Storage (WSS) and Eminence Storage Service (ESS) storage fields; (ii)  the sale to WGL Midstream of any storage gas balances associated with the WSS and ESS agreements; and (iii)  the assignment to WGL Midstream of Washington Gas' rights to buy base gas in the WSS storage field. The SCC of VA did not approve the transfer of the agreements on the grounds that ratepayers funded a portion of the costs associated with the assets. On June 5, 2013, Washington Gas filed a petition for a declaratory judgment that because the proposed transfers are governed by the FERC, the SCC of VA does not have jurisdiction over the transaction.
	On August 30, 2013, Staff filed its response to Washington Gas' petition. Staff argued that the transaction at debate in this proceeding is appropriately regulated by the SCC of VA. On September 27, 2013, Washington Gas filed its response to Staff's argument. The Senior Hearing Examiner's findings, issued in his October 31, 2013 report, were that the proposed transfer is not preempted by FERC and is subject to commission jurisdiction under the Affiliates Act.
	The SCC of VA appointed a hearing examiner to conduct all further proceedings. On October 31, 2013, the Senior Hearing Examiner issued a report finding that the SCC of VA has jurisdiction over the proposed transfers. Washington Gas filed comments on the report on December 5, 2013. The case is pending commission review.
	CONSTRUCTION PROJECT FINANCING
	To fund certain of its construction projects, Washington Gas enters into financing arrangements with third party lenders. As part of these financing arrangements, Washington Gas' customers agree to make principal and interest payments over time, typically beginning after the projects are completed. Washington Gas assigns these customer payment streams to the lender. As the lender funds the construction project, Washington Gas establishes a receivable representing its customers' obligations to remit principal and interest and a long-term payable to the lender. When these projects are formally “accepted” by the customer as completed, Washington Gas transfers the ownership of the receivable to the lender and removes both the receivable and the long-term financing from its financial statements. As of December 31, 2013 and September 30, 2013, work on these construction projects that was not completed or accepted by customers was valued at $8.3 million and $6.7 million, respectively. These amounts are recorded on the balance sheet as a receivable in “Deferred Charges and Other Assets—Other” with the corresponding long-term obligation to the lender recorded under “Long-term debt.” At any time before these contracts are accepted by the customer, should there be a contract default, such as, among other things, a delay in completing the project, the lender may call on Washington Gas to fund the unpaid principal in exchange for which Washington Gas would receive the right to the stream of payments from the customer. Construction projects are financed primarily for government agencies, which Washington Gas considers to have minimal credit risk. Based on this assessment and previous collection experience, Washington Gas did not record any corresponding reserves for bad debt related to these receivables at December 31, 2013 or September 30, 2013.
	FINANCIAL GUARANTEES
	WGL has guaranteed payments primarily for certain purchases of natural gas and electricity on behalf of WGEServices and for certain purchase commitments on behalf of WGL Midstream. At December 31, 2013, these guarantees totaled $313.5 million and $185.7 million for WGEServices and WGL Midstream, respectively. The amount of such guarantees is periodically adjusted to reflect changes in the level of financial exposure related to these purchase commitments. We also receive financial guarantees or other collateral from counterparties when required by our credit policy (refer to the section entitled “Credit Risk” for a further discussion of our credit policy). WGL also issued guarantees totaling $7.8 million at December 31, 2013 on behalf of certain of our non-utility subsidiaries and unconsolidated investments associated with their banking transactions. Of the total guarantees of $507.0 million, $4.0 million expires in January 2014, $6.0 million expires in October 2014 and $0.5 million expires in September 2033. The remaining guarantees do not have specific maturity dates. For all of its financial guarantees, WGL may cancel any or all future obligations upon written notice to the counterparty, but WGL would continue to be responsible for the obligations created under the guarantees prior to the effective date of the cancellation.

Pension_and_Other_PostRetireme

Pension and Other Post-Retirement Benefit Plans	3 Months Ended
	Dec. 31, 2013
Pension and Other Post-Retirement Benefit Plans [Abstract]	'
Pension and Other Post-Retirement Benefit Plans	'
	NOTE 14. PENSION AND OTHER POST-RETIREMENT BENEFIT PLANS
	The following table shows the components of net periodic benefit costs recognized in our financial statements during the three months ended December 31, 2013 and 2012:
	Components of Net Periodic Benefit Costs (Income)
			Three Months Ended December 31,
			2013				2012
			Pension		Health and		Pension		Health and
	(In millions)		Benefits		Life Benefits		Benefits		Life Benefits
	Components of net periodic benefit costs (income)
	Service cost	$	3.5	$	2.1	$	4.2	$	2.4
	Interest cost		10.1		5.4		9.1		4.7
	Expected return on plan assets		-10.3		-4.7		-10.5		-4.6
	Amortization of prior service cost (credit)		0.1		-1		0.3		-1
	Amortization of actuarial loss		4.2		0.7		7.2		2.3
	Amortization of transition obligation		-		-		-		0.3
	Net periodic benefit cost		7.6		2.5		10.3		4.1
	Amount allocated to construction projects		-1		-0.4		-1.4		-0.7
	Amount amortized/deferred as regulatory asset		1.8		0.1		-2.4		0.8
	Amount charged to expense	$	8.4	$	2.2	$	6.5	$	4.2
	Amounts included in the line item “Amount amortized/deferred as regulatory asset,” as shown in the table above, represent the amortization of a regulatory asset as of December 31, 2013 and the difference between the cost of the applicable Pension Benefits or the Health and Life Benefits and the amount that Washington Gas is permitted to recover in rates that it charges to customers in the District of Columbia as of December 31, 2012.

Changes_in_Accumulated_Other_C

Changes in Accumulated Other Comprehensive Income	3 Months Ended
	Dec. 31, 2013
Accumulated Other Comprehensive Income [Abstract]	'
Changes in Accumulated Other Comprehensive Income by Component	'
	NOTE 15. CHANGES IN ACCUMULATED OTHER COMPREHENSIVE INCOME
	All components of other comprehensive income are related to the amortization of pension and other post-retirement benefit costs. The following table shows the changes in accumulated other comprehensive income for both WGL and Washington Gas by component during the three months ended December 31, 2013 and 2012:
	Changes in Accumulated Other Comprehensive Income by Component
			Three Months Ended December 31,
			2013		2012
	(In thousands)
	Beginning Balance	$	-11,048	$	-12,201
	Amortization of prior service cost (a)		-35		-12
	Amortization of actuarial loss (a)		364		462
	Amortization of transition obligation (a)		-		9
	Current-period other comprehensive income		329		459
	Income tax expense related to other comprehensive income		130		182
	Ending Balance	$	-10,849	$	-11,924
	(a) These accumulated other comprehensive income components are included in the computation of net periodic benefit cost. Refer to Note 14-Pension and other post-retirement benefit plans for additional details.

Accounting_Policies_Policies

Accounting Policies (Policies)	3 Months Ended
	Dec. 31, 2013
Organization And Significant Accounting Policies [Abstract]	'
Basis of Presentation	'
	Basis of Presentation
	WGL Holdings, Inc. (WGL) is a holding company that owns all of the shares of common stock of Washington Gas Light Company (Washington Gas), a regulated natural gas utility, and all of the shares of common stock of Washington Gas Resources Corporation (Washington Gas Resources), Hampshire Gas Company (Hampshire) and Crab Run Gas Company. Washington Gas Resources owns all of the shares of common stock of four non-utility subsidiaries that include Washington Gas Energy Services, Inc. (WGEServices), Washington Gas Energy Systems, Inc. (WGESystems), WGL Midstream, Inc. (WGL Midstream) and WGSW, Inc. (WGSW). Except where the content clearly indicates otherwise, “WGL,” “we,” “us” or “our” refers to the holding company or the consolidated entity of WGL Holdings, Inc. and all of its subsidiaries. Unless otherwise noted, these notes apply equally to WGL and Washington Gas.
	The interim consolidated financial statements 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 consolidated financial statements and accompanying notes should be read in conjunction with the combined Annual Report on Form 10-K for WGL and Washington Gas for the fiscal year ended September 30, 2013. Due to the seasonal nature of our businesses, the results of operations for the periods presented in this report are not necessarily indicative of actual results for the full fiscal years ending September 30, 2014 and 2013 of either WGL or Washington Gas.
	The accompanying unaudited financial statements for WGL and Washington Gas reflect all normal recurring adjustments that are necessary, in our opinion, to present fairly the results of operations in accordance with GAAP. Certain reclassifications have been recast to conform to current year presentation.
	For a complete description of our accounting policies, refer to Note 1 of the Notes to Consolidated Financial Statements of the combined Annual Report on Form 10-K for WGL and Washington Gas for the fiscal year ended September 30, 2013.
New Accounting Pronouncements	'
	Accounting Standards Adopted in the Current Fiscal Year
	Balance Sheet Offsetting. In December 2011, the FASB issued ASU 2011-11, Disclosures about Offsetting Assets and Liabilities. This standard amends the disclosure requirements on offsetting in ASC Topic 210 by requiring enhanced disclosures about financial instruments and derivative instruments that are either: (i) offset in accordance with existing guidance or (ii) subject to an enforceable master netting arrangement or similar agreement, irrespective of whether they are offset on the balance sheet. In January 2013, the FASB issued ASU 2013-01, Clarifying the Scope of the Disclosures about Offsetting Assets and Liabilities. ASU 2013-01 limits the scope of the required disclosures to derivatives, repurchase agreements and securities borrowing and securities lending transactions. The disclosures are required irrespective of whether the transactions are offset in the statement of financial position. ASU 2011-11 and ASU 2013-01 were effective for us on October 1, 2013. As a result of the standard, additional disclosures regarding master netting arrangements were added to Note 8 - Derivatives and Weather-Related Instruments. The adoption of these standards did not otherwise affect our financial statements.
	Comprehensive Income. In February 2013, the FASB issued ASU 2013-02, Comprehensive Income (Topic 220): Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income. This standard requires entities to (i) present information about reclassification adjustments from accumulated other comprehensive income (AOCI) to net income in their entirety – the effect on the reclassification on each affected net income line item and (ii) for AOCI reclassification items that are not reclassified in their entirety into net income – a cross-reference to other required US GAAP disclosures. The reclassification information may be presented in a single note or on the face of the financial statements. ASU 2013-02 was effective for us on October 1, 2013. As a result of this standard, we have presented information about reclassification adjustments out of accumulated other comprehensive income in a new footnote to the financial statements. Refer to Note 15 – Changes in Accumulated Other Comprehensive Income for the details of this disclosure. The adoption of this standard did not otherwise affect our financial statements.
	Other Newly Issued Accounting Standards
	Income Taxes. In July 2013, the FASB issued ASU 2013-11, Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists. This standard amends the disclosure requirement of ASC Topic 740 by requiring an unrecognized tax benefit, or a portion of an unrecognized tax benefit be presented in the financial statements as a reduction to a deferred tax asset in most circumstances. ASU 2013-11 will be effective for us on October 1, 2014. We do not expect the adoption of this standard to have a material effect on our financial statements.
Storage Gas Valuation Methods	'
	Storage Gas Valuations
	For Washington Gas and WGEServices, storage gas inventory is stated at the lower-of-cost or market as determined using the first-in, first-out method. For WGL Midstream, storage gas inventory is stated at the lower-of-cost or market using the weighted average cost method. For the three months ended December 31, 2013, WGL Midstream recorded a minimal reduction to net income for lower of cost or market adjustments. For the three months ended December 31, 2012, WGL Midstream recorded a reduction to net income of $8.4 million for lower-of cost or market adjustments.
	In conjunction with optimizing Washington Gas' storage capacity, storage gas inventory may be subject to lower-of-cost or market adjustments. For the three months ended December 31, 2013 and 2012, Washington Gas did not record any lower-of-cost or market adjustments related to its storage gas inventory.
Fair Value Measurement Policy	'
	Recurring Basis
	We measure the fair value of our financial assets and liabilities using a combination of the income and market approach in accordance with ASC Topic 820. These financial assets and liabilities primarily consist of (i) derivatives recorded on our balance sheet under ASC Topic 815, (ii) weather-related instruments and (iii) 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 WGL. We value our derivative contracts based on an “in-exchange” premise, and 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.
Investment Policy	'
	Our agreements with Skyline and EchoFirst are accounted for as direct financing leases. WGSW records lease receipts and associated interest in the "Other Income" line in the accompanying Consolidated Statement of Income.
	Our investment in ASD Solar, LP is accounted for under the equity method of accounting referred to as the hypothetical liquidation at book value method (HLBV) for allocating profits and losses; any profits and losses are included in “Earnings from Equity Method Investments” in the accompanying Consolidated Statement of Income and are added to or subtracted from the carrying amount of WGSW's investment balance.
	Crab Run is accounted for under the equity method of accounting; any profits and losses are included in “Earnings from Equity Method Investments” in the accompanying Consolidated Statement of Income and are added to or subtracted from the carrying amount of WGL's investment balance.
	Washington Gas Resources held a $5.6 million investment in American Solar Direct Holdings Inc. (ASDHI), at both December 31, 2013 and September 30, 2013. This investment is recorded at cost. The profits and losses are included in "Other Income" in the accompanying Consolidated Statement of Income.
	Constitution is accounted for under the equity method of accounting; any profits and losses are included in “Earnings from Equity Method Investments” in the accompanying Consolidated Statement of Income and are added to or subtracted from the carrying amount of WGL's investment balance. The equity method is considered appropriate because Constitution is an LLC with specific ownership accounts and ownership between five and fifty percent resulting in WGL Midstream maintaining a more than minor influence over the partnership operating and financing policies.

Accounts_Payable_and_Other_Acc1

Accounts Payable and Other Accrued Liabilities (Tables)	3 Months Ended
	Dec. 31, 2013
WGL Holdings, Inc.	'
Accounts Payable and Other Accrued Liabilities	'
		WGL Holdings, Inc.
		(In millions)		31-Dec-13		30-Sep-13
		Accounts payable—trade	$	277	$	216.3
		Employee benefits and payroll accruals		14.2		23.4
		Embedded derivatives and other accrued liabilities		22.7		30.9
		Total	$	313.9	$	270.6
Washington Gas Light Company	'
Accounts Payable and Other Accrued Liabilities	'
		Washington Gas Light Company
		(In millions)		31-Dec-13		30-Sep-13
		Accounts payable—trade	$	142.7	$	99.7
		Employee benefits and payroll accruals		13.5		21.4
		Embedded derivatives and other accrued liabilities		15.3		11.7
		Total	$	171.5	$	132.8

ShortTerm_Debt_Tables

Short-Term Debt (Tables)	3 Months Ended
	Dec. 31, 2013
Short Term Debt Tables [Abstract]	'
Commited Credit Available	'
	Committed Credit Available (In millions)
	As of December 31, 2013		WGL Holdings, Inc. (b)		Washington Gas		Total Consolidated
	Committed credit agreements
	Unsecured revolving credit facility, expires April 3, 2017(a)	$	450	$	350	$	800
	Less: Commercial Paper		-255.3		-188		-443.3
	Net committed credit available	$	194.7	$	162	$	356.7
	As of September 30, 2013		WGL Holdings, Inc. (b)		Washington Gas		Total Consolidated
	Committed credit agreements
	Unsecured revolving credit facility, expires April 3, 2017(a)	$	450	$	350	$	800
	Less: Commercial Paper		-248.6		-124.5		-373.1
	Net committed credit available	$	201.4	$	225.5	$	426.9
	(a)Both WGL and Washington Gas have the right to request extensions with the banks’ approval. WGL's revolving credit facility permits it to borrow an additional $100 million, with the banks’ approval, for a total of $550 million. Washington Gas’ revolving credit facility permits it to borrow an additional $100 million, with the banks’ approval, for a total of $450 million.
	(b)WGL Holdings, Inc. includes all subsidiaries other than Washington Gas Light Company.

LongTerm_Debt_Table

Long-Term Debt (Table)	3 Months Ended
	Dec. 31, 2013
Long Term Debt Tables	'
MTN and Private Placement Issuances and Retirements	'
	MTN and Private Placement Issuances and Retirements
	($ In millions)	Principal		Interest Rate	Nominal Maturity Date
	Quarter Ended December 31, 2013
	Issuances:
	12/5/13	$	75	5.00%(a)	12/15/43
	Total	$	75
	Retirements:
	11/7/13	$	37	4.88%	11/7/13
	Total	$	37
	(a)The estimated effective cost of the issued notes, including consideration of issuance fees and hedge costs, is 4.95%.

Common_Shareholders_Equity_Tab

Common Shareholders' Equity (Tables)	3 Months Ended
	Dec. 31, 2013
WGL Holdings, Inc.	'
Components of Common Shareholders' Equity	'
	WGL Holdings, Inc.
	Components of Common Shareholders’ Equity
	(In thousands)	Common Stock Amount		Paid-In Capital		Retained Earnings			Accumulated Other Comprehensive Loss, Net of Taxes		Total
	Balance at September 30, 2013	$	574,461	$	10,710	$	700,422		$	-11,048	$	1,274,545
	Net income		-		-		18,959			-		18,959
	Other comprehensive income		-		-		-			199		199
	Dividends reinvestment		1,503		-		-			-		1,503
	Stock-based compensation		1,524		-1,744		-			-		-220
	Dividends declared:
	Common stock		-		-		-21,795			-		-21,795
	Preferred stock		-		-		-330			-		-330
	Balance at December 31, 2013	$	577,488	$	8,966	$	697,256		$	-10,849	$	1,272,861
Washington Gas Light Company	'
Components of Common Shareholders' Equity	'
	Washington Gas Light Company
	Components of Common Shareholder's Equity
	(In thousands)	Common Stock Amount		Paid-In Capital			Retained Earnings		Accumulated Other Comprehensive Loss, Net of Taxes		Total
	Balance at September 30, 2013	$	46,479	$	477,968		$	511,184	$	-11,048	$	1,024,583
	Net income		-		-			38,807		-		38,807
	Other comprehensive income		-		-			-		199		199
	Stock-based compensation		-		-266			-		-		-266
	Dividends declared:
	Common stock		-		-			-19,075		-		-19,075
	Preferred stock		-		-			-330		-		-330
	Balance at December 31, 2013	$	46,479	$	477,702		$	530,586	$	-10,849	$	1,043,918

Earnings_Per_Share_Tables

Earnings Per Share (Tables)	3 Months Ended
	Dec. 31, 2013
Earnings Per Share Tables [Abstract]	'
Earnings per Share	'
		Basic and Diluted EPS
		(in thousands, except per share data)		Net Income Applicable to Common Stock	Shares		Per Share Amount
		Three Months Ended December 31, 2013
		Basic EPS	$	18,629	51,816	$	0.36
		Stock-based compensation plans		-	11
		Diluted EPS	$	18,629	51,827	$	0.36
		Three Months Ended December 31, 2012
		Basic EPS	$	52,388	51,631	$	1.01
		Stock-based compensation plans		-	57
		Diluted EPS	$	52,388	51,688	$	1.01

Derivative_and_Weather_Related1

Derivative and Weather Related Instruments (Tables)	3 Months Ended
	Dec. 31, 2013
Absolute Notional Amounts of Open Positions on Derivative Instruments	'
		Absolute Notional Amounts
		of Open Positions on Derivative Instruments
		As of December 31, 2013	Notional Amounts
		Derivative transactions	WGL Holdings, Inc.			Washington Gas Light Company
		Natural Gas (In millions of therms)
		Asset optimization		12,771.70			11,010.00
		Retail sales		83			-
		Other risk-management activities		1,763.50			1,442.50
		Electricity (In millions of kWhs)
		Retail sales		4,684.00			-
		Other risk-management activities		19,151.00			-
		Warrants (In millions of shares)		4.6			-
	Absolute Notional Amounts
	of Open Positions on Derivative Instruments
	As of September 30, 2013		Notional Amounts
	Derivative transactions	WGL Holdings, Inc.			Washington Gas Light Company
	Natural Gas (In millions of therms)
	Asset optimization		13,289.60			11,115.80
	Retail sales		98.9			-
	Other risk-management activities		1,803.60			1,455.70
	Electricity (In millions of kWhs)
	Retail sales		4,790.20			-
	Other risk-management activities		17,647.90			-
	Warrants (In millions of shares)		4.6			-
	Interest Rate Swaps (In millions of dollars)(a)		75			75
	(a) The fair value of our interest rate swaps was minimal at 9/30/13.
Gains and (Losses) on Derivative Instruments	'
		Gains and Losses on Derivative Instruments
				WGL Holdings, Inc.				Washington Gas Light Company
		(In millions)
		Three Months Ended December 31,		2013		2012		2013		2012
		Recorded to income
		Operating revenues—non-utility	$	-48.5	$	12.2	$	-	$	-
		Utility cost of gas		-27.3		-7.2		-27.3		-7.2
		Non-utility cost of energy-related sales		16.3		-7.5		-		-
		Other income-net		0.1		0.1		-		-
		Recorded to regulatory assets
		Gas costs		-78.3		-11.9		-78.3		-11.9
		Total	$	-137.7	$	-14.3	$	-105.6	$	-19.1
Potential Collateral Requirements for Derivative Liabilities with Credit-risk-Contingent Features	'
	Potential Collateral Requirements for Derivative Liabilities
	with Credit-risk-Contingent Features
	(In millions)	WGL Holdings, Inc.			Washington Gas Light Company
	31-Dec-13
	Derivative liabilities with credit-risk-contingent features	$	63.5		$	38
	Maximum potential collateral requirements		27			3.9
	30-Sep-13
	Derivative liabilities with credit-risk-contingent features	$	77		$	44.7
	Maximum potential collateral requirements		33.6			1.7
WGL Holdings, Inc.	'
Balance Sheet Classification of Derivative Instruments	'
	WGL Holdings, Inc.
	Balance Sheet Classification of Derivative Instruments
	(In millions)
	As of December 31, 2013	Gross Derivative Assets		Gross Derivative Liabilities		Netting of Collateral		Total(a)
	Current Assets—Derivatives	$	35.6	$	-12.1	$	-	$	23.5
	Deferred Charges and Other Assets—Derivatives		9.2		-		-		9.2
	Accounts Payable and Other Accrued Liabilities		0.4		-		-		0.4
	Current Liabilities—Derivatives		10.3		-54.2		2.5		-41.4
	Deferred Credits—Derivatives		27.5		-275.7		2.6		-245.6
	Total	$	83	$	-342	$	5.1	$	-253.9
	As of September 30, 2013
	Current Assets—Derivatives	$	57.3	$	-19.3	$	-2.7	$	35.3
	Deferred Charges and Other Assets—Derivatives		57.4		-31.1		-		26.3
	Accounts Payable and Other Accrued Liabilities		1.5		-		-		1.5
	Current Liabilities—Derivatives		4.1		-53.4		0.9		-48.4
	Deferred Credits—Derivatives		-		-144		2.7		-141.3
	Total	$	120.3	$	-247.8	$	0.9	$	-126.6
Washington Gas Light Company	'
Balance Sheet Classification of Derivative Instruments	'
	Washington Gas Light Company
	Balance Sheet Classification of Derivative Instruments
	(In millions)
	As of December 31, 2013	Gross Derivative Assets		Gross Derivative Liabilities		Netting of Collateral		Total(a)
	Current Assets—Derivatives	$	10.9	$	-4.7	$	-	$	6.2
	Deferred Charges and Other Assets—Derivatives		-		-		-		-
	Current Liabilities—Derivatives		7.4		-34.1		-		-26.7
	Deferred Credits—Derivatives		27.2		-215.8		-		-188.6
	Total	$	45.5	$	-254.6	$	-	$	-209.1
	As of September 30, 2013
	Current Assets—Derivatives	$	19.3	$	-12.3	$	-2.7	$	4.3
	Deferred Charges and Other Assets—Derivatives		47.2		-31.1		-		16.1
	Current Liabilities—Derivatives		1.5		-26.2		-		-24.7
	Deferred Credits—Derivatives		-		-106.1		-		-106.1
	Total	$	68	$	-175.7	$	-2.7	$	-110.4
	(a)WGL 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 815. All recognized derivative contracts and associated financial collateral subject to a master netting arrangement or similar that is eligible for offset under ASC 815 have been presented net in the balance sheet.

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	3 Months Ended
	Dec. 31, 2013
Quantitative Information about Level 3 Fair Value Measurements	'
	Quantitative Information about Level 3 Fair Value Measurements
		Net Fair Value December 31, 2013	Valuation Techniques	Unobservable Inputs	Range
	WGL Holdings, Inc.	(In millions)
	Natural gas related derivatives	($264.50)	Discounted Cash Flow	Natural Gas Basis Price (per dekatherm)	($1.594) -	$3.21
			Option Model	Natural Gas Basis Price (per dekatherm)	($0.372) -	$1.54
				Annualized Volatility of Spot Market Natural Gas	34.6% -	276.60%
	Electricity related derivatives	($1.70)	Discounted Cash Flow	Electricity Congestion Price (per megawatt hour)	($1.888) -	$66.20
			Load-Shaping Option Model	Electricity Congestion Price (per megawatt hour)	$31.965 -	$71.19
	Washington Gas Light Company
	Natural gas related derivatives	($220.00)	Discounted Cash Flow	Natural Gas Basis Price (per dekatherm)	($1.594) -	$3.21
			Option Model	Natural Gas Basis Price (per dekatherm)	$0.027 -	$1.54
				Annualized Volatility of Spot Market Natural Gas	46.8% -	276.60%
	Quantitative Information about Level 3 Fair Value Measurements
		Net Fair Value September 30, 2013	Valuation Techniques	Unobservable Inputs	Range
	WGL Holdings, Inc.	(In millions)
	Natural gas related derivatives	($155.20)	Discounted Cash Flow	Natural Gas Basis Price (per dekatherm)	($1.780) -	$2.21
			Option Model	Natural Gas Basis Price (per dekatherm)	($0.181) -	$0.63
				Annualized Volatility of Spot Market Natural Gas	34.6% -	276.60%
	Electricity related derivatives	$2.40	Discounted Cash Flow	Electricity Congestion Price (per megawatt hour)	($1.995) -	$64.15
			Washington Gas Light Company
	Natural gas related derivatives	($133.60)	Discounted Cash Flow	Natural Gas Basis Price (per dekatherm)	($1.780) -	$2.21
			Option Model	Natural Gas Basis Price (per dekatherm)	$0.024 -	$0.63
				Annualized Volatility of Spot Market Natural Gas	46.8% -	276.60%
WGL Holdings, Inc.	'
Fair Value Measurements Under the Fair Value Hierarchy	'
	WGL Holdings, Inc.
	Fair Value Measurements Under the Fair Value Hierarchy
	(In millions)		Level 1		Level 2		Level 3		Total
	At December 31, 2013
	Assets
	Natural gas related derivatives	$	-	$	44.2	$	17.7	$	61.9
	Electricity related derivatives		-		0.1		19.8		19.9
	Warrants		-		-		1.2		1.2
	Total Assets	$	-	$	44.3	$	38.7	$	83
	Liabilities
	Natural gas related derivatives	$	-	$	-34.2	$	-282.2	$	-316.4
	Electricity related derivatives		-		-4.1		-21.5		-25.6
	Total Liabilities	$	-	$	-38.3	$	-303.7	$	-342
	At September 30, 2013
	Assets
	Natural gas related derivatives	$	-	$	72.3	$	21.5	$	93.8
	Electricity related derivatives		-		-		25.4		25.4
	Warrants		-		-		1.1		1.1
	Total Assets	$	-	$	72.3	$	48	$	120.3
	Liabilities
	Natural gas related derivatives	$	-	$	-41.1	$	-176.7	$	-217.8
	Electricity related derivatives		-		-7		-23		-30
	Total Liabilities	$	-	$	-48.1	$	-199.7	$	-247.8
Reconciliation of Fair Value Measurements Using Significant Level 3 Inputs	'
	WGL Holdings, Inc. Reconciliation of Fair Value Measurements Using Significant Level 3 Inputs
	(In millions)		Natural Gas Related Derivatives		Electricity Related Derivatives		Weather Related Instruments		Warrants		Total
	Three Months Ended December 31, 2013
	Balance at October 1, 2013	$	-155.2	$	2.4	$	-	$	1.1	$	-151.7
	Realized and unrealized gains (losses)
	Recorded to income		-46.7		-7.9		-		0.1		-54.5
	Recorded to regulatory assets - gas costs		-72		-		-		-		-72
	Purchases		-		1.4		-		-		1.4
	Settlements		9.4		2.4		-		-		11.8
	Balance at December 31, 2013	$	-264.5	$	-1.7	$	-	$	1.2	$	-265
	WGL Holdings, Inc. Reconciliation of Fair Value Measurements Using Significant Level 3 Inputs
	(In millions)		Natural Gas Related Derivatives		Electricity Related Derivatives		Weather Related Instruments		Warrants		Total
	Three Months Ended December 31, 2012
	Balance at October 1, 2012	$	39.6	$	2.8	$	-0.5	$	0.9	$	42.8
	Realized and unrealized gains (losses)
	Recorded to income		-8.6		-10.9		0.6		0.1		-18.8
	Recorded to regulatory assets - gas costs		-12.1		-		-		-		-12.1
	Purchases		-		2.5		-		-		2.5
	Settlements		2.6		10.2		-		-		12.8
	Balance at December 31, 2012	$	21.5	$	4.6	$	0.1	$	1	$	27.2
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'
	WGL Holdings, Inc. Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements
	Three Months Ended December 31, 2013
	(In millions)	Natural Gas Related Derivatives		Electricity Related Derivatives		Weather Related Instruments		Warrants		Total
	Operating revenues—non-utility	$	-25.8	$	-10	$	-	$	-	$	-35.8
	Utility cost of gas		-23.4		-		-		-		-23.4
	Other income-net		-		-		-		0.1		0.1
	Non-utility cost of energy-related sales		2.5		2.1		-		-		4.6
	Total	$	-46.7	$	-7.9	$	-	$	0.1	$	-54.5
	WGL Holdings, Inc. Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements
	Three Months Ended December 31, 2012
	(In millions)	Natural Gas Related Derivatives		Electricity Related Derivatives		Weather Related Instruments		Warrants		Total
	Operating revenues—non-utility	$	-0.5	$	-1.1	$	-	$	-	$	-1.6
	Utility cost of gas		-7.7		-		-		-		-7.7
	Other income-net		-		-		-		0.1		0.1
	Non-utility cost of energy-related sales		-0.4		-9.8		-		-		-10.2
	Operation and maintenance expense		-		-		0.6		-		0.6
	Total	$	-8.6	$	-10.9	$	0.6	$	0.1	$	-18.8
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'
	WGL Holdings, Inc. Unrealized Gains (Losses) Recorded for Level 3 Measurements
	Three Months Ended December 31, 2013
	(In millions)	Natural Gas Related Derivatives		Electricity Related Derivatives		Weather Related Instruments		Warrants		Total
	Recorded to income
	Operating revenues—non-utility	$	-25.2	$	-5	$	-	$	-	$	-30.2
	Utility cost of gas		-22.9		-		-		-		-22.9
	Non-utility cost of energy-related sales		2.3		1		-		-		3.3
	Other income—net		-		-		-		0.1		0.1
	Recorded to regulatory assets—gas costs		-71.1		-		-		-		-71.1
	Total	$	-116.9	$	-4	$	-	$	0.1	$	-120.8
	WGL Holdings, Inc. Unrealized Gains (Losses) Recorded for Level 3 Measurements
	Three Months Ended December 31, 2012
	(In millions)	Natural Gas Related Derivatives		Electricity Related Derivatives		Weather Related Instruments		Warrants		Total
	Recorded to income
	Operating revenues—non-utility	$	0.3	$	4.3	$	-	$	-	$	4.6
	Utility cost of gas		-7.5		-		-		-		-7.5
	Non-utility cost of energy-related sales		0.6		9.2		-		-		9.8
	Other income-net		-		-		-		0.1		0.1
	Operation and maintenance expense		-		-		0.6		-		0.6
	Recorded to regulatory assets—gas costs		-11.9		-		-		-		-11.9
	Total	$	-18.5	$	13.5	$	0.6	$	0.1	$	-4.3
Fair Value of Financial Instruments	'
	WGL Holdings, Inc. Fair Value of Financial Instruments
		31-Dec-13				30-Sep-13
	(In millions)	Carrying Amount		Fair Value		Carrying Amount		Fair Value
	Money market funds(a)	$	6.8	$	6.8	$	6.5	$	6.5
	Other short-term investments(a)	$	0.2	$	0.2	$	0.1	$	0.1
	Commercial paper (b)	$	443.3	$	443.3	$	373.1	$	373.1
	Long-term debt(c)	$	599.3	$	688.7	$	524.1	$	630.2
Washington Gas Light Company	'
Fair Value Measurements Under the Fair Value Hierarchy	'
	Washington Gas Light Company
	Fair Value Measurements Under the Fair Value Hierarchy
	(In millions)		Level 1		Level 2		Level 3		Total
	At December 31, 2013
	Assets
	Natural gas related derivatives	$	-	$	30.6	$	14.9	$	45.5
	Total Assets	$	-	$	30.6	$	14.9	$	45.5
	Liabilities
	Natural gas related derivatives	$	-	$	-19.7	$	-234.9	$	-254.6
	Total Liabilities	$	-	$	-19.7	$	-234.9	$	-254.6
	At September 30, 2013
	Assets
	Natural gas related derivatives	$	-	$	51	$	17	$	68
	Total Assets	$	-	$	51	$	17	$	68
	Liabilities
	Natural gas related derivatives	$	-	$	-25.1	$	-150.6	$	-175.7
	Total Liabilities	$	-	$	-25.1	$	-150.6	$	-175.7
Reconciliation of Fair Value Measurements Using Significant Level 3 Inputs	'
	Washington Gas Light Company Reconciliation of Fair Value Measurements Using Significant Level 3 Inputs
	(In millions)		Natural Gas Related Derivatives		Electricity Related Derivatives		Weather Related Instruments		Warrants		Total
	Three Months Ended December 31, 2013
	Balance at October 1, 2013	$	-133.6	$	-	$	-	$	-	$	-133.6
	Realized and unrealized gains (losses)
	Recorded to income		-23.4		-		-		-		-23.4
	Recorded to regulatory assets - gas costs		-72		-		-		-		-72
	Settlements		9		-		-		-		9
	Balance at December 31, 2013	$	-220	$	-	$	-	$	-	$	-220
	Washington Gas Light Company Reconciliation of Fair Value Measurements Using Significant Level 3 Inputs
	(In millions)		Natural Gas Related Derivatives		Electricity Related Derivatives		Weather Related Instruments		Warrants		Total
	Three Months Ended December 31, 2012
	Balance at October 1, 2012	$	35.6	$	-	$	-0.5	$	-	$	35.1
	Realized and unrealized gains (losses)
	Recorded to income		-7.7		-		0.6		-		-7.1
	Recorded to regulatory assets - gas costs		-12.1		-		-		-		-12.1
	Settlements		2		-		-		-		2
	Balance at December 31, 2012	$	17.8	$	-	$	0.1	$	-	$	17.9
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'
	Washington Gas Light Company Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements
	Three Months Ended December 31, 2013
	(In millions)	Natural Gas Related Derivatives		Electricity Related Derivatives		Weather Related Instruments		Warrants		Total
	Utility cost of gas	$	-23.4	$	-	$	-	$	-	$	-23.4
	Total	$	-23.4	$	-	$	-	$	-	$	-23.4
	Washington Gas Light Company Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements
	Three Months Ended December 31, 2012
	(In millions)	Natural Gas Related Derivatives		Electricity Related Derivatives		Weather Related Instruments		Warrants		Total
	Utility cost of gas	$	-7.7	$	-	$	-	$	-	$	-7.7
	Operation and maintenance expense		-		-		0.6		-		0.6
	Total	$	-7.7	$	-	$	0.6	$	-	$	-7.1
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'
	Washington Gas Light Company Unrealized Gains (Losses) Recorded for Level 3 Measurements
	Three Months Ended December 31, 2013
	(In millions)	Natural Gas Related Derivatives		Electricity Related Derivatives		Weather Related Instruments		Warrants		Total
	Recorded to income
	Utility cost of gas	$	-22.9	$	-	$	-	$	-	$	-22.9
	Recorded to regulatory assets—gas costs		-71.1		-		-		-		-71.1
	Total	$	-94	$	-	$	-	$	-	$	-94
	Washington Gas Light Company Unrealized Gains (Losses) Recorded for Level 3 Measurements
	Three Months Ended December 31, 2012
	(In millions)	Natural Gas Related Derivatives		Electricity Related Derivatives		Weather Related Instruments		Warrants		Total
	Recorded to income
	Utility cost of gas	$	-7.5	$	-	$	-	$	-	$	-7.5
	Operation and maintenance expense		-		-		0.6		-		0.6
	Recorded to regulatory assets—gas costs		-11.9		-		-		-		-11.9
	Total	$	-19.4	$	-	$	0.6	$	-	$	-18.8
Fair Value of Financial Instruments	'
	Washington Gas Light Company Fair Value of Financial Instruments
		31-Dec-13				30-Sep-13
	(In millions)	Carrying Amount		Fair Value		Carrying Amount		Fair Value
	Money market funds(a)	$	3.2	$	3.2	$	3.1	$	3.1
	Other short-term investments(a)	$	0.2	$	0.2	$	0.1	$	0.1
	Commercial paper (b)	$	188	$	188	$	124.5	$	124.5
	Long-term debt(c)	$	599.3	$	688.7	$	524.1	$	630.2
	(a)Balance is located in cash and cash equivalents in the accompanying balance sheets. These amounts may be offset by outstanding checks.
	(b)Balance is located in notes payable in the accompanying balance sheets.
	(c)Excludes current maturities and unamortized discounts.

Operating_Segment_Reporting_Ta

Operating Segment Reporting (Tables)	3 Months Ended
	Dec. 31, 2013
Segment Reporting Information Operating Income Loss Table [Abstract]	'
Operating Segment Financial Information	'
	Operating Segment Financial Information
							Non-Utility Operations
	(In thousands)				Regulated Utility	Retail Energy-Marketing		Commercial Energy Systems		Midstream Energy Services		Other Activities		Eliminations(b)		Consolidated
	Three Months Ended December 31, 2013
	Operating revenues (a)			$	390,415	$	322,938	$	4,717	$	-33,173	$	-	$	-4,600	$	680,297
	Operating expenses:
		Cost of energy-related sales			190,695		303,268		3,145		-		-		-4,876		492,232
		Operation			57,430		11,251		1,474		1,124		3,004		17		74,300
		Maintenance			13,842		-		-		-		-		-		13,842
		Depreciation and amortization			25,369		174		1,093		31		-		-77		26,590
		General taxes and other assessments:
			Revenue taxes		24,671		1,947		1		-		-		-		26,619
			Other		12,775		1,068		52		87		21		-1		14,002
			Total operating expenses	$	324,782	$	317,708	$	5,765	$	1,242	$	3,025	$	-4,937	$	647,585
	Operating income (loss)				65,633		5,230		-1,048		-34,415		-3,025		337		32,712
	Equity in earnings of unconsolidated affiliates				-		-		284		206		-		-		490
	Other income (expense) — net				-180		61		65		-83		356		-		219
	Interest expense				8,879		-		-		-		113		-		8,992
	Dividends on Washington Gas preferred stock				330		-		-		-		-		-		330
	Income tax expense (benefit)				17,523		1,976		-562		-12,504		-1,099		136		5,470
	Net income (loss) applicable to common stock			$	38,721	$	3,315	$	-137	$	-21,788	$	-1,683	$	201	$	18,629
	Total assets at December 31, 2013			$	3,828,709	$	418,633	$	380,241	$	171,420	$	299,769	$	-467,246	$	4,631,526
	Capital expenditures			$	55,092	$	75	$	3,138	$	-	$	-	$	-	$	58,305
	Equity method investments at December 31, 2013			$	-	$	-	$	66,526	$	10,813	$	413	$	-	$	77,752
	Three Months Ended December 31, 2012
	Operating revenues (a)			$	355,817	$	324,059	$	11,985	$	2,854	$	-	$	-7,979	$	686,736
	Operating expenses:
		Cost of energy-related sales			150,448		290,133		9,111		-		-		-7,573		442,119
		Operation			58,208		11,359		1,232		844		791		-254		72,180
		Maintenance			11,450		-		-		-		-		-		11,450
		Depreciation and amortization			26,792		175		459		31		-		-153		27,304
		General taxes and other assessments:
			Revenue taxes		24,221		1,431		1		-		-		-		25,653
			Other		12,287		871		79		166		10		1		13,414
			Total operating expenses	$	283,406	$	303,969	$	10,882	$	1,041	$	801	$	-7,979	$	592,120
	Operating income (loss)				72,411		20,090		1,103		1,813		-801		-		94,616
	Equity in earnings of unconsolidated affiliates				-		-		245		-		-		-		245
	Other income (expenses) — net				133		50		80		-		218		-52		429
	Interest expense				9,095		3		43		-		104		-52		9,193
	Dividends on Washington Gas preferred stock				330		-		-		-		-		-		330
	Income tax expense				24,453		7,116		347		537		926		-		33,379
	Net income (loss) applicable to common stock			$	38,666	$	13,021	$	1,038	$	1,276	$	-1,613	$	-	$	52,388
	Total assets at December 31, 2012			$	3,673,308	$	400,951	$	168,761	$	201,111	$	226,221	$	-329,415	$	4,340,937
	Capital expenditures			$	60,615	$	201	$	15,101	$	-	$	-	$	-	$	75,917
	Equity method investments at December 31, 2012			$	-	$	-	$	29,005	$	-	$	285	$	-	$	29,290
	(a) Operating revenues are reported gross of revenue taxes. Revenue taxes of both the regulated utility and the retail energy-marketing segments include gross receipt taxes. Revenue taxes of the regulated utility segment also include PSC fees, franchise fees and energy taxes. Operating revenue amounts in the "Eliminations" column represent total intersegment revenues associated with sales from the regulated utility segment to the retail energy-marketing segment. Midstream Energy Services' cost of energy related sales is netted with its gross revenues.
	(b)Intersegment eliminations net income represents a timing difference between Commercial Energy Systems’ recognition of revenue for the sale of Solar Renewable Energy Credits (SRECs) to Retail Energy-Marketing and Retail Energy-Marketing’s recognition of the associated expense. Retail Energy-Marketing has recorded a portion of the SREC’s purchased as inventory to be used in future periods and will expense them at that time.

Other_Investment_Tables

Other Investment (Tables)	3 Months Ended
	Dec. 31, 2013
Other Investments [Abstract]	'
FutureMinimumLease	'
		Minimum Payments Receivable for Direct Financing Leases
		(In millions)
		2014	$	2.2
		2015		1.2
		2016		1.2
		2017		1.2
		2018		1.2
		Thereafter		12.8
		Total	$	19.8
InvestmentTable	'
	WGL Holdings, Inc.
	Balance Sheet Location of Other Investments
	As of December 31, 2013 (in millions)	VIEs		Non-VIEs		Total
	Assets
	Investments in unconsolidated affiliates	$	67	$	16.4	$	83.4
	Investments in direct financing leases receivable		23		-		23
	Derivatives		-		1.1		1.1
	Other		2.6		-		2.6
	Total assets	$	92.6	$	17.5	$	110.1
	Liabilities
	Other	$	8.3	$	-	$	8.3
	Total liabilities	$	8.3	$	-	$	8.3
	WGL Holdings, Inc.
	Balance Sheet Location of Other Investments
	As of September 30, 2013 (in millions)	VIEs		Non-VIEs		Total
	Assets
	Investments in unconsolidated affiliates	$	55.4	$	12.1	$	67.5
	Investment in direct financing leases receivable		23.4		-		23.4
	Derivatives		-		1.1		1.1
	Other		5.8		-		5.8
	Total assets	$	84.6	$	13.2	$	97.8
	Liabilities
	Other	$	8.5	$	-	$	8.5
	Total liabilities	$	8.5	$	-	$	8.5
	WGL Holdings, Inc.
	Income Statement Location of Other Investments
	Three Months Ended December 31, 2013 (in millions)	VIEs		Non-VIEs		Total
	Equity in earnings of unconsolidated affiliates	$	0.3	$	0.2	$	0.5
	Depreciation and amortization		0.1		-		0.1
	Other income		0.5		0.2		0.7
	Net income	$	0.7	$	0.4	$	1.1
	WGL Holdings, Inc.
	Income Statement Location of Other Investments
	Three Months Ended December 31, 2012 (in millions)	VIEs		Non-VIEs		Total
	Equity in earnings of unconsolidated affiliates	$	0.2	$	-	$	0.2
	Other income		0.2		0.1		0.3
	Net income	$	0.4	$	0.1	$	0.5

Related_Party_Transactions_Tab

Related Party Transactions (Tables)	3 Months Ended
	Dec. 31, 2013
RelatedP arty Transactions [Abstract]	'
Related Party Transactions	'
	Washington Gas Receivables / Payables from Associated Companies
	(In millions)	31-Dec-13			30-Sep-13
	Receivables from Associated Companies	$	4.8		$	7.2
	Payables to Associated Companies	$	36		$	20.6
	Washington Gas-Gas Balancing Service Charges
			Three Months Ended
			December 31,
	(In millions)		2013		2012
	Gas balancing service charge	$	3.8	$	7.6

Pension_and_Other_PostRetireme1

Pension and Other Post-Retirement Benefit Plan (Tables)	3 Months Ended
	Dec. 31, 2013
Pension And Other Post Retirement Benefit Plans Tables [Abstract]	'
Components of Net Periodic Benefit Costs (Income)	'
	Components of Net Periodic Benefit Costs (Income)
			Three Months Ended December 31,
			2013				2012
			Pension		Health and		Pension		Health and
	(In millions)		Benefits		Life Benefits		Benefits		Life Benefits
	Components of net periodic benefit costs (income)
	Service cost	$	3.5	$	2.1	$	4.2	$	2.4
	Interest cost		10.1		5.4		9.1		4.7
	Expected return on plan assets		-10.3		-4.7		-10.5		-4.6
	Amortization of prior service cost (credit)		0.1		-1		0.3		-1
	Amortization of actuarial loss		4.2		0.7		7.2		2.3
	Amortization of transition obligation		-		-		-		0.3
	Net periodic benefit cost		7.6		2.5		10.3		4.1
	Amount allocated to construction projects		-1		-0.4		-1.4		-0.7
	Amount amortized/deferred as regulatory asset		1.8		0.1		-2.4		0.8
	Amount charged to expense	$	8.4	$	2.2	$	6.5	$	4.2

Changes_in_Accumulated_Other_C1

Changes in Accumulated Other Comprehensive Income (Tables)	3 Months Ended
	Dec. 31, 2013
Accumulated Other Comprehensive Income [Abstract]	'
Changes in Accumulated Other Comprehensive Income by Component	'
	Changes in Accumulated Other Comprehensive Income by Component
			Three Months Ended December 31,
			2013		2012
	(In thousands)
	Beginning Balance	$	-11,048	$	-12,201
	Amortization of prior service cost (a)		-35		-12
	Amortization of actuarial loss (a)		364		462
	Amortization of transition obligation (a)		-		9
	Current-period other comprehensive income		329		459
	Income tax expense related to other comprehensive income		130		182
	Ending Balance	$	-10,849	$	-11,924
	(a) These accumulated other comprehensive income components are included in the computation of net periodic benefit cost. Refer to Note 14-Pension and other post-retirement benefit plans for additional details.

Accounting_Policies_details

Accounting Policies (details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Washington Gas Light Company	'	'
Accounting Policies [Line Items]	'	'
Inventory Adjustments	$0	$0
WGL Midstream	'	'
Accounting Policies [Line Items]	'	'
Inventory Adjustments	$0	($8.40)

Accounts_Payable_and_Other_Acc2

Accounts Payable and Other Accrued Liabilities (Details) (USD $)	Dec. 31, 2013	Sep. 30, 2013
WGL Holdings, Inc.	'	'
Accounts payable - trade	$277,000,000	$216,300,000
Employee benefits and payroll accruals	14,200,000	23,400,000
Embedded derivatives and other accrued liabilities	22,700,000	30,900,000
Accounts Payable and Accrued Liabilities, Current, Total	313,955,000	270,658,000
Washington Gas Light Company	'	'
Accounts payable - trade	142,700,000	99,700,000
Employee benefits and payroll accruals	13,500,000	21,400,000
Embedded derivatives and other accrued liabilities	15,300,000	11,700,000
Accounts Payable and Accrued Liabilities, Current, Total	$171,579,000	$132,814,000

ShortTerm_Debt_Details

Short-Term Debt (Details) (USD $)	Dec. 31, 2013		Sep. 30, 2013
Committed Credit	'		'
Line Of Credit Facility [Line Items]	'		'
Unsecured revolving credit facility	$800,000,000	[1]	$800,000,000	[1]
Less: Commercial Paper	-443,300,000		-373,100,000
Net committed credit available	356,700,000		426,900,000
Short-term debt weighted average interest rate	0.18%		0.19%
WGL Holdings, Inc.	'		'
Line Of Credit Facility [Line Items]	'		'
Less: Commercial Paper	-443,300,000		-373,100,000
Outstanding bank loans	0		0
WGL Holdings, Inc. | Committed Credit	'		'
Line Of Credit Facility [Line Items]	'		'
Unsecured revolving credit facility	450,000,000	[1],[2]	450,000,000	[1],[2]
Less: Commercial Paper	-255,300,000	[2]	-248,600,000	[2]
Net committed credit available	194,700,000	[2]	201,400,000	[2]
Revolving credit facility maximum borrowing capacity	550,000,000		550,000,000
Revolving credit facility additional borrowings	100,000,000		100,000,000
Washington Gas Light Company	'		'
Line Of Credit Facility [Line Items]	'		'
Less: Commercial Paper	-188,000,000		-124,500,000
Outstanding bank loans	0		0
Washington Gas Light Company | Committed Credit	'		'
Line Of Credit Facility [Line Items]	'		'
Unsecured revolving credit facility	350,000,000	[1]	350,000,000	[1]
Less: Commercial Paper	-188,000,000		-124,500,000
Net committed credit available	162,000,000		225,500,000
Revolving credit facility maximum borrowing capacity	450,000,000		450,000,000
Revolving credit facility additional borrowings	$100,000,000		$100,000,000
[1]	Both WGL and Washington Gas have the right to request extensions with the banksb approval. WGL's revolving credit facility permits it to borrow an additional $100 million, with the banksb approval, for a total of $550 million. Washington Gasb revolving credit facility permits it to borrow an additional $100 million, with the banksb approval, for a total of $450 million.
[2]	WGL Holdings, Inc. includes all subsidiaries other than Washington Gas Light Company.

LongTerm_Debt_Details

Long-Term Debt (Details) (Washington Gas Light Company, USD $)	Dec. 31, 2013	Sep. 30, 2013
In Millions, unless otherwise specified
Long Term Debt Details [Line Items]	'	'
Debt Instrument Unused Borrowing Capacity Amount	$375	$450
Medium Term and Private Placement Notes	621	583
Long-term Debt, Weighted Average Interest Rate	5.86%	5.91%
Issuances [Member]	'	'
Long Term Debt Details [Line Items]	'	'
Debt Instrument Interest Rate Stated Percentage	5.00%	'
Debt Instrument Interest Rate Effective Percentage Net	4.95%	'
Debt Instrument Face Amount	75	'
Medium Term and Private Placement Notes	'	0
Retirements [Member]	'	'
Long Term Debt Details [Line Items]	'	'
Debt Instrument Interest Rate Stated Percentage	4.88%	'
Debt Instrument Face Amount	37	'
Medium Term and Private Placement Notes	'	$0

Common_Shareholders_Equity_Det

Common Shareholders' Equity (Details) (USD $)	3 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
WGL Holdings, Inc.	'	'
Common shareholders' equity, beginning balance	$1,274,545	'
Shares outstanding, beginning balance	51,774,204	'
Net Income (Loss)	18,959	52,718
OTHER COMPREHENSIVE INCOME	199	277
Dividend reinvestment	1,503	'
Stock-based compensation	-220	'
Dividends declared:	'	'
Common Stock	-21,795	'
Preferred Stock	-330	'
Common shareholders' equity, ending balance	1,272,861	'
Shares outstanding, ending balance	51,841,665	'
WGL Holdings, Inc. | Common Stock	'	'
Common shareholders' equity, beginning balance	574,461	'
Net Income (Loss)	0	'
OTHER COMPREHENSIVE INCOME	0	'
Dividend reinvestment	1,503	'
Stock-based compensation	1,524	'
Dividends declared:	'	'
Common Stock	0	'
Preferred Stock	0	'
Common shareholders' equity, ending balance	577,488	'
WGL Holdings, Inc. | Paid-In Capital	'	'
Common shareholders' equity, beginning balance	10,710	'
Net Income (Loss)	0	'
OTHER COMPREHENSIVE INCOME	0	'
Dividend reinvestment	0	'
Stock-based compensation	-1,744	'
Dividends declared:	'	'
Common Stock	0	'
Preferred Stock	0	'
Common shareholders' equity, ending balance	8,966	'
WGL Holdings, Inc. | Retained Earnings	'	'
Common shareholders' equity, beginning balance	700,422	'
Net Income (Loss)	18,959	'
OTHER COMPREHENSIVE INCOME	0	'
Dividend reinvestment	0	'
Stock-based compensation	0	'
Dividends declared:	'	'
Common Stock	-21,795	'
Preferred Stock	-330	'
Common shareholders' equity, ending balance	697,256	'
WGL Holdings, Inc. | Accumulated Other Comprehensive Loss, Net of Taxes	'	'
Common shareholders' equity, beginning balance	-11,048	'
Net Income (Loss)	0	'
OTHER COMPREHENSIVE INCOME	199	'
Dividend reinvestment	0	'
Stock-based compensation	0	'
Dividends declared:	'	'
Common Stock	0	'
Preferred Stock	0	'
Common shareholders' equity, ending balance	-10,849	'
Washington Gas Light Company	'	'
Common shareholders' equity, beginning balance	1,024,583	'
Shares outstanding, beginning balance	46,479,536	'
Net Income (Loss)	38,807	38,717
OTHER COMPREHENSIVE INCOME	199	277
Stock-based compensation	-266	'
Dividends declared:	'	'
Common Stock	-19,075	'
Preferred Stock	-330	'
Common shareholders' equity, ending balance	1,043,918	'
Shares outstanding, ending balance	46,479,536	'
Washington Gas Light Company | Common Stock	'	'
Common shareholders' equity, beginning balance	46,479	'
Net Income (Loss)	0	'
OTHER COMPREHENSIVE INCOME	0	'
Stock-based compensation	0	'
Dividends declared:	'	'
Common Stock	0	'
Preferred Stock	0	'
Common shareholders' equity, ending balance	46,479	'
Washington Gas Light Company | Paid-In Capital	'	'
Common shareholders' equity, beginning balance	477,968	'
Net Income (Loss)	0	'
OTHER COMPREHENSIVE INCOME	0	'
Stock-based compensation	-266	'
Dividends declared:	'	'
Common Stock	0	'
Preferred Stock	0	'
Common shareholders' equity, ending balance	477,702	'
Washington Gas Light Company | Retained Earnings	'	'
Common shareholders' equity, beginning balance	511,184	'
Net Income (Loss)	38,807	'
OTHER COMPREHENSIVE INCOME	0	'
Stock-based compensation	0	'
Dividends declared:	'	'
Common Stock	-19,075	'
Preferred Stock	-330	'
Common shareholders' equity, ending balance	530,586	'
Washington Gas Light Company | Accumulated Other Comprehensive Loss, Net of Taxes	'	'
Common shareholders' equity, beginning balance	-11,048	'
Net Income (Loss)	0	'
OTHER COMPREHENSIVE INCOME	199	'
Stock-based compensation	0	'
Dividends declared:	'	'
Common Stock	0	'
Preferred Stock	0	'
Common shareholders' equity, ending balance	($10,849)	'

Earnings_Per_Share_Details

Earnings Per Share (Details) (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Net Income (Loss) applicable to common stock	$18,629	$52,388
Weighted Average Number of Shares Outstanding, Basic	51,816	51,631
Stock-based compensation plans	11	57
Diluted EPS	51,827	51,688
Earnings Per Share, Basic	$0.36	$1.01
Earnings Per Share, Diluted	$0.36	$1.01
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	0	0

Income_Taxes_Details

Income Taxes (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Sep. 30, 2014	Sep. 30, 2013
Income Tax Expense Benefit Details [Line Items]	'	'	'	'
Unrecognized Tax Benefits	$25.60	'	'	$25.10
WGL Holdings, Inc.	'	'	'	'
Income Tax Expense Benefit Details [Line Items]	'	'	'	'
Effective Income Tax Rate	22.40%	'	'	'
Effective Income Tax Rate Expected	'	'	34.90%	'
Washington Gas Light Company	'	'	'	'
Income Tax Expense Benefit Details [Line Items]	'	'	'	'
Accrued interest related to uncertain tax positions	0.1	'	'	0.1
Interest Expense For Uncertain Tax Position	$0	$0	'	'
Effective Income Tax Rate	30.90%	'	'	'
Effective Income Tax Rate Expected	'	'	35.00%	'

Derivative_and_Weather_Related2

Derivative and Weather Related Instruments (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012	Sep. 30, 2013
WGEServices	'		'	'
DerivativeCollateralAbstract	'		'	'
Right to Reclaim Cash	$12.60		'	$12.10
Collateral Already Posted Aggregate Fair Value	5.1		'	3.6
WGL Midstream	'		'	'
DerivativeCollateralAbstract	'		'	'
Right to Reclaim Cash	9.6		'	8.1
Collateral Already Posted Aggregate Fair Value	0		'	0
WGL Holdings, Inc.	'		'	'
Absolute Notional Amounts of Open Positions on Derivative Instruments	'		'	'
Interest Rate Swap Notional Principal Value	0		'	75	[1]
Warrant Transaction Volume	4.6		'	4.6
Balance Sheet Classification of Derivative Instruments	'		'	'
Derivative Assets	83		'	120.3
Derivative Liabilities	-342		'	-247.8
Netting of Collateral	5.1		'	0.9
Total	-253.9	[2]	'	-126.6	[2]
WGL Holdings, Inc. | Current assets- derivatives	'		'	'
Balance Sheet Classification of Derivative Instruments	'		'	'
Derivative Assets	35.6		'	57.3
Derivative Liabilities	-12.1		'	-19.3
Netting of Collateral	0		'	-2.7
Total	23.5	[2]	'	35.3	[2]
WGL Holdings, Inc. | Non current assets- derivatives	'		'	'
Balance Sheet Classification of Derivative Instruments	'		'	'
Derivative Assets	9.2		'	57.4
Derivative Liabilities	0		'	-31.1
Netting of Collateral	0		'	0
Total	9.2	[2]	'	26.3	[2]
WGL Holdings, Inc. | Accounts Payable And Other Accrued Liabilities [Member]	'		'	'
Balance Sheet Classification of Derivative Instruments	'		'	'
Derivative Assets	0.4		'	1.5
Derivative Liabilities	0		'	0
Netting of Collateral	0		'	0
Total	0.4	[2]	'	1.5	[2]
WGL Holdings, Inc. | Current liabilities- Derivatives	'		'	'
Balance Sheet Classification of Derivative Instruments	'		'	'
Derivative Assets	10.3		'	4.1
Derivative Liabilities	-54.2		'	-53.4
Netting of Collateral	2.5		'	0.9
Total	-41.4	[2]	'	-48.4	[2]
WGL Holdings, Inc. | Non current liabilities- derivatives	'		'	'
Balance Sheet Classification of Derivative Instruments	'		'	'
Derivative Assets	27.5		'	0
Derivative Liabilities	-275.7		'	-144
Netting of Collateral	2.6		'	2.7
Total	-245.6	[2]	'	-141.3	[2]
WGL Holdings, Inc. | Asset Optimization [Member]	'		'	'
Absolute Notional Amounts of Open Positions on Derivative Instruments	'		'	'
Natural Gas Derivative Transaction, Volume	12,771,700,000		'	13,289,600,000
WGL Holdings, Inc. | Retail Sales [Member]	'		'	'
Absolute Notional Amounts of Open Positions on Derivative Instruments	'		'	'
Natural Gas Derivative Transaction, Volume	83,000,000		'	98,900,000
Electricity Derivative Transaction, Volume	4,684,000,000		'	4,790,200,000
WGL Holdings, Inc. | Other Risk Management Activities [Member]	'		'	'
Absolute Notional Amounts of Open Positions on Derivative Instruments	'		'	'
Natural Gas Derivative Transaction, Volume	1,763,500,000		'	1,803,600,000
Electricity Derivative Transaction, Volume	19,151,000,000		'	17,647,900,000
Washington Gas Light Company	'		'	'
Asset Optimization [Abstract]	'		'	'
Gain (Loss) on Asset Optimization Transactions Net Pretax	-19.8		-5	'
Unrealized Gains (Losses) On Asset Optimization Derivative Instruments Net Pretax	-26.2		-8.7	'
DerivativeCollateralAbstract	'		'	'
Right to Reclaim Cash	3.8		'	3
Derivative Collateral Obligation to Return Cash	10.2		'	4.6
Collateral Already Posted Aggregate Fair Value	0		'	0
Absolute Notional Amounts of Open Positions on Derivative Instruments	'		'	'
Interest Rate Swap Notional Principal Value	0		'	75	[1]
Warrant Transaction Volume	0		'	0
Balance Sheet Classification of Derivative Instruments	'		'	'
Derivative Assets	45.5		'	68
Derivative Liabilities	-254.6		'	-175.7
Netting of Collateral	0		'	-2.7
Total	-209.1	[2]	'	-110.4	[2]
Washington Gas Light Company | Current assets- derivatives	'		'	'
Balance Sheet Classification of Derivative Instruments	'		'	'
Derivative Assets	10.9		'	19.3
Derivative Liabilities	-4.7		'	-12.3
Netting of Collateral	0		'	-2.7
Total	6.2	[2]	'	4.3	[2]
Washington Gas Light Company | Non current assets- derivatives	'		'	'
Balance Sheet Classification of Derivative Instruments	'		'	'
Derivative Assets	0		'	47.2
Derivative Liabilities	0		'	-31.1
Netting of Collateral	0		'	0
Total	0	[2]	'	16.1	[2]
Washington Gas Light Company | Current liabilities- Derivatives	'		'	'
Balance Sheet Classification of Derivative Instruments	'		'	'
Derivative Assets	7.4		'	1.5
Derivative Liabilities	-34.1		'	-26.2
Netting of Collateral	0		'	0
Total	-26.7	[2]	'	-24.7	[2]
Washington Gas Light Company | Non current liabilities- derivatives	'		'	'
Balance Sheet Classification of Derivative Instruments	'		'	'
Derivative Assets	27.2		'	0
Derivative Liabilities	-215.8		'	-106.1
Netting of Collateral	0		'	0
Total	($188.60)	[2]	'	($106.10)	[2]
Washington Gas Light Company | Asset Optimization [Member]	'		'	'
Absolute Notional Amounts of Open Positions on Derivative Instruments	'		'	'
Natural Gas Derivative Transaction, Volume	11,010,000,000		'	11,115,800,000
Washington Gas Light Company | Retail Sales [Member]	'		'	'
Absolute Notional Amounts of Open Positions on Derivative Instruments	'		'	'
Natural Gas Derivative Transaction, Volume	0		'	0
Electricity Derivative Transaction, Volume	0		'	0
Washington Gas Light Company | Other Risk Management Activities [Member]	'		'	'
Absolute Notional Amounts of Open Positions on Derivative Instruments	'		'	'
Natural Gas Derivative Transaction, Volume	1,442,500,000		'	1,455,700,000
Electricity Derivative Transaction, Volume	0		'	0
[1]	B The fair value of our interest rate swaps was minimal at 9/30/13.
[2]	WGL 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 815. All recognized derivative contracts and associated financial collateral subject to a master netting arrangement or similar that is eligible for offset under ASC 815 have been presented net in the balance sheet.

Derivative_and_Weather_Related3

Derivative and Weather Related Instruments (Gains and Losses) (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
WGL Holdings, Inc.	'	'
Gains and (Losses) on Derivative Instruments	'	'
Gains (Losses) On Derivative Instruments	($137.70)	($14.30)
WGL Holdings, Inc. | Operating Revenues Non Utility [Member]	'	'
Gains and (Losses) on Derivative Instruments	'	'
Recorded to income	-48.5	12.2
WGL Holdings, Inc. | Utility Cost Of Gas [Member]	'	'
Gains and (Losses) on Derivative Instruments	'	'
Recorded to income	-27.3	-7.2
WGL Holdings, Inc. | Non Utility Cost Of Energy Related Sales [Member]	'	'
Gains and (Losses) on Derivative Instruments	'	'
Recorded to income	16.3	-7.5
WGL Holdings, Inc. | Other Income [Member]	'	'
Gains and (Losses) on Derivative Instruments	'	'
Recorded to income	0.1	0.1
WGL Holdings, Inc. | Gas Costs [Member]	'	'
Gains and (Losses) on Derivative Instruments	'	'
Recorded to regulatory assets/liabilities	-78.3	-11.9
Washington Gas Light Company	'	'
Gains and (Losses) on Derivative Instruments	'	'
Gains (Losses) On Derivative Instruments	-105.6	-19.1
Washington Gas Light Company | Operating Revenues Non Utility [Member]	'	'
Gains and (Losses) on Derivative Instruments	'	'
Recorded to income	0	0
Washington Gas Light Company | Utility Cost Of Gas [Member]	'	'
Gains and (Losses) on Derivative Instruments	'	'
Recorded to income	-27.3	-7.2
Washington Gas Light Company | Non Utility Cost Of Energy Related Sales [Member]	'	'
Gains and (Losses) on Derivative Instruments	'	'
Recorded to income	0	0
Washington Gas Light Company | Other Income [Member]	'	'
Gains and (Losses) on Derivative Instruments	'	'
Recorded to income	0	0
Washington Gas Light Company | Gas Costs [Member]	'	'
Gains and (Losses) on Derivative Instruments	'	'
Recorded to regulatory assets/liabilities	($78.30)	($11.90)

Derivative_and_Weather_Related4

Derivative and Weather Related Instruments (Details 2) (USD $)	Dec. 31, 2013
In Millions, unless otherwise specified	Customers
WGEServices	'
Concentration of Credit Risk	'
Obligation to counterparties	$0.70
Percentage Of Credit Exposure	10.00%
Number of Counterparties	4
WGL Midstream	'
Concentration of Credit Risk	'
Obligation to counterparties	11
Percentage Of Credit Exposure	10.00%
Number of Counterparties	2
Washington Gas Light Company	'
Concentration of Credit Risk	'
Obligation to counterparties	$4.40
Percentage Of Credit Exposure	10.00%
Number of Counterparties	2

Derivative_and_Weather_Related5

Derivative and Weather Related Instruments (Details 3) (USD $)	Dec. 31, 2013	Sep. 30, 2013
In Millions, unless otherwise specified
WGL Holdings, Inc.	'	'
Potential Collateral Requirements for Derivative Liabilities with Credit-risk-Contingent Features	'	'
Derivative Gross Liability Position Aggregate Fair Value	$63.50	$77
Maximum Potential Future Exposure On Credit Risk Derivatives	27	33.6
Washington Gas Light Company	'	'
Potential Collateral Requirements for Derivative Liabilities with Credit-risk-Contingent Features	'	'
Derivative Gross Liability Position Aggregate Fair Value	38	44.7
Maximum Potential Future Exposure On Credit Risk Derivatives	$3.90	$1.70

Derivative_and_Weather_Related6

Derivative and Weather Related Instruments (Details 4) (USD $)	3 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
WGEServices	'	'
Gain (Loss) On Derivative Instruments Net Pretax [Abstract]	'	'
Gain (losses) on weather related instruments, pretax	($1,100,000)	$400,000
Washington Gas Light Company	'	'
Gain (Loss) On Derivative Instruments Net Pretax [Abstract]	'	'
Gain (losses) on weather related instruments, pretax	$0	$0.60

Fair_Value_Measurements_Detail

Fair Value Measurements (Details) (USD $)	Dec. 31, 2013	Sep. 30, 2013
In Millions, unless otherwise specified
WGL Holdings, Inc.	'	'
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]	'	'
Assets	$83	$120.30
Liabilities	-342	-247.8
WGL Holdings, Inc. | Natural Gas Related Derivatives [Member]	'	'
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]	'	'
Assets	61.9	93.8
Liabilities	-316.4	-217.8
WGL Holdings, Inc. | Electricity Related Derivatives [Member]	'	'
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]	'	'
Assets	19.9	25.4
Liabilities	-25.6	-30
WGL Holdings, Inc. | Warrant [Member]	'	'
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]	'	'
Assets	1.2	1.1
WGL Holdings, Inc. | Level 1	'	'
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]	'	'
Assets	0	0
Liabilities	0	0
WGL Holdings, Inc. | Level 1 | Natural Gas Related Derivatives [Member]	'	'
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]	'	'
Assets	0	0
Liabilities	0	0
WGL Holdings, Inc. | Level 1 | Electricity Related Derivatives [Member]	'	'
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]	'	'
Assets	0	0
Liabilities	0	0
WGL Holdings, Inc. | Level 1 | Warrant [Member]	'	'
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]	'	'
Assets	0	0
WGL Holdings, Inc. | Level 2	'	'
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]	'	'
Assets	44.3	72.3
Liabilities	-38.3	-48.1
WGL Holdings, Inc. | Level 2 | Natural Gas Related Derivatives [Member]	'	'
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]	'	'
Assets	44.2	72.3
Liabilities	-34.2	-41.1
WGL Holdings, Inc. | Level 2 | Electricity Related Derivatives [Member]	'	'
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]	'	'
Assets	0.1	0
Liabilities	-4.1	-7
WGL Holdings, Inc. | Level 2 | Warrant [Member]	'	'
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]	'	'
Assets	0	0
WGL Holdings, Inc. | Level 3	'	'
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]	'	'
Assets	38.7	48
Liabilities	-303.7	-199.7
WGL Holdings, Inc. | Level 3 | Natural Gas Related Derivatives [Member]	'	'
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]	'	'
Assets	17.7	21.5
Liabilities	-282.2	-176.7
WGL Holdings, Inc. | Level 3 | Electricity Related Derivatives [Member]	'	'
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]	'	'
Assets	19.8	25.4
Liabilities	-21.5	-23
WGL Holdings, Inc. | Level 3 | Warrant [Member]	'	'
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]	'	'
Assets	1.2	1.1
Washington Gas Light Company	'	'
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]	'	'
Assets	45.5	68
Liabilities	-254.6	-175.7
Washington Gas Light Company | Natural Gas Related Derivatives [Member]	'	'
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]	'	'
Assets	45.5	68
Liabilities	-254.6	-175.7
Washington Gas Light Company | Level 1	'	'
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]	'	'
Assets	0	0
Liabilities	0	0
Washington Gas Light Company | Level 1 | Natural Gas Related Derivatives [Member]	'	'
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]	'	'
Assets	0	0
Liabilities	0	0
Washington Gas Light Company | Level 2	'	'
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]	'	'
Assets	30.6	51
Liabilities	-19.7	-25.1
Washington Gas Light Company | Level 2 | Natural Gas Related Derivatives [Member]	'	'
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]	'	'
Assets	30.6	51
Liabilities	-19.7	-25.1
Washington Gas Light Company | Level 3	'	'
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]	'	'
Assets	14.9	17
Liabilities	-234.9	-150.6
Washington Gas Light Company | Level 3 | Natural Gas Related Derivatives [Member]	'	'
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]	'	'
Assets	14.9	17
Liabilities	($234.90)	($150.60)

Fair_Value_Measurements_Reconc

Fair Value Measurements (Reconciliation with Level 3 Inputs) (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
WGL Holdings, Inc.	'	'
Reconciliation of Fair Value Measurements Using Significant Level 3 Inputs	'	'
Balance at beginning of period	($151.70)	$42.80
Realized and unrealized gains (losses)	'	'
Recorded to income	-54.5	-18.8
Recorded to regulatory assets - gas costs	-72	-12.1
Purchases	1.4	2.5
Settlements	11.8	12.8
Balance at end of period	-265	27.2
WGL Holdings, Inc. | Weather Instruments [Member]	'	'
Reconciliation of Fair Value Measurements Using Significant Level 3 Inputs	'	'
Balance at beginning of period	0	-0.5
Realized and unrealized gains (losses)	'	'
Recorded to income	0	0.6
Recorded to regulatory assets - gas costs	0	0
Purchases	0	0
Settlements	0	0
Balance at end of period	0	0.1
WGL Holdings, Inc. | Natural Gas Related Derivatives [Member]	'	'
Reconciliation of Fair Value Measurements Using Significant Level 3 Inputs	'	'
Balance at beginning of period	-155.2	39.6
Realized and unrealized gains (losses)	'	'
Recorded to income	-46.7	-8.6
Recorded to regulatory assets - gas costs	-72	-12.1
Purchases	0	0
Settlements	9.4	2.6
Balance at end of period	-264.5	21.5
WGL Holdings, Inc. | Electricity Related Derivatives [Member]	'	'
Reconciliation of Fair Value Measurements Using Significant Level 3 Inputs	'	'
Balance at beginning of period	2.4	2.8
Realized and unrealized gains (losses)	'	'
Recorded to income	-7.9	-10.9
Recorded to regulatory assets - gas costs	0	0
Purchases	1.4	2.5
Settlements	2.4	10.2
Balance at end of period	-1.7	4.6
WGL Holdings, Inc. | Warrant [Member]	'	'
Reconciliation of Fair Value Measurements Using Significant Level 3 Inputs	'	'
Balance at beginning of period	1.1	0.9
Realized and unrealized gains (losses)	'	'
Recorded to income	0.1	0.1
Recorded to regulatory assets - gas costs	0	0
Purchases	0	0
Settlements	0	0
Balance at end of period	1.2	1
Washington Gas Light Company	'	'
Reconciliation of Fair Value Measurements Using Significant Level 3 Inputs	'	'
Balance at beginning of period	-133.6	35.1
Realized and unrealized gains (losses)	'	'
Recorded to income	-23.4	-7.1
Recorded to regulatory assets - gas costs	-72	-12.1
Settlements	9	2
Balance at end of period	-220	17.9
Washington Gas Light Company | Weather Instruments [Member]	'	'
Reconciliation of Fair Value Measurements Using Significant Level 3 Inputs	'	'
Balance at beginning of period	0	-0.5
Realized and unrealized gains (losses)	'	'
Recorded to income	0	0.6
Recorded to regulatory assets - gas costs	0	0
Settlements	0	0
Balance at end of period	0	0.1
Washington Gas Light Company | Natural Gas Related Derivatives [Member]	'	'
Reconciliation of Fair Value Measurements Using Significant Level 3 Inputs	'	'
Balance at beginning of period	-133.6	35.6
Realized and unrealized gains (losses)	'	'
Recorded to income	-23.4	-7.7
Recorded to regulatory assets - gas costs	-72	-12.1
Settlements	9	2
Balance at end of period	-220	17.8
Washington Gas Light Company | Electricity Related Derivatives [Member]	'	'
Reconciliation of Fair Value Measurements Using Significant Level 3 Inputs	'	'
Balance at beginning of period	0	0
Realized and unrealized gains (losses)	'	'
Recorded to income	0	0
Recorded to regulatory assets - gas costs	0	0
Settlements	0	0
Balance at end of period	0	0
Washington Gas Light Company | Warrant [Member]	'	'
Reconciliation of Fair Value Measurements Using Significant Level 3 Inputs	'	'
Balance at beginning of period	0	0
Realized and unrealized gains (losses)	'	'
Recorded to income	0	0
Recorded to regulatory assets - gas costs	0	0
Settlements	0	0
Balance at end of period	$0	$0

Fair_Value_Measurements_Realiz

Fair Value Measurements (Realized and Unrealized Gains and Losses with Level 3 Measurements) (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
WGL Holdings, Inc.	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	($54.50)	($18.80)
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to regulatory assets - gas costs	-71.1	-11.9
Total	-120.8	-4.3
WGL Holdings, Inc. | Natural Gas Related Derivatives [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	-46.7	-8.6
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to regulatory assets - gas costs	-71.1	-11.9
Total	-116.9	-18.5
WGL Holdings, Inc. | Electricity Related Derivatives [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	-7.9	-10.9
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to regulatory assets - gas costs	0	0
Total	-4	13.5
WGL Holdings, Inc. | Weather Instruments [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	0	0.6
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to regulatory assets - gas costs	0	0
Total	0	0.6
WGL Holdings, Inc. | Warrant [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	0.1	0.1
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to regulatory assets - gas costs	0	0
Total	0.1	0.1
WGL Holdings, Inc. | Operating Revenues Non Utility [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	-35.8	-1.6
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to income	-30.2	4.6
WGL Holdings, Inc. | Operating Revenues Non Utility [Member] | Natural Gas Related Derivatives [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	-25.8	-0.5
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to income	-25.2	0.3
WGL Holdings, Inc. | Operating Revenues Non Utility [Member] | Electricity Related Derivatives [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	-10	-1.1
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to income	-5	4.3
WGL Holdings, Inc. | Operating Revenues Non Utility [Member] | Weather Instruments [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	0	0
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to income	0	0
WGL Holdings, Inc. | Operating Revenues Non Utility [Member] | Warrant [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	0	0
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to income	0	0
WGL Holdings, Inc. | Utility Cost Of Gas [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	-23.4	-7.7
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to income	-22.9	-7.5
WGL Holdings, Inc. | Utility Cost Of Gas [Member] | Natural Gas Related Derivatives [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	-23.4	-7.7
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to income	-22.9	-7.5
WGL Holdings, Inc. | Utility Cost Of Gas [Member] | Electricity Related Derivatives [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	0	0
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to income	0	0
WGL Holdings, Inc. | Utility Cost Of Gas [Member] | Weather Instruments [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	0	0
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to income	0	0
WGL Holdings, Inc. | Utility Cost Of Gas [Member] | Warrant [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	0	0
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to income	0	0
WGL Holdings, Inc. | Non Utility Cost Of Energy Related Sales [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	4.6	-10.2
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to income	3.3	9.8
WGL Holdings, Inc. | Non Utility Cost Of Energy Related Sales [Member] | Natural Gas Related Derivatives [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	2.5	-0.4
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to income	2.3	0.6
WGL Holdings, Inc. | Non Utility Cost Of Energy Related Sales [Member] | Electricity Related Derivatives [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	2.1	-9.8
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to income	1	9.2
WGL Holdings, Inc. | Non Utility Cost Of Energy Related Sales [Member] | Weather Instruments [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	0	0
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to income	0	0
WGL Holdings, Inc. | Non Utility Cost Of Energy Related Sales [Member] | Warrant [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	0	0
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to income	0	0
WGL Holdings, Inc. | Operation And Maintenance Expense [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	0	0.6
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to income	0	0.6
WGL Holdings, Inc. | Operation And Maintenance Expense [Member] | Natural Gas Related Derivatives [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	0	0
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to income	0	0
WGL Holdings, Inc. | Operation And Maintenance Expense [Member] | Electricity Related Derivatives [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	0	0
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to income	0	0
WGL Holdings, Inc. | Operation And Maintenance Expense [Member] | Weather Instruments [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	0	0.6
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to income	0	0.6
WGL Holdings, Inc. | Operation And Maintenance Expense [Member] | Warrant [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	0	0
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to income	0	0
WGL Holdings, Inc. | Other Income [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	0.1	0.1
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to income	0.1	0.1
WGL Holdings, Inc. | Other Income [Member] | Natural Gas Related Derivatives [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	0	0
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to income	0	0
WGL Holdings, Inc. | Other Income [Member] | Electricity Related Derivatives [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	0	0
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to income	0	0
WGL Holdings, Inc. | Other Income [Member] | Weather Instruments [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	0	0
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to income	0	0
WGL Holdings, Inc. | Other Income [Member] | Warrant [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	0.1	0.1
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to income	0.1	0.1
Washington Gas Light Company	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	-23.4	-7.1
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to regulatory assets - gas costs	-71.1	-11.9
Total	-94	-18.8
Washington Gas Light Company | Natural Gas Related Derivatives [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	-23.4	-7.7
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to regulatory assets - gas costs	-71.1	-11.9
Total	-94	-19.4
Washington Gas Light Company | Electricity Related Derivatives [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	0	0
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to regulatory assets - gas costs	0	0
Total	0	0
Washington Gas Light Company | Weather Instruments [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	0	0.6
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to regulatory assets - gas costs	0	0
Total	0	0.6
Washington Gas Light Company | Warrant [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	0	0
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to regulatory assets - gas costs	0	0
Total	0	0
Washington Gas Light Company | Utility Cost Of Gas [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	-23.4	-7.7
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to income	-22.9	-7.5
Washington Gas Light Company | Utility Cost Of Gas [Member] | Natural Gas Related Derivatives [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	-23.4	-7.7
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to income	-22.9	-7.5
Washington Gas Light Company | Utility Cost Of Gas [Member] | Electricity Related Derivatives [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	0	0
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to income	0	0
Washington Gas Light Company | Utility Cost Of Gas [Member] | Weather Instruments [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	0	0
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to income	0	0
Washington Gas Light Company | Utility Cost Of Gas [Member] | Warrant [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	0	0
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to income	0	0
Washington Gas Light Company | Operation And Maintenance Expense [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	0	0.6
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to income	0	0.6
Washington Gas Light Company | Operation And Maintenance Expense [Member] | Natural Gas Related Derivatives [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	0	0
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to income	0	0
Washington Gas Light Company | Operation And Maintenance Expense [Member] | Electricity Related Derivatives [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	0	0
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to income	0	0
Washington Gas Light Company | Operation And Maintenance Expense [Member] | Weather Instruments [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	0	0.6
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to income	0	0.6
Washington Gas Light Company | Operation And Maintenance Expense [Member] | Warrant [Member]	'	'
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	'	'
Recorded to income	0	0
Unrealized Gains (Losses) Recorded for Level 3 Measurements	'	'
Recorded to income	$0	$0

Fair_Value_Measurements_Longte

Fair Value Measurements (Long-term Debt) (Details) (USD $)	Dec. 31, 2013		Sep. 30, 2013
WGL Holdings, Inc.	'		'
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]	'		'
Commercial Paper	$443,300,000		$373,100,000
Washington Gas Light Company	'		'
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]	'		'
Commercial Paper	188,000,000		124,500,000
Carrying Amount | WGL Holdings, Inc.	'		'
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]	'		'
Money Market Funds At Carrying Value	6,800,000	[1]	6,500,000	[1]
Other Short Term Investments	200,000	[1]	100,000	[1]
Commercial Paper	443,300,000	[2]	373,100,000	[2]
Long-term debt	599,300,000	[3]	524,100,000	[3]
Carrying Amount | Washington Gas Light Company	'		'
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]	'		'
Money Market Funds At Carrying Value	3,200,000	[1]	3,100,000	[1]
Other Short Term Investments	200,000	[1]	100,000	[1]
Commercial Paper	188,000,000	[2]	124,500,000	[2]
Long-term debt	599,300,000	[3]	524,100,000	[3]
Fair Value | WGL Holdings, Inc.	'		'
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]	'		'
Money Market Funds At Carrying Value	6,800,000	[1]	6,500,000	[1]
Other Short Term Investments	200,000	[1]	100,000	[1]
Commercial Paper	443,300,000	[2]	373,100,000	[2]
Long-term debt	688,700,000	[3]	630,200,000	[3]
Fair Value | Washington Gas Light Company	'		'
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]	'		'
Money Market Funds At Carrying Value	3,200,000	[1]	3,100,000	[1]
Other Short Term Investments	200,000	[1]	100,000	[1]
Commercial Paper	188,000,000	[2]	124,500,000	[2]
Long-term debt	$688,700,000	[3]	$630,200,000	[3]
[1]	Balance is located in cash and cash equivalents in the accompanying balance sheets. These amounts may be offset by outstanding checks.
[2]	Balance is located in notes payable in the accompanying balance sheets.
[3]	Excludes current maturities and unamortized discounts.

Fair_Value_Measurements_Quanti

Fair Value Measurements (Quantitative information WGLH) (Details) (WGL Holdings, Inc., USD $)

Dec. 31, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Dec. 31, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Dec. 31, 2013

Sep. 30, 2013

Dec. 31, 2013

Sep. 30, 2013

Dec. 31, 2013

Sep. 30, 2013

Dec. 31, 2013

Sep. 30, 2013

Dec. 31, 2013

Sep. 30, 2013

Dec. 31, 2013

Sep. 30, 2013

Dec. 31, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Dec. 31, 2013

Sep. 30, 2013

Dec. 31, 2013

Sep. 30, 2013

Dec. 31, 2013

Dec. 31, 2013

Natural Gas Related Derivatives [Member]

Natural Gas Related Derivatives [Member]

Natural Gas Related Derivatives [Member]

Natural Gas Related Derivatives [Member]

Natural Gas Related Derivatives [Member]

Natural Gas Related Derivatives [Member]

Natural Gas Related Derivatives [Member]

Natural Gas Related Derivatives [Member]

Natural Gas Related Derivatives [Member]

Natural Gas Related Derivatives [Member]

Natural Gas Related Derivatives [Member]

Natural Gas Related Derivatives [Member]

Natural Gas Related Derivatives [Member]

Natural Gas Related Derivatives [Member]

Natural Gas Related Derivatives [Member]

Natural Gas Related Derivatives [Member]

Electricity Related Derivatives [Member]

Electricity Related Derivatives [Member]

Electricity Related Derivatives [Member]

Electricity Related Derivatives [Member]

Electricity Related Derivatives [Member]

Electricity Related Derivatives [Member]

Electricity Related Derivatives [Member]

Electricity Related Derivatives [Member]

Electricity Related Derivatives [Member]

Electricity Related Derivatives [Member]

Discounted Cash Flow [Member]

Discounted Cash Flow [Member]

Discounted Cash Flow [Member]

Discounted Cash Flow [Member]

Option Model [Member]

Option Model [Member]

Option Model [Member]

Option Model [Member]

Option Model [Member]

Option Model [Member]

Option Model [Member]

Option Model [Member]

Discounted Cash Flow [Member]

Discounted Cash Flow [Member]

Discounted Cash Flow [Member]

Discounted Cash Flow [Member]

Load-Shaping Option Model

Load-Shaping Option Model

Maximum [Member]

Maximum [Member]

Minimum [Member]

Minimum [Member]

Maximum [Member]

Maximum [Member]

Maximum [Member]

Maximum [Member]

Minimum [Member]

Minimum [Member]

Minimum [Member]

Minimum [Member]

Maximum [Member]

Maximum [Member]

Minimum [Member]

Minimum [Member]

Maximum [Member]

Minimum [Member]

Natural Gas Basis Price [Member]

Natural Gas Basis Price [Member]

Natural Gas Basis Price [Member]

Natural Gas Basis Price [Member]

Natural Gas Basis Price [Member]

Natural Gas Basis Price [Member]

Annualized Volatility Price [Member]

Annualized Volatility Price [Member]

Natural Gas Basis Price [Member]

Natural Gas Basis Price [Member]

Annualized Volatility Price [Member]

Annualized Volatility Price [Member]

Electricity Congestion Price [Member]

Electricity Congestion Price [Member]

Electricity Congestion Price [Member]

Electricity Congestion Price [Member]

Electricity Congestion Price [Member]

Electricity Congestion Price [Member]

Net Fair Value

($265,000,000)

($151,700,000)

$27,200,000

$42,800,000

($264,500,000)

($155,200,000)

$21,500,000

$39,600,000

'

'

'

'

'

'

'

'

'

'

'

'

($1,700,000)

$2,400,000

$4,600,000

$2,800,000

'

'

'

'

'

'

Input Price

'

'

'

'

'

'

'

'

$3.21

$2.21

($1.59)

($1.78)

$1.54

$0.63

'

'

($0.37)

($0.18)

'

'

'

'

'

'

$66.20

$64.15

($1.89)

($2.00)

$71.19

$31.96

Option Volatility Percentage

'

'

'

'

'

'

'

'

'

'

'

'

'

'

276.60%

276.60%

'

'

34.60%

34.60%

'

'

'

'

'

'

'

'

'

'

Fair_Value_Measurements_Quanti1

Fair Value Measurements (Quantitative information WGL) (Details) (Washington Gas Light Company, USD $)

Dec. 31, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Dec. 31, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Dec. 31, 2013

Sep. 30, 2013

Dec. 31, 2013

Sep. 30, 2013

Dec. 31, 2013

Sep. 30, 2013

Dec. 31, 2013

Sep. 30, 2013

Dec. 31, 2013

Sep. 30, 2013

Dec. 31, 2013

Sep. 30, 2013

Natural Gas Related Derivatives [Member]

Natural Gas Related Derivatives [Member]

Natural Gas Related Derivatives [Member]

Natural Gas Related Derivatives [Member]

Natural Gas Related Derivatives [Member]

Natural Gas Related Derivatives [Member]

Natural Gas Related Derivatives [Member]

Natural Gas Related Derivatives [Member]

Natural Gas Related Derivatives [Member]

Natural Gas Related Derivatives [Member]

Natural Gas Related Derivatives [Member]

Natural Gas Related Derivatives [Member]

Natural Gas Related Derivatives [Member]

Natural Gas Related Derivatives [Member]

Natural Gas Related Derivatives [Member]

Natural Gas Related Derivatives [Member]

Discounted Cash Flow [Member]

Discounted Cash Flow [Member]

Discounted Cash Flow [Member]

Discounted Cash Flow [Member]

Option Model [Member]

Option Model [Member]

Option Model [Member]

Option Model [Member]

Option Model [Member]

Option Model [Member]

Option Model [Member]

Option Model [Member]

Maximum [Member]

Maximum [Member]

Minimum [Member]

Minimum [Member]

Maximum [Member]

Maximum [Member]

Maximum [Member]

Maximum [Member]

Minimum [Member]

Minimum [Member]

Minimum [Member]

Minimum [Member]

Natural Gas Basis Price [Member]

Natural Gas Basis Price [Member]

Natural Gas Basis Price [Member]

Natural Gas Basis Price [Member]

Natural Gas Basis Price [Member]

Natural Gas Basis Price [Member]

Annualized Volatility Price [Member]

Annualized Volatility Price [Member]

Natural Gas Basis Price [Member]

Natural Gas Basis Price [Member]

Annualized Volatility Price [Member]

Annualized Volatility Price [Member]

Net Fair Value

($220,000,000)

($133,600,000)

$17,900,000

$35,100,000

($220,000,000)

($133,600,000)

$17,800,000

$35,600,000

'

'

'

'

'

'

'

'

'

'

'

'

Input Price

'

'

'

'

'

'

'

'

$3.21

$2.21

($1.59)

($1.78)

$1.54

$0.63

'

'

$0.03

$0.02

'

'

Option Volatility Percentage

'

'

'

'

'

'

'

'

'

'

'

'

'

'

276.60%

276.60%

'

'

46.80%

46.80%

Fair_Value_Measurements_Nonrec

Fair Value Measurements (Nonrecurring Basis) (Details) (USD $)	3 Months Ended				12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Sep. 30, 2013	Dec. 31, 2013
	WGL Holdings, Inc.	WGL Holdings, Inc.	Washington Gas Light Company	Washington Gas Light Company	Washington Gas Light Company	Washington Gas Light Company
					Springfield Operations Center	Springfield Operations Center
Carrying Amount Of Long Lived Assets Held For Use	'	'	'	'	$24,900,000	$22,300,000
Fair Value Of Long Lived Assets Held For Use	'	'	'	'	22,300,000	21,500,000
Impairment loss	$770,000	$0	$770,000	$0	$2,600,000	'

Operating_Segment_Details

Operating Segment (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012		Sep. 30, 2013
Operating Expenses:	'		'		'
Net Income (Loss) applicable to common stock	$18,629		$52,388		'
Regulated Operation [Member]	'		'		'
Segment Reporting Information [Line Items]	'		'		'
Operating Revenues	390,415	[1]	355,817	[1]	'
Operating Expenses:	'		'		'
Cost of energy-related sales	190,695		150,448		'
Operation	57,430		58,208		'
Maintenance	13,842		11,450		'
Depreciation and amortization	25,369		26,792		'
Revenue taxes	24,671		24,221		'
Other	12,775		12,287		'
Total Operating Expenses	324,782		283,406		'
OPERATING INCOME (LOSS)	65,633		72,411		'
Equity in earnings of unconsolidated affiliates	0		0		'
Other income (expense) - net	-180		133		'
Interest Expense	8,879		9,095		'
Dividends on Washington Gas preferred stock	330		330		'
INCOME TAX EXPENSE (BENEFIT)	17,523		24,453		'
Net Income (Loss) applicable to common stock	38,721		38,666		'
Segment Reporting Information Additional Elements For Bank Presentation [Abstract]	'		'		'
Total Assets	3,828,709		3,673,308		'
Capital Expenditures	55,092		60,615		'
Equity Method Investments	0		0		'
Retail Energy Marketing [Member] | Unregulated Operation [Member]	'		'		'
Segment Reporting Information [Line Items]	'		'		'
Operating Revenues	322,938	[1]	324,059	[1]	'
Operating Expenses:	'		'		'
Cost of energy-related sales	303,268		290,133		'
Operation	11,251		11,359		'
Maintenance	0		0		'
Depreciation and amortization	174		175		'
Revenue taxes	1,947		1,431		'
Other	1,068		871		'
Total Operating Expenses	317,708		303,969		'
OPERATING INCOME (LOSS)	5,230		20,090		'
Equity in earnings of unconsolidated affiliates	0		0		'
Other income (expense) - net	61		50		'
Interest Expense	0		3		'
Dividends on Washington Gas preferred stock	0		0		'
INCOME TAX EXPENSE (BENEFIT)	1,976		7,116		'
Net Income (Loss) applicable to common stock	3,315		13,021		'
Segment Reporting Information Additional Elements For Bank Presentation [Abstract]	'		'		'
Total Assets	418,633		400,951		'
Capital Expenditures	75		201		'
Equity Method Investments	0		0		'
Commercial Energy Systems [Member] | Unregulated Operation [Member]	'		'		'
Segment Reporting Information [Line Items]	'		'		'
Operating Revenues	4,717	[1]	11,985	[1]	'
Operating Expenses:	'		'		'
Cost of energy-related sales	3,145		9,111		'
Operation	1,474		1,232		'
Maintenance	0		0		'
Depreciation and amortization	1,093		459		'
Revenue taxes	1		1		'
Other	52		79		'
Total Operating Expenses	5,765		10,882		'
OPERATING INCOME (LOSS)	-1,048		1,103		'
Equity in earnings of unconsolidated affiliates	284		245		'
Other income (expense) - net	65		80		'
Interest Expense	0		43		'
Dividends on Washington Gas preferred stock	0		0		'
INCOME TAX EXPENSE (BENEFIT)	-562		347		'
Net Income (Loss) applicable to common stock	-137		1,038		'
Segment Reporting Information Additional Elements For Bank Presentation [Abstract]	'		'		'
Total Assets	380,241		168,761		'
Capital Expenditures	3,138		15,101		'
Equity Method Investments	66,526		29,005		'
Midstream Energy Services | Unregulated Operation [Member]	'		'		'
Segment Reporting Information [Line Items]	'		'		'
Operating Revenues	-33,173	[1]	2,854	[1]	'
Operating Expenses:	'		'		'
Cost of energy-related sales	0		0		'
Operation	1,124		844		'
Maintenance	0		0		'
Depreciation and amortization	31		31		'
Revenue taxes	0		0		'
Other	87		166		'
Total Operating Expenses	1,242		1,041		'
OPERATING INCOME (LOSS)	-34,415		1,813		'
Equity in earnings of unconsolidated affiliates	206		0		'
Other income (expense) - net	-83		0		'
Interest Expense	0		0		'
Dividends on Washington Gas preferred stock	0		0		'
INCOME TAX EXPENSE (BENEFIT)	-12,504		537		'
Net Income (Loss) applicable to common stock	-21,788		1,276		'
Segment Reporting Information Additional Elements For Bank Presentation [Abstract]	'		'		'
Total Assets	171,420		201,111		'
Capital Expenditures	0		0		'
Equity Method Investments	10,813		0		'
Other Activities [Member] | Unregulated Operation [Member]	'		'		'
Segment Reporting Information [Line Items]	'		'		'
Operating Revenues	0	[1]	0	[1]	'
Operating Expenses:	'		'		'
Cost of energy-related sales	0		0		'
Operation	3,004		791		'
Maintenance	0		0		'
Depreciation and amortization	0		0		'
Revenue taxes	0		0		'
Other	21		10		'
Total Operating Expenses	3,025		801		'
OPERATING INCOME (LOSS)	-3,025		-801		'
Equity in earnings of unconsolidated affiliates	0		0		'
Other income (expense) - net	356		218		'
Interest Expense	113		104		'
Dividends on Washington Gas preferred stock	0		0		'
INCOME TAX EXPENSE (BENEFIT)	-1,099		926		'
Net Income (Loss) applicable to common stock	-1,683		-1,613		'
Segment Reporting Information Additional Elements For Bank Presentation [Abstract]	'		'		'
Total Assets	299,769		226,221		'
Capital Expenditures	0		0		'
Equity Method Investments	413		285		'
Corporate Elimination [Member]	'		'		'
Segment Reporting Information [Line Items]	'		'		'
Operating Revenues	-4,600	[1]	-7,979	[1],[2]	'
Operating Expenses:	'		'		'
Cost of energy-related sales	-4,876		-7,573	[2]	'
Operation	17		-254	[2]	'
Maintenance	0		0		'
Depreciation and amortization	-77		-153	[2]	'
Revenue taxes	0		0		'
Other	-1		1	[2]	'
Total Operating Expenses	-4,937		-7,979	[2]	'
OPERATING INCOME (LOSS)	337		0		'
Equity in earnings of unconsolidated affiliates	0		0		'
Other income (expense) - net	0		-52	[2]	'
Interest Expense	0		-52	[2]	'
Dividends on Washington Gas preferred stock	0		0		'
INCOME TAX EXPENSE (BENEFIT)	136		0		'
Net Income (Loss) applicable to common stock	201		0		'
Segment Reporting Information Additional Elements For Bank Presentation [Abstract]	'		'		'
Total Assets	-467,246		-329,415	[2]	'
Capital Expenditures	0		0		'
Equity Method Investments	0		0		'
WGL Holdings, Inc.	'		'		'
Segment Reporting Information [Line Items]	'		'		'
Operating Revenues	680,297	[1]	686,736	[1]	'
Operating Expenses:	'		'		'
Cost of energy-related sales	492,232		442,119		'
Operation	74,300		72,180		'
Maintenance	13,842		11,450		'
Depreciation and amortization	26,590		27,304		'
Revenue taxes	26,619		25,653		'
Other	14,002		13,414		'
Total Operating Expenses	647,585		592,120		'
OPERATING INCOME (LOSS)	32,712		94,616		'
Equity in earnings of unconsolidated affiliates	490		245		'
Other income (expense) - net	219		429		'
Interest Expense	8,992		9,193		'
Dividends on Washington Gas preferred stock	330		330		'
INCOME TAX EXPENSE (BENEFIT)	5,470		33,379		'
Net Income (Loss) applicable to common stock	18,629		52,388		'
Segment Reporting Information Additional Elements For Bank Presentation [Abstract]	'		'		'
Total Assets	4,631,526		4,340,937		4,260,060
Capital Expenditures	58,305		75,917		'
Equity Method Investments	$77,752		$29,290		'
[1]	B Operating revenues are reported gross of revenue taxes. Revenue taxes of both the regulated utility and the retail energy-marketing segments include gross receipt taxes. Revenue taxes of the regulated utility segment also include PSC fees, franchise fees and energy taxes. Operating revenue amounts in the "Eliminations" column represent total intersegment revenues associated with sales from the regulated utility segment to the retail energy-marketing segment. Midstream Energy Services' cost of energy related sales is netted with its gross revenues.
[2]	Intersegment eliminations net income represents a timing difference between Commercial Energy Systemsb recognition of revenue for the sale of Solar Renewable Energy Credits (SRECs) to Retail Energy-Marketing and Retail Energy-Marketingbs recognition of the associated expense. Retail Energy-Marketing has recorded a portion of the SRECbs purchased as inventory to be used in future periods and will expense them at that time.

Other_Investments_Narrative_De

Other Investments Narrative (Details) (USD $)	Dec. 31, 2013	Sep. 30, 2013
In Millions, unless otherwise specified
Summary Of Investments Other Than Investments In Related Parties Reportable Data [LineItems]	'	'
Financing Receivable Recorded Investment Current	$2.20	'
WGL Holdings, Inc.	'	'
Summary Of Investments Other Than Investments In Related Parties Reportable Data [LineItems]	'	'
Capital Leases Future Minimum Payments Receivable	25.5	29.2
Financing Receivable Recorded Investment Current	2.2	5.8
Assets	83	120.3
Anticipated Investment In Constitution	68	'
Equity Method Investment Ownership Percentage	10.00%	'
WGL Holdings, Inc. | Warrant	'	'
Summary Of Investments Other Than Investments In Related Parties Reportable Data [LineItems]	'	'
Assets	1.2	1.1
Willams Partners L.P.	'	'
Summary Of Investments Other Than Investments In Related Parties Reportable Data [LineItems]	'	'
Equity Method Investment Ownership Percentage	41.00%	'
Cabot Oil And Gas Corporation	'	'
Summary Of Investments Other Than Investments In Related Parties Reportable Data [LineItems]	'	'
Equity Method Investment Ownership Percentage	25.00%	'
Piedmont Natural Gas	'	'
Summary Of Investments Other Than Investments In Related Parties Reportable Data [LineItems]	'	'
Equity Method Investment Ownership Percentage	24.00%	'
ASD Solar, LP	'	'
Summary Of Investments Other Than Investments In Related Parties Reportable Data [LineItems]	'	'
Equity Method Investment Difference Between Carrying Amount And Underlying Equity	35.6	'
American Solar Direct Holding Inc	'	'
Summary Of Investments Other Than Investments In Related Parties Reportable Data [LineItems]	'	'
Cost Method Investments	5.6	5.6
American Solar Direct Holding Inc | Warrant	'	'
Summary Of Investments Other Than Investments In Related Parties Reportable Data [LineItems]	'	'
Assets	$1.10	$1.10

Other_Investments_Financing_Le

Other Investments Financing Leases Table (Details) (USD $)	Dec. 31, 2013
Capital Leases Net Investment In Direct Financing Leases [Abstract]	'
2014	$2,200,000
2015	1,200,000
2016	1,200,000
2017	1,200,000
2018	1,200,000
Thereafter	12,800,000
Total	19,800,000
Direct Financing Leases - Unearned Income	45,000
Direct Financing Leases - Residual Value	4,400,000
Direct Financing Leases - Initial Direct Costs	700,000
Direct Financing Leases- Taxes	$1,300,000

Other_Investments_Location_Tab

Other Investments Location Table (Details) (USD $)	3 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Sep. 30, 2013
Assets [Abstract]	'	'	'
Capital Leases Net Investment In Direct Financing Leases	$19,800,000	'	'
Other	2,200,000	'	'
VIEs	'	'	'
Assets [Abstract]	'	'	'
Non-Consolidated Investments	67,000,000	'	55,400,000
Capital Leases Net Investment In Direct Financing Leases	23,000,000	'	23,400,000
DerivativeAssets	0	'	0
Other	2,600,000	'	5,800,000
VIEs - Total assets	92,600,000	'	84,600,000
Liabilities Abstract	'	'	'
VIEs - Liabilities - Other	8,300,000	'	8,500,000
Total Liabilities	8,300,000	'	8,500,000
Net Income Loss Abstract	'	'	'
Income Loss From Equity Method Investments	300,000	200,000	'
Depreciation Expense	100,000	0	'
Other Income	500,000	200,000	'
Net Income	700,000	400,000	'
Non VIEs	'	'	'
Assets [Abstract]	'	'	'
Non-Consolidated Investments	16,400,000	'	12,100,000
Capital Leases Net Investment In Direct Financing Leases	0	'	0
DerivativeAssets	1,100,000	'	1,100,000
Other	0	'	0
VIEs - Total assets	17,500,000	'	13,200,000
Liabilities Abstract	'	'	'
VIEs - Liabilities - Other	0	'	0
Total Liabilities	0	'	0
Net Income Loss Abstract	'	'	'
Income Loss From Equity Method Investments	200,000	0	'
Depreciation Expense	0	0	'
Other Income	200,000	100,000	'
Net Income	400,000	100,000	'
Total	'	'	'
Assets [Abstract]	'	'	'
Non-Consolidated Investments	83,400,000	'	67,500,000
Capital Leases Net Investment In Direct Financing Leases	23,000,000	'	23,400,000
DerivativeAssets	1,100,000	'	1,100,000
Other	2,600,000	'	5,800,000
VIEs - Total assets	110,100,000	'	97,800,000
Liabilities Abstract	'	'	'
VIEs - Liabilities - Other	8,300,000	'	8,500,000
Total Liabilities	8,300,000	'	8,500,000
Net Income Loss Abstract	'	'	'
Income Loss From Equity Method Investments	500,000	200,000	'
Depreciation Expense	100,000	0	'
Other Income	700,000	300,000	'
Net Income	$1,100,000	$500,000	'

Related_Party_Transactions_Det

Related Party Transactions (Details) (USD $)	Dec. 31, 2013	Sep. 30, 2013
WGEServices	'	'
Related Party Transaction [Line Items]	'	'
Accounts Receivable, Related Parties	'	$1,000,000
Accounts Receivable Related Parties Current	300,000	'
Washington Gas Light Company	'	'
Related Party Transaction [Line Items]	'	'
Receivables from associated companies	4,800,000	7,200,000
Due to Related Parties, Current	36,000,000	20,600,000
Receivables purchsed from related party	$19,900,000	$106,600,000

Related_Party_Transactions_Det1

Related Party Transactions (Details 2) (Washington Gas Light Company, USD $)	3 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Washington Gas Light Company	'	'
Related Party Transaction [Line Items]	'	'
Related Party Transaction, Revenues from Transactions with Related Party	$3.80	$7.60

Commitments_and_Contingencies_

Commitments and Contingencies (Details) (USD $)	Dec. 31, 2013	Sep. 30, 2013
Commitments And Contingencies [Line Items]	'	'
Recorded Unconditional Purchase Obligation	$507,000,000	'
Washington Gas Light Company	'	'
Commitments And Contingencies [Line Items]	'	'
Public Utilities Property Plant And Equipment Construction Work In Progress	8,300,000	6,700,000
Reserve For Bad Debt	16,014,000	17,498,000
Washington Gas Light Company | Construction Project Financing [Member]	'	'
Commitments And Contingencies [Line Items]	'	'
Reserve For Bad Debt	0	0
WGL Holdings, Inc.	'	'
Commitments And Contingencies [Line Items]	'	'
Reserve For Bad Debt	18,518,000	20,433,000
October 2014 [Member] | WGL Holdings, Inc.	'	'
Commitments And Contingencies [Line Items]	'	'
Recorded Unconditional Purchase Obligation	6,000,000	'
September 2033 [Member]	'	'
Commitments And Contingencies [Line Items]	'	'
Recorded Unconditional Purchase Obligation	500,000	'
January 2014 [Member]	'	'
Commitments And Contingencies [Line Items]	'	'
Recorded Unconditional Purchase Obligation	4,000,000	'
Retail Energy Marketing [Member] | WGL Holdings, Inc.	'	'
Commitments And Contingencies [Line Items]	'	'
Recorded Unconditional Purchase Obligation	313,500,000	'
WGL Midstream | WGL Holdings, Inc.	'	'
Commitments And Contingencies [Line Items]	'	'
Recorded Unconditional Purchase Obligation	185,700,000	'
Other Non-Utility [Member] | WGL Holdings, Inc.	'	'
Commitments And Contingencies [Line Items]	'	'
Recorded Unconditional Purchase Obligation	7,800,000	'
District of Columbia [Member] | Washington Gas Light Company	'	'
Commitments And Contingencies [Line Items]	'	'
Mechanically coupled pipe replacement program	110,000,000	'
Maryland [Member] | Washington Gas Light Company	'	'
Commitments And Contingencies [Line Items]	'	'
Authorized Overall Rate Of Return	7.70%	'
Approved Increase In Utility Revenue	$8,900,000	'
Approved Rate Of Return On Common Equity	9.50%	'

Pension_and_Other_PostRetireme2

Pension and Other Post-Retirement Benefit Plans (Details) (USD $)	3 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Pension Benefits	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Service cost	$3,500,000	$4,200,000
Interest cost	10,100,000	9,100,000
Expected return on plan assets	-10,300,000	-10,500,000
Amortization of prior service cost (credit)	100,000	300,000
Amortization of actuarial loss	4,200,000	7,200,000
Amortization of transition obligation	0	0
Net periodic benefit cost	7,600,000	10,300,000
Amount allocated to construction projects	-1,000,000	-1,400,000
Amount amortized/deferred as regulatory asset	1,800,000	-2,400,000
Amount charged to expense	8,400,000	6,500,000
Health and Life Benefits	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Service cost	2,100,000	2,400,000
Interest cost	5,400,000	4,700,000
Expected return on plan assets	-4,700,000	-4,600,000
Amortization of prior service cost (credit)	-1,000,000	-1,000,000
Amortization of actuarial loss	700,000	2,300,000
Amortization of transition obligation	0	300,000
Net periodic benefit cost	2,500,000	4,100,000
Amount allocated to construction projects	-400,000	-700,000
Amount amortized/deferred as regulatory asset	100,000	800,000
Amount charged to expense	$2,200,000	$4,200,000

Changes_in_Accumulated_Other_C2

Changes in Accumulated Other Comprehensive Income (Details) (Washington Gas Light Company, USD $)	3 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012
Amortization of prior service cost	($35)		($12)
Amortization of actuarial loss	364		462
Amortization of transition obligation	0		9
Total pension and other postretirement benefit plans/Current-period other comprehensive income	329		459
INCOME TAX EXPENSE RELATED TO OTHER COMPREHENSIVE INCOME	130		182
Changes in Accumulated Other Comprehensive Income by Component	'		'
Beginning Balance	-11,048		-12,201
Amortization of prior service cost	-35	[1]	-12	[1]
Amortization of actuarial loss	364	[1]	462	[1]
Amortization of transition obligation	0	[1]	9	[1]
Total pension and other postretirement benefit plans/Current-period other comprehensive income	329		459
INCOME TAX EXPENSE RELATED TO OTHER COMPREHENSIVE INCOME	130		182
Ending Balance	($10,849)		($11,924)
[1]	(a) These accumulated other comprehensive income components are included in the computation of net periodic benefit cost. Refer to Note 14-Pension and other post-retirement benefit plans for additional details.