WGL (WGL) 10-K 19 Nov 15 2015 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Sep. 30, 2015	Oct. 31, 2015	Mar. 31, 2015
Document Information [Line Items]
Entity Registrant Name	WGL Holdings Inc.
Entity Central Index Key	1,103,601
Document Type	10-K
Document Period End Date	Sep. 30, 2015
Amendment Flag	false
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY
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 Public Float			$ 2,785,557,535
Entity Common Stock, Shares Outstanding		49,831,775
Washington Gas Light Company
Document Information [Line Items]
Entity Registrant Name	Washington Gas Light Company
Entity Central Index Key	104,819
Document Type	10-K
Document Period End Date	Sep. 30, 2015
Amendment Flag	false
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--09-30
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2015	Sep. 30, 2014
Property, Plant and Equipment
At original cost	$ 5,003,910	$ 4,582,764
Accumulated depreciation and amortization	(1,331,182)	(1,268,319)
Net property, plant and equipment	3,672,728	3,314,445
Current Assets
Cash and cash equivalents	6,733	8,811
Receivables
Accounts receivable	276,358	222,253
Gas costs and other regulatory assets	5,797	3,752
Unbilled revenues	102,560	96,314
Allowance for doubtful accounts	(26,224)	(23,341)
Net receivables	358,491	298,978
Materials and supplies—principally at average cost	21,402	23,647
Storage gas	211,443	333,602
Deferred income taxes	32,842	26,664
Prepaid taxes	48,726	66,578
Other prepayments	32,850	34,269
Derivatives	22,933	18,331
Assets held for sale	22,906	0
Other	23,057	24,635
Total current assets	781,383	835,515
Deferred Charges and Other Assets
Gas costs	190,676	191,346
Pension and other post-retirement benefits	212,041	192,981
Other	80,018	71,638
Prepaid post-retirement benefits	138,629	96,385
Derivatives	32,132	18,739
Investments in direct financing leases, capital leases	35,234	18,159
Investments in unconsolidated affiliates	136,884	100,528
Other	14,476	16,763
Total deferred charges and other assets	840,090	706,539
Total Assets	5,294,201	4,856,499
Capitalization
Common shareholders’ equity	1,243,247	1,246,576
Washington Gas Light Company preferred stock	28,173	28,173
Long-term debt	944,201	679,228
Total capitalization	2,215,621	1,953,977
Current Liabilities
Current maturities of long-term debt	25,000	20,000
Notes payable	332,000	453,500
Accounts payable and other accrued liabilities	325,146	313,221
Wages payable	21,091	19,995
Accrued interest	7,835	3,488
Dividends declared	23,377	22,449
Customer deposits and advance payments	88,897	68,318
Gas costs and other regulatory liabilities	34,551	22,563
Accrued taxes	13,867	14,133
Derivatives	63,504	48,555
Liabilities held for sale	1,621	0
Other	46,025	34,063
Total current liabilities	982,914	1,020,285
Deferred Credits
Unamortized investment tax credits	135,673	99,351
Deferred income taxes	705,805	660,908
Accrued pensions and benefits	176,128	120,446
Asset retirement obligations	200,732	175,203
Regulatory liabilities
Accrued asset removal costs	325,496	327,388
Other post-retirement benefits	104,382	86,428
Other	17,067	17,588
Derivatives	322,259	294,745
Other	108,124	100,180
Total deferred credits	$ 2,095,666	$ 1,882,237
Commitments and Contingencies (Note 13)
Total Capitalization and Liabilities	$ 5,294,201	$ 4,856,499
Washington Gas Light Company
Property, Plant and Equipment
At original cost	4,521,535	4,250,194
Accumulated depreciation and amortization	(1,278,089)	(1,228,130)
Net property, plant and equipment	3,243,446	3,022,064
Current Assets
Cash and cash equivalents	1	1,060
Receivables
Accounts receivable	126,356	121,419
Gas costs and other regulatory assets	5,797	3,752
Unbilled revenues	21,027	20,881
Allowance for doubtful accounts	(19,254)	(19,209)
Net receivables	133,926	126,843
Materials and supplies—principally at average cost	21,356	23,600
Storage gas	94,489	156,083
Deferred income taxes	24,700	22,916
Prepaid taxes	30,365	16,137
Other prepayments	11,899	14,272
Receivables from associated companies	3,176	4,821
Derivatives	4,588	3,884
Assets held for sale	22,906	0
Total current assets	347,406	369,616
Deferred Charges and Other Assets
Gas costs	190,676	191,346
Pension and other post-retirement benefits	210,811	191,896
Other	79,946	71,584
Prepaid post-retirement benefits	137,754	95,660
Derivatives	13,155	9,455
Other	5,638	13,457
Total deferred charges and other assets	637,980	573,398
Total Assets	4,228,832	3,965,078
Capitalization
Common shareholders’ equity	1,081,292	1,050,166
Washington Gas Light Company preferred stock	28,173	28,173
Long-term debt	695,885	679,228
Total capitalization	1,805,350	1,757,567
Current Liabilities
Current maturities of long-term debt	25,000	20,000
Notes payable	89,000	89,000
Accounts payable and other accrued liabilities	159,280	176,467
Wages payable	19,456	18,290
Accrued interest	4,023	3,488
Dividends declared	20,269	19,722
Customer deposits and advance payments	88,450	68,318
Gas costs and other regulatory liabilities	34,551	22,563
Accrued taxes	11,659	24,610
Payables to associated companies	68,623	54,685
Derivatives	33,856	33,858
Liabilities held for sale	1,621	0
Other	7,013	7,199
Total current liabilities	562,801	538,200
Deferred Credits
Unamortized investment tax credits	5,646	6,479
Deferred income taxes	693,464	619,946
Accrued pensions and benefits	174,318	118,954
Asset retirement obligations	198,938	173,775
Regulatory liabilities
Accrued asset removal costs	325,496	327,388
Other post-retirement benefits	103,683	85,814
Other	17,067	17,588
Derivatives	269,661	260,789
Other	72,408	58,578
Total deferred credits	$ 1,860,681	$ 1,669,311
Commitments and Contingencies (Note 13)
Total Capitalization and Liabilities	$ 4,228,832	$ 3,965,078

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
OPERATING REVENUES
Utility		$ 1,303,044	$ 1,416,951	$ 1,174,724
Non-utility		1,356,786	1,363,996	1,291,414
Total Operating Revenues	[1]	2,659,830	2,780,947	2,466,138
OPERATING EXPENSES
Utility cost of gas		510,900	700,305	496,487
Non-utility cost of energy-related sales		1,218,331	1,255,279	1,187,844
Operation and maintenance		395,770	365,873	366,889
Depreciation and amortization		121,892	110,772	103,284
General taxes and other assessments		152,164	151,196	145,816
Total Operating Expenses		2,399,057	2,583,425	2,300,320
OPERATING INCOME		260,773	197,522	165,818
Equity in earnings of unconsolidated affiliates		5,468	3,194	1,510
Other income (expense) —net		653	1,536	2,548
Interest expense		50,511	37,738	36,011
INCOME BEFORE INCOME TAXES		216,383	164,514	133,865
INCOME TAX EXPENSE		83,804	57,254	52,292
NET INCOME		132,579	107,260	81,573
Dividends on Washington Gas Light Company preferred stock		1,320	1,320	1,320
NET INCOME APPLICABLE TO COMMON STOCK		$ 131,259	$ 105,940	$ 80,253
WEIGHTED AVERAGE COMMON SHARES OUTSTANDING
Basic (in shares)		49,794	51,759	51,697
Diluted (in shares)		50,060	51,770	51,808
EARNINGS PER AVERAGE COMMON SHARE
Basic		$ 2.64	$ 2.05	$ 1.55
Diluted		2.62	2.05	1.55
DIVIDENDS DECLARED PER COMMON SHARE (in dollars per share)		$ 1.8275	$ 1.7400	$ 1.6600
Washington Gas Light Company
OPERATING REVENUES
Total Operating Revenues		$ 1,328,191	$ 1,443,800	$ 1,200,357
OPERATING EXPENSES
Utility cost of gas		536,027	726,879	521,508
Operation and maintenance		323,967	294,613	295,664
Depreciation and amortization		108,902	102,713	99,188
General taxes and other assessments		136,911	137,472	133,391
Total Operating Expenses		1,105,807	1,261,677	1,049,751
OPERATING INCOME		222,384	182,123	150,606
Other income (expense) —net		(487)	862	1,544
Interest expense		41,828	37,127	35,631
INCOME BEFORE INCOME TAXES		180,069	145,858	116,519
INCOME TAX EXPENSE		71,391	47,534	44,197
NET INCOME		108,678	98,324	72,322
Dividends on Washington Gas Light Company preferred stock		1,320	1,320	1,320
NET INCOME APPLICABLE TO COMMON STOCK		$ 107,358	$ 97,004	$ 71,002
[1]	(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 public service commission fees, franchise fees and energy taxes. Operating revenue amounts in the “Eliminations” row 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 Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2015		Sep. 30, 2014		Sep. 30, 2013
NET INCOME	$ 132,579		$ 107,260		$ 81,573
OTHER COMPREHENSIVE INCOME (LOSS), BEFORE INCOME TAXES:
Qualified cash flow hedging instruments	(11,309)	[1]	(1,548)	[1]	0
Pension and other post-retirement benefit plans
Change in prior service (cost) credit	696	[2]	6,095	[2]	(1,671)
Change in actuarial net gain (loss)	(1,195)	[2]	1,594	[2]	3,399
Change in transition obligation	0		0		238
TOTAL OTHER COMPREHENSIVE INCOME (LOSS) BEFORE TAXES	(11,808)		6,141		1,966
INCOME TAX EXPENSE (BENEFIT) RELATED TO OTHER COMPREHENSIVE INCOME (LOSS)	(5,533)		3,054		813
OTHER COMPREHENSIVE INCOME (LOSS)	(6,275)		3,087		1,153
COMPREHENSIVE INCOME	126,304		110,347		82,726
Washington Gas Light Company
NET INCOME	108,678		98,324		72,322
Pension and other post-retirement benefit plans
Change in prior service (cost) credit	696	[3]	6,095	[3]	(1,671)
Change in actuarial net gain (loss)	(1,195)	[3]	1,594	[3]	3,399
Change in transition obligation	0		0		238
Total pension and other post-retirement benefit plans	(499)		7,689		1,966
TOTAL OTHER COMPREHENSIVE INCOME (LOSS) BEFORE TAXES	(499)		7,689
INCOME TAX EXPENSE (BENEFIT) RELATED TO OTHER COMPREHENSIVE INCOME (LOSS)	(200)		3,054		813
OTHER COMPREHENSIVE INCOME (LOSS)	(299)		4,635		1,153
COMPREHENSIVE INCOME	$ 108,379		$ 102,959		$ 73,475
[1]	(a) Cash flow hedging instruments represent interest rate swap agreements related to debt issuances. Refer to Note 14—Derivative and Weather-related Instruments for further discussion of the interest rate swap agreements.
[2]	(b) These accumulated other comprehensive income (loss) components are included in the computation of net periodic benefit cost. Refer to Note 10-Pension and other post-retirement benefit plans for additional details.
[3]	(a) These accumulated other comprehensive income (loss) components are included in the computation of net periodic benefit cost. Refer to Note 10-Pension and other post-retirement benefit plans for additional details.

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
OPERATING ACTIVITIES
Net income	$ 132,579	$ 107,260	$ 81,573
ADJUSTMENTS TO RECONCILE NET INCOME TO NET CASH PROVIDED BY OPERATING ACTIVITIES
Depreciation and amortization	121,892	110,772	103,284
Amortization of:
Other regulatory assets and liabilities—net	1,305	610	574
Debt related costs	1,187	886	873
Deferred income taxes—net	104,405	25,795	1,431
Accrued/deferred pension and other post-retirement benefit cost	25,572	33,384	36,127
Compensation expense related to stock-based awards	16,478	4,105	3,050
Provision for doubtful accounts	18,197	14,252	9,258
Impairment loss	5,625	2,639	2,600
Other non-cash charges (credits)—net	(3,903)	(3,079)	2,536
CHANGES IN ASSETS AND LIABILITIES
Accounts receivable and unbilled revenues—net	(71,514)	(1,769)	12,105
Gas costs and other regulatory assets/liabilities—net	9,943	2,623	36,359
Storage gas	122,159	13,689	(64,283)
Prepaid Taxes	(38,630)	(42,128)	33,506
Accounts payable and other accrued liabilities	21,841	21,326	2,017
Customer deposits and advance payments	20,579	1,164	(22,166)
Accrued taxes	(266)	(1,923)	(6,980)
Unamortized investment tax credits	36,322	56,639	19,296
Other current assets	5,583	(16,130)	(2,513)
Other current liabilities	13,583	(1,062)	22,106
Deferred gas costs—net	670	(97,383)	(113,474)
Deferred assets—other	(10,153)	(7,525)	(133)
Deferred liabilities—other	(39,968)	(3,130)	45
Derivatives	24,468	178,104	163,571
Pension and other post-retirement benefits	(14,546)	(16,602)	(4,417)
Other—net	651	(350)	1,679
Net Cash Provided by Operating Activities	504,059	382,167	318,024
FINANCING ACTIVITIES
Common stock issued	0	714	0
Long-term debt issued	298,227	175,253	4,157
Long-term debt retired	(20,000)	(67,000)	(2,295)
Debt issuance costs	(3,497)	(1,543)	0
Notes payable issued (retired)—net	(121,500)	80,400	125,400
Dividends on common stock and preferred stock	(91,316)	(85,901)	(86,078)
Repurchase of common stock	(41,485)	(56,136)	0
Other financing activities—net	(1,457)	(560)	5,156
Net Cash Provided By Financing Activities	18,972	45,227	46,340
INVESTING ACTIVITIES
Capital expenditures (excluding AFUDC)	(464,291)	(394,762)	(312,345)
Investments in non-utility interests	(67,447)	(31,415)	(62,894)
Distributions from non-utility interests	10,780	4,116	4,090
Loans to external parties	(4,151)	0	0
Net Cash Used in Investing Activities	(525,109)	(422,061)	(371,149)
INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(2,078)	5,333	(6,785)
Cash and Cash Equivalents at Beginning of Year	8,811	3,478	10,263
Cash and Cash Equivalents at End of Year	6,733	8,811	3,478
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION
Income taxes paid (refunded)—net	6,935	20,110	(10,741)
Interest paid	45,654	36,991	35,471
SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING AND FINANCING ACTIVITIES
Project debt financing activities—net	(8,350)	253	1,386
Capital expenditure accruals included in accounts payable and other accrued liabilities	45,780	55,164	32,040
Dividends paid in common stock	0	5,312	6,863
Washington Gas Light Company
OPERATING ACTIVITIES
Net income	108,678	98,324	72,322
ADJUSTMENTS TO RECONCILE NET INCOME TO NET CASH PROVIDED BY OPERATING ACTIVITIES
Depreciation and amortization	108,902	102,713	99,188
Amortization of:
Other regulatory assets and liabilities—net	1,305	610	911
Debt related costs	1,275	886	527
Deferred income taxes—net	76,621	7,050	(2,915)
Accrued/deferred pension and other post-retirement benefit cost	24,757	33,670	35,707
Compensation expense related to stock-based awards	14,958	3,185	2,292
Provision for doubtful accounts	12,734	11,839	7,183
Impairment loss	0	2,639	2,600
Other non-cash charges (credits)—net	1,679	8,838	7,615
CHANGES IN ASSETS AND LIABILITIES
Accounts receivable and unbilled revenues—net	(16,127)	(39,253)	(464)
Gas costs and other regulatory assets/liabilities—net	9,943	2,623	36,359
Storage gas	61,594	(23,857)	(17,400)
Prepaid Taxes	(14,228)	(1,269)	31,937
Accounts payable and other accrued liabilities	(1,007)	49,429	(24,949)
Customer deposits and advance payments	20,132	1,164	(22,166)
Accrued taxes	(12,951)	(770)	6,272
Other current assets	4,958	(5,089)	5,843
Other current liabilities	1,435	(526)	19,253
Deferred gas costs—net	670	(97,383)	(113,474)
Deferred assets—other	(10,036)	(10,073)	(757)
Deferred liabilities—other	(13,912)	(3,007)	(966)
Derivatives	4,466	170,744	137,559
Pension and other post-retirement benefits	(13,750)	(16,973)	(4,261)
Other—net	258	(359)	(4,167)
Net Cash Provided by Operating Activities	372,354	295,155	274,049
FINANCING ACTIVITIES
Long-term debt issued	50,000	175,253	4,157
Long-term debt retired	(20,000)	(67,000)	(2,295)
Debt issuance costs	(741)	(1,543)	0
Notes payable issued (retired)—net	0	(35,500)	25,700
Dividends on common stock and preferred stock	(79,763)	(79,665)	(76,522)
Other financing activities—net	0	(1,749)	336
Net Cash Provided By Financing Activities	(50,504)	(10,204)	(48,624)
INVESTING ACTIVITIES
Capital expenditures (excluding AFUDC)	(322,909)	(283,891)	(225,426)
Net Cash Used in Investing Activities	(322,909)	(283,891)	(225,426)
INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(1,059)	1,060	(1)
Cash and Cash Equivalents at Beginning of Year	1,060	0	1
Cash and Cash Equivalents at End of Year	1	1,060	0
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION
Income taxes paid (refunded)—net	8,902	19,007	(15,799)
Interest paid	36,971	36,380	35,091
SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING AND FINANCING ACTIVITIES
Project debt financing activities—net	(8,350)	253	1,386
Capital expenditure accruals included in accounts payable and other accrued liabilities	$ 40,926	$ 46,331	$ 16,429

Consolidated Statements of Capi

Consolidated Statements of Capitalization - USD ($) $ in Thousands	Sep. 30, 2015	Sep. 30, 2014
Common Shareholders' Equity
Accumulated other comprehensive loss, net of taxes	$ (14,236)	$ (7,961)
Total Common shareholders' Equity	1,243,247	1,246,576
Preferred Stock
Washington Gas Light Company preferred stock	28,173	28,173
Long-Term Debt
Medium Term Notes	971,000	691,000
Other long-term debt	0	8,350
Unamortized discount	(1,799)	(122)
Less-current maturities	25,000	20,000
Long-term debt	$ 944,201	$ 679,228
Long Term Debt As Percentage Of Total Capitalization	42.60%	34.80%
Capitalization, Long-term Debt and Equity	$ 2,215,621	$ 1,953,977
Total Capitalization As Percentage	100.00%	100.00%
Due fiscal year 2015
Long-Term Debt
Medium Term Notes	$ 0	$ 20,000
Due fiscal year 2016
Long-Term Debt
Medium Term Notes	25,000	25,000
Due fiscal year 2019
Long-Term Debt
Medium Term Notes	50,000	50,000
Due fiscal year 2020
Long-Term Debt
Medium Term Notes	150,000	50,000
Due fiscal year 2023
Long-Term Debt
Medium Term Notes	20,000	20,000
Due fiscal year 2025
Long-Term Debt
Medium Term Notes	40,500	40,500
Due fiscal year 2027
Long-Term Debt
Medium Term Notes	125,000	125,000
Due fiscal year 2028
Long-Term Debt
Medium Term Notes	52,000	52,000
Due fiscal year 2030
Long-Term Debt
Medium Term Notes	8,500	8,500
Due fiscal year 2036
Long-Term Debt
Medium Term Notes	50,000	50,000
Due fiscal year 2041
Long-Term Debt
Medium Term Notes	75,000	75,000
Due fiscal year 2044
Long-Term Debt
Medium Term Notes	175,000	175,000
Due fiscal year 2045
Long-Term Debt
Medium Term Notes	200,000	0
Common Stock
Common Shareholders' Equity
Common stock, value	485,456	525,932
Paid-in capital	14,934	11,847
Retained earnings	757,093	716,758
Accumulated other comprehensive loss, net of taxes	(14,236)	(7,961)
Total Common shareholders' Equity	$ 1,243,247	$ 1,246,576
Common shareholders equity, percentage of total capitalization	56.10%	63.80%
Preferred Stock
Preferred Stock
Preferred Stock, Value, Issued	$ 0	$ 0
Washington Gas Light Company preferred stock	$ 28,173	$ 28,173
Preferred stock, percentage of total capitalization	1.30%	1.40%
Series One
Preferred Stock
Washington Gas Light Company preferred stock	$ 15,000	$ 15,000
Series Two
Preferred Stock
Washington Gas Light Company preferred stock	7,173	7,173
Series Three
Preferred Stock
Washington Gas Light Company preferred stock	6,000	6,000
Washington Gas Light Company
Common Shareholders' Equity
Accumulated other comprehensive loss, net of taxes	(6,712)	(6,413)
Total Common shareholders' Equity	1,081,292	1,050,166
Preferred Stock
Washington Gas Light Company preferred stock	28,173	28,173
Long-Term Debt
Medium Term Notes	721,000	691,000
Other long-term debt		8,350
Unamortized discount	(115)	(122)
Less-current maturities	25,000	20,000
Long-term debt	$ 695,885	$ 679,228
Long Term Debt As Percentage Of Total Capitalization	38.50%	38.60%
Capitalization, Long-term Debt and Equity	$ 1,805,350	$ 1,757,567
Total Capitalization As Percentage	100.00%	100.00%
Washington Gas Light Company | Due fiscal year 2015
Long-Term Debt
Medium Term Notes	$ 0	$ 20,000
Washington Gas Light Company | Due fiscal year 2016
Long-Term Debt
Medium Term Notes	25,000	25,000
Washington Gas Light Company | Due fiscal year 2019
Long-Term Debt
Medium Term Notes	50,000	50,000
Washington Gas Light Company | Due fiscal year 2020
Long-Term Debt
Medium Term Notes	50,000	50,000
Washington Gas Light Company | Due fiscal year 2023
Long-Term Debt
Medium Term Notes	20,000	20,000
Washington Gas Light Company | Due fiscal year 2025
Long-Term Debt
Medium Term Notes	40,500	40,500
Washington Gas Light Company | Due fiscal year 2027
Long-Term Debt
Medium Term Notes	125,000	125,000
Washington Gas Light Company | Due fiscal year 2028
Long-Term Debt
Medium Term Notes	52,000	52,000
Washington Gas Light Company | Due fiscal year 2030
Long-Term Debt
Medium Term Notes	8,500	8,500
Washington Gas Light Company | Due fiscal year 2036
Long-Term Debt
Medium Term Notes	50,000	50,000
Washington Gas Light Company | Due fiscal year 2041
Long-Term Debt
Medium Term Notes	75,000	75,000
Washington Gas Light Company | Due fiscal year 2044
Long-Term Debt
Medium Term Notes	175,000	175,000
Washington Gas Light Company | Due fiscal year 2045
Long-Term Debt
Medium Term Notes	50,000	0
Washington Gas Light Company | Common Stock
Common Shareholders' Equity
Common stock, value	46,479	46,479
Paid-in capital	483,677	480,620
Retained earnings	557,848	529,480
Accumulated other comprehensive loss, net of taxes	(6,712)	(6,413)
Total Common shareholders' Equity	$ 1,081,292	$ 1,050,166
Common shareholders equity, percentage of total capitalization	59.90%	59.80%
Washington Gas Light Company | Preferred Stock
Preferred Stock
Washington Gas Light Company preferred stock	$ 28,173	$ 28,173
Preferred stock, percentage of total capitalization	1.60%	1.60%
Washington Gas Light Company | Series One
Preferred Stock
Washington Gas Light Company preferred stock	$ 15,000	$ 15,000
Washington Gas Light Company | Series Two
Preferred Stock
Washington Gas Light Company preferred stock	7,173	7,173
Washington Gas Light Company | Series Three
Preferred Stock
Washington Gas Light Company preferred stock	$ 6,000	$ 6,000

Consolidated Statements of Cap7

Consolidated Statements of Capitalization - (Parenthetical) - $ / shares	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Common Shareholders' Equity
Common Stock, Par or Stated Value Per Share	$ 0	$ 0
Common Stock, Shares Authorized	120,000,000	120,000,000
Common Stock, Shares, Issued	49,728,662	50,656,553
Preferred Stock [Abstract]
Preferred Stock, Shares Authorized	3,000,000	3,000,000
Preferred Stock, Issued	0	0
Preferred Stock, Par or Stated Value Per Share (in dollars per share)	$ 0	$ 0
Due fiscal year 2015
Preferred Stock [Abstract]
Note Rate		4.83%
Due fiscal year 2016
Preferred Stock [Abstract]
Note Rate	5.17%	5.17%
Due fiscal year 2019
Preferred Stock [Abstract]
Note Rate	7.46%	7.46%
Due fiscal year 2020
Preferred Stock [Abstract]
Minimum Note Rate Range	2.25%	2.25%
Maximum Note Rate Range	4.76%	4.76%
Due fiscal year 2023
Preferred Stock [Abstract]
Note Rate	6.65%	6.65%
Due fiscal year 2025
Preferred Stock [Abstract]
Note Rate	5.44%	5.44%
Due fiscal year 2027
Preferred Stock [Abstract]
Minimum Note Rate Range	6.40%	6.40%
Maximum Note Rate Range	6.82%	6.82%
Due fiscal year 2028
Preferred Stock [Abstract]
Minimum Note Rate Range	6.57%	6.57%
Maximum Note Rate Range	6.85%	6.85%
Due fiscal year 2030
Preferred Stock [Abstract]
Maximum Note Rate Range	7.50%	7.50%
Due fiscal year 2036
Preferred Stock [Abstract]
Minimum Note Rate Range	5.70%	5.70%
Maximum Note Rate Range	5.78%	5.78%
Due fiscal year 2041
Preferred Stock [Abstract]
Note Rate	5.21%	5.21%
Due fiscal year 2044
Preferred Stock [Abstract]
Minimum Note Rate Range	4.22%	4.22%
Maximum Note Rate Range	5.00%	5.00%
Due fiscal year 2045
Preferred Stock [Abstract]
Minimum Note Rate Range	4.24%
Maximum Note Rate Range	4.60%
Washington Gas Light Company
Preferred Stock [Abstract]
Preferred Stock, Shares Authorized	1,500,000	1,500,000
Preferred Stock, Par or Stated Value Per Share (in dollars per share)	$ 0	$ 0
Washington Gas Light Company | Due fiscal year 2015
Preferred Stock [Abstract]
Note Rate		4.83%
Washington Gas Light Company | Due fiscal year 2016
Preferred Stock [Abstract]
Note Rate	5.17%	5.17%
Washington Gas Light Company | Due fiscal year 2019
Preferred Stock [Abstract]
Note Rate	7.46%	7.46%
Washington Gas Light Company | Due fiscal year 2020
Preferred Stock [Abstract]
Note Rate	4.76%	4.76%
Washington Gas Light Company | Due fiscal year 2023
Preferred Stock [Abstract]
Note Rate	6.65%	6.65%
Washington Gas Light Company | Due fiscal year 2025
Preferred Stock [Abstract]
Note Rate	5.44%	5.44%
Washington Gas Light Company | Due fiscal year 2027
Preferred Stock [Abstract]
Minimum Note Rate Range	6.40%	6.40%
Maximum Note Rate Range	6.82%	6.82%
Washington Gas Light Company | Due fiscal year 2028
Preferred Stock [Abstract]
Minimum Note Rate Range	6.57%	6.57%
Maximum Note Rate Range	6.85%	6.85%
Washington Gas Light Company | Due fiscal year 2030
Preferred Stock [Abstract]
Note Rate	7.50%	7.50%
Washington Gas Light Company | Due fiscal year 2036
Preferred Stock [Abstract]
Minimum Note Rate Range	5.70%	5.70%
Maximum Note Rate Range	5.78%	5.78%
Washington Gas Light Company | Due fiscal year 2041
Preferred Stock [Abstract]
Note Rate	5.21%	5.21%
Washington Gas Light Company | Due fiscal year 2044
Preferred Stock [Abstract]
Minimum Note Rate Range	4.22%	4.22%
Maximum Note Rate Range	5.00%	5.00%
Washington Gas Light Company | Due fiscal year 2045
Preferred Stock [Abstract]
Note Rate	4.24%
Common Stock | Washington Gas Light Company
Common Shareholders' Equity
Common Stock, Par or Stated Value Per Share	$ 1	$ 1
Common Stock, Shares Authorized	80,000,000	80,000,000
Common Stock, Shares, Issued	46,479,536	46,479,536
Preferred Stock | Washington Gas Light Company
Preferred Stock [Abstract]
Preferred Stock, Shares Authorized	1,500,000	1,500,000
Preferred Stock, Par or Stated Value Per Share (in dollars per share)	$ 0	$ 0
Series One | Washington Gas Light Company
Preferred Stock [Abstract]
Preferred Stock, Shares Outstanding (in shares)	150,000	150,000
Preferred Stock, Par or Stated Value Per Share (in dollars per share)	$ 4.80	$ 4.80
Series Two | Washington Gas Light Company
Preferred Stock [Abstract]
Preferred Stock, Shares Outstanding (in shares)	70,600	70,600
Preferred Stock, Par or Stated Value Per Share (in dollars per share)	$ 4.25	$ 4.25
Series Three | Washington Gas Light Company
Preferred Stock [Abstract]
Preferred Stock, Shares Outstanding (in shares)	60,000	60,000
Preferred Stock, Par or Stated Value Per Share (in dollars per share)	$ 5	$ 5

Consolidated Statements of Comm

Consolidated Statements of Common Shareholders Equity - USD ($) $ in Thousands	Total	Common Stock	Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss, Net of Taxes	Washington Gas Light Company		Washington Gas Light CompanyCommon Stock	Washington Gas Light CompanyPaid-In Capital		Washington Gas Light CompanyRetained Earnings	Washington Gas Light CompanyAccumulated Other Comprehensive Loss, Net of Taxes
Beginning Balance, shares at Sep. 30, 2012		51,611,647						46,479,536
Common shareholders' equity, beginning balance at Sep. 30, 2012	$ 1,269,556	$ 567,598	$ 8,132	$ 706,027	$ (12,201)	$ 1,025,743		$ 46,479	$ 475,634		$ 515,831	$ (12,201)
NET INCOME	81,573			81,573		72,322					72,322
OTHER COMPREHENSIVE INCOME (LOSS)	1,153				1,153	1,153						1,153
Dividend reinvestment	6,254	$ 6,254				2,334	[1]
Dividend reinvestment, shares		145,920
Stock-based compensation	3,187	$ 609	2,578						2,334	[1]
Stock-based compensation, Shares		16,637
Dividends Abstract
Common Stock	(85,858)			(85,858)		(75,649)					(75,649)
Preferred Stock	(1,320)			(1,320)		(1,320)					(1,320)
Common shareholders' equity, ending balance at Sep. 30, 2013	1,274,545	$ 574,461	10,710	700,422	(11,048)	1,024,583		$ 46,479	477,968		511,184	(11,048)
Ending Balance, shares at Sep. 30, 2013		51,774,204						46,479,536
NET INCOME	107,260			107,260		98,324					98,324
OTHER COMPREHENSIVE INCOME (LOSS)	3,087				3,087	4,635						4,635
Dividend reinvestment	4,649	$ 4,649
Dividend reinvestment, shares		114,883
Repurchase of common stock	(56,136)	$ (56,136)
Repurchase of common stock, shares		(1,304,504)
Stock-based compensation	4,095	$ 2,958	1,137			2,652	[1]		2,652	[1]
Stock-based compensation, Shares		71,970
Dividends Abstract
Common Stock	(89,604)			(89,604)		(78,708)					(78,708)
Preferred Stock	(1,320)			(1,320)		(1,320)					(1,320)
Common shareholders' equity, ending balance at Sep. 30, 2014	1,246,576	$ 525,932	11,847	716,758	(7,961)	1,050,166		$ 46,479	480,620		529,480	(6,413)
Ending Balance, shares at Sep. 30, 2014		50,656,553						46,479,536
NET INCOME	132,579			132,579		108,678					108,678
OTHER COMPREHENSIVE INCOME (LOSS)	(6,275)				(6,275)	(299)						(299)
Repurchase of common stock	(41,485)	$ (41,485)
Repurchase of common stock, shares		(948,604)
Stock-based compensation	4,096	$ 1,009	3,087			3,057	[1]		3,057	[1]
Stock-based compensation, Shares		20,713
Dividends Abstract
Common Stock	(90,924)			(90,924)		(78,990)					(78,990)
Preferred Stock	(1,320)			(1,320)		(1,320)					(1,320)
Common shareholders' equity, ending balance at Sep. 30, 2015	$ 1,243,247	$ 485,456	$ 14,934	$ 757,093	$ (14,236)	$ 1,081,292		$ 46,479	$ 483,677		$ 557,848	$ (6,712)
Ending Balance, shares at Sep. 30, 2015		49,728,662						46,479,536
[1]	(a) Stock-based compensation is based on the stock awards of WGL that are allocated to Washington Gas Light Company for its pro-rata share.

Consolidated Statements of Com9

Consolidated Statements of Common Shareholders Equity (Parenthetical) - $ / shares	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
DIVIDENDS DECLARED PER COMMON SHARE (in dollars per share)	$ 1.8275	$ 1.7400	$ 1.6600

Accounting Policies

Accounting Policies	12 Months Ended
	Sep. 30, 2015
Accounting Policies [Abstract]
Accounting Policies	NOTE 1. ACCOUNTING POLICIES GENERAL 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 (Crab Run). Washington Gas Resources owns all of the shares of common stock of four non-utility subsidiaries that include WGL Energy Services, Inc. (WGL Energy Services), WGL Energy Systems, Inc. (WGL Energy Systems), 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. NATURE OF OPERATIONS Washington Gas and Hampshire comprise our regulated utility segment. Washington Gas is a public utility that sells and delivers natural gas to more than one million customers primarily in the District of Columbia, and the surrounding metropolitan areas in Maryland and Virginia. Deliveries to firm residential and commercial customers accounted for 77.2% of the total therms delivered to customers by Washington Gas in the fiscal year ended September 30, 2015 . Deliveries to interruptible customers accounted for 13.6% and deliveries to customers who use natural gas to generate electricity accounted for 9.2% . These amounts do not include deliveries related to Washington Gas’ asset optimization program discussed below. Hampshire operates an underground natural gas storage facility that provides services exclusively to Washington Gas. Hampshire is regulated under a cost of service tariff by the Federal Energy Regulatory Commission (FERC). The retail energy-marketing segment consists of WGL Energy Services which competes with regulated utilities and other unregulated third party marketers to sell natural gas and electricity directly to residential, commercial, industrial and governmental customers with the objective of earning a profit through competitive pricing. The commodities that WGL Energy Services sells are delivered to retail customers through assets owned by regulated utilities. Washington Gas delivers the majority of natural gas sold by WGL Energy Services, and unaffiliated electric utilities deliver all of the electricity sold. WGL Energy Services owned multiple solar PV distributed generation assets at September 30, 2015 , though the results from these activities are presented in the commercial energy systems segment. Other than these facilities, WGL Energy Services does not own or operate any other natural gas or electric generation, production, transmission or distribution assets. At September 30, 2015 , WGL Energy Services served approximately 143,800 natural gas customers and approximately 138,000 electricity customers located in Maryland, Virginia, Delaware, Pennsylvania and the District of Columbia. The commercial energy systems segment consists of WGL Energy Systems, WGSW and the results of operations of affiliate-owned commercial distributed energy projects. This segment focuses on clean and energy efficient solutions for its customers, driving earnings through (i) upgrading the mechanical, electrical, water and energy-related infrastructure of large governmental and commercial facilities by implementing both traditional and alternative energy technologies; (ii) owning and operating distributed generation assets such as solar PV systems, combined heat and power plants, and natural gas fuel cells and (iii) passive investments in residential and commercial retail solar PV companies. In addition to our primary markets, this segment provides customized energy solutions across a much wider footprint, with business activities across the United States. The midstream energy services segment, which consists of the operations of WGL Midstream, engages in investing in and optimizing natural gas pipeline and storage facilities in the Midwest and Eastern United States. WGL Midstream enters into both physical and financial transactions in a manner intended to utilize energy risk management products to mitigate risks while seeking to maximize potential profits from the optimization of the transportation and storage assets it has under contract. Refer to Note 16— Operating Segment Reporting for further discussion of our segments. CONSOLIDATION OF FINANCIAL STATEMENTS The consolidated financial statements include the accounts of WGL and its subsidiaries during the fiscal years reported. Certain prior period amounts have been recast to conform to current period presentation. Inter-company transactions have been eliminated. Refer to Note 18— Related Party Transactions for a discussion of inter-company transactions. WGL has a variable interest in four investments that qualify as variable interest entities (VIEs). At September 30, 2015 , WGL and its subsidiaries are not the primary beneficiary for any of the VIEs, therefore we have not consolidated any of the VIE entities. Our other investment projects are recorded using the cost method, equity method and as direct financing leases. Refer to Note 17— Other Investments for a discussion of VIEs and other investments. USE OF ESTIMATES IN THE PREPARATION OF FINANCIAL STATEMENTS In accordance with generally accepted accounting principles in the United States of America (GAAP), we make certain estimates and assumptions regarding: (i) reported assets and liabilities; (ii) disclosed contingent assets and liabilities at the date of the financial statements and (iii) reported revenues, revenues subject to refund, and expenses during the reporting period. Actual results could differ from those estimates. PROPERTY, PLANT AND EQUIPMENT Property, plant and equipment (comprised principally of utility plant) are stated at original cost, including labor, materials, taxes and overhead costs incurred during the construction period. The cost of utility plant of Washington Gas includes an allowance for funds used during construction (AFUDC) that is calculated under a formula prescribed by our regulators in Maryland and the District of Columbia. Washington Gas capitalizes AFUDC as a component of construction overhead. The before-tax rates for AFUDC for fiscal years September 30, 2015 , 2014 and 2013 were 4.12% , 3.36% and 5.43% , respectively. Washington Gas charges maintenance and repairs directly to operating expenses. Washington Gas capitalizes betterments and renewal costs, and calculates depreciation applicable to its utility gas plant in service primarily using a straight-line method over the estimated remaining life of the plant. The composite depreciation and amortization rate of the regulated utility segment was 2.73% , 2.77% and 2.86% during fiscal years 2015 , 2014 and 2013 , respectively. In accordance with regulatory requirements, such rates include a component related to asset removal costs for Washington Gas. These asset removal costs are accrued through depreciation expense with a corresponding credit to “Regulatory liabilities—Accrued asset removal costs.” When Washington Gas retires depreciable utility plant and equipment, it charges the associated original costs to “Accumulated depreciation and amortization” and any related removal costs incurred are charged to “Regulatory liabilities—Accrued asset removal costs.” Washington Gas periodically reviews the adequacy of its depreciation rates by considering estimated remaining lives and other factors. For information about Asset Retirement Obligations (ARO’s), refer to the section entitled “Asset Retirement Obligations” . At September 30, 2015 and 2014 , 91.2% and 93.6% , respectively, of WGL’s consolidated original cost of property, plant and equipment was related to the regulated utility segment as shown below. Property, Plant and Equipment at Original Cost ($ In millions) September 30, 2015 2014 Regulated utility segment Distribution, transmission and storage $ 3,927.2 78.5 % $ 3,635.3 79.3 % General, miscellaneous and intangibles 424.8 8.5 448.3 9.8 Construction work in progress (CWIP) 210.4 4.2 203.9 4.5 Total regulated utility segment 4,562.4 91.2 4,287.5 93.6 Unregulated segments 441.5 8.8 295.3 6.4 Total $ 5,003.9 100.0 % $ 4,582.8 100.0 % ASSETS HELD FOR SALE During fiscal year 2015, the Springfield Operations Center met the criteria to be reported as held for sale. Those criteria specify that (i) the asset must be available for immediate sale in its present condition subject only to terms that are usual and customary for sales of such assets and (ii) the sale of the asset must be probable, and its transfer expected to qualify for recognition as a completed sale, within one year, with certain exceptions. At September 30, 2015, the assets and liabilities associated with the Springfield Operations Center are reported at their expected selling price, less selling expenses, as "Assets held for sale" and "Liabilities held for sale" on WGL's and Washington Gas' balance sheets. Washington Gas recorded approximately $0.5 million in transaction fees in "Operations and maintenance expense" in the accompanying statements of income related to selling the facility. IMPAIRMENT OF LONG-LIVED ASSETS Management regularly reviews property and equipment and other long-lived assets, including certain definite-lived intangible assets and our equity method investments for possible impairment. For our equity and cost method investments, an impairment is recorded when the investment has experienced decline in value that is other-than-temporary. Additionally, if the projects in which we hold an investment recognize an impairment loss, we would record our proportionate share of that impairment loss and evaluate the investment for decline in value that is other-than-temporary. This review occurs quarterly, or more frequently if events or changes in circumstances indicate the carrying amount of the asset may not be recoverable. During the fiscal year ended September 30, 2015 , Washington Gas Resources recorded an impairment charge of its investment in ASDHI to its fair value using the income approach. The amount of the impairment was equivalent to the amount of the carrying value of $5.6 million and was due to management's updated estimates of the expected return from the investment. There were no other events or transactions resulting in the impairment of long-lived assets during the year ended September 30, 2015 . During the year ended September 30, 2014 and 2013 , Washington Gas recorded impairment charges of $0.8 million and $2.6 million , respectively, in operation and maintenance expense related to its Springfield Operations Center asset (refer to "Assets Held for Sale" above). At September 30, 2014 and 2013, Washington Gas recorded an impairment loss of $1.9 million and $0.5 million , respectively, for the unrecoverable portion of the costs incurred associated with an abandoned LNG storage project. There were no events or circumstances related to the Springfield Operations Center or LNG storage project during the fiscal year ended September 30, 2015 that resulted in an impairment charge. OPERATING LEASES We have classified the lease of our corporate headquarters as an operating lease. We amortize as rent expense the total of all scheduled lease payments (including lease payment escalations) and tenant allowances on a straight-line basis over the term of the lease. For this purpose, the lease term began on the date when the lessor commenced constructing the leasehold improvements which allowed us to occupy our corporate headquarters. Leasehold improvement costs are classified as “Property, Plant and Equipment” on the Balance Sheets, and are being amortized to depreciation and amortization expense on a straight-line basis over the 15 -year non-cancelable period of the lease. Refer to Note 13— Commitments and Contingencies for financial data for all of our operating leases. CASH AND CASH EQUIVALENTS We consider all investments with original maturities of three months or less to be cash equivalents. We did not have any restrictions on our cash balances that would impact the payment of dividends by WGL or our subsidiaries as of September 30, 2015 and 2014 . REVENUE AND COST RECOGNITION Regulated Utility Operations Revenues. For regulated deliveries of natural gas, Washington Gas reads meters and bills customers on a 21 -day monthly cycle basis. The billing cycles for customers do not coincide with the accounting periods used for financial reporting purposes; therefore, Washington Gas accrues unbilled revenues for gas delivered, but not yet billed, at the end of each accounting period. Cost of Gas. Washington Gas’ jurisdictional tariffs contain mechanisms that provide for the recovery of the cost of gas incurred on behalf of firm customers, including related pipeline transportation and storage capacity charges. Under these mechanisms, Washington Gas periodically adjusts its firm customers’ rates to reflect increases and decreases in these costs. Under or over-collections of gas costs in the current cycle are charged or credited to deferred charges or credits on the balance sheet as non-current regulatory assets or liabilities. Amounts deferred at the end of the cycle, August 31 of each year, are fully reconciled and transferred to current assets or liabilities under the balance sheet captions “Gas costs and other regulatory assets” and “Gas costs and other regulatory liabilities.” These balances are recovered or refunded to customers over the subsequent 12 month period. Revenue Taxes. Revenue taxes such as gross receipts taxes, Public Service Commission (PSC) fees, franchise fees and energy taxes are reported gross in operating revenues. Refer to Note 16— Operating Segment Reporting for amounts recorded related to revenue taxes. Transportation Gas Imbalance. Interruptible shippers and third party marketer shippers transport gas to Washington Gas’ distribution system as part of the unbundled services offered. The delivered volumes of gas from third party shippers into Washington Gas’ distribution system rarely equal the volumes billed to third party marketer customers, resulting in transportation gas imbalances. These imbalances are usually short-term in duration, and Washington Gas monitors the activity and regularly notifies the shippers when their accounts have an imbalance. In accordance with regulatory treatment, Washington Gas does not record a receivable from or liability to third party marketers associated with gas volumes related to these transportation imbalances but, rather, reflects the financial impact as a regulatory asset or liability related to its gas cost adjustment mechanism, thereby eliminating any profit or loss that would occur as a result of the imbalance. The regulatory treatment combines the imbalance for all marketers, including WGL Energy Services, into a single “net” adjustment to the regulatory asset or liability. Refer to Note 18— Related Party Transactions for further discussion of the accounting for these imbalance transactions. Asset Optimization Program. Washington Gas optimizes the value of its long-term natural gas transportation and storage capacity resources by entering into physical and financial transactions in the form of forwards, futures and option contracts for periods when these resources are not being used to physically serve utility customers. Refer to “Derivative Activities” below for further discussion of the accounting for derivative transactions entered into under this program. Regulatory sharing mechanisms in all three jurisdictions allow the profit from these transactions to be shared between Washington Gas’ customers and shareholders. All unrealized fair value gains and losses, and margins generated from the physical and financial settlement of these asset optimization contracts are recorded in utility cost of gas or, in the case of amounts to be shared with rate payers, regulatory assets/liabilities. Non-Utility Operations Retail Energy-Marketing Segment. WGL Energy Services sells natural gas and electricity on an unregulated basis to residential, commercial and industrial customers both inside and outside the Washington Gas service territory. WGL Energy Services enters into indexed or fixed-rate contracts with residential, commercial and industrial customers for sales of natural gas and electricity. Customer contracts, which typically have terms less than 24 months, but may extend up to five years, allow WGL Energy Services to bill customers based upon metered gas and electricity usage. Usage is measured either on a cycle basis at customer premises or based on quantities delivered to the local utility, both of which may vary by month. The billing cycles for customers do not coincide with the accounting periods used for financial reporting purposes; therefore, WGL Energy Services accrues unbilled revenues for gas and electricity delivered, but not yet billed, at the end of each accounting period. Revenues are reflected in “Operating Revenues—Non utility.” WGL Energy Services procures natural gas and electricity supply under contract structures in which it assembles the various components of supply from multiple suppliers to match its customer requirements. The cost of natural gas and electricity for these purchases is recorded using the contracted volumes and prices in “Non-Utility cost of energy-related sales.” Commercial Energy Systems Segment. WGL Energy Systems recognizes income and expenses for all design-build construction contracts using the percentage-of-completion method in “Operating Revenues—Non-utility” and “Non-Utility cost of energy-related sales.” WGL Energy Systems also recognizes income from its distributed energy assets based on the terms of the related power purchase agreements. Renewable Energy Certificates (RECs) are recorded as inventory by WGL Energy Systems after every 1,000 Kilowatt-hours (kWh) of electricity are produced by an eligible solar facility. WGL Energy Systems recognizes income on the sale of RECs based on the contractual terms and conditions of the sale. Refer to Note 17— Other Investments for discussion of our sale leaseback arrangements and equity method investments. Midstream Energy Services Segment. WGL Midstream nets its revenues and costs related to its trading activities in "Operating Revenues--Non-utility". Other Activities. Washington Gas Resources recognizes income on its investment using the cost approach of investment accounting. STORAGE GAS VALUATION METHODS For Washington Gas and WGL Energy Services, storage gas inventories are 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. The following table shows the lower-of-cost or market adjustments recorded to net income for the years ended September 30, 2015 , 2014 and 2013 . Lower-of-Cost or Market Adjustments Pre-Tax Increase (Decrease) to Net Income (In millions) September 30, 2015 2014 2013 WGL (a) Operating revenues - non-utility $ (21.5 ) $ (3.0 ) $ (10.1 ) Washington Gas Utility cost of gas $ (1.3 ) $ (0.2 ) $ — Total Consolidated $ (22.8 ) $ (3.2 ) $ (10.1 ) (a) WGL includes WGL Holdings and all subsidiaries other than Washington Gas. WEATHER-RELATED INSTRUMENTS Periodically, we purchase certain weather-related instruments, such as HDD derivatives and CDD derivatives. We account for these weather related instruments in accordance with Financial Accounting Standards Board Accounting Standards Codification (ASC) Subtopic 815-45, Derivatives and Hedging — Weather Derivatives . For weather insurance policies and HDD derivatives, benefits or costs are ultimately recognized to the extent actual HDDs fall above or below the contractual HDDs for each instrument. Benefits or costs are recognized for CDD derivatives when the average temperature exceeds or is below a contractually stated level during the contract period. Premiums for weather-related instruments are amortized based on the pattern of normal temperature days over the coverage period. Weather-related instruments for which we collect a premium are carried at fair value. Washington Gas’ weather related instrument premium expense or benefit is not considered in establishing retail rates. Washington Gas does not purchase such instruments for jurisdictions in which it has received rate mechanisms that compensate it on a normal weather basis. Refer to Note 14— Derivative and Weather-Related Instruments for further discussion of our weather-related instruments. DERIVATIVE ACTIVITIES Regulated Utility . Washington Gas enters into both physical and financial derivative contracts for the purchase and sale of natural gas that are subject to mark-to-market accounting. Changes in the fair value of derivative instruments recoverable or refundable to customers and therefore subject to ASC Topic 980, Regulated Operations , are recorded as regulatory assets or liabilities while changes in the fair value of derivative instruments not affected by rate regulation are reflected in earnings. As part of its asset optimization program, Washington Gas enters into derivative contracts related to the sale and purchase of natural gas at a future price with the primary objective of locking in operating margins that Washington Gas expects to ultimately realize. The derivatives used under this program may cause significant period-to-period volatility in earnings for the portion of net profits retained for shareholders; however, this volatility will not change the margins that Washington Gas expects to realize from these transactions. In accordance with ASC Topic 815, all financially and physically settled contracts under our asset optimization program are reported on a net basis in the statements of income in “Utility cost of gas”. From time to time, Washington Gas also utilizes derivative instruments that are designed to minimize the risk of interest-rate volatility associated with planned issuances of long-term debt. Gains or losses associated with these derivative transactions are deferred as regulatory assets or liabilities and amortized to interest expense in accordance with regulatory accounting requirements. Refer to Note 14— Derivative and Weather-Related Instruments for further discussion of our derivative activities. Non-Utility Operations. WGL Energy Services enters into both physical and financial contracts for the purchase and sale of natural gas and electricity. WGL Energy Services designates a portion of these physical contracts related to the purchase of natural gas and electricity to serve our customers as “normal purchases and normal sales;” therefore, they are not subject to the mark-to-market accounting requirements of ASC Topic 815. WGL Energy Services records these derivatives as revenues or expenses depending on the nature of the economically hedged item. 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. The financial contracts and the portion of the physical contracts that qualify as derivative instruments are subject to the mark-to-market accounting requirements and are recorded on the balance sheet at fair value and are reflected in earnings. WGL Midstream nets financial and physical contracts in "Operating Revenues-Non-utility". WGL may, from time to time, designate interest rate swaps used to manage the interest rate risk associated with future debt issuances, as cash flow hedges. Any gains or losses arising from the effective portion of cash flow hedges are recorded in other comprehensive income and are amortized using the effective interest rate method into earnings over the same period as the hedged interest payments are made. Gains or losses arising from the ineffective portion of cash flow hedges are recognized in earnings immediately. INCOME TAXES We recognize deferred income tax assets and liabilities for all temporary differences between the financial statement basis and the tax basis of assets and liabilities, including those that are currently excluded for ratemaking purposes of Washington Gas. Regulatory assets or liabilities, corresponding to such additional deferred income tax assets or liabilities, may be recorded to the extent recoverable from or payable to customers through the ratemaking process in future periods. Refer to Note 2— Regulated Operations for Washington Gas’ regulatory assets and liabilities associated with income taxes due from and to customers at September 30, 2015 and 2014 . Amounts applicable to income taxes due from and due to customers primarily represent differences between the book and tax basis of net utility plant in service. We amortize investment tax credits as reductions to income tax expense over the estimated service lives of the related properties. Refer to Note 9— Income Taxes which provides detailed financial information related to our income taxes. STOCK-BASED COMPENSATION We account for stock-based compensation expense in accordance with ASC Topic 718, Compensation—Stock Compensation, which requires us to measure and recognize stock-based compensation expense in our financial statements based on the fair value at the date of grant for our equity-classified share-based awards, which include performance shares granted to certain employees and shares issued to directors. For liability-classified share-based awards, which include performance units, we recognize stock-based compensation expense based on their fair value at the end of each reporting period. For both equity-classified and liability-classified share-based awards, we estimate forfeitures over the requisite service period when recognizing compensation expense; these estimates are periodically adjusted to the extent to which actual forfeitures differ from such estimates. Refer to Note 11— Stock-Based Compensation for further discussion of the accounting for our stock-based compensation plans. ASSET RETIREMENT OBLIGATIONS Washington Gas accounts for its AROs in accordance with ASC Subtopic 410-20, Asset Retirement and Environmental Obligations—Asset Retirement Obligations. Our asset retirement obligations include the costs to cut, purge and cap Washington Gas' distribution and transmission system and plug storage wells upon their retirement. We also have asset retirement obligations associated with our distributed generation assets. These standards require recording the estimated retirement cost over the life of the related asset by depreciating the present value of the retirement obligation, measured at the time of the asset’s acquisition, and accreting the liability until it is settled. There are timing differences between the ARO-related accretion and depreciation amounts being recorded pursuant to GAAP and the recognition of depreciation expense for legal asset removal costs that we are currently recovering in rates. These timing differences are recorded as a reduction to “Regulatory liabilities—Accrued asset removal costs” in accordance with ASC Topic 980. We do not have any assets that are legally restricted related to the settlement of asset retirement obligations. WGL Holdings, Inc. Changes in Asset Retirement Obligations (In millions) September 30, 2015 2014 Asset retirement obligations at beginning of year $ 181.2 $ 104.0 Liabilities incurred in the period 8.4 4.9 Liabilities settled in the period (a) (14.6 ) (5.2 ) Accretion expense 7.8 4.4 Revisions in estimated cash flows (b) 24.9 73.1 Asset retirement obligations at the end of the year (c) $ 207.7 $ 181.2 Washington Gas Light Company Changes in Asset Retirement Obligations (In millions) September 30, 2015 2014 Asset retirement obligations at beginning of year $ 179.8 $ 102.7 Liabilities incurred in the period 8.1 4.9 Liabilities settled in the period (a) (14.6 ) (5.2 ) Accretion expense 7.7 4.3 Revisions in estimated cash flows (b) 24.9 73.1 Asset retirement obligations at the end of the year (c) $ 205.9 $ 179.8 (a) Includes asset retirement obligations of $1.6 million related to the Springfield Operations Center that were reclassified to "Current Liabilities - Liabilities held for sale". (b) WGL revised its assumptions regarding the timing and amounts related to its obligation to cut, cap and purge pipeline. The revision is primarily driven by our accelerated pipeline replacement programs. (c) Includes short-term asset retirement obligations of $7.0 million and $6.0 million for fiscal year 2015 and 2014 , respectively. ACCOUNTING STANDARDS ADOPTED IN FISCAL YEAR 2015 Standard Description Date of adoption Effect on the financial statements or other significant matters 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 (Topic 740) The standard requires an unrecognized tax benefit, or a portion of an unrecognized tax benefit to be presented in the financial statements as a reduction to a deferred tax asset for a net operating loss carryforward, a similar loss, or a tax credit carryforward. October 1, 2014 As a result of the implementation of this standard, we reduced our deferred tax assets by a portion of our unrecognized tax benefits. ASU 2015-13, Derivatives and Hedging (Topic 815)- Application of the Normal Purchases and Normal Sales Scope Exception to Certain Electricity Contracts within Nodal Energy Markets (a consensus of the FASB Emerging Issues Task Force) The standard requires that a forward purchase or sale of electricity in which electricity must be physically delivered through a nodal energy market operated by an independent system operator, and in which an entity incurs transmission costs on the basis of locational marginal pricing charges, would meet the physical delivery requirement under the NPNS scope exception. August 10, 2015 The adoption of this standard did not have a material effect on our financial statements. OTHER NEWLY ISSUED ACCOUNTING STANDARDS Standard Description Date of adoption Effect on the financial statements or other significant matters ASU 2015-03, Interest - Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Cost The standard requires an entity to present debt issuance costs in the balance sheet as a direct deduction of the debt liability in a manner consistent with its accounting treatment of debt discounts. The standard permits prospective or retrospective application. WGL will apply the standard retrospectively. October 1, 2016 We are in the process of evaluating the impact the adoption of this standard will have on our financial statements. ASU 2015-02, Consolidation (Topic 810): Amendments to the Consolidation Analysis The standard changes the analysis to be performed in determining whether certain types of legal entities should be consolidated, specifically the analysis of limited partnerships and similar entities, fee arrangements and related party relationships. The standard permits prospective or retrospective application for different parts. October 1, 2016 We are in the process of evaluating the impact the adoption of this standard will have on our financial statements. ASU 2014-09, Revenue from Contracts with Customers (Topic 606) The standard establishes a comprehensive revenue recognition model clarifying the method used to determine the timing and requirements for revenue recognition from contracts with customers. The disclosure requirements under the new standard will enable users of financial statements to understand the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. The standard permits retrospective application. October 1, 2019 We are in the process of evaluating the impact the adoption of this standard will have on our financial statements.

Regulated Operations

Regulated Operations	12 Months Ended
	Sep. 30, 2015
Regulated Operations [Abstract]
Regulated Operations	REGULATED OPERATIONS Washington Gas accounts for its regulated operations in accordance with ASC Topic 980. This standard includes accounting principles for companies whose rates are determined by independent third party regulators. When setting rates, regulators may require us to record expense in different periods than may be appropriate for unregulated enterprises. When this occurs, Washington Gas defers the associated costs as assets (regulatory assets) on its balance sheet and records them as expenses on its income statement as it collects the revenues designed to recover these costs through customers’ rates. Further, regulators can also impose liabilities upon a company for amounts previously collected from customers and for future outflows that are expected to be incurred in the future (regulatory liabilities). When Washington Gas files a request with certain regulatory commissions to modify customers’ rates, it is permitted to charge customers new rates, subject to refund, until the regulatory commission renders a final decision on the amount of the authorized change in rates. During this interim period, Washington Gas records a provision for a rate refund regulatory liability based on the difference between the amount it collects in rates and the amount it expects to recover from a final regulatory decision. Similarly, Washington Gas periodically records provisions for rate refunds related to other transactions. Actual results for these regulatory contingencies are often difficult to predict and could differ significantly from the estimates reflected in the financial statements. Refer to Note 13— Commitments and Contingencies for further discussion of regulatory matters and related contingencies. At September 30, 2015 and 2014 , we recorded the following regulatory assets and liabilities on our balance sheets. These assets and liabilities will be recognized as revenues or expenses in future periods as they are reflected in customers’ rates. Regulatory Assets and Liabilities (In millions) Regulatory Assets Regulatory Liabilities September 30, 2015 2014 2015 2014 Current: Gas costs due from/to customers (a) $ 1.7 $ — $ 22.6 $ 16.2 Interruptible sharing (a) 3.3 3.4 2.6 — Revenue normalization mechanisms for Maryland and Virginia (a) — — 8.4 5.5 Plant recovery mechanisms 0.8 0.4 1.0 0.9 Total current $ 5.8 $ 3.8 $ 34.6 $ 22.6 Deferred: Accrued asset removal costs $ — $ — $ 325.5 $ 327.4 Deferred gas costs (a) 190.7 191.3 — — Pension and other post-retirement benefits Other post-retirement benefit costs—trackers (b) 0.1 — — — Deferred pension costs—trackers (b) 38.0 45.1 — — ASC Topic 715 unrecognized costs/income (a)(c) Pensions 173.9 147.9 — — Other post-retirement benefits — — 104.4 86.4 Total pension and other post-retirement benefits 212.0 193.0 104.4 86.4 Other Income tax-related amounts due from/to customers (d) 31.7 30.4 4.2 4.8 Losses/gains on issuance and extinguishments of debt and interest-rate derivative instruments (a)(e) 11.1 12.0 1.6 1.7 Deferred gain on sale of assets (a) — — 1.4 1.4 Rights-of-way fees (a) 1.6 1.5 — — Business process outsourcing and related costs (a) 2.7 1.0 — — Nonretirement postemployment benefits (a)(f) 18.9 16.3 — — Deferred integrity management expenditures (a)(g) 5.1 2.7 — — Recoverable portion of abandoned LNG facility (a) 5.0 5.6 — — Environmental response costs (a,h) 1.8 0.6 — — Other regulatory expenses (a) 2.1 1.5 9.9 9.7 Total other $ 80.0 $ 71.6 $ 17.1 $ 17.6 Total deferred $ 482.7 $ 455.9 $ 447.0 $ 431.4 Total $ 488.5 $ 459.7 $ 481.6 $ 454.0 (a) Washington Gas does not earn its overall rate of return on these assets. Washington Gas is allowed to recover and required to pay, using short-term interest rates, the carrying costs related to billed gas costs due from and to its customers in the District of Columbia and Virginia jurisdictions. (b) Relates to the District of Columbia jurisdiction. (c) Refer to Note 10-Pension and Other Post-Retirement Benefit Plans for a further discussion of these amounts. (d) This balance represents amounts due from customers for deferred tax liabilities related to tax benefits on deduction flowed directly to customers prior to the adoption of income tax normalization for ratemaking purposes. (e) The losses or gains on the issuance and extinguishment of debt and interest-rate derivative instruments include unamortized balances from transactions executed in prior fiscal years. These transactions create gains and losses that are amortized over the remaining life of the debt as prescribed by regulatory accounting requirements. (f) Represents the timing difference between the recognition of workers compensation and short-term disability costs in accordance with generally accepted accounting principles and the way these costs are recovered through rates. (g) This balance represents amounts for deferred expenditures associated with Washington Gas’ Distribution Integrity Management Program (DIMP) in Virginia. (h) This balance represents allowed remediation expenditures at Washington Gas sites to be recovered through rates for Maryland and the District of Columbia. The recovery period is over several years. As required by ASC Topic 980, Washington Gas monitors its regulatory and competitive environment to determine whether the recovery of its regulatory assets remains probable. If Washington Gas were to determine that recovery of these assets is no longer probable, it would write off the assets against earnings. We have determined that ASC Topic 980 continues to apply to our regulated operations, and the recovery of our regulatory assets at September 30, 2015 is probable.

Accounts Payable and Other Accr

Accounts Payable and Other Accrued Liabilities	12 Months Ended
	Sep. 30, 2015
Accounts Payable and Accrued Liabilities [Abstract]
Accounts Payable and Other Accrued Liabilities	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. September 30, (In millions) 2015 2014 Accounts payable—trade $ 277.3 $ 278.8 Employee benefits and payroll accruals 31.4 19.8 Other accrued liabilities 16.4 14.6 Total $ 325.1 $ 313.2 Washington Gas Light Company September 30, (In millions) 2015 2014 Accounts payable—trade $ 122.2 $ 146.4 Employee benefits and payroll accruals 29.5 18.2 Other accrued liabilities 7.6 11.9 Total $ 159.3 $ 176.5

Short-Term Debt

Short-Term Debt	12 Months Ended
	Sep. 30, 2015
Short-term Debt [Abstract]
Short-Term Debt	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. The policy of each WGL and Washington Gas 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 September 30, 2015 and 2014 . Committed Credit Available (In millions) September 30, 2015 WGL (b) Washington Gas Total Consolidated Committed credit agreements Unsecured revolving credit facility, expires December 19, 2019 (a) $ 450.0 $ 350.0 $ 800.0 Less: Commercial Paper (243.0 ) (89.0 ) (332.0 ) Net committed credit available $ 207.0 $ 261.0 $ 468.0 Weighted average interest rate 0.30 % 0.16 % 0.26 % September 30, 2014 Committed credit agreements Unsecured revolving credit facility, expires April 3, 2017 (a) $ 450.0 $ 350.0 $ 800.0 Less: Commercial Paper (364.5 ) (89.0 ) (453.5 ) Net committed credit available $ 85.5 $ 261.0 $ 346.5 Weighted average interest rate 0.20 % 0.13 % 0.19 % (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 includes all subsidiaries other than Washington Gas. In December 2014, both WGL and Washington Gas entered into a first amendment to their respective credit agreements, each dated April 3, 2012. The amendments extend the maturity date of the credit facilities from April 3, 2017 to December 19, 2019, provided that all necessary governmental approvals have been renewed by September 30, 2017. Under the credit agreements, as amended, WGL and Washington Gas each have the right to request two one-year-extensions, with the banks' approval. At September 30, 2015 and 2014 , there were no outstanding bank loans from WGL’s or Washington Gas’ revolving credit facilities. Under the terms of the credit agreements, the ratio of consolidated financial indebtedness to consolidated total capitalization may not exceed 0.65 to 1.0 ( 65% ). At September 30, 2015 , WGL's and Washington Gas' ratios of consolidated financial indebtedness to consolidated total capitalization were 51% and 42% , respectively. In addition, WGL and Washington Gas are required to inform lenders of changes in corporate existence, financial conditions, litigation and environmental warranties that might have a material adverse effect. Failure to inform the lenders’ agent of these material changes might constitute default under the agreements. Another potential default may be deemed to exist if WGL or Washington Gas were to fail to pay principal or interest when due on any other indebtedness. Such defaults, if not remedied, could lead to suspension of further loans and/or acceleration in which obligations become immediately due and payable. At September 30, 2015 , WGL and Washington Gas were in compliance with all of the covenants under their revolving credit facilities.

Long-Term Debt

Long-Term Debt	12 Months Ended
	Sep. 30, 2015
Debt Disclosure [Abstract]
Long-Term Debt	LONG-TERM DEBT FIRST MORTGAGE BONDS The Mortgage of Washington Gas dated January 1, 1933 (Mortgage), as supplemented and amended, securing any First Mortgage Bonds (FMBs) it issues, constitutes a direct lien on substantially all property and franchises owned by Washington Gas, other than a small amount of property that is expressly excluded. At September 30, 2015 and 2014 , Washington Gas had no debt outstanding under the Mortgage. Any FMBs that may be issued in the future will represent indebtedness of Washington Gas. SHELF REGISTRATION At September 30, 2015 and 2014 , WGL had the capacity under a shelf registration to issue an unspecified amount of long-term debt securities. On September 10, 2015, a shelf registration statement of Washington Gas became effective; Washington Gas has the capacity to issue up to $600.0 million of additional MTNs. UNSECURED NOTES Washington Gas issues unsecured MTNs and private placement notes with individual terms regarding interest rates, maturities and call or put options. These notes can have maturity dates of one or more years from the date of issuance. The following tables show the outstanding notes as of September 30, 2015 and 2014 . Senior Notes, MTNs and Private Placement Notes Outstanding ($ In millions) WGL (a) Washington Gas Total Consolidated September 30, 2015 Long-term notes (b) $ 250.0 $ 721.0 $ 971.0 Weighted average interest rate 3.66 % 5.58 % 5.08 % September 30, 2014 Long-term notes (b) $ — $ 691.0 $ 691.0 Weighted average interest rate n/a 5.65 % 5.65 % (a) WGL includes WGL Holdings and all subsidiaries other than Washington Gas. (b) Includes Senior Notes for WGL and both MTNs and private placement notes for Washington Gas. Represents face value including current maturities. The indenture for the unsecured MTNs and the note purchase agreement for the private placement notes provide that Washington Gas will not issue any FMBs under its Mortgage without securing all MTNs and the subject private placement notes with the Mortgage. Certain of Washington Gas’ outstanding MTNs and private placement notes have a make-whole call feature that pays the holder a premium based on a spread over the yield to maturity of a U.S. Treasury security having a comparable maturity, when that particular note is called by Washington Gas before its stated maturity date. With the exception of this make-whole call feature, Washington Gas is not required to pay call premiums for calling debt prior to the stated maturity date. The following tables show senior notes, MTN and private placement issuances and retirements for the years ended September 30, 2015 and 2014 . Senior Notes, MTNs and Private Placement Issuances and Retirements ($ In millions) Principal (b) Interest Rate Effective Cost (c) Nominal Maturity Date Year Ended September 30, 2015 WGL (a) Issuances: 10/24/2014 $ 100.0 2.25 % 2.42 % 11/1/2019 10/24/2014 125.0 4.60 % 5.11 % 11/1/2044 12/16/2014 25.0 4.60 % 5.53 % 11/1/2044 Total $ 250.0 Washington Gas Issuances: 12/15/2014 $ 50.0 4.24 % 4.41 % 12/15/2044 Total 50.0 Total consolidated issuances $ 300.0 Washington Gas Retirements: 8/9/2015 $ 20.0 4.83 % 8/9/2015 Total $ 20.0 Year Ended September 30, 2014 Washington Gas Issuances: 12/5/2013 $ 75.0 5.00 % 4.95 % 12/15/2043 9/12/2014 100.0 4.22 % 4.27 % 9/15/2044 Total $ 175.0 Retirements: 11/7/2013 $ 37.0 4.88 % 11/7/2013 9/10/2014 30.0 5.17 % 9/10/2014 Total $ 67.0 (a) WGL includes WGL Holdings and all subsidiaries other than Washington Gas. (b) Represents face amount. (c) The estimated effective cost of the issued notes, including consideration of issuance fees and hedge costs. LONG-TERM DEBT MATURITIES Maturities of long-term debt for each of the next five fiscal years and thereafter as of September 30, 2015 are summarized in the following table. Long-Term Debt Maturities (a) (In millions) WGL (b) Washington Gas Total 2016 $ — $ 25.0 $ 25.0 2017 — — — 2018 — — — 2019 — 50.0 50.0 2020 100.0 50.0 150.0 Thereafter 150.0 596.0 746.0 Total $ 250.0 $ 721.0 $ 971.0 Less: current maturities — 25.0 25.0 Total non-current $ 250.0 $ 696.0 $ 946.0 (a) Excludes unamortized discounts of $ 1.7 million and $0.1 million at September 30, 2015 , for WGL and Washington Gas, respectively. (b) WGL includes WGL Holdings and all subsidiaries other than Washington Gas.

Common Stock

Common Stock	12 Months Ended
	Sep. 30, 2015
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Common Stock	COMMON STOCK — WGL COMMON STOCK OUTSTANDING Shares of common stock outstanding were 49,728,662 and 50,656,553 at September 30, 2015 and 2014 , respectively. COMMON STOCK RESERVES At September 30, 2015 , there were 4,561,588 authorized, but unissued, shares of common stock reserved under the following plans: Common Stock Reserves Number of Shares Reserve for: Omnibus incentive compensation plan (a) 993,825 Dividend reinvestment and common stock purchase plan 2,849,012 Employee savings plans 637,196 Directors’ stock compensation plan 81,555 Total common stock reserves 4,561,588 (a) In March 2007, WGL adopted a shareholder-approved Omnibus Incentive Compensation Plan to replace on a prospective basis the 1999 Incentive Compensation Plan. Included are shares that may be issued upon the vesting of 304,089 performance shares that have been granted but not yet vested. Upon vesting, a number of shares equal to up to 200% of the number of performance shares granted may be issued, which would reduce the number of shares available for issuance under the Omnibus Incentive Compensation Plan. Refer to Note 11—Stock-Based Compensation for a discussion regarding our stock-based compensation plans.

Preferred Stock

Preferred Stock	12 Months Ended
	Sep. 30, 2015
Preferred Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Preferred Stock	PREFERRED STOCK Washington Gas has three series of cumulative preferred stock outstanding, and each series is subject to redemption by Washington Gas. All three series have a dividend preference that prohibits Washington Gas from declaring and paying dividends on shares of its common stock unless dividends on all outstanding shares of the preferred stock have been fully paid for all past quarterly dividend periods. In addition, all outstanding shares of preferred stock have a preference as to the amounts that would be distributed in the event of a liquidation or dissolution of Washington Gas. The following table presents this information, as well as call prices for each preferred stock series outstanding. Preferred Stock Preferred Liquidation Preference Series Shares Per Share Call Price Outstanding Outstanding Involuntary Voluntary Per Share $4.80 150,000 $100 $101 $101 $4.25 70,600 $100 $105 $105 $5.00 60,000 $100 $102 $102

Earnings Per Share

Earnings Per Share	12 Months Ended
	Sep. 30, 2015
Earnings Per Share [Abstract]
Earnings Per Share	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 (refer to Note 11 —Stock-Based Compensation ). As of September 30, 2015 , there were no outstanding stock options. There were no anti-dilutive shares for any of the periods presented. The following table reflects the computation of our basic and diluted EPS for the fiscal years ended September 30, 2015 , 2014 and 2013 . Basic and Diluted EPS Years Ended September 30, (In thousands, except per share data) 2015 2014 2013 Basic earnings per average common share: Net income applicable to common stock $ 131,259 $ 105,940 $ 80,253 Average common shares outstanding—basic 49,794 51,759 51,697 Basic earnings per average common share $ 2.64 $ 2.05 $ 1.55 Diluted earnings per average common share: Net income applicable to common stock $ 131,259 $ 105,940 $ 80,253 Average common shares outstanding—basic 49,794 51,759 51,697 Stock-based compensation plans 266 11 111 Total average common shares outstanding—diluted 50,060 51,770 51,808 Diluted earnings per average common share $ 2.62 $ 2.05 $ 1.55

Income Taxes

Income Taxes	12 Months Ended
	Sep. 30, 2015
Income Tax Disclosure [Abstract]
Income Taxes	INCOME TAXES WGL files a consolidated federal tax return and various other state returns. We are no longer subject to income tax examinations by the Internal Revenue Service (IRS) for years ended prior to September 30, 2012. Substantially all state income tax years in major jurisdictions are closed for years ended prior to September 30, 2011. WGL and each of its subsidiaries also participate in a tax sharing agreement that establishes the method for allocating tax benefits from losses that are utilized on the consolidated income tax return. The consolidated tax is apportioned among the subsidiaries on the separate return method and losses of the parent, WGL, are allocated to the subsidiaries that have taxable income. In fiscal year 2015 , Washington Gas shared $0.5 million of tax benefits from the tax sharing agreement that was reflected as a tax decrease on Washington Gas’ statements of income. During fiscal years 2014 and 2013 , Washington Gas realized $2.9 million and $1.3 million of tax savings as a result of this tax sharing agreement. The effect of this allocation of benefits to Washington Gas has no effect on our consolidated financial statements. State income tax returns are filed on a separate company basis in most states where we have operations and/or a requirement to file. Washington Gas charged the Maryland portion of the Med D regulatory asset to tax expense during the fiscal year ended September 30, 2012, based on positions taken by the PSC of MD in Washington Gas’ rate case during the fiscal year that did not permit recovery. Washington Gas received an order in the first quarter of fiscal year end September 30, 2014 in its rate case from the PSC of MD that allowed recovery of the Med D regulatory asset over a 5 -year amortization period. Therefore, the tax benefit was recognized to reinstate the regulatory asset. On September 13, 2013, the U.S. Treasury Department issued final income tax regulations to address the costs incurred in acquiring, producing, or improving tangible property. The regulations are effective for WGL and Washington Gas for the tax year beginning October 1, 2014. WGL and Washington Gas will file Forms 3115 along with its income tax return for the year ended September 30, 2015 . The financial impact of these regulations did not have a material impact on the financial statements. Any changes in method of accounting for income tax purposes required to conform to the final regulations will be made for the taxable year ending September 30, 2015. The tables below provide the following for WGL and Washington Gas: (i) the components of income tax expense; (ii) a reconciliation between the statutory federal income tax rate and the effective income tax rate and (iii) the components of accumulated deferred income tax assets and liabilities at September 30, 2015 and 2014 . WGL Holdings, Inc. Components of Income Tax Expense Years Ended September 30, (In thousands) 2015 2014 2013 INCOME TAX EXPENSE Current: Federal $ (18,639 ) $ 29,976 $ 41,425 State 2,977 5,149 11,258 Total current (15,662 ) 35,125 52,683 Deferred: Federal Accelerated depreciation 71,529 35,747 33,394 Other 17,726 (18,014 ) (31,173 ) State Accelerated depreciation 13,739 9,822 6,795 Other 1,411 (1,760 ) (7,585 ) Total deferred 104,405 25,795 1,431 Amortization of investment tax credits (4,939 ) (3,666 ) (1,822 ) Total income tax expense $ 83,804 $ 57,254 $ 52,292 WGL Holdings, Inc. Reconciliation Between the Statutory Federal Income Tax Rate and Effective Tax Rate Years Ended September 30, ($ In thousands) 2015 2014 2013 Income taxes at statutory federal income tax rate $ 75,760 35.00 % $ 57,580 35.00 % $ 46,853 35.00 % Increase (decrease) in income taxes resulting from: Accelerated depreciation less amount deferred 1,187 0.55 1,875 1.14 2,106 1.57 Amortization of investment tax credits (4,939 ) (2.28 ) (3,666 ) (2.23 ) (1,822 ) (1.36 ) Cost of removal (2,721 ) (1.26 ) (4,902 ) (2.98 ) (2,356 ) (1.76 ) State income taxes-net of federal benefit 11,109 5.13 8,734 5.31 7,448 5.56 Medicare Part D adjustment — — (3,621 ) (2.20 ) — — ASDHI impairment 1,969 0.91 — — — — Other items-net 1,439 0.66 1,254 0.76 63 0.05 Total income tax expense and effective tax rate $ 83,804 38.71 % $ 57,254 34.80 % $ 52,292 39.06 % WGL Holdings, Inc. Components of Deferred Income Tax Assets (Liabilities) September 30, (In thousands) 2015 2014 ACCUMULATED DEFERRED INCOME TAXES Current Non-current Current Non-current Deferred income tax assets: Pensions $ — $ 44,468 $ — $ 24,349 Uncollectible accounts 10,389 — 9,268 — Inventory overheads 5,873 — 6,591 — Employee compensation and benefits 4,733 52,497 6,306 37,873 Derivatives 8,580 35,311 6,503 31,555 Deferred gas costs 2,406 — — 4,218 Solar grant/investment tax credit — 53,067 — 39,184 Tax credit carry forward — 55,040 — — Other 861 4,779 814 1,422 Total assets 32,842 245,162 29,482 138,601 Deferred income tax liabilities: Other post-retirement benefits — 54,860 — 38,299 Accelerated depreciation and other plant related items — 794,099 — 669,040 Losses/gains on reacquired debt — 1,292 — 1,426 Income taxes recoverable through future rates — 68,245 — 65,374 Deferred gas costs — 815 2,818 — Partnership basis differences — 29,468 — 25,370 Valuation allowances — 2,188 — — Total liabilities — 950,967 2,818 799,509 Net accumulated deferred income tax assets (liabilities) $ 32,842 $ (705,805 ) $ 26,664 $ (660,908 ) Washington Gas Light Company Components of Income Tax Expense Years Ended September 30, (In thousands) 2015 2014 2013 INCOME TAX EXPENSE Current: Federal $ (5,305 ) $ 37,098 $ 40,492 State 907 4,262 7,515 Total current (4,398 ) 41,360 48,007 Deferred: Federal Accelerated depreciation 71,046 34,833 34,518 Other (6,619 ) (30,523 ) (35,982 ) State Accelerated depreciation 13,701 9,540 6,770 Other (1,507 ) (6,800 ) (8,221 ) Total deferred 76,621 7,050 (2,915 ) Amortization of investment tax credits (832 ) (876 ) (895 ) Total income tax expense $ 71,391 $ 47,534 $ 44,197 Washington Gas Light Company Reconciliation Between the Statutory Federal Income Tax Rate and Effective Tax Rate Years Ended September 30, ($ In thousands) 2015 2014 2013 Income taxes at statutory federal income tax rate $ 63,024 35.00 % $ 51,050 35.00 % $ 40,782 35.00 % Increase (decrease) in income taxes resulting from: Accelerated depreciation less amount deferred 2,108 1.17 1,875 1.29 2,106 1.81 Amortization of investment tax credits (832 ) (0.46 ) (876 ) (0.60 ) (895 ) (0.77 ) Cost of removal (2,721 ) (1.51 ) (4,902 ) (3.36 ) (2,356 ) (2.02 ) State income taxes-net of federal benefit 8,986 4.99 6,711 4.60 5,487 4.71 Consolidated tax sharing allocation (533 ) (0.30 ) (2,862 ) (1.96 ) (1,290 ) (1.11 ) Medicare Part D adjustment — — (3,621 ) (2.48 ) — — Other items-net 1,359 0.76 159 0.09 363 0.31 Total income tax expense and effective tax rate $ 71,391 39.65 % $ 47,534 32.58 % $ 44,197 37.93 % Washington Gas Light Company Components of Deferred Income Tax Assets (Liabilities) Years Ended September 30, (In thousands) 2015 2014 ACCUMULATED DEFERRED INCOME TAXES Current Non-current Current Non-current Deferred income tax assets: Pensions $ — $ 43,748 $ — $ 23,738 Uncollectible accounts 7,637 — 7,618 — Inventory overheads 5,873 — 6,591 — Employee compensation and benefits 4,346 34,511 5,902 27,961 Derivatives 3,576 35,311 4,809 31,555 Deferred gas costs 2,406 — — 4,218 Investment tax credit — — — 312 Other 862 — 814 197 Total assets 24,700 113,570 25,734 87,981 Deferred income tax liabilities: Other post-retirement benefits — 54,566 — 38,065 Accelerated depreciation and other plant related items — 681,108 — 602,376 Losses/gains on reacquired debt — 1,292 — 1,426 Income taxes recoverable through future rates — 67,953 — 65,128 Deferred gas costs — 815 2,818 — Other — 1,300 — 932 Total liabilities — 807,034 2,818 707,927 Net accumulated deferred income tax assets (liabilities) $ 24,700 $ (693,464 ) $ 22,916 $ (619,946 ) In June 2015 , we filed our tax return for the year ended September 30, 2014 . The following table summarizes the change in unrecognized tax benefits during fiscal year 2015 , 2014 , 2013 and our total unrecognized tax benefits at September 30, under the provisions of ASC Topic 740, Income Taxes: Unrecognized Tax Benefits (In thousands) 2015 2014 2013 Total unrecognized tax benefits, October 1, $ 32,613 $ 25,051 $ 22,082 Increases in tax positions relating to current year 12,848 10,512 5,251 Decreases in tax positions relating to prior year (6,834 ) (2,950 ) (2,282 ) Total unrecognized tax benefits, September 30, $ 38,627 $ 32,613 $ 25,051 During the year, the unrecognized tax benefits for WGL and Washington Gas increased by approximately $6.0 million relating to uncertain tax positions, 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. The IRS completed its audit of the tax years related to the change in accounting method for repairs without proposing any changes, however, they could re-examine this issue in the future. WGL and Washington Gas recognize 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 fiscal years ended September 30, 2015 , 2014 and 2013 , interest expense on uncertain tax positions was minimal.

Pension and Other Post-Retireme

Pension and Other Post-Retirement Benefit Plans	12 Months Ended
	Sep. 30, 2015
Compensation and Retirement Disclosure [Abstract]
Pension and Other Post-Retirement Benefit Plans	PENSION AND OTHER POST-RETIREMENT BENEFIT PLANS Washington Gas maintains a qualified, trusteed, non-contributory defined benefit pension plan (qualified pension plan) covering most active and vested former employees of Washington Gas. The non-contributory defined benefit pension plan is closed to all employees hired on or after January 1, 2010. Washington Gas accounts for the qualified pension plan and other post-retirement benefit plans under the provisions of ASC 715, Compensation-Retirement Benefits. Several executive officers of Washington Gas also participate in a non-funded defined benefit supplemental executive retirement plan (DB SERP), a non-qualified pension plan. A rabbi trust has been established for the potential future funding of the DB SERP liability. The DB SERP was closed to new entrants beginning January 1, 2010 and instead, executive officers are eligible to participate in a non-funded defined contribution SERP (DC SERP). In addition, effective January 1, 2010, Washington Gas established a non-funded defined benefit restoration plan (DB restoration) for the purpose of providing supplemental pension and pension-related benefits to a select group of management employees. WGL subsidiaries offer defined-contribution savings plans to all eligible employees. These plans allow participants to defer on a pre-tax or after-tax basis, a portion of their salaries for investment in various alternatives. We make matching contributions to the amounts contributed by employees in accordance with the specific plan provisions. Total matching contributions to our savings plans were $4.6 million , $4.2 million and $4.3 million during fiscal years 2015 , 2014 and 2013 , respectively. All employees not participating in the qualified pension plan receive an employer provided supplemental contribution ranging from 4% to 6% depending on years of service. Total supplemental contributions to the plan were $2.1 million , $1.6 million and $0.8 million during fiscal years ended September 30, 2015 , 2014 and 2013 , respectively. Washington Gas provides certain healthcare and life insurance benefits for retired employees. Substantially all employees of Washington Gas may become eligible for such benefits if they attain retirement status while working for Washington Gas. Washington Gas accounts for these benefits under the provisions of ASC 715, Compensation-Retirement Benefits. Washington Gas elected to amortize the accumulated post-retirement benefit obligation of $190.6 million existing at the October 1, 1993 adoption date of this standard, known as the transition obligation, over a twenty-year period, which ended in 2013. On September 25, 2015, the Washington Gas Light Company Retiree Medical Plan was amended to limit the aggregate cost of applicable employer-sponsored coverage, thereby avoiding the 40% excise tax enacted by the Patient Protection and Affordable Care Act of 2010. The resolution, which is effective September 30, 2015 and applies to plan years beginning on or after January 1, 2018, includes a limit of $11,850 per participant, with a maximum limit of $30,950 for family coverage. This amendment resulted in a prior service credit of $26.1 million . On April 24, 2014, Washington Gas replaced the existing retiree medical benefit plan and dental plan options for Medicare-eligible retirees age 65 and older with a special tax-free Health Reimbursement Account (HRA) plan effective January 1, 2015. With the introduction of the new plan, effective January 1, 2015, participating retirees and dependents will receive a subsidy each year through the HRA account to help purchase supplemental medical and dental coverage in the marketplace. As part of the new HRA plan, participants who enroll in a Medicare Part D prescription drug plan and meet the threshold for Medicare catastrophic prescription drug coverage will be eligible for an additional reimbursement of their out-of-pocket prescription drug costs in excess of the threshold. Retirees and dependents under age 65 will still be covered under the existing Washington Gas Retiree Medical Plan until they become eligible for Medicare at age 65 and can obtain coverage through the new HRA plan. Due to the impact of the amendment, we remeasured the funded status of the plan in April 2014. The funded status of the plan changed by approximately $127.5 million from an underfunded liability to an overfunded asset as a result of the plan amendment. The offsetting amount for this remeasurement was recorded as a decrease to regulatory assets and accumulated other comprehensive income/loss. Almost all costs associated with Washington Gas’ defined benefit post-retirement plans have historically been, and will continue to be, recovered through Washington Gas’ rates. Therefore, in accordance with ASC Topic 980 and ASC Topic 715, Washington Gas established a regulatory asset/liability for the substantial majority of the unrecognized costs/income associated with its defined benefit post-retirement plans. To the extent these amounts will not be recovered through Washington Gas’ rates, they are recorded directly to “Accumulated other comprehensive loss, net of taxes.” Obligations and Assets Washington Gas uses a measurement date of September 30 for its pension, and retiree healthcare and life insurance benefit plans. The following table provides certain information about Washington Gas’ post-retirement benefits: Post-Retirement Benefits Health and Life (In millions) Pension Benefits (a) Benefits Year Ended September 30, 2015 2014 2015 2014 Change in projected benefit obligation (b) Benefit obligation at beginning of year $ 917.1 $ 837.4 $ 343.2 $ 429.8 Service cost 15.5 14.0 7.1 7.6 Interest cost 39.1 40.4 14.7 18.7 Change in plan benefits 0.6 — (26.1 ) (136.5 ) Actuarial loss (gain) 19.2 68.6 (23.7 ) 38.2 Retiree contributions — — 2.0 4.4 Employer group waiver plan rebates — — 2.4 0.5 Benefits paid (44.0 ) (43.3 ) (19.7 ) (19.5 ) Projected benefit obligation at end of year (b) $ 947.5 $ 917.1 $ 299.9 $ 343.2 Change in plan assets Fair value of plan assets at beginning of year $ 804.7 $ 745.2 $ 439.6 $ 380.9 Actual return on plan assets 19.9 103.3 (0.3 ) 57.8 Company contributions 1.8 1.7 16.0 16.0 Retiree contributions and employer group waiver plan rebates — — 3.6 4.4 Expenses (2.2 ) (2.2 ) (0.7 ) — Benefits paid (44.0 ) (43.3 ) (19.7 ) (19.5 ) Fair value of plan assets at end of year $ 780.2 $ 804.7 $ 438.5 $ 439.6 Funded status at end of year $ (167.3 ) $ (112.4 ) $ 138.6 $ 96.4 Total amounts recognized on balance sheet Non-current asset $ — $ — $ 138.6 $ 96.4 Current liability (4.8 ) (4.2 ) — — Non-current liability (162.5 ) (108.2 ) — — Total recognized $ (167.3 ) $ (112.4 ) $ 138.6 $ 96.4 (a) The DB SERP and DB Restoration, included in pension benefits in the table above, have no assets. (b) For the Health and Life Benefits, the change in projected benefit obligation represents the accumulated benefit obligation. The following table provides the projected benefit obligation (PBO) and accumulated benefit (ABO) for the qualified pension plan, DB SERP and DB Restoration at September 30, 2015 and 2014 . Projected and accumulated benefit obligation (In millions) Qualified Pension Plan DB SERP DB Restoration September 30, 2015 2014 2015 2014 2015 2014 Projected benefit obligation $ 892.2 $ 865.2 $ 53.0 $ 50.7 $ 2.3 $ 1.2 Accumulated benefit obligation $ 822.8 $ 801.9 $ 48.7 $ 46.2 $ 1.2 $ 0.7 AMOUNTS RECOGNIZED IN REGULATORY ASSETS/LIABILITIES AND ACCUMULATED OTHER COMPREHENSIVE INCOME The following table provides amounts recorded to regulatory assets, regulatory liabilities and accumulated other comprehensive loss/(income) at September 30, 2015 and 2014 : Unrecognized Costs/Income Recorded on the Balance Sheet (In millions) Pension Benefits Health and Life Benefits September 30, 2015 2014 2015 2014 Actuarial net loss $ 190.1 $ 162.6 $ 43.8 $ 50.1 Prior service cost (credit) 1.5 1.2 (160.2 ) (149.3 ) Total $ 191.6 $ 163.8 $ (116.4 ) $ (99.2 ) Regulatory asset (liability) (a) $ 173.9 $ 147.9 $ (110.5 ) $ (94.6 ) Pre-tax accumulated other comprehensive loss (gain) (b) 17.7 15.9 (5.9 ) (4.6 ) Total $ 191.6 $ 163.8 $ (116.4 ) $ (99.2 ) (a) The regulatory liability recorded on our balance sheets at September 30, 2015 and 2014 is net of a deferred income tax benefit of $ 6.1 million and $8.2 million , respectively. (b) The total amount of accumulated other comprehensive loss recorded on our balance sheets at September 30, 2015 and 2014 is net of an income tax benefit of $5.1 million and $4.9 million , respectively. The following table provides amounts that are included in regulatory assets/liabilities and accumulated other comprehensive loss associated with our unrecognized pension and other post-retirement benefit costs that were recognized as components of net periodic benefit cost during fiscal year 2015 . Amounts Recognized During Fiscal Year 2015 Regulatory assets/liabilities Accumulated other comprehensive loss (In millions) Pension Benefits Health and Life Benefits Pension Benefits Health and Life Benefits Actuarial net loss (income) $ 16.9 $ 4.2 $ 1.8 $ 0.2 Prior service cost (credit) 0.3 (14.6 ) — (0.7 ) Total $ 17.2 $ (10.4 ) $ 1.8 $ (0.5 ) The following table provides amounts that are included in regulatory assets/liabilities and accumulated other comprehensive loss associated with our unrecognized pension and other post-retirement benefit costs that are expected to be recognized as components of net periodic benefit cost during fiscal year 2016 . Amounts to be Recognized During Fiscal Year 2016 Regulatory assets/liabilities Accumulated other comprehensive loss (In millions) Pension Benefits Health and Life Benefits Pension Benefits Health and Life Benefits Actuarial net loss $ 15.3 $ 1.2 $ 1.5 $ 0.1 Prior service cost (credit) 0.2 (16.8 ) 0.1 (0.9 ) Total $ 15.5 $ (15.6 ) $ 1.6 $ (0.8 ) Realized and unrealized gains and losses for assets under Washington Gas’ post-retirement benefit plans are spread over a period of five years. Each year, 20% of the prior five years’ asset gains and losses are recognized. The market-related value of assets is equal to the market value of assets less the following percentages of prior years’ realized and unrealized gains and losses on equities: 80% of the prior year, 60% of the second prior year, 40% of the third prior year and 20% of the fourth prior year. Net Periodic Benefit Cost The components of the net periodic benefit costs (income) for fiscal years ended September 30, 2015 , 2014 and 2013 related to pension and other postretirement benefits were as follows: Components of Net Periodic Benefit Costs (Income) (In millions) Pension Benefits Health and Life Benefits Year Ended September 30, 2015 2014 2013 2015 2014 2013 Service cost $ 15.5 $ 14.0 $ 17.0 $ 7.1 $ 7.6 $ 9.6 Interest cost 39.1 40.4 36.6 14.7 18.7 18.8 Expected return on plan assets (44.6 ) (41.0 ) (41.9 ) (20.8 ) (19.3 ) (18.3 ) Recognized prior service cost (credit) 0.3 0.3 1.0 (15.3 ) (9.6 ) (3.9 ) Recognized actuarial loss 18.7 16.8 28.7 4.4 5.0 9.2 Amortization of transition obligation — — — — — 1.1 Net periodic benefit cost 29.0 30.5 41.4 (9.9 ) 2.4 16.5 Amount allocated to construction projects (4.6 ) (4.3 ) (5.7 ) 1.9 (0.4 ) (2.8 ) Amount deferred as regulatory asset (liability)-net 7.1 7.0 (3.7 ) (0.2 ) (2.3 ) 2.4 Amount charged (credited) to expense $ 31.5 $ 33.2 $ 32.0 $ (8.2 ) $ (0.3 ) $ 16.1 Amounts included in the line item “Amount deferred as regulatory asset/liability-net,” as shown in the table above, represent the amortization of previously unrecovered costs of the applicable pension benefits or the health and life benefits as approved in the District of Columbia. These balances are being amortized over a five year period. ASSUMPTIONS The weighted average assumptions used to determine net periodic benefit obligations and net periodic benefit costs were as follows: Benefit Obligations Assumptions Pension Benefits Health and Life Benefits September 30, 2015 2014 2015 2014 Discount rate (a) 4.10%-4.50% 4.00%-4.40% 4.50 % 4.40 % Rate of compensation increase 3.50%-4.10% 3.50%-4.10% 4.10 % 4.10 % (a) The increase in the discount rate in fiscal year 2015 compared to prior years primarily reflects the increase in long-term interest rates. Net Periodic Benefit Cost Assumptions Pension Benefits Health and Life Benefits Years Ended September 30, 2015 2014 2013 2015 2014 2013 Discount rate (a) 4.00%-4.40% 4.50%-5.00% 4.00 % 4.40 % 4.60%-5.10% 4.00 % Expected long-term return on plan assets (b) 6.75 % 6.50 % 6.75 % 6.25 % 6.25 % 6.75 % Rate of compensation increase (c) 3.50%-4.10% 3.85%-5.15% 3.85%-5.15% 4.10 % 3.85 % 3.85 % (a) The changes in the discount rates over the last three fiscal years primarily reflect the changes in long-term interest rates. (b) For health and life benefits, the expected returns for certain funds may be lower due to certain portions of income that are subject to an assumed income tax rate of 45.6% . (c) The changes in the rate of compensation reflects the best estimates of actual future compensation levels including consideration of general price levels, productivity, seniority, promotion, and other factors such as inflation rates. Expected long-term return on plan assets Washington Gas determines the expected long-term rate of return on plan assets by averaging the expected earnings for the target asset portfolio. In developing the expected rate of return assumption, Washington Gas evaluates an analysis of historical actual performance and long-term return projections, which gives consideration to our asset mix and anticipated length of obligation of our plan. Mortality Assumptions For purposes of the September 30, 2015 measurement date, Washington Gas adopted new mortality assumptions for its pension and other post-retirement benefit obligations, which reflect increased life expectancies in the U.S. The adoption of new mortality assumptions increased the projected benefit obligations for Washington Gas' pension and other post-retirement benefit plans by approximately $46.8 million and $15.3 million , respectively. Healthcare cost trend Washington Gas assumed the healthcare cost trend rates related to the accumulated post-retirement benefit obligation for non-Medicare eligible retirees to be 6.7% for fiscal year 2016. Washington Gas expects the rate to decrease to 6.3% in fiscal 2017, 3.2% in fiscal 2018 and to 2.2% in fiscal 2019, and remain at that level thereafter. The significant decrease in the expected trend rate between fiscal 2017 and 2018 is driven by the amendment to the Washington Gas Light Company Retiree Medical Plan discussed above. The healthcare cost trend rate used to measure the accumulated post-retirement benefit obligation for non-Medicare eligible retirees as of September 30, 2014 was 7.0% for fiscal year 2015 . This rate was expected to decrease gradually to 5.0% in 2021 and remain at that level thereafter. For Medicare eligible retirees age 65 and older that will receive a subsidy each year through an HRA account, Washington Gas assumed no increase to the annual subsidy in fiscal year 2016 and a 3.0% increase thereafter in order to approximate possible future increases to the stipend. While the plan terms do not guarantee increases to the stipend, Washington Gas intends to review the stipend annually. Healthcare Trends (In millions) One Percentage-Point Increase One Percentage-Point Decrease Increase (decrease) total service and interest cost components $ 1.3 $ (1.1 ) Increase (decrease) post-retirement benefit obligation $ 5.7 $ (5.1 ) INVESTMENT POLICIES AND STRATEGIES The investment objective of the qualified pension, healthcare, and life insurance benefit plans (“Plan” or “Plans”) is to allocate each Plan’s assets to appropriate investment asset classes (asset categories) so that the benefit obligations of each Plan are adequately funded, consistent with appropriate risk tolerance guidelines for the Plans’ and Washington Gas’ tolerance for risk. Washington Gas' portion of retired employee healthcare and life insurance benefits obligation is funded through two trusts: (i) the Washington Gas Light Company Postretirement Benefit Master Trust for Retired Previously Union-Eligible Employees ("union-eligible truest") and (ii) the Washington Gas Light Company Postretirement Benefit Master Trust for Retired Management Employees ("management trust"). In order to best achieve the investment objectives for each Plan, strategic allocation targets and ranges are established that control exposure to selected investment asset classes. Target qualified pension plan trust asset allocations are 32.5% U.S. Large-Cap Equities, 4.5% U.S. Small/Mid-Cap Equities, 8% International Equities, 5% Real Estate and 50% Fixed Income. Target asset allocations are 50% U.S. Large-Cap Equities and 50% Fixed Income for the union-eligible trust. Target asset allocations are 60% U.S. Large-Cap Equities and 40% Fixed Income for the management trust. Actual asset balances are reviewed monthly and are allowed to range within plus or minus 5% or less of the target allocations. Assets are generally rebalanced to target allocations before actual amounts fall below or rise above the allowable ranges. Asset/liability modeling (ALM) is used to test the benefits and risks of several potential strategic asset allocation mixes. Simulated investment performance results based on assumptions about expected return, volatility, and correlation characteristics of the selected asset classes are tested for their effects on contributions, pension expense, PBO funded status, and downside Value at Risk metrics over a ten-year planning time horizon. Important outcomes from past ALM studies include decisions to increase fixed income exposure, lengthen the duration of those fixed income assets and implement a dynamic asset allocation strategy that allows for the de-risking of the portfolio over time. Under this strategy, the target fixed income allocation percentage will increase by 5% for each 5% improvement in the plan’s funded ratio, as measured by an investment consultant. This strategy resulted in portfolio de-risking during October 2012 including increased fixed income exposure and reduced U.S. large-cap equity exposure. The most recent pension plan ALM study was completed during November 2014. The study did not result in any changes to investment strategy. For the qualified pension plan, Washington Gas’ funding policy is to contribute an amount sufficient to satisfy the minimum annual funding requirements under the Pension Protection Act. Any contributions above the minimum annual funding requirements would be limited to amounts that are deductible under appropriate tax law. For the healthcare and life insurance benefit plans, Washington Gas’ funding policy is to contribute amounts that are collected from ratepayers. Significant amounts of the various Plans’ assets are managed by the same financial institution. In addition, the Plans have a high exposure to U.S. based investments. There are no other significant risk concentrations related to investments in any entity, industry, country, commodity, or investment fund. Investment vehicles used to manage qualified pension plan trust and management trust assets include commingled funds and pooled separate accounts. A private placement mutual fund is also employed to manage a portion of qualified pension plan trust assets. Commingled funds are used in the management of union-eligible trust assets. U.S. and international equity assets are diversified across sectors, industries, and investment styles. Fixed income assets are primarily diversified across U.S. government and investment grade corporate debt instruments, with some exposure to foreign sovereign debt and minor exposure to non-investment-grade securities. Real estate is diversified geographically across the U.S. by property type. The qualified pension plan’s investment policy allows the use of futures, options, and other derivatives for purposes of reducing portfolio risk and as a low-cost option for gaining market exposure, but derivatives may not be used for leverage. The qualified pension plan’s investment policy prohibits investments in Washington Gas securities. The prohibition applies to separately managed portfolios but does not apply to any commingled fund investments. The following tables present the fair value of the pension plan assets and health and life insurance plan assets by asset category as of September 30, 2015 and 2014 : Pension Plan Assets % of ($ In millions) Level 1 Level 2 Level 3 Total Total At September 30, 2015 Cash and cash equivalents $ 0.8 $ — $ — $ 0.8 0.1 % Equity securities U.S. Small Cap 28.7 — — 28.7 3.7 Preferred Securities — 0.1 — 0.1 — Fixed income securities U.S. Treasuries — 101.3 — 101.3 13.0 U.S. Corporate Debt — 204.6 — 204.6 26.2 U.S. Agency Obligations and Government Sponsored Entities — 23.9 — 23.9 3.1 Asset-Backed Securities and Collateralized Mortgage Obligations — 1.7 — 1.7 0.2 Municipalities — 14.0 — 14.0 1.8 Non-U.S. Corporate Debt — 37.1 — 37.1 4.8 Repurchase Agreements (a) — 5.3 — 5.3 0.7 Other (b) — 4.7 — 4.7 0.6 Mutual Funds (c) — 29.3 — 29.3 3.7 Commingled Funds and Pooled Separate Accounts (d) — 274.8 27.7 302.5 38.7 Private Equity/Limited Partnerships (e) — 28.0 — 28.0 3.6 Derivatives (f) — (0.1 ) — (0.1 ) — Total fair value of plan investments $ 29.5 $ 724.7 $ 27.7 $ 781.9 100.2 % Receivable (payable) (g) (1.7 ) (0.2 ) Total plan assets at fair value $ 780.2 100.0 % Pension Plan Assets % of ($ In millions) Level 1 Level 2 Level 3 Total Total At September 30, 2014 Cash and cash equivalents $ 0.6 $ — $ — $ 0.6 0.1 % Equity securities U.S. Small Cap 32.3 — — 32.3 4.0 Preferred Securities — 0.1 — 0.1 — Fixed income securities U.S. Treasuries — 110.6 — 110.6 13.8 U.S. Corporate Debt — 108.4 — 108.4 13.5 U.S. Agency Obligations and Government Sponsored Entities — 24.6 — 24.6 3.0 Asset-Backed Securities and Collateralized Mortgage Obligations — 1.8 — 1.8 0.2 Municipalities — 9.2 — 9.2 1.1 Non-U.S. Corporate Debt — 23.8 — 23.8 3.0 Repurchase Agreements (a) — 2.5 — 2.5 0.3 Other (b) — 7.0 — 7.0 0.8 Mutual Funds (c) — 112.4 — 112.4 14.0 Commingled Funds and Pooled Separate Accounts (d) — 316.2 23.8 340.0 42.3 Private Equity/Limited Partnerships (e) — 30.5 — 30.5 3.8 Derivatives (f) — (0.1 ) — (0.1 ) — Total fair value of plan investments $ 32.9 $ 747.0 $ 23.8 $ 803.7 99.9 % Receivable (payable) (g) 1.0 0.1 Total plan assets at fair value $ 804.7 100.0 % (a) This category includes Treasury Bills with a pre-commitment from the counterparty to repurchase the same securities on the next business day at an agreed-upon price. (b) This category primarily includes Yankee bonds and non-U.S. government bonds. (c) At September 30, 2015 , investments in mutual funds consisited primarily of common stock of non-U.S. companies. At September 30, 2014 , investments in mutual funds consisted primarily of corporate fixed income instruments. (d) At September 30, 2015 , investments in commingled funds and pooled separate accounts consisted primarily of 80% common stock of large-cap U.S. companies; 18% income producing properties located in the United States; and 2% short-term money market investments. At September 30, 2014 , investments in commingled funds and pooled separate accounts consisted primarily of 75% common stock of large-cap U.S. companies; 14% income producing properties located in the United States; 9% equity securities of non-U.S. companies; and 2% short-term money market investments. (e) At September 30, 2015 and 2014 , investments in private equity/limited partnership consisted of common stock of international companies. (f) At September 30, 2015 , this category included long-term U.S. Treasury interest rate futures contracts, interest rate put options and credit default swap indexes. At September 30, 2014 , this category included long-term U.S. Treasury interest rate futures contracts and interest rate put options. (g) At September 30, 2015 , this payable represents a pending trade for investment purchases. At September 30, 2014 , this receivable represents a pending trade for investment sales. Healthcare and Life Insurance Plan Assets % of ($ In millions) Level 1 Level 2 Level 3 Total Total At September 30, 2015 Cash and Cash Equivalents $ — $ — $ — $ — — % Mutual Funds (a) 1.9 — — 1.9 0.4 Fixed Income Securities U.S Agency Obligations — 1.8 — 1.8 0.4 U.S. Treasuries — 27.7 — 27.7 6.3 U.S. Corporate Debt — 33.5 — 33.5 7.7 Municipalities — 4.0 — 4.0 0.9 Non-U.S. Corporate Debt — 4.9 — 4.9 1.1 Others (b) — 4.3 — 4.3 1.0 Commingled Funds (c) — 359.7 — 359.7 82.0 Total fair value of plan investments $ 1.9 $ 435.9 $ — $ 437.8 99.8 % Receivable (payable) 0.7 0.2 Total plan assets at fair value $ 438.5 100.0 % At September 30, 2014 Cash and Cash Equivalents $ 0.8 $ — $ — $ 0.8 0.2 % Mutual Funds (a) — 1.9 — 1.9 0.4 Fixed Income Securities U.S Agency Obligations — 2.0 — 2.0 0.5 U.S. Treasuries — 25.6 — 25.6 5.8 U.S. Corporate Debt — 34.0 — 34.0 7.7 Municipalities — 4.8 — 4.8 1.1 Non-U.S. Corporate Debt — 5.7 — 5.7 1.3 Others (b) — 5.3 — 5.3 1.2 Commingled Funds (c) — 359.7 — 359.7 81.8 Total fair value of plan investments $ 0.8 $ 439.0 $ — $ 439.8 100.0 % Receivable (payable) (0.2 ) — Total plan assets at fair value $ 439.6 100.0 % (a) At September 30, 2015 , investments in mutual funds consisted of a short-term money market fund valued at $1.00 per share. At September 30, 2014 , investments in mutual funds consisted primarily of 63% short-term obligations consisting of certificates of deposit and time deposits, 23% high-quality commercial paper, 6% repurchase agreements, 4% corporate notes of U.S. and foreign corporations and 4% U.S. governmental and U.S. agency securities. (b) At September 30, 2015 and 2014 , this category consisted primarily of 76% non-U.S. government bonds and 24% Yankee bonds. (c) At September 30, 2015 , investments in commingled funds consisted primarily of 68% common stock of large-cap U.S. companies, 16% governmental fixed income securities and 16% corporate bonds. At September 30, 2014 , investments in commingled funds consisted primarily of 66% common stock of large-cap U.S. companies, 17% U.S. agency obligations and government sponsored entities and 17% corporate bonds. Valuation Methods Equity securities are traded on a securities exchange and are valued at the closing quoted market price as of the balance sheet date. Mutual funds are valued at the quoted net asset value (NAV) per share, which is computed as of the close of business on the balance sheet date. Mutual funds with a publicly quoted NAV per share are classified as Level 1; mutual funds with a NAV per share that is not made publicly available are classified as Level 2. Real Estate Investment Funds which have redemption restrictions are classified as Level 3. Commingled funds and pooled separate accounts are valued at the quoted NAV per unit, computed as of the close of business on the balance sheet date. Private Equity/Limited Partnership funds are valued at the quoted NAV, which is computed monthly and allocated based on ownership interest in partners’ capital. Fixed income securities are valued using pricing models that consider various observable inputs such as benchmark yields, reported trades, broker quotes and issuer spreads to determine fair value. The Plans may engage in repurchase transactions. Generally, in accordance with the terms of a repurchase agreement, the Plans take possession of Treasury Bills in exchange for cash and the counterparty is obligated to repurchase, and the Plan to resell, the same securities at an agreed-upon price and time. The repurchase agreements have a one-day maturity and a fair value equal to the Plan’s cash outlay at the time the agreement is executed. The following table summarizes the changes in the fair value of the Level 3 assets for the fiscal years ended 2015 and 2014 : (In millions) Years Ended September 30, 2015 2014 Balance, beginning of year $ 23.8 $ 21.1 Actual return on plan assets: Assets still held at year end 3.9 2.7 Balance, end of year $ 27.7 $ 23.8 Benefit Contribution During fiscal year 2015 , Washington Gas did not contribute to its qualified pension but did contribute $1.8 million to its non-funded DB SERP plan. During fiscal year 2016 , Washington Gas does not expect to make a contribution to its qualified pension plan and expects to make a payment of $4.8 million to its non-funded DB SERP. During fiscal year 2015 , Washington Gas contributed $16.0 million to its health and life insurance benefit plans. Washington Gas expects to make a contribution of $16.0 million to its health and life insurance benefit plans during fiscal year 2016 . Expected Benefit Payments Expected benefit payments, including benefits attributable to estimated future employee service, which are expected to be paid over the next ten years are as follows: Expected Benefit Payments (In millions) Pension Benefits Health and Life Benefits 2016 $ 49.1 $ 17.2 2017 50.5 17.6 2018 51.5 17.2 2019 53.2 17.4 2020 54.3 17.4 2021—2025 284.1 86.9 MEDICARE SUBSIDY RECEIPTS / EMPLOYER GROUP WAIVER PLAN Prior to 2013 Washington Gas sponsored a post-65 retiree prescription drug plan that was at least actuarially equivalent to Medicare (Medicare Part D), and as a result was eligible to receive a federal subsidy under the Medicare Prescription Drug, Improvement and Modernization Act of 2003. Effective January 1, 2013 Washington Gas implemented an Employer Group Waiver Plan with a wraparound supplemental plan (“EGWP/wrap”). Accordingly, the Washington Gas retiree medical plan began receiving direct reimbursements and discounts from Medicare and the large pharmaceutical companies. During the years ended September 30, 2015 and 2014, Washington Gas received $0.8 million and $0.5 million in reimbursements related to the EGWP/wrap, respectively. Effective January 1, 2015, Washington Gas ceased to participate in the EGWP/wrap because participants age 65 and older will be transitioning into the new WGL Retiree HRA Plan, where such participants will receive an annual stipend that could be used to purchase health and prescription drug insurance. REGULATORY MATTERS A significant portion of the estimated pension and post-retirement medical and life insurance benefits apply to our regulated activities. Each regulatory commission having jurisdiction over Washington Gas requires it to fund amounts reflected in rates for post-retirement medical and life insurance benefits into irrevocable trusts. District of Columbia Jurisdiction The PSC of DC has approved a level of rates sufficient to recover annual costs associated with the qualified pension and other post-retirement benefits. Expenses of the SERP allocable to the District of Columbia are not recovered through rates. The PSC of DC granted the recovery of post-retirement medical and life insurance benefit costs determined in accordance with GAAP through a five-year phase-in plan that ended September 30, 1998. Washington Gas deferred the difference generated during the phase-in period as a regulatory asset. Effective October 1, 1998, the PSC of DC granted Washington Gas full recovery of costs determined under GAAP, plus a fifteen-year amortization of the regulatory asset established during the phase-in period that ended in fiscal year 2014. On May 15, 2013, the PSC of DC issued an order providing for recovery of unrecovered costs for pension and other post-retirement benefits as of November 30, 2012. The order allowed a five-year amortization period. Maryland Jurisdiction In Washington Gas’ most recent rate case, the PSC of MD approved 50% of the expenses of the SERP for recovery through rates. The PSC of MD has approved a level of rates sufficient to recover pension and other post-retirement benefit costs as determined under GAAP. Virginia Jurisdiction On September 28, 1995, the SCC of VA issued a generic order that allowed Washington Gas to recover most costs determined under GAAP for post-retirement medical and life insurance benefits in rates over twenty years. The SCC of VA, however, set a forty-year recovery period of the transition obligation. As prescribed by GAAP, Washington Gas amortizes these costs over a twenty-year period. With the exception of the transition obligation, the SCC of VA has approved a level of rates sufficient to recover annual costs for all pension and other post-retirement medical and life insurance benefit costs determined under GAAP.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Sep. 30, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	STOCK-BASED COMPENSATION STOCK-BASED COMPENSATION FOR KEY EMPLOYEES We have stock-based awards outstanding in the form of performance shares and performance units. In March 2007, WGL adopted a shareholder-approved Omnibus Incentive Compensation Plan (Omnibus Plan) to replace, on a prospective basis, the 1999 Plan. Stock options, stock appreciation rights, restricted stock, deferred stock and stock as a bonus in lieu of other awards, dividend equivalents, other stock-based awards and cash awards may be granted under the Omnibus Plan. The Omnibus Plan allows WGL to issue up to 1,700,000 shares of common stock, subject to adjustment as provided by the plan, to persons including officers and key employees, designated by the Human Resources Committee of the Board of Directors. Refer to Note 6— Common Stock —W GL for amounts remaining to be issued under these plans. During the fiscal year ended September 30, 2015 , we granted performance shares and performance units under the Omnibus Plan. We have not issued stock options under either plan since October 2006. For both performance shares and performance units issued through September 30, 2015, the actual award that may be earned varies based on the total shareholder return of WGL relative to a selected peer group of companies. These performance awards generally vest three years from the date of grant. Performance shares earned are paid in shares of common stock of WGL. Performance units are earned pursuant to terms of the grant, are paid in cash and are valued at $1.00 per performance unit. Performance units and performance shares provide for accelerated vesting upon a change in control of WGL under certain circumstances. We generally issue new shares of common stock to provide for redemption of performance shares; however, we may, from time to time, repurchase shares of our common stock on the open market in order to meet these requirements. Performance shares are accounted for as equity awards, and performance units are accounted for as liability awards as they are settled in cash. For the fiscal years ended September 30, 2015 , 2014 and 2013 , we recognized stock-based compensation expense of $15.5 million , $3.4 million and $6.5 million , net of related income tax benefits of $6.2 million , $1.3 million and $2.6 million , respectively. As of September 30, 2015 , total unrecognized compensation expense related to stock-based awards granted was $11.4 million . Performance shares and performance units comprised $4.4 million and $7.0 million of total unrecognized compensation expense, respectively. The total unrecognized compensation expense is expected to be recognized over a weighted average cost period of 1.7 years for performance shares and performance units. Performance Shares The following table summarizes information regarding performance share activity during the fiscal year ended September 30, 2015 . Performance Share Activity Year Ended September 30, 2015 Number of Shares (a) Weighted Average Grant- Date Fair Value Non-vested and outstanding, beginning of year 301,378 $ 40.57 Granted 113,626 44.44 Vested — — Cancelled/forfeited (110,915 ) 39.71 Non-vested and outstanding, end of year 304,089 $ 44.49 (a) The number of common shares issued related to performance shares may range from zero to 200 percent of the number of shares shown in the table above based on our achievement of performance goals for total shareholder return relative to a selected peer group of companies. The total fair value of the performance shares outstanding at September 30, 2015 for the shares expected to vest in the future was $12.9 million . There were no performance shares vested during the years ended September 30, 2015 and 2013. The total intrinsic value of performance shares vested during the year ended September 30, 2014 was $2.2 million . We measure compensation expense related to performance shares based on the fair value of these awards at their date of grant. Compensation expense for performance shares is recognized for awards that ultimately vest and is not adjusted based on the actual achievement of performance goals. We estimated the fair value of performance shares on the date of grant using a Monte Carlo simulation model and the following assumptions: Fair Value Assumptions Years Ended September 30, 2015 2014 2013 Expected stock-price volatility 18.30 % 19.10 % 19.40 % Dividend yield 4.18 % 3.93 % 3.98 % Weighted average grant-date fair value $ 44.44 $ 42.88 $ 39.73 Expected stock-price volatility is based on the daily historical volatility of our common shares for the past three fiscal years. The dividend yield represents our annualized dividend yield on the closing market price of our common stock at the date of the grant. Performance Units Our performance units are liability awards as they settle in cash; therefore, we measure and record compensation expense for these awards based on their fair value at the end of each period until their vesting date. Consequently, fluctuations in earnings may result that do not occur under the accounting requirements for our performance shares. The following table summarizes information regarding performance unit activity during the fiscal year ended September 30, 2015 . Performance Unit Activity Year Ended September 30, 2015 Number of Units Non-vested and outstanding, beginning of year 12,268,921 Granted 4,785,921 Vested — Cancelled/forfeited (4,369,209 ) Non-vested and outstanding, end of year 12,685,633 The total fair value of performance units outstanding at September 30, 2015 for the units expected to vest in the future was $20.3 million . As of September 30, 2015 , 2014 and 2013 , we recorded a current and deferred liability of $13.3 million , $2.4 million and $4.9 million , respectively, related to our performance units. The current liability was recorded in "Accounts payable and other accrued liabilities—other" in the amounts of $6.4 million and $ 2.0 million at September 30, 2015 and 2013 , respectively. There was no current liability recorded in "Accounts payable and other accrued liabilities—other" at September 30, 2014 . The deferred liability was recorded in “Deferred Credits—other” in the amounts of $ 6.9 million , $ 2.4 million , and $ 2.9 million at September 30, 2015 , 2014 and 2013 , respectively. During the fiscal years ended September 30, 2015 and 2013, we did not make any cash payments to settle performance unit awards. During the fiscal year ended September 30, 2014, we paid $2.0 million in cash to settle performance unit awards. We estimated the fair value of performance units using a Monte Carlo simulation model. The following table provides the year-end assumptions used to value our performance units: Fair Value Assumptions September 30, 2015 10/1/2014 Grant 10/1/2013 Grant Expected stock-price volatility 20.20 % 20.80 % Expected stock-price volatility is based on the daily historical volatility of our common shares for a period equal to the remaining term of the performance units. Stock Options All remaining 5,318 stock options were exercised during fiscal year 2015; therefore, no remaining stock options were outstanding at September 30, 2015. We received $0.2 million and $0.7 million from the exercise of stock options during the years ended September 30, 2015 and 2014. There were no stock options exercised during the year ended September 30, 2013 and no related tax benefits realized. The related tax benefits realized for the fiscal years ended September 30, 2015 and 2014 were minimal and $0.1 million , respectively. STOCK GRANTS TO DIRECTORS Non-employee directors receive a portion of their annual retainer fee in the form of common stock through the Directors’ Stock Compensation Plan. Up to 270,000 shares of common stock may be awarded under the plan. Shares granted to directors were approximately 15,100 , 17,000 and 16,600 for the fiscal years ended September 30, 2015 , 2014 and 2013 , respectively. For those years, the weighted average fair value of the stock on the grant dates was $54.05 , $40.06 , and $40.46 , respectively. Shares awarded to the participants; (i) vest immediately and cannot be forfeited; (ii) may be sold or transferred and (iii) have voting and dividend rights. For the year ended September 30, 2015 , WGL recognized stock-based compensation expense related to stock grants of $0.8 million , net of related income tax benefits of $0.3 million . For each of the years ended September 30, 2014 and 2013 , WGL recognized stock-based compensation expense related to stock grants of $0.7 million , net of related income tax benefits of $0.3 million .

Environmental Matters

Environmental Matters	12 Months Ended
	Sep. 30, 2015
Environmental Remediation Obligations [Abstract]
Environmental Matters	ENVIRONMENTAL MATTERS We are subject to federal, state and local laws and regulations related to environmental matters. These laws and regulations may require expenditures over a long time frame to control environmental effects. Almost all of the environmental liabilities we have recorded are for costs expected to be incurred to remediate sites where we or a predecessor affiliate operated MGPs. Estimates of liabilities for environmental response costs are difficult to determine with precision because of the various factors that can affect their ultimate level. These factors include, but are not limited to, the following: • the complexity of the site; • changes in environmental laws and regulations at the federal, state and local levels; • the number of regulatory agencies or other parties involved; • new technology that renders previous technology obsolete or experience with existing technology that proves ineffective; • the level of remediation required; and • variations between the estimated and actual period of time that must be dedicated to respond to an environmentally-contaminated site. Washington Gas has identified up to ten sites where it or its predecessors may have operated MGPs. Washington Gas last used any such plant in 1984. In connection with these operations, we are aware that coal tar and certain other by-products of the gas manufacturing process are present at or near some former sites, and may be present at others. Based on the information available to us, we have concluded that none of the sites are likely to present an unacceptable risk to human health or the environment, and either the appropriate remediation is being undertaken or Washington Gas believes no remediation is necessary. At September 30, 2015 and 2014 , Washington Gas reported a liability of $6.6 million and $8.5 million , respectively, on an undiscounted basis related to future environmental response costs, which included the estimated costs for four MGP sites. These estimates principally include the minimum liabilities associated with a range of environmental response costs expected to be incurred at the sites identified. At September 30, 2015 and 2014 , Washington Gas estimated the maximum liability associated with all of its sites to be approximately $17.2 million and $19.3 million , respectively. The estimates were determined by Washington Gas’ environmental experts, based on experience in remediating MGP sites and advice from legal counsel and environmental consultants. The variation between the recorded and estimated maximum liability primarily results from differences in the number of years that will be required to perform environmental response processes at each site and the extent of remediation that may be required. Regulatory orders issued by the PSC of MD allow Washington Gas to recover the costs associated with the sites applicable to Maryland over the period ending in 2025. Rate orders issued by the PSC of DC allow Washington Gas a three -year recovery of prudently incurred environmental response costs, and allow Washington Gas to defer additional costs incurred between rate cases. Regulatory orders from the SCC of VA have generally allowed the recovery of prudent environmental remediation costs to the extent they were included in the underlying financial data supporting an application for rate change. At September 30, 2015 and 2014 , Washington Gas reported a regulatory asset of $1.8 million and $0.6 million , respectively, for the portion of environmental response costs that are expected to be recoverable in future rates. We do not expect that the ultimate impact of these matters will have a material effect on our financial position, cash flows, capital expenditures, earnings or competitive position.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Sep. 30, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	COMMITMENTS AND CONTINGENCIES OPERATING LEASES Minimum future rental payments under operating leases over the next five years and thereafter are as follows: Minimum Payments Under Operating Leases (In millions) 2016 $ 6.4 2017 5.8 2018 5.9 2019 2.7 2020 2.8 Thereafter 23.1 Total $ 46.7 Rent expense totaled $6.0 million , $5.5 million and $5.6 million in fiscal years ended September 30, 2015 , 2014 and 2013 , respectively. REGULATED UTILITY OPERATIONS Natural Gas Contracts—Minimum Commitments At September 30, 2015 , Washington Gas had service agreements with four pipeline companies that provide direct service for firm transportation and/or storage services. These agreements, which have expiration dates ranging from fiscal years 2016 to 2034, require Washington Gas to pay fixed charges each month. Additionally, Washington Gas had agreements for other pipeline and peaking services with expiration dates ranging from 2016 to 2028. These agreements were entered into based on current estimates of growth of the Washington Gas system, together with other factors, such as current expectations of the timing and extent of unbundling initiatives in the Washington Gas service territory. The following table summarizes the minimum contractual payments that Washington Gas will make under its pipeline transportation, storage and peaking contracts, as well as minimum contractual payments to purchase natural gas at prices based on market conditions during the next five fiscal years and thereafter. Washington Gas Contract Minimums (In millions) Pipeline Contracts (a) Gas Purchase Commitments (b) 2016 $ 208.8 $ 340.6 2017 200.8 413.8 2018 199.1 403.4 2019 211.1 396.6 2020 199.7 413.6 Thereafter 1,191.7 4,819.0 Total $ 2,211.2 $ 6,787.0 (a) Represents minimum payments for natural gas transportation, storage and peaking contracts that have expiration dates through fiscal year 2034. (b) Includes known and reasonably likely commitments to purchase natural gas. Cost estimates are based on forward market prices at September 30, 2015 . When a customer selects a third party marketer to provide supply, Washington Gas generally assigns pipeline and storage capacity to unregulated third party marketers to deliver gas to Washington Gas’ city gate. In order to provide the gas commodity to customers who do not select an unregulated third party marketer, Washington Gas has a commodity acquisition plan to acquire the natural gas supply to serve the customers. To the extent these commitments are to serve its customers, Washington Gas has rate provisions in each of its jurisdictions that would allow it to continue to recover these commitments in rates. Washington Gas also actively manages its supply portfolio to ensure its sales and supply obligations remain balanced. This reduces the likelihood that the contracted supply commitments would exceed supply obligations. However, to the extent Washington Gas were to determine that changes in regulation would cause it to discontinue recovery of these costs in rates, Washington Gas would be required to charge these costs to expense without any corresponding revenue recovery. If this occurred, depending upon the timing of the occurrence, the related impact on our financial position, results of operations and cash flows would likely be significant. Regulatory Contingencies Certain legal and administrative proceedings incidental to our business, including regulatory contingencies, involve WGL and/or its subsidiaries. In our opinion, we have recorded an adequate provision for probable losses or refunds to customers for regulatory contingencies related to these proceedings. NON-UTILITY OPERATIONS WGEServices enters into contracts to purchase natural gas and electricity designed to match the duration of its sales commitments, and to effectively lock in a margin on estimated sales over the terms of existing sales contracts. WGL Midstream enters into contracts to acquire, invest in, manage and optimize natural gas storage and transportation assets. Gas purchase commitments increased during fiscal year 2015 due to purchase commitments related to investment pipeline infrastructure and long-term sales agreements. The following table summarizes the minimum commitments and contractual obligations of WGL Energy Services and WGL Midstream for the next five fiscal years and thereafter. Contract Minimums WGL Energy Services WGL Midstream (In millions) Gas Purchase Commitments (a) Pipeline Contracts (b) Electric Purchase Commitments (c) Gas Purchase Commitments (d) Pipeline Contracts (b) Total 2016 $ 156.4 $ 3.2 $ 477.4 $ 252.9 $ 20.4 $ 910.3 2017 67.8 2.0 215.8 348.6 18.4 652.6 2018 9.7 1.4 56.3 1,082.6 15.9 1,165.9 2019 0.5 0.8 6.2 1,650.9 60.9 1,719.3 2020 — 0.5 1.1 1,866.4 65.0 1,933.0 Thereafter — 1.2 — 32,117.1 1,031.7 33,150.0 Total $ 234.4 $ 9.1 $ 756.8 $ 37,318.5 $ 1,212.3 $ 39,531.1 (a) Represents fixed price commitments with city gate equivalent deliveries. (b) Represents minimum payments for natural gas transportation and storage contracts that have expiration dates through fiscal year 2044. (c) Represents electric purchase commitments that are based on existing fixed price and fixed volume contracts. Includes $15.7 million of commitments related to renewable energy credits. (d) Includes known and reasonably likely commitments to purchase natural gas. Cost estimates are based on forward market prices as of September 30, 2015 . Certain of our gas purchase agreements have optionality, which may cause increases in these commitments. Financial Guarantees WGL has guaranteed payments primarily for certain commitments on behalf of Washington Gas, WGL Energy Services, WGL Energy Systems and WGL Midstream. At September 30, 2015 , these guarantees totaled $30.7 million , $230.1 million , $8.5 million and $318.3 million for Washington Gas, WGL Energy Services, WGL Energy Systems and WGL Midstream, respectively. At September 30, 2015 , WGL also had guarantees on behalf of other subsidiaries totaling $2.0 million . The amount of such guarantees is periodically adjusted to reflect changes in the level of WGL's financial exposure related to these commitments. For all of our 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. WGL has also guaranteed payments for certain of our external partners. At September 30, 2015 , these guarantees totaled $8.1 million and the fair value of these guarantees was insignificant.

Derivative and Weather Related

Derivative and Weather Related Instruments	12 Months Ended
	Sep. 30, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative and Weather-Related Instruments	DERIVATIVE AND WEATHER-RELATED INSTRUMENTS DERIVATIVE INSTRUMENTS Regulated Utility Operations Washington Gas enters into contracts that qualify as derivative instruments and are accounted for under ASC Topic 815. These derivative instruments are recorded at fair value on our balance 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 utilizes its storage capacity assets to benefit from favorable natural gas prices between different time periods. As part of this asset optimization program, Washington Gas enters into physical and financial derivative transactions in the form of forward, futures and option contracts with the primary objective of 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 fiscal year ended September 30, 2015 was a net gain of $27.9 million including an unrealized loss of $6.3 million . During the fiscal year ended September 30, 2014 we recorded a net loss of $35.4 million including an unrealized loss of $66.2 million . During the fiscal year ended September 30, 2013 we recorded a net loss of $33.2 million including an unrealized loss of $45.4 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 Asset Optimization. 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. WGL Midstream does 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. The storage and transportation capacities utilized by WGL Midstream are not considered to be derivative instruments, and thus they are not recorded at fair value on our consolidated balance sheets. Managing Price Risk . WGL Energy Services enters into certain derivative contracts as part of managing the price risk associated with the sale and purchase of natural gas and electricity. WGL Energy Services designates a portion of these physical contracts related to the purchase of natural gas and electricity to serve our customers as "normal purchases and normal sales" and therefore, they are not subject to the fair value accounting requirements of ASC Topic 815. Derivative instruments not designated as "normal purchases and normal sales" are recorded at fair value on our consolidated balance sheets, and changes in the fair value of these derivative instruments are reflected in the earnings of our non-utility operations, which may cause significant period-to-period volatility in earnings. WGL Energy Services does not designate derivatives as hedges under ASC Topic 815. Managing Interest-Rate Risk . WGL utilizes derivative instruments that are designed to minimize the risk of interest-rate volatility associated with future debt issuances. WGL elected cash flow hedge accounting for its interest rate derivative instruments, which settled with the issuance of the related debt issuance in the first quarter of 2015. The effective portion of the gains and losses on the hedge were recorded within other comprehensive income and are being amortized over the life of the debt (through 2044). The amortization is minimal for fiscal 2015 . In August 2015, WGL entered into two forward starting interest rate swap agreements, with a total notional amount of $125.0 million , and designated them as cash flow hedges in accordance with ASC 815. These derivatives hedge the variability in future interest payments due to changes in interest rates prior to WGL's expected issuance of 30-year debt in January 2018. The effective portion of changes in the fair value of qualified derivatives designated as cash flow hedges is recorded in accumulated other comprehensive income (loss) and subsequently reclassified into earnings in the period that the hedged forecasted transactions affects earnings. The ineffective portion of the change in fair value of the derivatives is recognized directly in earnings with interest expense. 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 September 30, 2015 and 2014 , respectively, the absolute notional amounts of our derivatives are as follows: Absolute Notional Amounts of Open Positions on Derivative Instruments Derivative transactions WGL Holdings Washington Gas September 30, 2015 Notional Amounts Natural Gas (In millions of therms) Asset Optimization 20,829.2 13,316.7 Retail sales 52.2 — Other risk-management activities 1,811.7 1,381.8 Electricity (In millions of kWhs) Retail sales 4,292.7 — Other risk-management activities 19,965.7 — Interest Rate Swaps (In millions of dollars) $ 125.0 $ — September 30, 2014 Natural Gas (In millions of therms) Asset Optimization 20,593.3 13,740.9 Retail sales 44.7 — Other risk-management activities 1,641.3 1,398.2 Electricity (In millions of kWhs) Retail sales 3,831.4 — Other risk-management activities 16,734.1 — Warrants (In millions of shares) 4.6 — Interest Rate Swaps (In millions of dollars) $ 150.0 $ — The following tables present the balance sheet classification for all derivative instruments as of September 30, 2015 and 2014 . WGL Holdings, Inc. Balance Sheet Classification of Derivative Instruments (In millions) Derivative Instruments Not Designated as Hedging Instruments Derivative Instruments Designated as Hedging Instruments As of September 30, 2015 Gross Derivative Assets Gross Derivative Liabilities Gross Derivative Assets Gross Derivative Liabilities Netting of Collateral Total (a) Current Assets—Derivatives $ 29.7 $ (6.8 ) $ — $ — $ — $ 22.9 Deferred Charges and Other Assets—Derivatives 32.3 (0.2 ) — — — 32.1 Current Liabilities—Derivatives 9.8 (76.2 ) — — 2.9 (63.5 ) Deferred Credits—Derivatives 2.7 (328.9 ) — (3.4 ) 7.3 (322.3 ) Total $ 74.5 $ (412.1 ) $ — $ (3.4 ) $ 10.2 $ (330.8 ) As of September 30, 2014 Current Assets—Derivatives $ 20.8 $ (2.5 ) $ — $ — $ — $ 18.3 Deferred Charges and Other Assets—Derivatives 18.7 — — — — 18.7 Current Liabilities—Derivatives 15.4 (70.3 ) — (1.7 ) 8.0 (48.6 ) Deferred Credits—Derivatives 17.7 (316.4 ) — — 4.0 (294.7 ) Total $ 72.6 $ (389.2 ) $ — $ (1.7 ) $ 12.0 $ (306.3 ) Washington Gas Light Company Balance Sheet Classification of Derivative Instruments (b) (In millions) As of September 30, 2015 Gross Gross Netting of Total (a) Current Assets—Derivatives $ 5.2 $ (0.6 ) $ — $ 4.6 Deferred Charges and Other Assets—Derivatives 13.3 (0.1 ) — 13.2 Current Liabilities—Derivatives 1.9 (35.8 ) — (33.9 ) Deferred Credits—Derivatives — (269.7 ) — (269.7 ) Total $ 20.4 $ (306.2 ) $ — $ (285.8 ) As of September 30, 2014 Current Assets—Derivatives $ 3.9 $ — $ — $ 3.9 Deferred Charges and Other Assets—Derivatives 9.5 — — 9.5 Current Liabilities—Derivatives 8.6 (43.2 ) 0.7 (33.9 ) Deferred Credits—Derivatives 4.2 (265.2 ) 0.2 (260.8 ) Total $ 26.2 $ (308.4 ) $ 0.9 $ (281.3 ) (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. (b) Washington Gas did not have any derivative instruments outstanding that were designated as hedging instruments at September 30, 2015 or 2014 . The following tables present all gains and losses associated with derivative instruments for the years ended September 30, 2015 , 2014 and 2013 . Gains and Losses on Derivative Instruments (In millions) WGL Holdings, Inc. Washington Gas Fiscal Year Ended September 30, 2015 2014 2013 2015 2014 2013 Recorded to income Operating revenues—non-utility $ 71.3 $ (47.9 ) $ (9.9 ) $ — $ — $ — Utility cost of gas (14.5 ) (87.3 ) (45.9 ) (14.5 ) (87.3 ) (45.9 ) Non-utility cost of energy-related sales (43.7 ) 36.2 (2.4 ) — — — Other income-net — (1.1 ) 0.2 — — — Interest expense (a) (0.6 ) (0.2 ) — — — — Recorded to regulatory assets Gas costs (18.4 ) (143.3 ) (115.1 ) (18.4 ) (143.3 ) (115.1 ) Other — 0.2 — — 0.2 — Recorded to other comprehensive income (b) (11.3 ) (1.5 ) — — — — Total $ (17.2 ) $ (244.9 ) $ (173.1 ) $ (32.9 ) $ (230.4 ) $ (161.0 ) (a) Fiscal year 2015 represents $(0.4) million of net ineffectiveness for our cash flow hedges and $(0.2) million of amortization of amounts previously recorded to Accumulated Other Comprehensive Income. Fiscal year 2014 amounts represent hedge ineffectiveness. (b) Fiscal year 2015 represents the effective portion of our cash flow hedges of $(11.5) million less $(0.2) million of amortization that was reclassified to interest expense. Fiscal year 2014 amounts represent hedge effectiveness. 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 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 September 30, 2015 , Washington Gas, WGL Energy Services and WGL Midstream posted $3.5 million , $12.4 million and $3.5 million , respectively, of collateral deposits with counterparties that were not offset against open and settled derivative contracts. At September 30, 2014 , Washington Gas, WGL Energy Services and WGL Midstream posted $8.2 million , $5.7 million and $11.4 million , respectively, of collateral deposits with counterparties that were not offset against open and settled derivative contracts. At September 30, 2015 , Washington Gas and WGL Midstream held $3.8 million and $0.4 million , respectively of cash collateral representing an obligation to counterparties that was not offset against open and settled derivative contracts. At September 30, 2014 , Washington Gas held $2.5 million 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 sheets. Collateral received and not offset against open and settled derivative contracts is included in “Customer deposits and advance payments” in the accompanying balance sheets. Certain derivative instruments of Washington Gas, WGL Energy Services and WGL Midstream contain contract provisions that require collateral to be posted if the credit rating of Washington Gas or WGL falls below certain levels or if counterparty exposure to WGL Energy Services or WGL Midstream exceeds a certain level. Due to counterparty exposure levels, at September 30, 2015 , WGL Energy Services posted $10.3 million of collateral related to its derivative liabilities that contained credit-related contingent features. At September 30, 2014 , WGL Energy Services posted $5.3 million of collateral related to these aforementioned derivative liabilities. Washington Gas and WGL Midstream were not required to post any collateral related to their respective derivative liabilities that contained credit-related contingent features at September 30, 2015 or 2014 . 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 September 30, 2015 and 2014 , respectively. Potential Collateral Requirements for Derivative Liabilities with Credit-Risk-Contingent Features (In millions) WGL Holdings, Inc. Washington Gas September 30, 2015 Derivative liabilities with credit-risk-contingent features $ 61.7 $ 18.9 Maximum potential collateral requirements 54.6 18.8 September 30, 2014 Derivative liabilities with credit-risk-contingent features $ 28.8 $ 20.6 Maximum potential collateral requirements 16.5 16.1 Washington Gas, WGL Energy Services 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 with wholesale counterparties, which is represented by the fair value of these instruments at the reporting date. We actively monitor and work to minimize counterparty concentration risk through various practices. At September 30, 2015 , one counterparty represented over 10% of Washington Gas’ credit exposure to wholesale derivative counterparties for a total credit risk of $17.5 million ; one counterparty represented over 10% of WGL Energy Services’ credit exposure to wholesale derivative counterparties for a total credit risk of $0.7 million ; and two counterparties each represented over 10% of WGL Midstream’s credit exposure to wholesale counterparties for a total credit risk of $17.4 million . WEATHER-RELATED INSTRUMENTS Washington Gas did not use any weather-related instruments during the years ended September 30, 2015 and 2014 . During the fiscal year ended September 30, 2013 , Washington Gas used 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 year ended September 30, 2013 , Washington Gas recorded a pre-tax net gain of $0.8 million related to weather derivatives. WGL Energy Services utilizes weather-related instruments for managing the financial effects of weather risks. These instruments cover a portion of WGL Energy Services’ estimated revenue or energy-related cost exposure to variations in heating or cooling degree days. These contracts provide for payment to WGL Energy Services 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. During the years ended September 30, 2015 , 2014 and 2013 , WGL Energy Services recorded pre-tax gains of $0.6 million and $3.4 million and a pre-tax loss of $0.8 million , respectively, related to these instruments.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Sep. 30, 2015
Fair Value Disclosures [Abstract]
Fair Value Measurements	NOTE 15. 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 derivatives recorded on our balance sheet under ASC Topic 815 and short-term investments, commercial paper and long-term debt outstanding required to be disclosed at fair value. Under ASC Topic 820, fair value is defined as the exit price, representing the amount that would be received in the sale of an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. To value our financial instruments, we use market data or assumptions that market participants would use, including assumptions about credit risk (both our own credit risk and the counterparty’s credit risk) and the risks inherent in the inputs to valuation. We enter into derivative contracts in the futures and over-the-counter (OTC) wholesale and retail markets. These markets are the principal markets for the respective wholesale and retail contracts. Our relevant market participants are our existing counterparties and others who have participated in energy transactions at our delivery points. These participants have access to the same market data as 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. WGL did not have any Level 1 derivatives at September 30, 2015 and 2014 . 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 September 30, 2015 and 2014 , 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, as well as our interest rate hedges. 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 determine the fair value of 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 September 30, 2015 and 2014 , Level 3 derivative assets and liabilities included: (i) physical contracts valued at illiquid market locations with no observable market data; (ii) long-dated positions where observable pricing is not available over the life of the contract; (iii) contracts valued using historical spot price volatility assumptions and (iv) valuations using indicative broker quotes for inactive market locations. The following tables set forth financial instruments recorded at fair value as of September 30, 2015 and 2014 , 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 September 30, 2015 Assets Natural gas related derivatives $ — $ 22.7 $ 28.5 $ 51.2 Electricity related derivatives — 2.0 21.3 23.3 Total Assets $ — $ 24.7 $ 49.8 $ 74.5 Liabilities Natural gas related derivatives $ — $ (33.9 ) $ (338.2 ) $ (372.1 ) Electricity related derivatives — (2.7 ) (37.3 ) (40.0 ) Interest rate derivatives — (3.4 ) — (3.4 ) Total Liabilities $ — $ (40.0 ) $ (375.5 ) $ (415.5 ) At September 30, 2014 Assets Natural gas related derivatives $ — $ 22.7 $ 33.7 $ 56.4 Electricity related derivatives — 0.3 15.9 16.2 Total Assets $ — $ 23.0 $ 49.6 $ 72.6 Liabilities Natural gas related derivatives $ — $ (39.8 ) $ (328.4 ) $ (368.2 ) Electricity related derivatives — (0.1 ) (20.9 ) (21.0 ) Interest rate derivatives — (1.7 ) — (1.7 ) Total Liabilities $ — $ (41.6 ) $ (349.3 ) $ (390.9 ) Washington Gas Light Company Fair Value Measurements Under the Fair Value Hierarchy (In millions) Level 1 Level 2 Level 3 Total At September 30, 2015 Assets Natural gas related derivatives $ — $ 6.9 $ 13.5 $ 20.4 Total Assets $ — $ 6.9 $ 13.5 $ 20.4 Liabilities Natural gas related derivatives $ — $ (11.6 ) $ (294.6 ) $ (306.2 ) Total Liabilities $ — $ (11.6 ) $ (294.6 ) $ (306.2 ) At September 30, 2014 Assets Natural gas related derivatives $ — $ 13.5 $ 12.7 $ 26.2 Total Assets $ — $ 13.5 $ 12.7 $ 26.2 Liabilities Natural gas related derivatives $ — $ (25.1 ) $ (283.3 ) $ (308.4 ) Total Liabilities $ — $ (25.1 ) $ (283.3 ) $ (308.4 ) 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 September 30, 2015 and 2014 . Quantitative Information about Level 3 Fair Value Measurements (In millions) Net Fair Value Valuation Techniques Unobservable Inputs Range WGL Holdings, Inc. Natural gas related derivatives $(309.7) Discounted Cash Flow Natural Gas Basis Price (per dekatherm) ($1.441) - $3.580 Option Model Natural Gas Basis Price (per dekatherm) ($1.283) - $2.950 Annualized Volatility of Spot Market Natural Gas 22.5% - 867.0% Electricity related derivatives $(16.0) Discounted Cash Flow Electricity Congestion Price (per megawatt hour) ($5.75) - $73.35 Washington Gas Light Company Natural gas related derivatives $(281.1) Discounted Cash Flow Natural Gas Basis Price (per dekatherm) ($1.441) - $3.500 Net Fair Value WGL Holdings, Inc. Natural gas related derivatives $(294.7) Discounted Cash Flow Natural Gas Basis Price (per dekatherm) ($2.101) - $6.154 Option Model Natural Gas Basis Price (per dekatherm) ($1.675) - $6.154 Annualized Volatility of Spot Market Natural Gas 30.9% - 589.6% Electricity related derivatives $(5.0) Discounted Cash Flow Electricity Congestion Price (per megawatt hour) ($2.85) - $90.95 Washington Gas Light Company Natural gas related derivatives $(270.6) Discounted Cash Flow Natural Gas Basis Price (per dekatherm) ($2.101) - $6.154 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 years ended September 30, 2015 and 2014 , respectively. WGL Holdings, Inc. Reconciliation of Fair Value Measurements Using Significant Level 3 Inputs (In millions) Natural Gas Related Derivatives Electricity Related Derivatives Warrants Total Fiscal Year Ended September 30, 2015 Balance at October 1, 2014 $ (294.7 ) $ (5.0 ) $ — $ (299.7 ) Realized and unrealized gains (losses) Recorded to income (30.7 ) (32.3 ) — (63.0 ) Recorded to regulatory assets—gas costs (30.9 ) — — (30.9 ) Transfers into Level 3 5.4 — — 5.4 Transfers out of Level 3 3.6 — — 3.6 Purchases — 10.5 — 10.5 Settlements 37.6 10.8 — 48.4 Balance at September 30, 2015 $ (309.7 ) $ (16.0 ) $ — $ (325.7 ) Fiscal Year Ended September 30, 2014 Balance at October 1, 2013 $ (155.2 ) $ 2.4 $ 1.1 $ (151.7 ) Realized and unrealized gains (losses) Recorded to income (72.6 ) (5.7 ) (1.1 ) (79.4 ) Recorded to regulatory assets—gas costs (113.6 ) — — (113.6 ) Transfers out of Level 3 1.7 — — 1.7 Purchases — 5.2 — 5.2 Settlements 45.0 (6.9 ) — 38.1 Balance at September 30, 2014 $ (294.7 ) $ (5.0 ) $ — $ (299.7 ) Washington Gas Light Company Reconciliation of Fair Value Measurements Using Significant Level 3 Inputs (In millions) Natural Gas Related Derivatives Fiscal Year Ended September 30, 2015 Balance at October 1, 2014 $ (270.6 ) Realized and unrealized gains (losses) Recorded to income (25.0 ) Recorded to regulatory assets—gas costs (30.9 ) Transfers into Level 3 5.4 Transfers out of Level 3 2.5 Settlements 37.5 Balance at September 30, 2015 $ (281.1 ) Fiscal Year Ended September 30, 2014 Balance at October 1, 2013 $ (133.6 ) Realized and unrealized gains (losses) Recorded to income (69.4 ) Recorded to regulatory assets—gas costs (113.6 ) Transfers out of Level 3 1.7 Settlements 44.3 Balance at September 30, 2014 $ (270.6 ) 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. Transfers out of Level 3 during the fiscal year ended September 30, 2015 and 2014 were due to an increase in valuations using observable market inputs. Transfers into Level 3 during the fiscal year ended September 30, 2015 were due to an increase in unobservable market inputs used in valuations. The table below sets forth the line items on the statements of income to which amounts are recorded for the fiscal years ended September 30, 2015 , 2014 and 2013 , 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 (In millions) Natural Gas Related Derivatives Electricity Related Derivatives Weather Related Instruments Warrants Total Fiscal Year Ended September 30, 2015 Operating revenues—non-utility $ (5.7 ) $ 19.9 $ — $ — $ 14.2 Utility cost of gas (25.0 ) — — — (25.0 ) Non-utility cost of energy-related sales — (52.2 ) — — (52.2 ) Total $ (30.7 ) $ (32.3 ) $ — $ — $ (63.0 ) Fiscal Year Ended September 30, 2014 Operating revenues—non-utility $ (2.3 ) $ (22.1 ) $ — $ — $ (24.4 ) Utility cost of gas (69.4 ) — — — (69.4 ) Other income-net — — — (1.1 ) (1.1 ) Non-utility cost of energy-related sales (0.9 ) 16.4 — — 15.5 Total $ (72.6 ) $ (5.7 ) $ — $ (1.1 ) $ (79.4 ) Fiscal Year Ended September 30, 2013 Operating revenues—non-utility $ (27.0 ) $ (9.1 ) $ — $ — $ (36.1 ) Utility cost of gas (45.8 ) — — — (45.8 ) Other income-net — — — 0.2 0.2 Non-utility cost of energy-related sales 0.4 (14.7 ) — — (14.3 ) Operation and maintenance expense — — 1.2 — 1.2 Total $ (72.4 ) $ (23.8 ) $ 1.2 $ 0.2 $ (94.8 ) Washington Gas Light Company Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements (In millions) Natural Gas Related Derivatives Weather Related Instruments Total Fiscal Year Ended September 30, 2015 Utility cost of gas $ (25.0 ) $ — $ (25.0 ) Total $ (25.0 ) $ — $ (25.0 ) Fiscal Year Ended September 30, 2014 Utility cost of gas $ (69.4 ) $ — $ (69.4 ) Total $ (69.4 ) $ — $ (69.4 ) Fiscal Year Ended September 30, 2013 Utility cost of gas $ (45.9 ) $ — $ (45.9 ) Operation and maintenance expense — 1.2 1.2 Total $ (45.9 ) $ 1.2 $ (44.7 ) Unrealized gains (losses) for the fiscal years ended September 30, 2015 , 2014 and 2013 , attributable to derivative assets and liabilities measured using significant Level 3 inputs were recorded as follows, respectively: WGL Holdings, Inc. Unrealized Gains (Losses) Recorded for Level 3 Measurements (In millions) Natural Gas Related Derivatives Electricity Related Derivatives Warrants Total Fiscal Year Ended September 30, 2015 Recorded to income Operating revenues—non-utility $ (2.2 ) $ 25.1 $ — $ 22.9 Utility cost of gas (15.8 ) — — (15.8 ) Non-utility cost of energy-related sales (1.7 ) (41.7 ) — (43.4 ) Recorded to regulatory assets—gas costs (20.9 ) — — (20.9 ) Total $ (40.6 ) $ (16.6 ) $ — $ (57.2 ) Fiscal Year Ended September 30, 2014 Recorded to income Operating revenues—non-utility $ (5.0 ) $ (33.8 ) $ — $ (38.8 ) Utility cost of gas (60.6 ) — — (60.6 ) Non-utility cost of energy-related sales 3.7 30.0 — 33.7 Other income-net — — (1.1 ) (1.1 ) Recorded to regulatory assets—gas costs (109.9 ) — — (109.9 ) Total $ (171.8 ) $ (3.8 ) $ (1.1 ) $ (176.7 ) Fiscal Year Ended September 30, 2013 Recorded to income Operating revenues—non-utility $ (25.3 ) $ 6.6 $ — $ (18.7 ) Utility cost of gas (44.3 ) — — (44.3 ) Non-utility cost of energy-related sales 0.2 (1.1 ) — (0.9 ) Other income-net — — 0.2 0.2 Recorded to regulatory assets—gas costs (111.6 ) — — (111.6 ) Total $ (181.0 ) $ 5.5 $ 0.2 $ (175.3 ) Washington Gas Light Company Unrealized Gains (Losses) Recorded for Level 3 Measurements (In millions) Natural Gas Related Derivatives Fiscal Year Ended September 30, 2015 Recorded to income - utility cost of gas $ (15.8 ) Recorded to regulatory assets—gas costs (20.9 ) Total $ (36.7 ) Fiscal Year Ended September 30, 2014 Recorded to income - utility cost of gas $ (60.6 ) Recorded to regulatory assets—gas costs (109.9 ) Total $ (170.5 ) Fiscal Year Ended September 30, 2013 Recorded to income - utility cost of gas $ (44.3 ) Recorded to regulatory assets—gas costs (111.6 ) Total $ (155.9 ) The following table presents the carrying amounts and estimated fair values of our financial instruments at September 30, 2015 and 2014 . WGL Holdings, Inc. Fair Value of Financial Instruments September 30, 2015 September 30, 2014 (In millions) Carrying Amount Fair Value Carrying Amount Fair Value Money market funds (a) $ 11.0 $ 11.0 $ 9.7 $ 9.7 Other short-term investments (a) $ 0.4 $ 0.4 $ — $ — Commercial paper (b) $ 332.0 $ 332.0 $ 453.5 $ 453.5 Long-term debt (c) $ 944.2 $ 1,057.9 $ 679.2 $ 809.3 Washington Gas Light Company Fair Value of Financial Instruments September 30, 2015 September 30, 2014 (In millions) Carrying Amount Fair Value Carrying Amount Fair Value Money market funds (a) $ 4.3 $ 4.3 $ 4.3 $ 4.3 Other short-term investments (a) $ 0.4 $ 0.4 $ — $ — Commercial paper (b) $ 89.0 $ 89.0 $ 89.0 $ 89.0 Long-term debt (c) $ 695.9 $ 811.9 $ 679.2 $ 809.3 (a) Balance 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) Less 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 September 30, 2015 and 2014 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. Neither WGL’s nor Washington Gas’ long-term debt is 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 the credit quality of the debt issuer, WGL or Washington Gas. Our long-term debt fair value measurement is classified as Level 3. Non Recurring Basis During the fiscal year ended September 30, 2015 , Washington Gas Resources recorded an impairment charge on its investment in ASDHI to its fair value using the income approach. The amount of the impairment was equivalent to the amount of the carrying value of $5.6 million and was due to management’s assumption of the current valuation and expected return from the investment. The fair value of this investment was a Level 3 measurement. During the fiscal year ended September 30, 2014 , Washington Gas recorded an impairment of its previous operations center 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 recorded an impairment of 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 based on the progress made towards selling the facility. The fair value of this investment is a Level 3 measurement. During the fiscal year ended September 30, 2014 , the SCC of VA disallowed full recovery of carrying costs related to an abandoned LNG storage facility. As a result, Washington Gas recorded an impairment charge of $1.9 million . During the fiscal year ended September 30, 2013 , Washington Gas recorded an impairment charge of $0.5 million to the abandoned LNG storage facility. The fair value of this investment was a Level 3 measurement.

Operating Segment Reporting

Operating Segment Reporting	12 Months Ended
	Sep. 30, 2015
Segment Reporting [Abstract]
Operating Segment Reporting	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. During the first quarter of 2015, our chief operating decision maker began evaluating segment performance based on Earnings Before Interest and Taxes (EBIT). EBIT is defined as earnings before interest and taxes from continuing operations. Items we do not include in EBIT are interest expense, intercompany financing activity, dividends on Washington Gas preferred stock, and income taxes. EBIT includes transactions between reportable segments. We also evaluate our operating segments based on other relevant factors, such as penetration into their respective markets and return on equity. 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 end use 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 WGL Energy Services, 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 WGL Energy Systems which provides clean and energy efficient solutions including commercial solar, energy efficiency and combined heat and power projects and other distributed generation solutions to government and commercial clients. In addition, this segment comprises the operations of WGSW, 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, investing in, managing and optimizing natural gas storage and transportation assets. Administrative and business development activity costs associated with WGL and Washington Gas Resources and 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” in the Operating Segment Financial Information presented below. The following tables present operating segment information for the fiscal years ended September 30, 2015 , 2014 and 2013 . Prior period amounts are presented based on the change in measure. Operating Segment Financial Information (In thousands) Operating Revenues (a) Depreciation and Amortization Equity in Earnings of Unconsolidated Affiliates EBIT Total Assets Capital Expenditures Equity Method Investments Fiscal Year Ended September 30, 2015 Regulated utility $ 1,328,191 $ 110,416 $ — $ 223,977 $ 4,253,552 $ 327,429 $ — Retail energy-marketing 1,306,758 671 — 46,629 470,251 28 — Commercial energy systems 51,813 10,733 2,095 9,688 691,629 136,749 63,521 Midstream energy services 3,191 129 2,623 (2,720 ) 237,839 85 73,363 Other activities — — 750 (9,667 ) 199,060 — — Eliminations (b) (30,123 ) (57 ) — (1,013 ) (558,130 ) — — Total consolidated $ 2,659,830 $ 121,892 $ 5,468 $ 266,894 $ 5,294,201 $ 464,291 $ 136,884 Fiscal Year Ended September 30, 2014 Regulated utility $ 1,443,800 $ 104,064 $ — $ 184,668 $ 3,979,522 $ 286,323 $ — Retail energy-marketing 1,310,279 756 1 14,015 389,700 76 — Commercial energy systems 40,679 6,178 1,953 6,863 521,570 108,363 66,810 Midstream energy services 16,555 124 771 8,412 211,824 — 28,076 Other activities — — 469 (11,539 ) 369,816 — 16 Eliminations (b) (30,366 ) (350 ) — (167 ) (615,933 ) — — Total consolidated $ 2,780,947 $ 110,772 $ 3,194 $ 202,252 $ 4,856,499 $ 394,762 $ 94,902 Fiscal Year Ended September 30, 2013 Regulated utility $ 1,200,357 $ 100,438 $ — $ 153,647 $ 3,486,296 $ 227,948 $ — Retail energy-marketing 1,279,364 726 — 53,264 403,082 730 — Commercial energy systems 35,217 2,411 1,070 3,019 318,995 83,667 54,977 Midstream energy services (20,390 ) 124 312 (29,359 ) 231,368 — 6,507 Other activities — — 128 (8,669 ) 290,440 — 413 Eliminations (b) (28,410 ) (415 ) — (2,026 ) (470,121 ) — — Total consolidated $ 2,466,138 $ 103,284 $ 1,510 $ 169,876 $ 4,260,060 $ 312,345 $ 61,897 (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 public service commission fees, franchise fees and energy taxes. Operating revenue amounts in the “Eliminations” row 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 include any mark-to market valuations associated with trading activities between WGL Midstream and WGL Energy Services, intercompany loans and a timing difference between Commercial Energy Systems’ recognition of revenue for the sale of Renewable Energy Credits (RECs) to Retail Energy-Marketing and Retail Energy-Marketing’s recognition of the associated expense. Retail Energy-Marketing has recorded a portion of the REC’s purchased as inventory to be used in future periods at which time they will be expensed. The following table provides a reconciliation from EBIT to net income applicable to common stock. Fiscal Year Ended September 30, (In thousands) 2015 2014 2013 Total consolidated EBIT $ 266,894 $ 202,252 $ 169,876 Interest expense 50,511 37,738 36,011 Income before income taxes 216,383 164,514 133,865 Income tax expense 83,804 57,254 52,292 Net income 132,579 107,260 81,573 Dividends on Washington Gas Light Company preferred stock 1,320 1,320 1,320 Net income applicable to common stock $ 131,259 $ 105,940 $ 80,253

Other Investments

Other Investments	12 Months Ended
	Sep. 30, 2015
Other Investments [Abstract]
Other Investments	OTHER INVESTMENTS When determining how to account for our interests in other legal entities, WGL first evaluates if we are required to apply the variable interest entity (VIE) model to the entity, otherwise the entity is evaluated under the voting interest model. Under the VIE model, we have a controlling financial interest in a VIE (i.e. are the primary beneficiary) when we have current or potential rights that give us the power to direct the activities of a VIE that most significantly impact the VIE’s economic performance combined with a variable interest that gives us the right to receive potentially significant benefits or the obligation to absorb potentially significant losses. When changes occur to the design of an entity we reconsider whether it is subject to the VIE model. We continuously evaluate whether we have a controlling financial interest in a VIE. Under the voting interest model, we generally have a controlling financial interest in an entity where we currently hold, directly or indirectly, more than 50% of the voting rights or where we exercise control through substantive participating rights. However, we consider substantive rights held by other partners in determining if we hold a controlling financial interest, and in some cases, despite owning more than 50% of the common stock of an investee, an evaluation of our rights results in the determination that we do not have a controlling financial interest. We reevaluate whether we have a controlling financial interest in these entities when our voting or substantive participating rights change. Unconsolidated affiliates are unconsolidated VIEs and other entities evaluated under the voting interest method in which we do not have a controlling financial interest, but over which we have varying degrees of influence. Where we have significant influence, the affiliates are accounted for as equity method investments. Where we do not have significant influence, the affiliates are accounted for under the cost method. Investments in, and advances to, affiliated companies are presented on a one-line basis in the caption “Investments in unconsolidated affiliates” on our Consolidated Balance Sheet. WGL uses the Hypothetical Liquidation at Book Value (HLBV) methodology for certain equity method investments when the capital structure of the equity investment results in different liquidation rights and priorities than what is reflected by the underlying percentage ownership interests as defined by an equity investment agreement. For investments accounted for under the HLBV method, simply applying the percentage ownership interest to GAAP net income in order to determine earnings or losses does not accurately represent the income allocation and cash flow distributions that will ultimately be received by the investors. The equity investment agreements for ASD Solar, LP (ASD), Meade Pipeline Co LLC (Meade) and Mountain Valley Pipeline, LLC (Mountain Valley) have liquidation rights and priorities that are sufficiently different from the ownership percentages that the HLBV method was deemed appropriate. The calculation may vary in its complexity depending on the capital structure and the tax considerations for the investments. WGL applies HLBV using a balance sheet approach. When applying HLBV, WGL determines the amount that it would receive if an equity investment entity were to liquidate all of its assets at book value (as valued in accordance with GAAP) and distribute that cash to the investors based on the contractually defined liquidation priorities. The change in WGL's claim on the investee's book value at the beginning and end of the reporting period (adjusted for contributions and distributions) is WGL’s share of the earnings or losses from the equity investment for the period. Variable Interest Entities WGL has a variable interest in four investments that qualify as VIEs: • Meade, • SunEdison, • Nextility, and • ASD. WGL previously had a variable interest in a partnership partially owned by Crab Run; however, this partnership interest was sold during the fiscal year ended September 30, 2015 . During the fiscal year ended September 30, 2015 , WGL recognized a gain of $0.7 million , which was recorded in "Equity in earnings of unconsolidated affiliates" on WGL's statements of income, related to the sale of this interest. 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. At September 30, 2015 , the nature of WGL’s involvement with these investments lacks the characteristics of a controlling financial interest. WGL either does not have control over any of the VIEs’ activities that are economically significant to the VIEs and/or WGL does not have the obligation to absorb expected losses or the right to receive expected gains that could be significant to the VIE. Meade In 2014, WGL through its subsidiary WGL Midstream, entered into a limited liability company agreement and formed Meade, a Delaware limited liability company with COG Holdings Pipeline Company, LLC, Vega Midstream MPC LLC and River Road Interests LLC. Meade was formed to partner with Transcontinental Gas Pipe Line Company, LLC (Williams) to invest in a regulated pipeline project called Central Penn Pipeline (Central Penn). The Central Penn will be an approximately 185 -mile pipeline originating in Susquehanna County, Pennsylvania and extending to Lancaster County, Pennsylvania that will have the capacity to transport and deliver up to approximately 1.7 million dekatherms per day of natural gas. WGL Midstream plans to invest an estimated $410.6 million for a 55% interest in Meade. WGL Midstream joins COG Holdings LLC ( 20% share), Vega Midstream MPC LLC ( 15% share) and River Road Interests LLC ( 10% share) in Meade. Meade is accounted for under the HLBV equity method of accounting, and any profits and losses are included in “Equity in earnings of unconsolidated affiliates” in the accompanying Consolidated Statement of Income and are added to or subtracted from the carrying amount of WGL’s investment balance. At September 30, 2015 and 2014 , WGL Midstream held a $30.5 million and $5.8 million , respectively, equity method investment in Meade. Our maximum financial exposure includes contributions and guarantees on behalf of WGL Midstream. Our maximum exposure to loss at September 30, 2015 was $59.4 million , which represents the minimum funding requirements owed to Williams under the Construction and Ownership Agreement should Meade terminate its agreement with Williams early. SunEdison/Nextility WGSW is party to two agreements to fund residential and commercial retail solar energy installations with two separate, privately held companies. WGSW has a master purchase agreement and master lease agreement with SunEdison, Inc. (SunEdison) and Nextility, Inc. (Nextility) for sale/leaseback arrangements for residential and commercial solar systems. Our agreements with SunEdison and Nextility are accounted for as direct financing leases. WGSW records associated interest in the financing leases in “Other income (expenses)-net” line in the accompanying Consolidated Statement of Income. WGSW held a $37.2 million and $19.9 million combined investment in direct financing leases at September 30, 2015 and 2014 , respectively, of which $2.0 million and $1.7 million are current receivables recorded in “Accounts Receivable” in the accompanying Consolidated Balance Sheets at September 30, 2015 and 2014 , respectively. Minimum future lease payments receivable under direct financing leases over the next five fiscal years and thereafter are as follows: Minimum Payments Receivable for Direct Financing Leases (In millions) 2016 $ 3.7 2017 2.8 2018 2.8 2019 2.7 2020 2.6 Thereafter 28.3 Total $ 42.9 Minimum payments receivable exclude $9.5 million of residual values and $4.6 million in tax credits. Associated with these investments, WGSW holds $19.8 million of unearned income on its balance sheet. The initial direct costs (incurred in FY 2012) associated with these investments was $0.7 million . Our maximum financial exposure from solar agreements is limited to WGSW's 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. ASD In addition to SunEdison and Nextility, WGSW is also a limited partner in ASD, a limited partnership formed to own and operate a portfolio of residential solar projects, primarily rooftop photovoltaic power generation systems. As a limited partner, WGSW provided funding to the partnership but does not have power to direct the activities that most significantly affect the operations and economic performance of the entity. In January 2014, the funding commitment period expired for the partnership. WGSW’s maximum financial exposure is limited to its contributions made to the partnership. Our investment in ASD is accounted for under the HLBV equity method of accounting; any profits and losses are included in “Equity in earnings of unconsolidated affiliates” in the accompanying Consolidated Statement of Income and are added to or subtracted from the carrying amount of WGSW’s investment balance. At September 30, 2015 and 2014 , WGSW held a $63.5 million and $66.8 million , respectively, equity method investment in ASD. ASD is consolidated by the general partner, Solar Direct LLC. Solar Direct LLC is a wholly owned subsidiary of American Solar Direct Inc. (ASDI). At September 30, 2015 , the carrying amount of WGSW’s investment in ASD exceeded the amount of the underlying equity in net assets by $35.9 million due to WGSW recording additions to its investment in ASD’s net assets at fair value of contributions in accordance with GAAP. This basis difference is being amortized over the life of the assets. Non-VIE Investments ASDHI At September 30, 2014 , Washington Gas Resources held a $5.6 million investment in American Solar Direct Holdings Inc. (ASDHI) consisting of warrants and preferred stock. During the fiscal year ended September 30, 2015 , Washington Gas Resources impaired its entire investment in ASDHI by its carrying value of $5.6 million based on management's assumption of the current valuation and expected return from the investment. See Note 15— Fair Value Measurements of the Notes to Consolidated Financial Statements for a discussion of the impairment. Constitution In 2013, WGL Midstream invested in Constitution Pipeline Company, LLC (Constitution). WGL Midstream will invest an estimated aggregate amount of $83.4 million in the project for a 10% share in the pipeline venture over the term of the agreement. At September 30, 2015 , WGL Midstream had invested $29.4 million in Constitution. Other investors in the project include Williams Partners L.P. ( 41% share), Cabot Oil and Gas Corporation ( 25% share) and Piedmont Natural Gas ( 24% share). 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 “Equity in earnings of unconsolidated affiliates” 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. WGL Midstream held a $33.1 million equity method investment in Constitution at September 30, 2015 . At September 30, 2015 , the maximum financial exposure is equivalent to total capital contributions made in Constitution on behalf of WGL Midstream, which was $29.4 million . Mountain Valley Pipeline In March 2015, WGL Midstream acquired a 7% equity interest in Mountain Valley Pipeline, LLC (Mountain Valley). The proposed pipeline to be developed, constructed, owned and operated by Mountain Valley, will transport approximately 2.0 million dekatherms of natural gas per day from interconnects with EQT Corporation's Equitrans system, near the MarkWest Mobley plant in West Virginia to Transcontinental Gas Pipe Line Company LLC's Station 165 in Pittsylvania County, Virginia. WGL Midstream expects to invest, in scheduled capital contributions through the in-service date of the pipeline, its pro rata share (based on its 7% equity interest) of project costs, an estimated aggregate amount of approximately $210 to $245 million . WGL Midstream held a $9.8 million equity method investment in Mountain Valley at September 30, 2015 . Our maximum financial exposure includes guarantees on behalf of WGL Midstream and another partner in the venture. WGL's maximum exposure to loss due to the provided guarantees was $20.0 million at September 30, 2015 which represents a $14.0 million minimum funding requirement for WGL Midstream and the guarantee on behalf of one of the other partners. In addition, WGL Midstream entered into an agreement to finance future capital commitments of one of the other partners in the venture for an estimated aggregate amount of approximately $96 to $105 million , which represents the estimated total funding requirements for that partner's 3% ownership interest in the joint venture, inclusive of the minimum funding requirement. WGL Midstream has provided funding of $4.2 million as of September 30, 2015 related to this agreement. The balance sheet location of the investments discussed in this footnote at September 30, 2015 and 2014 are as follows: WGL Holdings, Inc Balance Sheet Location of Other Investments (in millions) VIEs Non-VIEs Total As of September 30, 2015 Assets Investments in unconsolidated affiliates $ 94.0 $ 42.9 $ 136.9 Investments in direct financing leases, capital leases 35.2 — $ 35.2 Accounts receivable 2.0 4.2 (a) $ 6.2 Total assets $ 131.2 $ 47.1 $ 178.3 As of September 30, 2014 Assets Investments in unconsolidated affiliates $ 72.6 $ 27.9 $ 100.5 Investments in direct financing leases, capital leases 18.2 — $ 18.2 Accounts receivable 1.7 — $ 1.7 Total assets $ 92.5 $ 27.9 $ 120.4 (a) Represents the financing provided to another partner in Mountain Valley to fund its capital commitment. Acquired ownership interest represents the collateral for repayment of the financing. The income statement location of the investments discussed in this footnote for the fiscal year September 30, 2015 , 2014 and 2013 are as follows: WGL Holdings, Inc. Income Statement Location of Other Investments (In millions) VIEs Non-VIEs Total Fiscal Year Ended September 30, 2015 Equity in earnings of unconsolidated affiliates $ 2.9 $ 2.6 $ 5.5 Depreciation and amortization 0.3 — $ 0.3 Other income (expenses) - net 3.2 (5.6 ) $ (2.4 ) Net income $ 5.8 $ (3.0 ) $ 2.8 Fiscal Year Ended September 30, 2014 Equity in earnings of unconsolidated affiliates $ 2.2 $ 1.0 $ 3.2 Depreciation and amortization 0.2 — $ 0.2 Other income - net 2.6 — $ 2.6 Net income $ 4.6 $ 1.0 $ 5.6 Fiscal Year Ended September 30, 2013 Equity in earnings of unconsolidated affiliates $ 1.0 $ 0.5 $ 1.5 Depreciation and amortization 0.1 — $ 0.1 Other income - net 1.4 — $ 1.4 Net income $ 2.3 $ 0.5 $ 2.8

Related Party Transactions

Related Party Transactions	12 Months Ended
	Sep. 30, 2015
Related Party Transactions [Abstract]
Related Party Transactions	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 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 for the fiscal years ended September 30, 2015 and 2014 . Washington Gas Light Company Receivables / Payables from Associated Companies (In millions) September 30, 2015 September 30, 2014 Receivables from Associated Companies $ 3.2 $ 4.8 Payables to Associated Companies $ 68.6 $ 54.7 Washington Gas provides gas balancing services related to storage, injections, withdrawals and deliveries to all energy marketers participating in the sale of natural gas on an unregulated basis through the customer choice programs that operate in its service territory. These balancing services include the sale of natural gas supply commodities related to various peaking arrangements contractually supplied to Washington Gas and then partially allocated and assigned by Washington Gas to the energy marketers, including WGL Energy Services. Washington Gas records revenues for these balancing services pursuant to tariffs approved by the appropriate regulatory bodies. These related party amounts related to balancing services provided to WGL Energy Services have been eliminated in the consolidated financial statements of WGL. The following table shows the amounts Washington Gas charged WGL Energy Services for balance services. Washington Gas - Gas Balancing Service Charges (In millions) Years Ended September 30, 2015 2014 2013 Gas balancing service charge $ 25.1 $ 26.6 $ 25.0 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. WGL Energy Services recognized accounts payable to Washington Gas of $0.5 million and accounts receivable from Washington Gas of $0.02 million at September 30, 2015 and 2014 , respectively, related to an imbalance in gas volumes. Due to regulatory treatment, these receivables and payables are not eliminated in the consolidated financial statements of WGL. Refer to Note 1—Accounting Policies for further discussion of these imbalance transactions. Washington Gas participates in a POR program as approved by the PSC of MD, whereby it purchases receivables from participating energy marketers at approved discount rates. In addition, WGL Energy Services 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 WGL Energy Services related to the POR program has been eliminated in the accompanying financial statements for WGL. At September 30, 2015 and 2014 , Washington Gas had balances of $6.6 million and $7.7 million , respectively, of purchased receivables from WGL Energy Services.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	12 Months Ended
	Sep. 30, 2015
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss)	ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) The following tables show the changes in accumulated other comprehensive income (loss) for WGL and Washington Gas by component for the fiscal years ended September 30, 2015 and 2014 . WGL Holdings, Inc. Changes in Accumulated Other Comprehensive Income (Loss) by Component September 30, (In thousands) 2015 2014 Beginning Balance $ (7,961 ) $ (11,048 ) Qualified cash flow hedging instruments (a) (11,309 ) (1,548 ) Change in prior service cost (b) 696 6,095 Amortization of actuarial gain (loss) (b) (1,195 ) 1,594 Current-period other comprehensive income (loss) (11,808 ) 6,141 Income tax expense (benefit) related to other comprehensive income (loss) (5,533 ) 3,054 Ending Balance $ (14,236 ) $ (7,961 ) (a) Cash flow hedging instruments represent interest rate swap agreements related to debt issuances. Refer to Note 14—Derivative and Weather-related Instruments for further discussion of the interest rate swap agreements. (b) These accumulated other comprehensive income (loss) components are included in the computation of net periodic benefit cost. Refer to Note 10-Pension and other post-retirement benefit plans for additional details. Washington Gas Light Company Changes in Accumulated Other Comprehensive Income (Loss) by Component September 30, (In thousands) 2015 2014 Beginning Balance $ (6,413 ) $ (11,048 ) Change in prior service cost (a) 696 6,095 Amortization of actuarial gain (loss) (a) (1,195 ) 1,594 Current-period other comprehensive income (loss) (499 ) 7,689 Income tax expense (benefit) related to other comprehensive income (loss) (200 ) 3,054 Ending Balance $ (6,712 ) $ (6,413 ) (a) These accumulated other comprehensive income (loss) components are included in the computation of net periodic benefit cost. Refer to Note 10-Pension and other post-retirement benefit plans for additional details.

Quarterly Financial Data

Quarterly Financial Data	12 Months Ended
	Sep. 30, 2015
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Data	SUPPLEMENTARY FINANCIAL INFORMATION (Unaudited) QUARTERLY FINANCIAL DATA All adjustments necessary for a fair presentation have been included in the quarterly information provided below. Due to the seasonal nature of our business, we report substantial variations in operations on a quarterly basis. Quarter Ended (In thousands, except per share data) December 31 (a) March 31 June 30 ( b) September 30 (c) Fiscal Year 2015 WGL Holdings, Inc. Operating revenues $ 749,237 $ 1,001,733 $ 441,173 $ 467,687 Operating income (loss) $ 121,842 $ 142,886 $ (17,567 ) $ 13,612 Net income (loss) applicable to common stock $ 63,888 $ 81,455 $ (15,690 ) $ 1,606 Earnings (loss) per average share of common stock: Basic $ 1.28 $ 1.64 $ (0.32 ) $ 0.03 Diluted $ 1.28 $ 1.63 $ (0.32 ) $ 0.03 Washington Gas Light Company Operating revenues $ 387,193 $ 615,694 $ 190,345 $ 134,959 Operating income (loss) $ 114,623 $ 129,944 $ (6,729 ) $ (15,454 ) Net income (loss) applicable to common stock $ 64,621 $ 74,364 $ (11,754 ) $ (19,873 ) Fiscal Year 2014 WGL Holdings, Inc. Operating revenues $ 680,297 $ 1,174,250 $ 467,500 $ 458,900 Operating income (loss) $ 32,712 $ 104,733 $ (9,489 ) $ 69,566 Net income (loss) applicable to common stock $ 18,629 $ 61,213 $ (11,940 ) $ 38,038 Earnings (loss) per average share of common stock: Basic $ 0.36 $ 1.18 $ (0.23 ) $ 0.74 Diluted $ 0.36 $ 1.18 $ (0.23 ) $ 0.74 Washington Gas Light Company Operating revenues $ 390,415 $ 716,808 $ 197,752 $ 138,825 Operating income $ 65,229 $ 88,038 $ 4,326 $ 24,530 Net income (loss) applicable to common stock $ 38,477 $ 49,176 $ (521 ) $ 9,872 (a) During the first quarter of fiscal year 2015, WGL recorded an impairment charge of $5.6 million related to its investment in ASDHI. During the first quarter of fiscal year 2014, Washington Gas recorded an impairment charge of $0.8 million related to the Springfield Operations Center. Refer to Note 1—Accounting Policies of the Notes to Consolidated Financial Statements for further discussion of the impairments. (b) During the third quarter of fiscal year 2015, WGL recorded a $3.0 million liability for un-recovered government contracting costs under the Small Business Administration Development 8(a) Program and Washington Gas recorded approximately $0.5 million in transaction fees related to the sale of its Springfield Operations Center. During the third quarter of fiscal year 2014, Washington Gas recorded a $1.9 million impairment charge on an abandoned LNG storage facility. Refer to Note 1—Accounting Policies of the Notes to Consolidated Financial Statements for further discussion of the impairments. (c) During the fourth quarter of fiscal year 2015, Washington Gas recorded a one time adjustment of $2.4 million as a result of charges associated with a regulatory proceeding.

Schedule II

Schedule II	12 Months Ended
	Sep. 30, 2015
Valuation and Qualifying Accounts [Abstract]
Schedule II - Valuation and Qualifying Accounts and Reserves	WGL Holdings, Inc. and Subsidiaries Schedule II—Valuation and Qualifying Accounts and Reserves Years Ended September 30, 2015, 2014 and 2013 Balance at Additions Charged To Balance Beginning Costs and Other at End of (In thousands) of Period Expenses Accounts (a) Deductions (b) Period 2015 Valuation and Qualifying Accounts Deducted from Assets in the Balance Sheet: Allowance for Doubtful Accounts $ 23,341 $ 18,250 $ 4,789 $ 20,156 $ 26,224 2014 Valuation and Qualifying Accounts Deducted from Assets in the Balance Sheet: Allowance for Doubtful Accounts $ 20,433 $ 15,874 $ 4,341 $ 17,307 $ 23,341 2013 Valuation and Qualifying Accounts Deducted from Assets in the Balance Sheet: Allowance for Doubtful Accounts $ 19,792 $ 9,527 $ 4,217 $ 13,103 $ 20,433 (a) Recoveries on receivables previously written off as uncollectible and unclaimed customer deposits, overpayments, etc., not refundable. (b) Includes deductions for purposes for which reserves were provided or revisions made of estimated exposure. Washington Gas Light Company Schedule II—Valuation and Qualifying Accounts and Reserves Years Ended September 30, 2015, 2014 and 2013 Balance at Additions Charged To Balance at Beginning Costs and Other End of (In thousands) of Period Expenses Accounts (a) Deductions (b) Period 2015 Valuation and Qualifying Accounts Deducted from Assets in the Balance Sheet: Allowance for Doubtful Accounts $ 19,209 $ 12,800 $ 4,686 $ 17,441 $ 19,254 2014 Valuation and Qualifying Accounts Deducted from Assets in the Balance Sheet: Allowance for Doubtful Accounts $ 17,498 $ 12,004 $ 4,198 $ 14,491 $ 19,209 2013 Valuation and Qualifying Accounts Deducted from Assets in the Balance Sheet: Allowance for Doubtful Accounts $ 17,129 $ 7,024 $ 3,978 $ 10,633 $ 17,498 (a) Recoveries on receivables previously written off as uncollectible and unclaimed customer deposits, overpayments, etc., not refundable. (b) Includes deductions for purposes for which reserves were provided or revisions made of estimated exposure.

Accounting Policies (Policies)

Accounting Policies (Policies)	12 Months Ended
	Sep. 30, 2015
Accounting Policies [Abstract]
Consolidation	CONSOLIDATION OF FINANCIAL STATEMENTS The consolidated financial statements include the accounts of WGL and its subsidiaries during the fiscal years reported. Certain prior period amounts have been recast to conform to current period presentation. Inter-company transactions have been eliminated. Refer to Note 18— Related Party Transactions for a discussion of inter-company transactions. WGL has a variable interest in four investments that qualify as variable interest entities (VIEs). At September 30, 2015 , WGL and its subsidiaries are not the primary beneficiary for any of the VIEs, therefore we have not consolidated any of the VIE entities. Our other investment projects are recorded using the cost method, equity method and as direct financing leases. Refer to Note 17— Other Investments for a discussion of VIEs and other investments.
Use of Estimates	USE OF ESTIMATES IN THE PREPARATION OF FINANCIAL STATEMENTS In accordance with generally accepted accounting principles in the United States of America (GAAP), we make certain estimates and assumptions regarding: (i) reported assets and liabilities; (ii) disclosed contingent assets and liabilities at the date of the financial statements and (iii) reported revenues, revenues subject to refund, and expenses during the reporting period. Actual results could differ from those estimates.
Property, Plant and Equipment	PROPERTY, PLANT AND EQUIPMENT Property, plant and equipment (comprised principally of utility plant) are stated at original cost, including labor, materials, taxes and overhead costs incurred during the construction period. The cost of utility plant of Washington Gas includes an allowance for funds used during construction (AFUDC) that is calculated under a formula prescribed by our regulators in Maryland and the District of Columbia. Washington Gas capitalizes AFUDC as a component of construction overhead. Washington Gas charges maintenance and repairs directly to operating expenses. Washington Gas capitalizes betterments and renewal costs, and calculates depreciation applicable to its utility gas plant in service primarily using a straight-line method over the estimated remaining life of the plant. In accordance with regulatory requirements, such rates include a component related to asset removal costs for Washington Gas. These asset removal costs are accrued through depreciation expense with a corresponding credit to “Regulatory liabilities—Accrued asset removal costs.” When Washington Gas retires depreciable utility plant and equipment, it charges the associated original costs to “Accumulated depreciation and amortization” and any related removal costs incurred are charged to “Regulatory liabilities—Accrued asset removal costs.” Washington Gas periodically reviews the adequacy of its depreciation rates by considering estimated remaining lives and other factors. For information about Asset Retirement Obligations (ARO’s), refer to the section entitled “Asset Retirement Obligations” .
Assets Held For Sale	ASSETS HELD FOR SALE During fiscal year 2015, the Springfield Operations Center met the criteria to be reported as held for sale. Those criteria specify that (i) the asset must be available for immediate sale in its present condition subject only to terms that are usual and customary for sales of such assets and (ii) the sale of the asset must be probable, and its transfer expected to qualify for recognition as a completed sale, within one year, with certain exceptions.
Impairment of Long-Lived Assets	IMPAIRMENT OF LONG-LIVED ASSETS Management regularly reviews property and equipment and other long-lived assets, including certain definite-lived intangible assets and our equity method investments for possible impairment. For our equity and cost method investments, an impairment is recorded when the investment has experienced decline in value that is other-than-temporary. Additionally, if the projects in which we hold an investment recognize an impairment loss, we would record our proportionate share of that impairment loss and evaluate the investment for decline in value that is other-than-temporary. This review occurs quarterly, or more frequently if events or changes in circumstances indicate the carrying amount of the asset may not be recoverable.
Operating Leases	OPERATING LEASES We have classified the lease of our corporate headquarters as an operating lease. We amortize as rent expense the total of all scheduled lease payments (including lease payment escalations) and tenant allowances on a straight-line basis over the term of the lease. For this purpose, the lease term began on the date when the lessor commenced constructing the leasehold improvements which allowed us to occupy our corporate headquarters. Leasehold improvement costs are classified as “Property, Plant and Equipment” on the Balance Sheets, and are being amortized to depreciation and amortization expense on a straight-line basis over the 15 -year non-cancelable period of the lease. Refer to Note 13— Commitments and Contingencies for financial data for all of our operating leases. WGSW is party to two agreements to fund residential and commercial retail solar energy installations with two separate, privately held companies. WGSW has a master purchase agreement and master lease agreement with SunEdison, Inc. (SunEdison) and Nextility, Inc. (Nextility) for sale/leaseback arrangements for residential and commercial solar systems. Our agreements with SunEdison and Nextility are accounted for as direct financing leases. WGSW records associated interest in the financing leases in “Other income (expenses)-net” line in the accompanying Consolidated Statement of Income.
Cash and Cash Equivalents	CASH AND CASH EQUIVALENTS We consider all investments with original maturities of three months or less to be cash equivalents. We did not have any restrictions on our cash balances that would impact the payment of dividends by WGL or our subsidiaries as of September 30, 2015 and 2014 .
Revenue Recognition	Non-Utility Operations Retail Energy-Marketing Segment. WGL Energy Services sells natural gas and electricity on an unregulated basis to residential, commercial and industrial customers both inside and outside the Washington Gas service territory. WGL Energy Services enters into indexed or fixed-rate contracts with residential, commercial and industrial customers for sales of natural gas and electricity. Customer contracts, which typically have terms less than 24 months, but may extend up to five years, allow WGL Energy Services to bill customers based upon metered gas and electricity usage. Usage is measured either on a cycle basis at customer premises or based on quantities delivered to the local utility, both of which may vary by month. The billing cycles for customers do not coincide with the accounting periods used for financial reporting purposes; therefore, WGL Energy Services accrues unbilled revenues for gas and electricity delivered, but not yet billed, at the end of each accounting period. Revenues are reflected in “Operating Revenues—Non utility.” WGL Energy Services procures natural gas and electricity supply under contract structures in which it assembles the various components of supply from multiple suppliers to match its customer requirements. The cost of natural gas and electricity for these purchases is recorded using the contracted volumes and prices in “Non-Utility cost of energy-related sales.” Commercial Energy Systems Segment. WGL Energy Systems recognizes income and expenses for all design-build construction contracts using the percentage-of-completion method in “Operating Revenues—Non-utility” and “Non-Utility cost of energy-related sales.” WGL Energy Systems also recognizes income from its distributed energy assets based on the terms of the related power purchase agreements. Renewable Energy Certificates (RECs) are recorded as inventory by WGL Energy Systems after every 1,000 Kilowatt-hours (kWh) of electricity are produced by an eligible solar facility. WGL Energy Systems recognizes income on the sale of RECs based on the contractual terms and conditions of the sale. Refer to Note 17— Other Investments for discussion of our sale leaseback arrangements and equity method investments. Midstream Energy Services Segment. WGL Midstream nets its revenues and costs related to its trading activities in "Operating Revenues--Non-utility". Other Activities. Washington Gas Resources recognizes income on its investment using the cost approach of investment accounting. Regulated Utility Operations Revenues. For regulated deliveries of natural gas, Washington Gas reads meters and bills customers on a 21 -day monthly cycle basis. The billing cycles for customers do not coincide with the accounting periods used for financial reporting purposes; therefore, Washington Gas accrues unbilled revenues for gas delivered, but not yet billed, at the end of each accounting period. Cost of Gas. Washington Gas’ jurisdictional tariffs contain mechanisms that provide for the recovery of the cost of gas incurred on behalf of firm customers, including related pipeline transportation and storage capacity charges. Under these mechanisms, Washington Gas periodically adjusts its firm customers’ rates to reflect increases and decreases in these costs. Under or over-collections of gas costs in the current cycle are charged or credited to deferred charges or credits on the balance sheet as non-current regulatory assets or liabilities. Amounts deferred at the end of the cycle, August 31 of each year, are fully reconciled and transferred to current assets or liabilities under the balance sheet captions “Gas costs and other regulatory assets” and “Gas costs and other regulatory liabilities.” These balances are recovered or refunded to customers over the subsequent 12 month period. Revenue Taxes. Revenue taxes such as gross receipts taxes, Public Service Commission (PSC) fees, franchise fees and energy taxes are reported gross in operating revenues. Refer to Note 16— Operating Segment Reporting for amounts recorded related to revenue taxes.
Transportation Gas Imbalance	Transportation Gas Imbalance. Interruptible shippers and third party marketer shippers transport gas to Washington Gas’ distribution system as part of the unbundled services offered. The delivered volumes of gas from third party shippers into Washington Gas’ distribution system rarely equal the volumes billed to third party marketer customers, resulting in transportation gas imbalances. These imbalances are usually short-term in duration, and Washington Gas monitors the activity and regularly notifies the shippers when their accounts have an imbalance. In accordance with regulatory treatment, Washington Gas does not record a receivable from or liability to third party marketers associated with gas volumes related to these transportation imbalances but, rather, reflects the financial impact as a regulatory asset or liability related to its gas cost adjustment mechanism, thereby eliminating any profit or loss that would occur as a result of the imbalance. The regulatory treatment combines the imbalance for all marketers, including WGL Energy Services, into a single “net” adjustment to the regulatory asset or liability. Refer to Note 18— Related Party Transactions for further discussion of the accounting for these imbalance transactions.
Asset Optimization Program	Asset Optimization Program. Washington Gas optimizes the value of its long-term natural gas transportation and storage capacity resources by entering into physical and financial transactions in the form of forwards, futures and option contracts for periods when these resources are not being used to physically serve utility customers. Refer to “Derivative Activities” below for further discussion of the accounting for derivative transactions entered into under this program. Regulatory sharing mechanisms in all three jurisdictions allow the profit from these transactions to be shared between Washington Gas’ customers and shareholders. All unrealized fair value gains and losses, and margins generated from the physical and financial settlement of these asset optimization contracts are recorded in utility cost of gas or, in the case of amounts to be shared with rate payers, regulatory assets/liabilities.
Storage Gas Valutation Methods	STORAGE GAS VALUATION METHODS For Washington Gas and WGL Energy Services, storage gas inventories are 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.
Derivatives Activities	WEATHER-RELATED INSTRUMENTS Periodically, we purchase certain weather-related instruments, such as HDD derivatives and CDD derivatives. We account for these weather related instruments in accordance with Financial Accounting Standards Board Accounting Standards Codification (ASC) Subtopic 815-45, Derivatives and Hedging — Weather Derivatives . For weather insurance policies and HDD derivatives, benefits or costs are ultimately recognized to the extent actual HDDs fall above or below the contractual HDDs for each instrument. Benefits or costs are recognized for CDD derivatives when the average temperature exceeds or is below a contractually stated level during the contract period. Premiums for weather-related instruments are amortized based on the pattern of normal temperature days over the coverage period. Weather-related instruments for which we collect a premium are carried at fair value. Washington Gas’ weather related instrument premium expense or benefit is not considered in establishing retail rates. Washington Gas does not purchase such instruments for jurisdictions in which it has received rate mechanisms that compensate it on a normal weather basis. Refer to Note 14— Derivative and Weather-Related Instruments for further discussion of our weather-related instruments. DERIVATIVE ACTIVITIES Regulated Utility . Washington Gas enters into both physical and financial derivative contracts for the purchase and sale of natural gas that are subject to mark-to-market accounting. Changes in the fair value of derivative instruments recoverable or refundable to customers and therefore subject to ASC Topic 980, Regulated Operations , are recorded as regulatory assets or liabilities while changes in the fair value of derivative instruments not affected by rate regulation are reflected in earnings. As part of its asset optimization program, Washington Gas enters into derivative contracts related to the sale and purchase of natural gas at a future price with the primary objective of locking in operating margins that Washington Gas expects to ultimately realize. The derivatives used under this program may cause significant period-to-period volatility in earnings for the portion of net profits retained for shareholders; however, this volatility will not change the margins that Washington Gas expects to realize from these transactions. In accordance with ASC Topic 815, all financially and physically settled contracts under our asset optimization program are reported on a net basis in the statements of income in “Utility cost of gas”. From time to time, Washington Gas also utilizes derivative instruments that are designed to minimize the risk of interest-rate volatility associated with planned issuances of long-term debt. Gains or losses associated with these derivative transactions are deferred as regulatory assets or liabilities and amortized to interest expense in accordance with regulatory accounting requirements. Refer to Note 14— Derivative and Weather-Related Instruments for further discussion of our derivative activities. Non-Utility Operations. WGL Energy Services enters into both physical and financial contracts for the purchase and sale of natural gas and electricity. WGL Energy Services designates a portion of these physical contracts related to the purchase of natural gas and electricity to serve our customers as “normal purchases and normal sales;” therefore, they are not subject to the mark-to-market accounting requirements of ASC Topic 815. WGL Energy Services records these derivatives as revenues or expenses depending on the nature of the economically hedged item. 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. The financial contracts and the portion of the physical contracts that qualify as derivative instruments are subject to the mark-to-market accounting requirements and are recorded on the balance sheet at fair value and are reflected in earnings. WGL Midstream nets financial and physical contracts in "Operating Revenues-Non-utility". WGL may, from time to time, designate interest rate swaps used to manage the interest rate risk associated with future debt issuances, as cash flow hedges. Any gains or losses arising from the effective portion of cash flow hedges are recorded in other comprehensive income and are amortized using the effective interest rate method into earnings over the same period as the hedged interest payments are made. Gains or losses arising from the ineffective portion of cash flow hedges are recognized in earnings immediately. 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 Asset Optimization. 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. WGL Midstream does 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. The storage and transportation capacities utilized by WGL Midstream are not considered to be derivative instruments, and thus they are not recorded at fair value on our consolidated balance sheets. Managing Price Risk . WGL Energy Services enters into certain derivative contracts as part of managing the price risk associated with the sale and purchase of natural gas and electricity. WGL Energy Services designates a portion of these physical contracts related to the purchase of natural gas and electricity to serve our customers as "normal purchases and normal sales" and therefore, they are not subject to the fair value accounting requirements of ASC Topic 815. Derivative instruments not designated as "normal purchases and normal sales" are recorded at fair value on our consolidated balance sheets, and changes in the fair value of these derivative instruments are reflected in the earnings of our non-utility operations, which may cause significant period-to-period volatility in earnings. WGL Energy Services does not designate derivatives as hedges under ASC Topic 815. Managing Interest-Rate Risk . WGL utilizes derivative instruments that are designed to minimize the risk of interest-rate volatility associated with future debt issuances. WGL elected cash flow hedge accounting for its interest rate derivative instruments, which settled with the issuance of the related debt issuance in the first quarter of 2015. The effective portion of the gains and losses on the hedge were recorded within other comprehensive income and are being amortized over the life of the debt (through 2044). The amortization is minimal for fiscal 2015 . 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 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. 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.
Income Taxes	INCOME TAXES We recognize deferred income tax assets and liabilities for all temporary differences between the financial statement basis and the tax basis of assets and liabilities, including those that are currently excluded for ratemaking purposes of Washington Gas. Regulatory assets or liabilities, corresponding to such additional deferred income tax assets or liabilities, may be recorded to the extent recoverable from or payable to customers through the ratemaking process in future periods. Refer to Note 2— Regulated Operations for Washington Gas’ regulatory assets and liabilities associated with income taxes due from and to customers at September 30, 2015 and 2014 . Amounts applicable to income taxes due from and due to customers primarily represent differences between the book and tax basis of net utility plant in service. We amortize investment tax credits as reductions to income tax expense over the estimated service lives of the related properties. Refer to Note 9— Income Taxes which provides detailed financial information related to our income taxes.
Share-based Compensation	STOCK-BASED COMPENSATION We account for stock-based compensation expense in accordance with ASC Topic 718, Compensation—Stock Compensation, which requires us to measure and recognize stock-based compensation expense in our financial statements based on the fair value at the date of grant for our equity-classified share-based awards, which include performance shares granted to certain employees and shares issued to directors. For liability-classified share-based awards, which include performance units, we recognize stock-based compensation expense based on their fair value at the end of each reporting period. For both equity-classified and liability-classified share-based awards, we estimate forfeitures over the requisite service period when recognizing compensation expense; these estimates are periodically adjusted to the extent to which actual forfeitures differ from such estimates. Refer to Note 11— Stock-Based Compensation for further discussion of the accounting for our stock-based compensation plans.
Asset Retirement Obligations	ASSET RETIREMENT OBLIGATIONS Washington Gas accounts for its AROs in accordance with ASC Subtopic 410-20, Asset Retirement and Environmental Obligations—Asset Retirement Obligations. Our asset retirement obligations include the costs to cut, purge and cap Washington Gas' distribution and transmission system and plug storage wells upon their retirement. We also have asset retirement obligations associated with our distributed generation assets. These standards require recording the estimated retirement cost over the life of the related asset by depreciating the present value of the retirement obligation, measured at the time of the asset’s acquisition, and accreting the liability until it is settled. There are timing differences between the ARO-related accretion and depreciation amounts being recorded pursuant to GAAP and the recognition of depreciation expense for legal asset removal costs that we are currently recovering in rates. These timing differences are recorded as a reduction to “Regulatory liabilities—Accrued asset removal costs” in accordance with ASC Topic 980. We do not have any assets that are legally restricted related to the settlement of asset retirement obligations.
New Accounting Pronouncements	ACCOUNTING STANDARDS ADOPTED IN FISCAL YEAR 2015 Standard Description Date of adoption Effect on the financial statements or other significant matters 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 (Topic 740) The standard requires an unrecognized tax benefit, or a portion of an unrecognized tax benefit to be presented in the financial statements as a reduction to a deferred tax asset for a net operating loss carryforward, a similar loss, or a tax credit carryforward. October 1, 2014 As a result of the implementation of this standard, we reduced our deferred tax assets by a portion of our unrecognized tax benefits. ASU 2015-13, Derivatives and Hedging (Topic 815)- Application of the Normal Purchases and Normal Sales Scope Exception to Certain Electricity Contracts within Nodal Energy Markets (a consensus of the FASB Emerging Issues Task Force) The standard requires that a forward purchase or sale of electricity in which electricity must be physically delivered through a nodal energy market operated by an independent system operator, and in which an entity incurs transmission costs on the basis of locational marginal pricing charges, would meet the physical delivery requirement under the NPNS scope exception. August 10, 2015 The adoption of this standard did not have a material effect on our financial statements. OTHER NEWLY ISSUED ACCOUNTING STANDARDS Standard Description Date of adoption Effect on the financial statements or other significant matters ASU 2015-03, Interest - Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Cost The standard requires an entity to present debt issuance costs in the balance sheet as a direct deduction of the debt liability in a manner consistent with its accounting treatment of debt discounts. The standard permits prospective or retrospective application. WGL will apply the standard retrospectively. October 1, 2016 We are in the process of evaluating the impact the adoption of this standard will have on our financial statements. ASU 2015-02, Consolidation (Topic 810): Amendments to the Consolidation Analysis The standard changes the analysis to be performed in determining whether certain types of legal entities should be consolidated, specifically the analysis of limited partnerships and similar entities, fee arrangements and related party relationships. The standard permits prospective or retrospective application for different parts. October 1, 2016 We are in the process of evaluating the impact the adoption of this standard will have on our financial statements. ASU 2014-09, Revenue from Contracts with Customers (Topic 606) The standard establishes a comprehensive revenue recognition model clarifying the method used to determine the timing and requirements for revenue recognition from contracts with customers. The disclosure requirements under the new standard will enable users of financial statements to understand the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. The standard permits retrospective application. October 1, 2019 We are in the process of evaluating the impact the adoption of this standard will have on our financial statements.
Fair Value Measurement	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 derivatives recorded on our balance sheet under ASC Topic 815 and short-term investments, commercial paper and long-term debt outstanding required to be disclosed at fair value. Under ASC Topic 820, fair value is defined as the exit price, representing the amount that would be received in the sale of an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. To value our financial instruments, we use market data or assumptions that market participants would use, including assumptions about credit risk (both our own credit risk and the counterparty’s credit risk) and the risks inherent in the inputs to valuation. 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. 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 September 30, 2015 and 2014 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. Neither WGL’s nor Washington Gas’ long-term debt is 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 the credit quality of the debt issuer, WGL or Washington Gas. Our long-term debt fair value measurement is classified as Level 3. Non Recurring Basis During the fiscal year ended September 30, 2015 , Washington Gas Resources recorded an impairment charge of its investment in ASDHI to its fair value using the income approach. The amount of the impairment was equivalent to the amount of the carrying value of $5.6 million and was due to management’s assumption of the current valuation and expected return from the investment. The fair value of this investment was a Level 3 measurement.
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. During the first quarter of 2015, our chief operating decision maker began evaluating segment performance based on Earnings Before Interest and Taxes (EBIT). EBIT is defined as earnings before interest and taxes from continuing operations. Items we do not include in EBIT are interest expense, intercompany financing activity, dividends on Washington Gas preferred stock, and income taxes. EBIT includes transactions between reportable segments. We also evaluate our operating segments based on other relevant factors, such as penetration into their respective markets and return on equity.
Investments	When determining how to account for our interests in other legal entities, WGL first evaluates if we are required to apply the variable interest entity (VIE) model to the entity, otherwise the entity is evaluated under the voting interest model. Under the VIE model, we have a controlling financial interest in a VIE (i.e. are the primary beneficiary) when we have current or potential rights that give us the power to direct the activities of a VIE that most significantly impact the VIE’s economic performance combined with a variable interest that gives us the right to receive potentially significant benefits or the obligation to absorb potentially significant losses. When changes occur to the design of an entity we reconsider whether it is subject to the VIE model. We continuously evaluate whether we have a controlling financial interest in a VIE. Under the voting interest model, we generally have a controlling financial interest in an entity where we currently hold, directly or indirectly, more than 50% of the voting rights or where we exercise control through substantive participating rights. However, we consider substantive rights held by other partners in determining if we hold a controlling financial interest, and in some cases, despite owning more than 50% of the common stock of an investee, an evaluation of our rights results in the determination that we do not have a controlling financial interest. We reevaluate whether we have a controlling financial interest in these entities when our voting or substantive participating rights change. Unconsolidated affiliates are unconsolidated VIEs and other entities evaluated under the voting interest method in which we do not have a controlling financial interest, but over which we have varying degrees of influence. Where we have significant influence, the affiliates are accounted for as equity method investments. Where we do not have significant influence, the affiliates are accounted for under the cost method. Investments in, and advances to, affiliated companies are presented on a one-line basis in the caption “Investments in unconsolidated affiliates” on our Consolidated Balance Sheet. WGL uses the Hypothetical Liquidation at Book Value (HLBV) methodology for certain equity method investments when the capital structure of the equity investment results in different liquidation rights and priorities than what is reflected by the underlying percentage ownership interests as defined by an equity investment agreement. For investments accounted for under the HLBV method, simply applying the percentage ownership interest to GAAP net income in order to determine earnings or losses does not accurately represent the income allocation and cash flow distributions that will ultimately be received by the investors. The equity investment agreements for ASD Solar, LP (ASD), Meade Pipeline Co LLC (Meade) and Mountain Valley Pipeline, LLC (Mountain Valley) have liquidation rights and priorities that are sufficiently different from the ownership percentages that the HLBV method was deemed appropriate. The calculation may vary in its complexity depending on the capital structure and the tax considerations for the investments. WGL applies HLBV using a balance sheet approach. When applying HLBV, WGL determines the amount that it would receive if an equity investment entity were to liquidate all of its assets at book value (as valued in accordance with GAAP) and distribute that cash to the investors based on the contractually defined liquidation priorities. The change in WGL's claim on the investee's book value at the beginning and end of the reporting period (adjusted for contributions and distributions) is WGL’s share of the earnings or losses from the equity investment for the period. Our investment in ASD is accounted for under the HLBV equity method of accounting; any profits and losses are included in “Equity in earnings of unconsolidated affiliates” in the accompanying Consolidated Statement of Income and are added to or subtracted from the carrying amount of WGSW’s investment balance. Meade is accounted for under the HLBV equity method of accounting, and any profits and losses are included in “Equity in earnings of unconsolidated affiliates” in the accompanying Consolidated Statement of Income and are added to or subtracted from the carrying amount of WGL’s investment balance. Constitution is accounted for under the equity method of accounting; any profits and losses are included in “Equity in earnings of unconsolidated affiliates” 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.

Accounting Policies (Tables)

Accounting Policies (Tables)	12 Months Ended
	Sep. 30, 2015
Accounting Policies [Line Items]
Public Utility Property, Plant, and Equipment	At September 30, 2015 and 2014 , 91.2% and 93.6% , respectively, of WGL’s consolidated original cost of property, plant and equipment was related to the regulated utility segment as shown below. Property, Plant and Equipment at Original Cost ($ In millions) September 30, 2015 2014 Regulated utility segment Distribution, transmission and storage $ 3,927.2 78.5 % $ 3,635.3 79.3 % General, miscellaneous and intangibles 424.8 8.5 448.3 9.8 Construction work in progress (CWIP) 210.4 4.2 203.9 4.5 Total regulated utility segment 4,562.4 91.2 4,287.5 93.6 Unregulated segments 441.5 8.8 295.3 6.4 Total $ 5,003.9 100.0 % $ 4,582.8 100.0 %
Storage gas inventory adjustments	The following table shows the lower-of-cost or market adjustments recorded to net income for the years ended September 30, 2015 , 2014 and 2013 . Lower-of-Cost or Market Adjustments Pre-Tax Increase (Decrease) to Net Income (In millions) September 30, 2015 2014 2013 WGL (a) Operating revenues - non-utility $ (21.5 ) $ (3.0 ) $ (10.1 ) Washington Gas Utility cost of gas $ (1.3 ) $ (0.2 ) $ — Total Consolidated $ (22.8 ) $ (3.2 ) $ (10.1 ) (a) WGL includes WGL Holdings and all subsidiaries other than Washington Gas.
Schedule of Change in Asset Retirement Obligation	WGL Holdings, Inc. Changes in Asset Retirement Obligations (In millions) September 30, 2015 2014 Asset retirement obligations at beginning of year $ 181.2 $ 104.0 Liabilities incurred in the period 8.4 4.9 Liabilities settled in the period (a) (14.6 ) (5.2 ) Accretion expense 7.8 4.4 Revisions in estimated cash flows (b) 24.9 73.1 Asset retirement obligations at the end of the year (c) $ 207.7 $ 181.2
Schedule of New Accounting Pronouncements and Changes in Accounting Principles	ACCOUNTING STANDARDS ADOPTED IN FISCAL YEAR 2015 Standard Description Date of adoption Effect on the financial statements or other significant matters 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 (Topic 740) The standard requires an unrecognized tax benefit, or a portion of an unrecognized tax benefit to be presented in the financial statements as a reduction to a deferred tax asset for a net operating loss carryforward, a similar loss, or a tax credit carryforward. October 1, 2014 As a result of the implementation of this standard, we reduced our deferred tax assets by a portion of our unrecognized tax benefits. ASU 2015-13, Derivatives and Hedging (Topic 815)- Application of the Normal Purchases and Normal Sales Scope Exception to Certain Electricity Contracts within Nodal Energy Markets (a consensus of the FASB Emerging Issues Task Force) The standard requires that a forward purchase or sale of electricity in which electricity must be physically delivered through a nodal energy market operated by an independent system operator, and in which an entity incurs transmission costs on the basis of locational marginal pricing charges, would meet the physical delivery requirement under the NPNS scope exception. August 10, 2015 The adoption of this standard did not have a material effect on our financial statements.
Schedule Of New Accounting Pronouncements Not Yet Adopted	OTHER NEWLY ISSUED ACCOUNTING STANDARDS Standard Description Date of adoption Effect on the financial statements or other significant matters ASU 2015-03, Interest - Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Cost The standard requires an entity to present debt issuance costs in the balance sheet as a direct deduction of the debt liability in a manner consistent with its accounting treatment of debt discounts. The standard permits prospective or retrospective application. WGL will apply the standard retrospectively. October 1, 2016 We are in the process of evaluating the impact the adoption of this standard will have on our financial statements. ASU 2015-02, Consolidation (Topic 810): Amendments to the Consolidation Analysis The standard changes the analysis to be performed in determining whether certain types of legal entities should be consolidated, specifically the analysis of limited partnerships and similar entities, fee arrangements and related party relationships. The standard permits prospective or retrospective application for different parts. October 1, 2016 We are in the process of evaluating the impact the adoption of this standard will have on our financial statements. ASU 2014-09, Revenue from Contracts with Customers (Topic 606) The standard establishes a comprehensive revenue recognition model clarifying the method used to determine the timing and requirements for revenue recognition from contracts with customers. The disclosure requirements under the new standard will enable users of financial statements to understand the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. The standard permits retrospective application. October 1, 2019 We are in the process of evaluating the impact the adoption of this standard will have on our financial statements.
Washington Gas Light Company
Accounting Policies [Line Items]
Schedule of Change in Asset Retirement Obligation	Washington Gas Light Company Changes in Asset Retirement Obligations (In millions) September 30, 2015 2014 Asset retirement obligations at beginning of year $ 179.8 $ 102.7 Liabilities incurred in the period 8.1 4.9 Liabilities settled in the period (a) (14.6 ) (5.2 ) Accretion expense 7.7 4.3 Revisions in estimated cash flows (b) 24.9 73.1 Asset retirement obligations at the end of the year (c) $ 205.9 $ 179.8 (a) Includes asset retirement obligations of $1.6 million related to the Springfield Operations Center that were reclassified to "Current Liabilities - Liabilities held for sale". (b) WGL revised its assumptions regarding the timing and amounts related to its obligation to cut, cap and purge pipeline. The revision is primarily driven by our accelerated pipeline replacement programs. (c) Includes short-term asset retirement obligations of $7.0 million and $6.0 million for fiscal year 2015 and 2014 , respectively.

Regulated Operations (Tables)

Regulated Operations (Tables)	12 Months Ended
	Sep. 30, 2015
Regulated Operations [Abstract]
Schedule of Regulatory Assets and Liabilities	Regulatory Assets and Liabilities (In millions) Regulatory Assets Regulatory Liabilities September 30, 2015 2014 2015 2014 Current: Gas costs due from/to customers (a) $ 1.7 $ — $ 22.6 $ 16.2 Interruptible sharing (a) 3.3 3.4 2.6 — Revenue normalization mechanisms for Maryland and Virginia (a) — — 8.4 5.5 Plant recovery mechanisms 0.8 0.4 1.0 0.9 Total current $ 5.8 $ 3.8 $ 34.6 $ 22.6 Deferred: Accrued asset removal costs $ — $ — $ 325.5 $ 327.4 Deferred gas costs (a) 190.7 191.3 — — Pension and other post-retirement benefits Other post-retirement benefit costs—trackers (b) 0.1 — — — Deferred pension costs—trackers (b) 38.0 45.1 — — ASC Topic 715 unrecognized costs/income (a)(c) Pensions 173.9 147.9 — — Other post-retirement benefits — — 104.4 86.4 Total pension and other post-retirement benefits 212.0 193.0 104.4 86.4 Other Income tax-related amounts due from/to customers (d) 31.7 30.4 4.2 4.8 Losses/gains on issuance and extinguishments of debt and interest-rate derivative instruments (a)(e) 11.1 12.0 1.6 1.7 Deferred gain on sale of assets (a) — — 1.4 1.4 Rights-of-way fees (a) 1.6 1.5 — — Business process outsourcing and related costs (a) 2.7 1.0 — — Nonretirement postemployment benefits (a)(f) 18.9 16.3 — — Deferred integrity management expenditures (a)(g) 5.1 2.7 — — Recoverable portion of abandoned LNG facility (a) 5.0 5.6 — — Environmental response costs (a,h) 1.8 0.6 — — Other regulatory expenses (a) 2.1 1.5 9.9 9.7 Total other $ 80.0 $ 71.6 $ 17.1 $ 17.6 Total deferred $ 482.7 $ 455.9 $ 447.0 $ 431.4 Total $ 488.5 $ 459.7 $ 481.6 $ 454.0 (a) Washington Gas does not earn its overall rate of return on these assets. Washington Gas is allowed to recover and required to pay, using short-term interest rates, the carrying costs related to billed gas costs due from and to its customers in the District of Columbia and Virginia jurisdictions. (b) Relates to the District of Columbia jurisdiction. (c) Refer to Note 10-Pension and Other Post-Retirement Benefit Plans for a further discussion of these amounts. (d) This balance represents amounts due from customers for deferred tax liabilities related to tax benefits on deduction flowed directly to customers prior to the adoption of income tax normalization for ratemaking purposes. (e) The losses or gains on the issuance and extinguishment of debt and interest-rate derivative instruments include unamortized balances from transactions executed in prior fiscal years. These transactions create gains and losses that are amortized over the remaining life of the debt as prescribed by regulatory accounting requirements. (f) Represents the timing difference between the recognition of workers compensation and short-term disability costs in accordance with generally accepted accounting principles and the way these costs are recovered through rates. (g) This balance represents amounts for deferred expenditures associated with Washington Gas’ Distribution Integrity Management Program (DIMP) in Virginia. (h) This balance represents allowed remediation expenditures at Washington Gas sites to be recovered through rates for Maryland and the District of Columbia. The recovery period is over several years.

Accounts Payable and Other Ac34

Accounts Payable and Other Accrued Liabilities (Tables)	12 Months Ended
	Sep. 30, 2015
Accounts Payable and Accrued Liabilities [Line Items]
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. September 30, (In millions) 2015 2014 Accounts payable—trade $ 277.3 $ 278.8 Employee benefits and payroll accruals 31.4 19.8 Other accrued liabilities 16.4 14.6 Total $ 325.1 $ 313.2
Washington Gas Light Company
Accounts Payable and Accrued Liabilities [Line Items]
Accounts Payable and Other Accrued Liabilities	Washington Gas Light Company September 30, (In millions) 2015 2014 Accounts payable—trade $ 122.2 $ 146.4 Employee benefits and payroll accruals 29.5 18.2 Other accrued liabilities 7.6 11.9 Total $ 159.3 $ 176.5

Short-Term Debt (Tables)

Short-Term Debt (Tables)	12 Months Ended
	Sep. 30, 2015
Short-term Debt [Abstract]
Commited Credit Available	The following is a summary of committed credit available at September 30, 2015 and 2014 . Committed Credit Available (In millions) September 30, 2015 WGL (b) Washington Gas Total Consolidated Committed credit agreements Unsecured revolving credit facility, expires December 19, 2019 (a) $ 450.0 $ 350.0 $ 800.0 Less: Commercial Paper (243.0 ) (89.0 ) (332.0 ) Net committed credit available $ 207.0 $ 261.0 $ 468.0 Weighted average interest rate 0.30 % 0.16 % 0.26 % September 30, 2014 Committed credit agreements Unsecured revolving credit facility, expires April 3, 2017 (a) $ 450.0 $ 350.0 $ 800.0 Less: Commercial Paper (364.5 ) (89.0 ) (453.5 ) Net committed credit available $ 85.5 $ 261.0 $ 346.5 Weighted average interest rate 0.20 % 0.13 % 0.19 % (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 includes all subsidiaries other than Washington Gas.

Long Term Debt (Tables)

Long Term Debt (Tables)	12 Months Ended
	Sep. 30, 2015
Debt Disclosure [Abstract]
Senior Notes, MTN And Private Placement Notes Outstanding	The following tables show the outstanding notes as of September 30, 2015 and 2014 . Senior Notes, MTNs and Private Placement Notes Outstanding ($ In millions) WGL (a) Washington Gas Total Consolidated September 30, 2015 Long-term notes (b) $ 250.0 $ 721.0 $ 971.0 Weighted average interest rate 3.66 % 5.58 % 5.08 % September 30, 2014 Long-term notes (b) $ — $ 691.0 $ 691.0 Weighted average interest rate n/a 5.65 % 5.65 % (a) WGL includes WGL Holdings and all subsidiaries other than Washington Gas. (b) Includes Senior Notes for WGL and both MTNs and private placement notes for Washington Gas. Represents face value including current maturities.
Senior Notes, MTN and Private Placement Issuances and Retirements	The following tables show senior notes, MTN and private placement issuances and retirements for the years ended September 30, 2015 and 2014 . Senior Notes, MTNs and Private Placement Issuances and Retirements ($ In millions) Principal (b) Interest Rate Effective Cost (c) Nominal Maturity Date Year Ended September 30, 2015 WGL (a) Issuances: 10/24/2014 $ 100.0 2.25 % 2.42 % 11/1/2019 10/24/2014 125.0 4.60 % 5.11 % 11/1/2044 12/16/2014 25.0 4.60 % 5.53 % 11/1/2044 Total $ 250.0 Washington Gas Issuances: 12/15/2014 $ 50.0 4.24 % 4.41 % 12/15/2044 Total 50.0 Total consolidated issuances $ 300.0 Washington Gas Retirements: 8/9/2015 $ 20.0 4.83 % 8/9/2015 Total $ 20.0 Year Ended September 30, 2014 Washington Gas Issuances: 12/5/2013 $ 75.0 5.00 % 4.95 % 12/15/2043 9/12/2014 100.0 4.22 % 4.27 % 9/15/2044 Total $ 175.0 Retirements: 11/7/2013 $ 37.0 4.88 % 11/7/2013 9/10/2014 30.0 5.17 % 9/10/2014 Total $ 67.0 (a) WGL includes WGL Holdings and all subsidiaries other than Washington Gas. (b) Represents face amount. (c) The estimated effective cost of the issued notes, including consideration of issuance fees and hedge costs.
Long Term Debt Maturities	Maturities of long-term debt for each of the next five fiscal years and thereafter as of September 30, 2015 are summarized in the following table. Long-Term Debt Maturities (a) (In millions) WGL (b) Washington Gas Total 2016 $ — $ 25.0 $ 25.0 2017 — — — 2018 — — — 2019 — 50.0 50.0 2020 100.0 50.0 150.0 Thereafter 150.0 596.0 746.0 Total $ 250.0 $ 721.0 $ 971.0 Less: current maturities — 25.0 25.0 Total non-current $ 250.0 $ 696.0 $ 946.0 (a) Excludes unamortized discounts of $ 1.7 million and $0.1 million at September 30, 2015 , for WGL and Washington Gas, respectively. (b) WGL includes WGL Holdings and all subsidiaries other than Washington Gas.

Common Stock (Tables)

Common Stock (Tables)	12 Months Ended
	Sep. 30, 2015
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Common Stock Reserves	At September 30, 2015 , there were 4,561,588 authorized, but unissued, shares of common stock reserved under the following plans: Common Stock Reserves Number of Shares Reserve for: Omnibus incentive compensation plan (a) 993,825 Dividend reinvestment and common stock purchase plan 2,849,012 Employee savings plans 637,196 Directors’ stock compensation plan 81,555 Total common stock reserves 4,561,588 (a) In March 2007, WGL adopted a shareholder-approved Omnibus Incentive Compensation Plan to replace on a prospective basis the 1999 Incentive Compensation Plan. Included are shares that may be issued upon the vesting of 304,089 performance shares that have been granted but not yet vested. Upon vesting, a number of shares equal to up to 200% of the number of performance shares granted may be issued, which would reduce the number of shares available for issuance under the Omnibus Incentive Compensation Plan. Refer to Note 11—Stock-Based Compensation for a discussion regarding our stock-based compensation plans.

Preferred Stock (Tables)

Preferred Stock (Tables)	12 Months Ended
	Sep. 30, 2015
Preferred Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Preferred Stock Table	The following table presents this information, as well as call prices for each preferred stock series outstanding. Preferred Stock Preferred Liquidation Preference Series Shares Per Share Call Price Outstanding Outstanding Involuntary Voluntary Per Share $4.80 150,000 $100 $101 $101 $4.25 70,600 $100 $105 $105 $5.00 60,000 $100 $102 $102

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Sep. 30, 2015
Earnings Per Share [Abstract]
Earnings per Share	The following table reflects the computation of our basic and diluted EPS for the fiscal years ended September 30, 2015 , 2014 and 2013 . Basic and Diluted EPS Years Ended September 30, (In thousands, except per share data) 2015 2014 2013 Basic earnings per average common share: Net income applicable to common stock $ 131,259 $ 105,940 $ 80,253 Average common shares outstanding—basic 49,794 51,759 51,697 Basic earnings per average common share $ 2.64 $ 2.05 $ 1.55 Diluted earnings per average common share: Net income applicable to common stock $ 131,259 $ 105,940 $ 80,253 Average common shares outstanding—basic 49,794 51,759 51,697 Stock-based compensation plans 266 11 111 Total average common shares outstanding—diluted 50,060 51,770 51,808 Diluted earnings per average common share $ 2.62 $ 2.05 $ 1.55

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Sep. 30, 2015
Income Taxes [Line Items]
Components of Income Tax Expense	The tables below provide the following for WGL and Washington Gas: (i) the components of income tax expense; (ii) a reconciliation between the statutory federal income tax rate and the effective income tax rate and (iii) the components of accumulated deferred income tax assets and liabilities at September 30, 2015 and 2014 . WGL Holdings, Inc. Components of Income Tax Expense Years Ended September 30, (In thousands) 2015 2014 2013 INCOME TAX EXPENSE Current: Federal $ (18,639 ) $ 29,976 $ 41,425 State 2,977 5,149 11,258 Total current (15,662 ) 35,125 52,683 Deferred: Federal Accelerated depreciation 71,529 35,747 33,394 Other 17,726 (18,014 ) (31,173 ) State Accelerated depreciation 13,739 9,822 6,795 Other 1,411 (1,760 ) (7,585 ) Total deferred 104,405 25,795 1,431 Amortization of investment tax credits (4,939 ) (3,666 ) (1,822 ) Total income tax expense $ 83,804 $ 57,254 $ 52,292
Reconciliation Between the Statutory Federal Income Tax Rate and Effective Tax Rate	WGL Holdings, Inc. Reconciliation Between the Statutory Federal Income Tax Rate and Effective Tax Rate Years Ended September 30, ($ In thousands) 2015 2014 2013 Income taxes at statutory federal income tax rate $ 75,760 35.00 % $ 57,580 35.00 % $ 46,853 35.00 % Increase (decrease) in income taxes resulting from: Accelerated depreciation less amount deferred 1,187 0.55 1,875 1.14 2,106 1.57 Amortization of investment tax credits (4,939 ) (2.28 ) (3,666 ) (2.23 ) (1,822 ) (1.36 ) Cost of removal (2,721 ) (1.26 ) (4,902 ) (2.98 ) (2,356 ) (1.76 ) State income taxes-net of federal benefit 11,109 5.13 8,734 5.31 7,448 5.56 Medicare Part D adjustment — — (3,621 ) (2.20 ) — — ASDHI impairment 1,969 0.91 — — — — Other items-net 1,439 0.66 1,254 0.76 63 0.05 Total income tax expense and effective tax rate $ 83,804 38.71 % $ 57,254 34.80 % $ 52,292 39.06 %
Components of Deferred Income Tax Assets (Liabilities)	WGL Holdings, Inc. Components of Deferred Income Tax Assets (Liabilities) September 30, (In thousands) 2015 2014 ACCUMULATED DEFERRED INCOME TAXES Current Non-current Current Non-current Deferred income tax assets: Pensions $ — $ 44,468 $ — $ 24,349 Uncollectible accounts 10,389 — 9,268 — Inventory overheads 5,873 — 6,591 — Employee compensation and benefits 4,733 52,497 6,306 37,873 Derivatives 8,580 35,311 6,503 31,555 Deferred gas costs 2,406 — — 4,218 Solar grant/investment tax credit — 53,067 — 39,184 Tax credit carry forward — 55,040 — — Other 861 4,779 814 1,422 Total assets 32,842 245,162 29,482 138,601 Deferred income tax liabilities: Other post-retirement benefits — 54,860 — 38,299 Accelerated depreciation and other plant related items — 794,099 — 669,040 Losses/gains on reacquired debt — 1,292 — 1,426 Income taxes recoverable through future rates — 68,245 — 65,374 Deferred gas costs — 815 2,818 — Partnership basis differences — 29,468 — 25,370 Valuation allowances — 2,188 — — Total liabilities — 950,967 2,818 799,509 Net accumulated deferred income tax assets (liabilities) $ 32,842 $ (705,805 ) $ 26,664 $ (660,908 )
Unrecognized Tax Benefits	The following table summarizes the change in unrecognized tax benefits during fiscal year 2015 , 2014 , 2013 and our total unrecognized tax benefits at September 30, under the provisions of ASC Topic 740, Income Taxes: Unrecognized Tax Benefits (In thousands) 2015 2014 2013 Total unrecognized tax benefits, October 1, $ 32,613 $ 25,051 $ 22,082 Increases in tax positions relating to current year 12,848 10,512 5,251 Decreases in tax positions relating to prior year (6,834 ) (2,950 ) (2,282 ) Total unrecognized tax benefits, September 30, $ 38,627 $ 32,613 $ 25,051
Washington Gas Light Company
Income Taxes [Line Items]
Components of Income Tax Expense	Washington Gas Light Company Components of Income Tax Expense Years Ended September 30, (In thousands) 2015 2014 2013 INCOME TAX EXPENSE Current: Federal $ (5,305 ) $ 37,098 $ 40,492 State 907 4,262 7,515 Total current (4,398 ) 41,360 48,007 Deferred: Federal Accelerated depreciation 71,046 34,833 34,518 Other (6,619 ) (30,523 ) (35,982 ) State Accelerated depreciation 13,701 9,540 6,770 Other (1,507 ) (6,800 ) (8,221 ) Total deferred 76,621 7,050 (2,915 ) Amortization of investment tax credits (832 ) (876 ) (895 ) Total income tax expense $ 71,391 $ 47,534 $ 44,197
Reconciliation Between the Statutory Federal Income Tax Rate and Effective Tax Rate	Washington Gas Light Company Reconciliation Between the Statutory Federal Income Tax Rate and Effective Tax Rate Years Ended September 30, ($ In thousands) 2015 2014 2013 Income taxes at statutory federal income tax rate $ 63,024 35.00 % $ 51,050 35.00 % $ 40,782 35.00 % Increase (decrease) in income taxes resulting from: Accelerated depreciation less amount deferred 2,108 1.17 1,875 1.29 2,106 1.81 Amortization of investment tax credits (832 ) (0.46 ) (876 ) (0.60 ) (895 ) (0.77 ) Cost of removal (2,721 ) (1.51 ) (4,902 ) (3.36 ) (2,356 ) (2.02 ) State income taxes-net of federal benefit 8,986 4.99 6,711 4.60 5,487 4.71 Consolidated tax sharing allocation (533 ) (0.30 ) (2,862 ) (1.96 ) (1,290 ) (1.11 ) Medicare Part D adjustment — — (3,621 ) (2.48 ) — — Other items-net 1,359 0.76 159 0.09 363 0.31 Total income tax expense and effective tax rate $ 71,391 39.65 % $ 47,534 32.58 % $ 44,197 37.93 %
Components of Deferred Income Tax Assets (Liabilities)	Washington Gas Light Company Components of Deferred Income Tax Assets (Liabilities) Years Ended September 30, (In thousands) 2015 2014 ACCUMULATED DEFERRED INCOME TAXES Current Non-current Current Non-current Deferred income tax assets: Pensions $ — $ 43,748 $ — $ 23,738 Uncollectible accounts 7,637 — 7,618 — Inventory overheads 5,873 — 6,591 — Employee compensation and benefits 4,346 34,511 5,902 27,961 Derivatives 3,576 35,311 4,809 31,555 Deferred gas costs 2,406 — — 4,218 Investment tax credit — — — 312 Other 862 — 814 197 Total assets 24,700 113,570 25,734 87,981 Deferred income tax liabilities: Other post-retirement benefits — 54,566 — 38,065 Accelerated depreciation and other plant related items — 681,108 — 602,376 Losses/gains on reacquired debt — 1,292 — 1,426 Income taxes recoverable through future rates — 67,953 — 65,128 Deferred gas costs — 815 2,818 — Other — 1,300 — 932 Total liabilities — 807,034 2,818 707,927 Net accumulated deferred income tax assets (liabilities) $ 24,700 $ (693,464 ) $ 22,916 $ (619,946 )

Pension and Other Post-Retire41

Pension and Other Post-Retirement Benefit Plans (Tables)	12 Months Ended
	Sep. 30, 2015
Defined Benefit Plan Disclosure [Line Items]
Post Retirement Benefits	The following table provides certain information about Washington Gas’ post-retirement benefits: Post-Retirement Benefits Health and Life (In millions) Pension Benefits (a) Benefits Year Ended September 30, 2015 2014 2015 2014 Change in projected benefit obligation (b) Benefit obligation at beginning of year $ 917.1 $ 837.4 $ 343.2 $ 429.8 Service cost 15.5 14.0 7.1 7.6 Interest cost 39.1 40.4 14.7 18.7 Change in plan benefits 0.6 — (26.1 ) (136.5 ) Actuarial loss (gain) 19.2 68.6 (23.7 ) 38.2 Retiree contributions — — 2.0 4.4 Employer group waiver plan rebates — — 2.4 0.5 Benefits paid (44.0 ) (43.3 ) (19.7 ) (19.5 ) Projected benefit obligation at end of year (b) $ 947.5 $ 917.1 $ 299.9 $ 343.2 Change in plan assets Fair value of plan assets at beginning of year $ 804.7 $ 745.2 $ 439.6 $ 380.9 Actual return on plan assets 19.9 103.3 (0.3 ) 57.8 Company contributions 1.8 1.7 16.0 16.0 Retiree contributions and employer group waiver plan rebates — — 3.6 4.4 Expenses (2.2 ) (2.2 ) (0.7 ) — Benefits paid (44.0 ) (43.3 ) (19.7 ) (19.5 ) Fair value of plan assets at end of year $ 780.2 $ 804.7 $ 438.5 $ 439.6 Funded status at end of year $ (167.3 ) $ (112.4 ) $ 138.6 $ 96.4 Total amounts recognized on balance sheet Non-current asset $ — $ — $ 138.6 $ 96.4 Current liability (4.8 ) (4.2 ) — — Non-current liability (162.5 ) (108.2 ) — — Total recognized $ (167.3 ) $ (112.4 ) $ 138.6 $ 96.4 (a) The DB SERP and DB Restoration, included in pension benefits in the table above, have no assets. (b) For the Health and Life Benefits, the change in projected benefit obligation represents the accumulated benefit obligation.
Projected and accumulated benefit obligation	The following table provides the projected benefit obligation (PBO) and accumulated benefit (ABO) for the qualified pension plan, DB SERP and DB Restoration at September 30, 2015 and 2014 . Projected and accumulated benefit obligation (In millions) Qualified Pension Plan DB SERP DB Restoration September 30, 2015 2014 2015 2014 2015 2014 Projected benefit obligation $ 892.2 $ 865.2 $ 53.0 $ 50.7 $ 2.3 $ 1.2 Accumulated benefit obligation $ 822.8 $ 801.9 $ 48.7 $ 46.2 $ 1.2 $ 0.7
Unrecognized Costs Income Recorded On Balance Sheet	The following table provides amounts recorded to regulatory assets, regulatory liabilities and accumulated other comprehensive loss/(income) at September 30, 2015 and 2014 : Unrecognized Costs/Income Recorded on the Balance Sheet (In millions) Pension Benefits Health and Life Benefits September 30, 2015 2014 2015 2014 Actuarial net loss $ 190.1 $ 162.6 $ 43.8 $ 50.1 Prior service cost (credit) 1.5 1.2 (160.2 ) (149.3 ) Total $ 191.6 $ 163.8 $ (116.4 ) $ (99.2 ) Regulatory asset (liability) (a) $ 173.9 $ 147.9 $ (110.5 ) $ (94.6 ) Pre-tax accumulated other comprehensive loss (gain) (b) 17.7 15.9 (5.9 ) (4.6 ) Total $ 191.6 $ 163.8 $ (116.4 ) $ (99.2 ) (a) The regulatory liability recorded on our balance sheets at September 30, 2015 and 2014 is net of a deferred income tax benefit of $ 6.1 million and $8.2 million , respectively. (b) The total amount of accumulated other comprehensive loss recorded on our balance sheets at September 30, 2015 and 2014 is net of an income tax benefit of $5.1 million and $4.9 million , respectively.
Amount Recognized During Current Year	The following table provides amounts that are included in regulatory assets/liabilities and accumulated other comprehensive loss associated with our unrecognized pension and other post-retirement benefit costs that were recognized as components of net periodic benefit cost during fiscal year 2015 . Amounts Recognized During Fiscal Year 2015 Regulatory assets/liabilities Accumulated other comprehensive loss (In millions) Pension Benefits Health and Life Benefits Pension Benefits Health and Life Benefits Actuarial net loss (income) $ 16.9 $ 4.2 $ 1.8 $ 0.2 Prior service cost (credit) 0.3 (14.6 ) — (0.7 ) Total $ 17.2 $ (10.4 ) $ 1.8 $ (0.5 )
Amount Recognized During Next Fiscal Year	The following table provides amounts that are included in regulatory assets/liabilities and accumulated other comprehensive loss associated with our unrecognized pension and other post-retirement benefit costs that are expected to be recognized as components of net periodic benefit cost during fiscal year 2016 . Amounts to be Recognized During Fiscal Year 2016 Regulatory assets/liabilities Accumulated other comprehensive loss (In millions) Pension Benefits Health and Life Benefits Pension Benefits Health and Life Benefits Actuarial net loss $ 15.3 $ 1.2 $ 1.5 $ 0.1 Prior service cost (credit) 0.2 (16.8 ) 0.1 (0.9 ) Total $ 15.5 $ (15.6 ) $ 1.6 $ (0.8 )
Components of Net Periodic Benefit Costs (Income)	The components of the net periodic benefit costs (income) for fiscal years ended September 30, 2015 , 2014 and 2013 related to pension and other postretirement benefits were as follows: Components of Net Periodic Benefit Costs (Income) (In millions) Pension Benefits Health and Life Benefits Year Ended September 30, 2015 2014 2013 2015 2014 2013 Service cost $ 15.5 $ 14.0 $ 17.0 $ 7.1 $ 7.6 $ 9.6 Interest cost 39.1 40.4 36.6 14.7 18.7 18.8 Expected return on plan assets (44.6 ) (41.0 ) (41.9 ) (20.8 ) (19.3 ) (18.3 ) Recognized prior service cost (credit) 0.3 0.3 1.0 (15.3 ) (9.6 ) (3.9 ) Recognized actuarial loss 18.7 16.8 28.7 4.4 5.0 9.2 Amortization of transition obligation — — — — — 1.1 Net periodic benefit cost 29.0 30.5 41.4 (9.9 ) 2.4 16.5 Amount allocated to construction projects (4.6 ) (4.3 ) (5.7 ) 1.9 (0.4 ) (2.8 ) Amount deferred as regulatory asset (liability)-net 7.1 7.0 (3.7 ) (0.2 ) (2.3 ) 2.4 Amount charged (credited) to expense $ 31.5 $ 33.2 $ 32.0 $ (8.2 ) $ (0.3 ) $ 16.1
Benefit Obligations Assumptions/Net Periodic Benefits Assumptions	The weighted average assumptions used to determine net periodic benefit obligations and net periodic benefit costs were as follows: Benefit Obligations Assumptions Pension Benefits Health and Life Benefits September 30, 2015 2014 2015 2014 Discount rate (a) 4.10%-4.50% 4.00%-4.40% 4.50 % 4.40 % Rate of compensation increase 3.50%-4.10% 3.50%-4.10% 4.10 % 4.10 % (a) The increase in the discount rate in fiscal year 2015 compared to prior years primarily reflects the increase in long-term interest rates. Net Periodic Benefit Cost Assumptions Pension Benefits Health and Life Benefits Years Ended September 30, 2015 2014 2013 2015 2014 2013 Discount rate (a) 4.00%-4.40% 4.50%-5.00% 4.00 % 4.40 % 4.60%-5.10% 4.00 % Expected long-term return on plan assets (b) 6.75 % 6.50 % 6.75 % 6.25 % 6.25 % 6.75 % Rate of compensation increase (c) 3.50%-4.10% 3.85%-5.15% 3.85%-5.15% 4.10 % 3.85 % 3.85 % (a) The changes in the discount rates over the last three fiscal years primarily reflect the changes in long-term interest rates. (b) For health and life benefits, the expected returns for certain funds may be lower due to certain portions of income that are subject to an assumed income tax rate of 45.6% . (c) The changes in the rate of compensation reflects the best estimates of actual future compensation levels including consideration of general price levels, productivity, seniority, promotion, and other factors such as inflation rates.
Healthcare Trends	Healthcare Trends (In millions) One Percentage-Point Increase One Percentage-Point Decrease Increase (decrease) total service and interest cost components $ 1.3 $ (1.1 ) Increase (decrease) post-retirement benefit obligation $ 5.7 $ (5.1 )
Valuation Methods Level 3 assets	The following table summarizes the changes in the fair value of the Level 3 assets for the fiscal years ended 2015 and 2014 : (In millions) Years Ended September 30, 2015 2014 Balance, beginning of year $ 23.8 $ 21.1 Actual return on plan assets: Assets still held at year end 3.9 2.7 Balance, end of year $ 27.7 $ 23.8
Expected Benefit Payments	Expected benefit payments, including benefits attributable to estimated future employee service, which are expected to be paid over the next ten years are as follows: Expected Benefit Payments (In millions) Pension Benefits Health and Life Benefits 2016 $ 49.1 $ 17.2 2017 50.5 17.6 2018 51.5 17.2 2019 53.2 17.4 2020 54.3 17.4 2021—2025 284.1 86.9
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Pension and OPEB Plan Assets	The following tables present the fair value of the pension plan assets and health and life insurance plan assets by asset category as of September 30, 2015 and 2014 : Pension Plan Assets % of ($ In millions) Level 1 Level 2 Level 3 Total Total At September 30, 2015 Cash and cash equivalents $ 0.8 $ — $ — $ 0.8 0.1 % Equity securities U.S. Small Cap 28.7 — — 28.7 3.7 Preferred Securities — 0.1 — 0.1 — Fixed income securities U.S. Treasuries — 101.3 — 101.3 13.0 U.S. Corporate Debt — 204.6 — 204.6 26.2 U.S. Agency Obligations and Government Sponsored Entities — 23.9 — 23.9 3.1 Asset-Backed Securities and Collateralized Mortgage Obligations — 1.7 — 1.7 0.2 Municipalities — 14.0 — 14.0 1.8 Non-U.S. Corporate Debt — 37.1 — 37.1 4.8 Repurchase Agreements (a) — 5.3 — 5.3 0.7 Other (b) — 4.7 — 4.7 0.6 Mutual Funds (c) — 29.3 — 29.3 3.7 Commingled Funds and Pooled Separate Accounts (d) — 274.8 27.7 302.5 38.7 Private Equity/Limited Partnerships (e) — 28.0 — 28.0 3.6 Derivatives (f) — (0.1 ) — (0.1 ) — Total fair value of plan investments $ 29.5 $ 724.7 $ 27.7 $ 781.9 100.2 % Receivable (payable) (g) (1.7 ) (0.2 ) Total plan assets at fair value $ 780.2 100.0 % Pension Plan Assets % of ($ In millions) Level 1 Level 2 Level 3 Total Total At September 30, 2014 Cash and cash equivalents $ 0.6 $ — $ — $ 0.6 0.1 % Equity securities U.S. Small Cap 32.3 — — 32.3 4.0 Preferred Securities — 0.1 — 0.1 — Fixed income securities U.S. Treasuries — 110.6 — 110.6 13.8 U.S. Corporate Debt — 108.4 — 108.4 13.5 U.S. Agency Obligations and Government Sponsored Entities — 24.6 — 24.6 3.0 Asset-Backed Securities and Collateralized Mortgage Obligations — 1.8 — 1.8 0.2 Municipalities — 9.2 — 9.2 1.1 Non-U.S. Corporate Debt — 23.8 — 23.8 3.0 Repurchase Agreements (a) — 2.5 — 2.5 0.3 Other (b) — 7.0 — 7.0 0.8 Mutual Funds (c) — 112.4 — 112.4 14.0 Commingled Funds and Pooled Separate Accounts (d) — 316.2 23.8 340.0 42.3 Private Equity/Limited Partnerships (e) — 30.5 — 30.5 3.8 Derivatives (f) — (0.1 ) — (0.1 ) — Total fair value of plan investments $ 32.9 $ 747.0 $ 23.8 $ 803.7 99.9 % Receivable (payable) (g) 1.0 0.1 Total plan assets at fair value $ 804.7 100.0 % (a) This category includes Treasury Bills with a pre-commitment from the counterparty to repurchase the same securities on the next business day at an agreed-upon price. (b) This category primarily includes Yankee bonds and non-U.S. government bonds. (c) At September 30, 2015 , investments in mutual funds consisited primarily of common stock of non-U.S. companies. At September 30, 2014 , investments in mutual funds consisted primarily of corporate fixed income instruments. (d) At September 30, 2015 , investments in commingled funds and pooled separate accounts consisted primarily of 80% common stock of large-cap U.S. companies; 18% income producing properties located in the United States; and 2% short-term money market investments. At September 30, 2014 , investments in commingled funds and pooled separate accounts consisted primarily of 75% common stock of large-cap U.S. companies; 14% income producing properties located in the United States; 9% equity securities of non-U.S. companies; and 2% short-term money market investments. (e) At September 30, 2015 and 2014 , investments in private equity/limited partnership consisted of common stock of international companies. (f) At September 30, 2015 , this category included long-term U.S. Treasury interest rate futures contracts, interest rate put options and credit default swap indexes. At September 30, 2014 , this category included long-term U.S. Treasury interest rate futures contracts and interest rate put options. (g) At September 30, 2015 , this payable represents a pending trade for investment purchases. At September 30, 2014 , this receivable represents a pending trade for investment sales.
Other post-retirement benefits
Defined Benefit Plan Disclosure [Line Items]
Pension and OPEB Plan Assets	Healthcare and Life Insurance Plan Assets % of ($ In millions) Level 1 Level 2 Level 3 Total Total At September 30, 2015 Cash and Cash Equivalents $ — $ — $ — $ — — % Mutual Funds (a) 1.9 — — 1.9 0.4 Fixed Income Securities U.S Agency Obligations — 1.8 — 1.8 0.4 U.S. Treasuries — 27.7 — 27.7 6.3 U.S. Corporate Debt — 33.5 — 33.5 7.7 Municipalities — 4.0 — 4.0 0.9 Non-U.S. Corporate Debt — 4.9 — 4.9 1.1 Others (b) — 4.3 — 4.3 1.0 Commingled Funds (c) — 359.7 — 359.7 82.0 Total fair value of plan investments $ 1.9 $ 435.9 $ — $ 437.8 99.8 % Receivable (payable) 0.7 0.2 Total plan assets at fair value $ 438.5 100.0 % At September 30, 2014 Cash and Cash Equivalents $ 0.8 $ — $ — $ 0.8 0.2 % Mutual Funds (a) — 1.9 — 1.9 0.4 Fixed Income Securities U.S Agency Obligations — 2.0 — 2.0 0.5 U.S. Treasuries — 25.6 — 25.6 5.8 U.S. Corporate Debt — 34.0 — 34.0 7.7 Municipalities — 4.8 — 4.8 1.1 Non-U.S. Corporate Debt — 5.7 — 5.7 1.3 Others (b) — 5.3 — 5.3 1.2 Commingled Funds (c) — 359.7 — 359.7 81.8 Total fair value of plan investments $ 0.8 $ 439.0 $ — $ 439.8 100.0 % Receivable (payable) (0.2 ) — Total plan assets at fair value $ 439.6 100.0 % (a) At September 30, 2015 , investments in mutual funds consisted of a short-term money market fund valued at $1.00 per share. At September 30, 2014 , investments in mutual funds consisted primarily of 63% short-term obligations consisting of certificates of deposit and time deposits, 23% high-quality commercial paper, 6% repurchase agreements, 4% corporate notes of U.S. and foreign corporations and 4% U.S. governmental and U.S. agency securities. (b) At September 30, 2015 and 2014 , this category consisted primarily of 76% non-U.S. government bonds and 24% Yankee bonds. (c) At September 30, 2015 , investments in commingled funds consisted primarily of 68% common stock of large-cap U.S. companies, 16% governmental fixed income securities and 16% corporate bonds. At September 30, 2014 , investments in commingled funds consisted primarily of 66% common stock of large-cap U.S. companies, 17% U.S. agency obligations and government sponsored entities and 17% corporate bonds.

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Sep. 30, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Performance Share Activity	The following table summarizes information regarding performance share activity during the fiscal year ended September 30, 2015 . Performance Share Activity Year Ended September 30, 2015 Number of Shares (a) Weighted Average Grant- Date Fair Value Non-vested and outstanding, beginning of year 301,378 $ 40.57 Granted 113,626 44.44 Vested — — Cancelled/forfeited (110,915 ) 39.71 Non-vested and outstanding, end of year 304,089 $ 44.49 (a) The number of common shares issued related to performance shares may range from zero to 200 percent of the number of shares shown in the table above based on our achievement of performance goals for total shareholder return relative to a selected peer group of companies.
Performance Share Fair Value Assumptions	We estimated the fair value of performance shares on the date of grant using a Monte Carlo simulation model and the following assumptions: Fair Value Assumptions Years Ended September 30, 2015 2014 2013 Expected stock-price volatility 18.30 % 19.10 % 19.40 % Dividend yield 4.18 % 3.93 % 3.98 % Weighted average grant-date fair value $ 44.44 $ 42.88 $ 39.73
Performance Unit Activity	The following table summarizes information regarding performance unit activity during the fiscal year ended September 30, 2015 . Performance Unit Activity Year Ended September 30, 2015 Number of Units Non-vested and outstanding, beginning of year 12,268,921 Granted 4,785,921 Vested — Cancelled/forfeited (4,369,209 ) Non-vested and outstanding, end of year 12,685,633
Performance Units Fair Value Assumptions	We estimated the fair value of performance units using a Monte Carlo simulation model. The following table provides the year-end assumptions used to value our performance units: Fair Value Assumptions September 30, 2015 10/1/2014 Grant 10/1/2013 Grant Expected stock-price volatility 20.20 % 20.80 %

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Sep. 30, 2015
Commitments and Contingencies [Line Items]
Schedule of Future Minimum Rental Payments for Operating Leases	Minimum future rental payments under operating leases over the next five years and thereafter are as follows: Minimum Payments Under Operating Leases (In millions) 2016 $ 6.4 2017 5.8 2018 5.9 2019 2.7 2020 2.8 Thereafter 23.1 Total $ 46.7
Washington Gas Light Company
Commitments and Contingencies [Line Items]
Long-term Purchase Commitment	The following table summarizes the minimum contractual payments that Washington Gas will make under its pipeline transportation, storage and peaking contracts, as well as minimum contractual payments to purchase natural gas at prices based on market conditions during the next five fiscal years and thereafter. Washington Gas Contract Minimums (In millions) Pipeline Contracts (a) Gas Purchase Commitments (b) 2016 $ 208.8 $ 340.6 2017 200.8 413.8 2018 199.1 403.4 2019 211.1 396.6 2020 199.7 413.6 Thereafter 1,191.7 4,819.0 Total $ 2,211.2 $ 6,787.0 (a) Represents minimum payments for natural gas transportation, storage and peaking contracts that have expiration dates through fiscal year 2034. (b) Includes known and reasonably likely commitments to purchase natural gas. Cost estimates are based on forward market prices at September 30, 2015 .
Non Utility
Commitments and Contingencies [Line Items]
Long-term Purchase Commitment	The following table summarizes the minimum commitments and contractual obligations of WGL Energy Services and WGL Midstream for the next five fiscal years and thereafter. Contract Minimums WGL Energy Services WGL Midstream (In millions) Gas Purchase Commitments (a) Pipeline Contracts (b) Electric Purchase Commitments (c) Gas Purchase Commitments (d) Pipeline Contracts (b) Total 2016 $ 156.4 $ 3.2 $ 477.4 $ 252.9 $ 20.4 $ 910.3 2017 67.8 2.0 215.8 348.6 18.4 652.6 2018 9.7 1.4 56.3 1,082.6 15.9 1,165.9 2019 0.5 0.8 6.2 1,650.9 60.9 1,719.3 2020 — 0.5 1.1 1,866.4 65.0 1,933.0 Thereafter — 1.2 — 32,117.1 1,031.7 33,150.0 Total $ 234.4 $ 9.1 $ 756.8 $ 37,318.5 $ 1,212.3 $ 39,531.1 (a) Represents fixed price commitments with city gate equivalent deliveries. (b) Represents minimum payments for natural gas transportation and storage contracts that have expiration dates through fiscal year 2044. (c) Represents electric purchase commitments that are based on existing fixed price and fixed volume contracts. Includes $15.7 million of commitments related to renewable energy credits. (d) Includes known and reasonably likely commitments to purchase natural gas. Cost estimates are based on forward market prices as of September 30, 2015 . Certain of our gas purchase agreements have optionality, which may cause increases in these commitments.

Derivative and Weather Relate44

Derivative and Weather Related Instruments (Tables)	12 Months Ended
	Sep. 30, 2015
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Absolute Notional Amounts of Open Positions on Derivative Instruments	At September 30, 2015 and 2014 , respectively, the absolute notional amounts of our derivatives are as follows: Absolute Notional Amounts of Open Positions on Derivative Instruments Derivative transactions WGL Holdings Washington Gas September 30, 2015 Notional Amounts Natural Gas (In millions of therms) Asset Optimization 20,829.2 13,316.7 Retail sales 52.2 — Other risk-management activities 1,811.7 1,381.8 Electricity (In millions of kWhs) Retail sales 4,292.7 — Other risk-management activities 19,965.7 — Interest Rate Swaps (In millions of dollars) $ 125.0 $ — September 30, 2014 Natural Gas (In millions of therms) Asset Optimization 20,593.3 13,740.9 Retail sales 44.7 — Other risk-management activities 1,641.3 1,398.2 Electricity (In millions of kWhs) Retail sales 3,831.4 — Other risk-management activities 16,734.1 — Warrants (In millions of shares) 4.6 — Interest Rate Swaps (In millions of dollars) $ 150.0 $ —
Balance Sheet Classification of Derivative Instruments	The following tables present the balance sheet classification for all derivative instruments as of September 30, 2015 and 2014 . WGL Holdings, Inc. Balance Sheet Classification of Derivative Instruments (In millions) Derivative Instruments Not Designated as Hedging Instruments Derivative Instruments Designated as Hedging Instruments As of September 30, 2015 Gross Derivative Assets Gross Derivative Liabilities Gross Derivative Assets Gross Derivative Liabilities Netting of Collateral Total (a) Current Assets—Derivatives $ 29.7 $ (6.8 ) $ — $ — $ — $ 22.9 Deferred Charges and Other Assets—Derivatives 32.3 (0.2 ) — — — 32.1 Current Liabilities—Derivatives 9.8 (76.2 ) — — 2.9 (63.5 ) Deferred Credits—Derivatives 2.7 (328.9 ) — (3.4 ) 7.3 (322.3 ) Total $ 74.5 $ (412.1 ) $ — $ (3.4 ) $ 10.2 $ (330.8 ) As of September 30, 2014 Current Assets—Derivatives $ 20.8 $ (2.5 ) $ — $ — $ — $ 18.3 Deferred Charges and Other Assets—Derivatives 18.7 — — — — 18.7 Current Liabilities—Derivatives 15.4 (70.3 ) — (1.7 ) 8.0 (48.6 ) Deferred Credits—Derivatives 17.7 (316.4 ) — — 4.0 (294.7 ) Total $ 72.6 $ (389.2 ) $ — $ (1.7 ) $ 12.0 $ (306.3 ) Washington Gas Light Company Balance Sheet Classification of Derivative Instruments (b) (In millions) As of September 30, 2015 Gross Gross Netting of Total (a) Current Assets—Derivatives $ 5.2 $ (0.6 ) $ — $ 4.6 Deferred Charges and Other Assets—Derivatives 13.3 (0.1 ) — 13.2 Current Liabilities—Derivatives 1.9 (35.8 ) — (33.9 ) Deferred Credits—Derivatives — (269.7 ) — (269.7 ) Total $ 20.4 $ (306.2 ) $ — $ (285.8 ) As of September 30, 2014 Current Assets—Derivatives $ 3.9 $ — $ — $ 3.9 Deferred Charges and Other Assets—Derivatives 9.5 — — 9.5 Current Liabilities—Derivatives 8.6 (43.2 ) 0.7 (33.9 ) Deferred Credits—Derivatives 4.2 (265.2 ) 0.2 (260.8 ) Total $ 26.2 $ (308.4 ) $ 0.9 $ (281.3 ) (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. (b) Washington Gas did not have any derivative instruments outstanding that were designated as hedging instruments at September 30, 2015 or 2014 .
Gains and (Losses) on Derivative Instruments	The following tables present all gains and losses associated with derivative instruments for the years ended September 30, 2015 , 2014 and 2013 . Gains and Losses on Derivative Instruments (In millions) WGL Holdings, Inc. Washington Gas Fiscal Year Ended September 30, 2015 2014 2013 2015 2014 2013 Recorded to income Operating revenues—non-utility $ 71.3 $ (47.9 ) $ (9.9 ) $ — $ — $ — Utility cost of gas (14.5 ) (87.3 ) (45.9 ) (14.5 ) (87.3 ) (45.9 ) Non-utility cost of energy-related sales (43.7 ) 36.2 (2.4 ) — — — Other income-net — (1.1 ) 0.2 — — — Interest expense (a) (0.6 ) (0.2 ) — — — — Recorded to regulatory assets Gas costs (18.4 ) (143.3 ) (115.1 ) (18.4 ) (143.3 ) (115.1 ) Other — 0.2 — — 0.2 — Recorded to other comprehensive income (b) (11.3 ) (1.5 ) — — — — Total $ (17.2 ) $ (244.9 ) $ (173.1 ) $ (32.9 ) $ (230.4 ) $ (161.0 ) (a) Fiscal year 2015 represents $(0.4) million of net ineffectiveness for our cash flow hedges and $(0.2) million of amortization of amounts previously recorded to Accumulated Other Comprehensive Income. Fiscal year 2014 amounts represent hedge ineffectiveness. (b) Fiscal year 2015 represents the effective portion of our cash flow hedges of $(11.5) million less $(0.2) million of amortization that was reclassified to interest expense. Fiscal year 2014 amounts represent hedge effectiveness.
Potential Collateral Requirements for Derivative Liabilities with Credit-risk-Contingent Features	The following table shows the aggregate fair value of all derivative instruments with credit-related contingent features that are in a liability position, as well as the maximum amount of collateral that would be required if the most intrusive credit-risk-related contingent features underlying these agreements were triggered on September 30, 2015 and 2014 , respectively. Potential Collateral Requirements for Derivative Liabilities with Credit-Risk-Contingent Features (In millions) WGL Holdings, Inc. Washington Gas September 30, 2015 Derivative liabilities with credit-risk-contingent features $ 61.7 $ 18.9 Maximum potential collateral requirements 54.6 18.8 September 30, 2014 Derivative liabilities with credit-risk-contingent features $ 28.8 $ 20.6 Maximum potential collateral requirements 16.5 16.1

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Sep. 30, 2015
Quantitative Information about Level 3 Fair Value Measurements	The following table includes quantitative information about the significant unobservable inputs used in the fair value measurement of our Level 3 financial instruments and the respective fair values of the net derivative asset and liability positions, by contract type, as of September 30, 2015 and 2014 . Quantitative Information about Level 3 Fair Value Measurements (In millions) Net Fair Value Valuation Techniques Unobservable Inputs Range WGL Holdings, Inc. Natural gas related derivatives $(309.7) Discounted Cash Flow Natural Gas Basis Price (per dekatherm) ($1.441) - $3.580 Option Model Natural Gas Basis Price (per dekatherm) ($1.283) - $2.950 Annualized Volatility of Spot Market Natural Gas 22.5% - 867.0% Electricity related derivatives $(16.0) Discounted Cash Flow Electricity Congestion Price (per megawatt hour) ($5.75) - $73.35 Washington Gas Light Company Natural gas related derivatives $(281.1) Discounted Cash Flow Natural Gas Basis Price (per dekatherm) ($1.441) - $3.500 Net Fair Value WGL Holdings, Inc. Natural gas related derivatives $(294.7) Discounted Cash Flow Natural Gas Basis Price (per dekatherm) ($2.101) - $6.154 Option Model Natural Gas Basis Price (per dekatherm) ($1.675) - $6.154 Annualized Volatility of Spot Market Natural Gas 30.9% - 589.6% Electricity related derivatives $(5.0) Discounted Cash Flow Electricity Congestion Price (per megawatt hour) ($2.85) - $90.95 Washington Gas Light Company Natural gas related derivatives $(270.6) Discounted Cash Flow Natural Gas Basis Price (per dekatherm) ($2.101) - $6.154
WGL
Fair Value Measurements Under the Fair Value Hierarchy	The following tables set forth financial instruments recorded at fair value as of September 30, 2015 and 2014 , 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 September 30, 2015 Assets Natural gas related derivatives $ — $ 22.7 $ 28.5 $ 51.2 Electricity related derivatives — 2.0 21.3 23.3 Total Assets $ — $ 24.7 $ 49.8 $ 74.5 Liabilities Natural gas related derivatives $ — $ (33.9 ) $ (338.2 ) $ (372.1 ) Electricity related derivatives — (2.7 ) (37.3 ) (40.0 ) Interest rate derivatives — (3.4 ) — (3.4 ) Total Liabilities $ — $ (40.0 ) $ (375.5 ) $ (415.5 ) At September 30, 2014 Assets Natural gas related derivatives $ — $ 22.7 $ 33.7 $ 56.4 Electricity related derivatives — 0.3 15.9 16.2 Total Assets $ — $ 23.0 $ 49.6 $ 72.6 Liabilities Natural gas related derivatives $ — $ (39.8 ) $ (328.4 ) $ (368.2 ) Electricity related derivatives — (0.1 ) (20.9 ) (21.0 ) Interest rate derivatives — (1.7 ) — (1.7 ) Total Liabilities $ — $ (41.6 ) $ (349.3 ) $ (390.9 )
Reconciliation of Fair Value Measurements Using Significant Level 3 Inputs	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 years ended September 30, 2015 and 2014 , respectively. WGL Holdings, Inc. Reconciliation of Fair Value Measurements Using Significant Level 3 Inputs (In millions) Natural Gas Related Derivatives Electricity Related Derivatives Warrants Total Fiscal Year Ended September 30, 2015 Balance at October 1, 2014 $ (294.7 ) $ (5.0 ) $ — $ (299.7 ) Realized and unrealized gains (losses) Recorded to income (30.7 ) (32.3 ) — (63.0 ) Recorded to regulatory assets—gas costs (30.9 ) — — (30.9 ) Transfers into Level 3 5.4 — — 5.4 Transfers out of Level 3 3.6 — — 3.6 Purchases — 10.5 — 10.5 Settlements 37.6 10.8 — 48.4 Balance at September 30, 2015 $ (309.7 ) $ (16.0 ) $ — $ (325.7 ) Fiscal Year Ended September 30, 2014 Balance at October 1, 2013 $ (155.2 ) $ 2.4 $ 1.1 $ (151.7 ) Realized and unrealized gains (losses) Recorded to income (72.6 ) (5.7 ) (1.1 ) (79.4 ) Recorded to regulatory assets—gas costs (113.6 ) — — (113.6 ) Transfers out of Level 3 1.7 — — 1.7 Purchases — 5.2 — 5.2 Settlements 45.0 (6.9 ) — 38.1 Balance at September 30, 2014 $ (294.7 ) $ (5.0 ) $ — $ (299.7 )
Realized and Unrealized Gains (Losses) Recorded to Income for Level 3 Measurements	The table below sets forth the line items on the statements of income to which amounts are recorded for the fiscal years ended September 30, 2015 , 2014 and 2013 , 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 (In millions) Natural Gas Related Derivatives Electricity Related Derivatives Weather Related Instruments Warrants Total Fiscal Year Ended September 30, 2015 Operating revenues—non-utility $ (5.7 ) $ 19.9 $ — $ — $ 14.2 Utility cost of gas (25.0 ) — — — (25.0 ) Non-utility cost of energy-related sales — (52.2 ) — — (52.2 ) Total $ (30.7 ) $ (32.3 ) $ — $ — $ (63.0 ) Fiscal Year Ended September 30, 2014 Operating revenues—non-utility $ (2.3 ) $ (22.1 ) $ — $ — $ (24.4 ) Utility cost of gas (69.4 ) — — — (69.4 ) Other income-net — — — (1.1 ) (1.1 ) Non-utility cost of energy-related sales (0.9 ) 16.4 — — 15.5 Total $ (72.6 ) $ (5.7 ) $ — $ (1.1 ) $ (79.4 ) Fiscal Year Ended September 30, 2013 Operating revenues—non-utility $ (27.0 ) $ (9.1 ) $ — $ — $ (36.1 ) Utility cost of gas (45.8 ) — — — (45.8 ) Other income-net — — — 0.2 0.2 Non-utility cost of energy-related sales 0.4 (14.7 ) — — (14.3 ) Operation and maintenance expense — — 1.2 — 1.2 Total $ (72.4 ) $ (23.8 ) $ 1.2 $ 0.2 $ (94.8 )
Unrealized Gains (Losses) Recorded for Level 3 Measurements	Unrealized gains (losses) for the fiscal years ended September 30, 2015 , 2014 and 2013 , attributable to derivative assets and liabilities measured using significant Level 3 inputs were recorded as follows, respectively: WGL Holdings, Inc. Unrealized Gains (Losses) Recorded for Level 3 Measurements (In millions) Natural Gas Related Derivatives Electricity Related Derivatives Warrants Total Fiscal Year Ended September 30, 2015 Recorded to income Operating revenues—non-utility $ (2.2 ) $ 25.1 $ — $ 22.9 Utility cost of gas (15.8 ) — — (15.8 ) Non-utility cost of energy-related sales (1.7 ) (41.7 ) — (43.4 ) Recorded to regulatory assets—gas costs (20.9 ) — — (20.9 ) Total $ (40.6 ) $ (16.6 ) $ — $ (57.2 ) Fiscal Year Ended September 30, 2014 Recorded to income Operating revenues—non-utility $ (5.0 ) $ (33.8 ) $ — $ (38.8 ) Utility cost of gas (60.6 ) — — (60.6 ) Non-utility cost of energy-related sales 3.7 30.0 — 33.7 Other income-net — — (1.1 ) (1.1 ) Recorded to regulatory assets—gas costs (109.9 ) — — (109.9 ) Total $ (171.8 ) $ (3.8 ) $ (1.1 ) $ (176.7 ) Fiscal Year Ended September 30, 2013 Recorded to income Operating revenues—non-utility $ (25.3 ) $ 6.6 $ — $ (18.7 ) Utility cost of gas (44.3 ) — — (44.3 ) Non-utility cost of energy-related sales 0.2 (1.1 ) — (0.9 ) Other income-net — — 0.2 0.2 Recorded to regulatory assets—gas costs (111.6 ) — — (111.6 ) Total $ (181.0 ) $ 5.5 $ 0.2 $ (175.3 )
Fair Value of Financial Instruments	The following table presents the carrying amounts and estimated fair values of our financial instruments at September 30, 2015 and 2014 . WGL Holdings, Inc. Fair Value of Financial Instruments September 30, 2015 September 30, 2014 (In millions) Carrying Amount Fair Value Carrying Amount Fair Value Money market funds (a) $ 11.0 $ 11.0 $ 9.7 $ 9.7 Other short-term investments (a) $ 0.4 $ 0.4 $ — $ — Commercial paper (b) $ 332.0 $ 332.0 $ 453.5 $ 453.5 Long-term debt (c) $ 944.2 $ 1,057.9 $ 679.2 $ 809.3
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 September 30, 2015 Assets Natural gas related derivatives $ — $ 6.9 $ 13.5 $ 20.4 Total Assets $ — $ 6.9 $ 13.5 $ 20.4 Liabilities Natural gas related derivatives $ — $ (11.6 ) $ (294.6 ) $ (306.2 ) Total Liabilities $ — $ (11.6 ) $ (294.6 ) $ (306.2 ) At September 30, 2014 Assets Natural gas related derivatives $ — $ 13.5 $ 12.7 $ 26.2 Total Assets $ — $ 13.5 $ 12.7 $ 26.2 Liabilities Natural gas related derivatives $ — $ (25.1 ) $ (283.3 ) $ (308.4 ) Total Liabilities $ — $ (25.1 ) $ (283.3 ) $ (308.4 )
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 Fiscal Year Ended September 30, 2015 Balance at October 1, 2014 $ (270.6 ) Realized and unrealized gains (losses) Recorded to income (25.0 ) Recorded to regulatory assets—gas costs (30.9 ) Transfers into Level 3 5.4 Transfers out of Level 3 2.5 Settlements 37.5 Balance at September 30, 2015 $ (281.1 ) Fiscal Year Ended September 30, 2014 Balance at October 1, 2013 $ (133.6 ) Realized and unrealized gains (losses) Recorded to income (69.4 ) Recorded to regulatory assets—gas costs (113.6 ) Transfers out of Level 3 1.7 Settlements 44.3 Balance at September 30, 2014 $ (270.6 )
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 (In millions) Natural Gas Related Derivatives Weather Related Instruments Total Fiscal Year Ended September 30, 2015 Utility cost of gas $ (25.0 ) $ — $ (25.0 ) Total $ (25.0 ) $ — $ (25.0 ) Fiscal Year Ended September 30, 2014 Utility cost of gas $ (69.4 ) $ — $ (69.4 ) Total $ (69.4 ) $ — $ (69.4 ) Fiscal Year Ended September 30, 2013 Utility cost of gas $ (45.9 ) $ — $ (45.9 ) Operation and maintenance expense — 1.2 1.2 Total $ (45.9 ) $ 1.2 $ (44.7 )
Unrealized Gains (Losses) Recorded for Level 3 Measurements	Washington Gas Light Company Unrealized Gains (Losses) Recorded for Level 3 Measurements (In millions) Natural Gas Related Derivatives Fiscal Year Ended September 30, 2015 Recorded to income - utility cost of gas $ (15.8 ) Recorded to regulatory assets—gas costs (20.9 ) Total $ (36.7 ) Fiscal Year Ended September 30, 2014 Recorded to income - utility cost of gas $ (60.6 ) Recorded to regulatory assets—gas costs (109.9 ) Total $ (170.5 ) Fiscal Year Ended September 30, 2013 Recorded to income - utility cost of gas $ (44.3 ) Recorded to regulatory assets—gas costs (111.6 ) Total $ (155.9 )
Fair Value of Financial Instruments	Washington Gas Light Company Fair Value of Financial Instruments September 30, 2015 September 30, 2014 (In millions) Carrying Amount Fair Value Carrying Amount Fair Value Money market funds (a) $ 4.3 $ 4.3 $ 4.3 $ 4.3 Other short-term investments (a) $ 0.4 $ 0.4 $ — $ — Commercial paper (b) $ 89.0 $ 89.0 $ 89.0 $ 89.0 Long-term debt (c) $ 695.9 $ 811.9 $ 679.2 $ 809.3 (a) Balance 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) Less current maturities and unamortized discounts.

Operating Segment Reporting (Ta

Operating Segment Reporting (Tables)	12 Months Ended
	Sep. 30, 2015
Segment Reporting [Abstract]
Operating Segment Financial Information	The following tables present operating segment information for the fiscal years ended September 30, 2015 , 2014 and 2013 . Prior period amounts are presented based on the change in measure. Operating Segment Financial Information (In thousands) Operating Revenues (a) Depreciation and Amortization Equity in Earnings of Unconsolidated Affiliates EBIT Total Assets Capital Expenditures Equity Method Investments Fiscal Year Ended September 30, 2015 Regulated utility $ 1,328,191 $ 110,416 $ — $ 223,977 $ 4,253,552 $ 327,429 $ — Retail energy-marketing 1,306,758 671 — 46,629 470,251 28 — Commercial energy systems 51,813 10,733 2,095 9,688 691,629 136,749 63,521 Midstream energy services 3,191 129 2,623 (2,720 ) 237,839 85 73,363 Other activities — — 750 (9,667 ) 199,060 — — Eliminations (b) (30,123 ) (57 ) — (1,013 ) (558,130 ) — — Total consolidated $ 2,659,830 $ 121,892 $ 5,468 $ 266,894 $ 5,294,201 $ 464,291 $ 136,884 Fiscal Year Ended September 30, 2014 Regulated utility $ 1,443,800 $ 104,064 $ — $ 184,668 $ 3,979,522 $ 286,323 $ — Retail energy-marketing 1,310,279 756 1 14,015 389,700 76 — Commercial energy systems 40,679 6,178 1,953 6,863 521,570 108,363 66,810 Midstream energy services 16,555 124 771 8,412 211,824 — 28,076 Other activities — — 469 (11,539 ) 369,816 — 16 Eliminations (b) (30,366 ) (350 ) — (167 ) (615,933 ) — — Total consolidated $ 2,780,947 $ 110,772 $ 3,194 $ 202,252 $ 4,856,499 $ 394,762 $ 94,902 Fiscal Year Ended September 30, 2013 Regulated utility $ 1,200,357 $ 100,438 $ — $ 153,647 $ 3,486,296 $ 227,948 $ — Retail energy-marketing 1,279,364 726 — 53,264 403,082 730 — Commercial energy systems 35,217 2,411 1,070 3,019 318,995 83,667 54,977 Midstream energy services (20,390 ) 124 312 (29,359 ) 231,368 — 6,507 Other activities — — 128 (8,669 ) 290,440 — 413 Eliminations (b) (28,410 ) (415 ) — (2,026 ) (470,121 ) — — Total consolidated $ 2,466,138 $ 103,284 $ 1,510 $ 169,876 $ 4,260,060 $ 312,345 $ 61,897 (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 public service commission fees, franchise fees and energy taxes. Operating revenue amounts in the “Eliminations” row 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 include any mark-to market valuations associated with trading activities between WGL Midstream and WGL Energy Services, intercompany loans and a timing difference between Commercial Energy Systems’ recognition of revenue for the sale of Renewable Energy Credits (RECs) to Retail Energy-Marketing and Retail Energy-Marketing’s recognition of the associated expense. Retail Energy-Marketing has recorded a portion of the REC’s purchased as inventory to be used in future periods at which time they will be expensed.
Reconciliation From EBIT To Net Income Applicable To Common Stock	The following table provides a reconciliation from EBIT to net income applicable to common stock. Fiscal Year Ended September 30, (In thousands) 2015 2014 2013 Total consolidated EBIT $ 266,894 $ 202,252 $ 169,876 Interest expense 50,511 37,738 36,011 Income before income taxes 216,383 164,514 133,865 Income tax expense 83,804 57,254 52,292 Net income 132,579 107,260 81,573 Dividends on Washington Gas Light Company preferred stock 1,320 1,320 1,320 Net income applicable to common stock $ 131,259 $ 105,940 $ 80,253

Other Investment (Tables)

Other Investment (Tables)	12 Months Ended
	Sep. 30, 2015
Other Investments [Abstract]
Minimum Payments Receivable for Direct Financing Leases	Minimum future lease payments receivable under direct financing leases over the next five fiscal years and thereafter are as follows: Minimum Payments Receivable for Direct Financing Leases (In millions) 2016 $ 3.7 2017 2.8 2018 2.8 2019 2.7 2020 2.6 Thereafter 28.3 Total $ 42.9
Location of Investments	The income statement location of the investments discussed in this footnote for the fiscal year September 30, 2015 , 2014 and 2013 are as follows: WGL Holdings, Inc. Income Statement Location of Other Investments (In millions) VIEs Non-VIEs Total Fiscal Year Ended September 30, 2015 Equity in earnings of unconsolidated affiliates $ 2.9 $ 2.6 $ 5.5 Depreciation and amortization 0.3 — $ 0.3 Other income (expenses) - net 3.2 (5.6 ) $ (2.4 ) Net income $ 5.8 $ (3.0 ) $ 2.8 Fiscal Year Ended September 30, 2014 Equity in earnings of unconsolidated affiliates $ 2.2 $ 1.0 $ 3.2 Depreciation and amortization 0.2 — $ 0.2 Other income - net 2.6 — $ 2.6 Net income $ 4.6 $ 1.0 $ 5.6 Fiscal Year Ended September 30, 2013 Equity in earnings of unconsolidated affiliates $ 1.0 $ 0.5 $ 1.5 Depreciation and amortization 0.1 — $ 0.1 Other income - net 1.4 — $ 1.4 Net income $ 2.3 $ 0.5 $ 2.8 The balance sheet location of the investments discussed in this footnote at September 30, 2015 and 2014 are as follows: WGL Holdings, Inc Balance Sheet Location of Other Investments (in millions) VIEs Non-VIEs Total As of September 30, 2015 Assets Investments in unconsolidated affiliates $ 94.0 $ 42.9 $ 136.9 Investments in direct financing leases, capital leases 35.2 — $ 35.2 Accounts receivable 2.0 4.2 (a) $ 6.2 Total assets $ 131.2 $ 47.1 $ 178.3 As of September 30, 2014 Assets Investments in unconsolidated affiliates $ 72.6 $ 27.9 $ 100.5 Investments in direct financing leases, capital leases 18.2 — $ 18.2 Accounts receivable 1.7 — $ 1.7 Total assets $ 92.5 $ 27.9 $ 120.4 (a) Represents the financing provided to another partner in Mountain Valley to fund its capital commitment. Acquired ownership interest represents the collateral for repayment of the financing.

Related Party Transactions (Tab

Related Party Transactions (Tables)	12 Months Ended
	Sep. 30, 2015
Related Party Transactions [Abstract]
Receivables and Payables from Associated Companies	The following table shows the amounts Washington Gas charged WGL Energy Services for balance services. Washington Gas - Gas Balancing Service Charges (In millions) Years Ended September 30, 2015 2014 2013 Gas balancing service charge $ 25.1 $ 26.6 $ 25.0 The following table presents the receivables and payables from associated companies for the fiscal years ended September 30, 2015 and 2014 . Washington Gas Light Company Receivables / Payables from Associated Companies (In millions) September 30, 2015 September 30, 2014 Receivables from Associated Companies $ 3.2 $ 4.8 Payables to Associated Companies $ 68.6 $ 54.7

Accumulated Other Comprehensi49

Accumulated Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Sep. 30, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Schedule of Accumulated Other Comprehensive Income (Loss)	The following tables show the changes in accumulated other comprehensive income (loss) for WGL and Washington Gas by component for the fiscal years ended September 30, 2015 and 2014 . WGL Holdings, Inc. Changes in Accumulated Other Comprehensive Income (Loss) by Component September 30, (In thousands) 2015 2014 Beginning Balance $ (7,961 ) $ (11,048 ) Qualified cash flow hedging instruments (a) (11,309 ) (1,548 ) Change in prior service cost (b) 696 6,095 Amortization of actuarial gain (loss) (b) (1,195 ) 1,594 Current-period other comprehensive income (loss) (11,808 ) 6,141 Income tax expense (benefit) related to other comprehensive income (loss) (5,533 ) 3,054 Ending Balance $ (14,236 ) $ (7,961 ) (a) Cash flow hedging instruments represent interest rate swap agreements related to debt issuances. Refer to Note 14—Derivative and Weather-related Instruments for further discussion of the interest rate swap agreements. (b) These accumulated other comprehensive income (loss) components are included in the computation of net periodic benefit cost. Refer to Note 10-Pension and other post-retirement benefit plans for additional details. Washington Gas Light Company Changes in Accumulated Other Comprehensive Income (Loss) by Component September 30, (In thousands) 2015 2014 Beginning Balance $ (6,413 ) $ (11,048 ) Change in prior service cost (a) 696 6,095 Amortization of actuarial gain (loss) (a) (1,195 ) 1,594 Current-period other comprehensive income (loss) (499 ) 7,689 Income tax expense (benefit) related to other comprehensive income (loss) (200 ) 3,054 Ending Balance $ (6,712 ) $ (6,413 ) (a) These accumulated other comprehensive income (loss) components are included in the computation of net periodic benefit cost. Refer to Note 10-Pension and other post-retirement benefit plans for additional details.

Quarterly Financial Data (Table

Quarterly Financial Data (Tables)	12 Months Ended
	Sep. 30, 2015
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Data	All adjustments necessary for a fair presentation have been included in the quarterly information provided below. Due to the seasonal nature of our business, we report substantial variations in operations on a quarterly basis. Quarter Ended (In thousands, except per share data) December 31 (a) March 31 June 30 ( b) September 30 (c) Fiscal Year 2015 WGL Holdings, Inc. Operating revenues $ 749,237 $ 1,001,733 $ 441,173 $ 467,687 Operating income (loss) $ 121,842 $ 142,886 $ (17,567 ) $ 13,612 Net income (loss) applicable to common stock $ 63,888 $ 81,455 $ (15,690 ) $ 1,606 Earnings (loss) per average share of common stock: Basic $ 1.28 $ 1.64 $ (0.32 ) $ 0.03 Diluted $ 1.28 $ 1.63 $ (0.32 ) $ 0.03 Washington Gas Light Company Operating revenues $ 387,193 $ 615,694 $ 190,345 $ 134,959 Operating income (loss) $ 114,623 $ 129,944 $ (6,729 ) $ (15,454 ) Net income (loss) applicable to common stock $ 64,621 $ 74,364 $ (11,754 ) $ (19,873 ) Fiscal Year 2014 WGL Holdings, Inc. Operating revenues $ 680,297 $ 1,174,250 $ 467,500 $ 458,900 Operating income (loss) $ 32,712 $ 104,733 $ (9,489 ) $ 69,566 Net income (loss) applicable to common stock $ 18,629 $ 61,213 $ (11,940 ) $ 38,038 Earnings (loss) per average share of common stock: Basic $ 0.36 $ 1.18 $ (0.23 ) $ 0.74 Diluted $ 0.36 $ 1.18 $ (0.23 ) $ 0.74 Washington Gas Light Company Operating revenues $ 390,415 $ 716,808 $ 197,752 $ 138,825 Operating income $ 65,229 $ 88,038 $ 4,326 $ 24,530 Net income (loss) applicable to common stock $ 38,477 $ 49,176 $ (521 ) $ 9,872 (a) During the first quarter of fiscal year 2015, WGL recorded an impairment charge of $5.6 million related to its investment in ASDHI. During the first quarter of fiscal year 2014, Washington Gas recorded an impairment charge of $0.8 million related to the Springfield Operations Center. Refer to Note 1—Accounting Policies of the Notes to Consolidated Financial Statements for further discussion of the impairments. (b) During the third quarter of fiscal year 2015, WGL recorded a $3.0 million liability for un-recovered government contracting costs under the Small Business Administration Development 8(a) Program and Washington Gas recorded approximately $0.5 million in transaction fees related to the sale of its Springfield Operations Center. During the third quarter of fiscal year 2014, Washington Gas recorded a $1.9 million impairment charge on an abandoned LNG storage facility. Refer to Note 1—Accounting Policies of the Notes to Consolidated Financial Statements for further discussion of the impairments. (c) During the fourth quarter of fiscal year 2015, Washington Gas recorded a one time adjustment of $2.4 million as a result of charges associated with a regulatory proceeding.

Accounting Policies (Narrative)

Accounting Policies (Narrative) (Details) $ in Thousands	12 Months Ended
	Sep. 30, 2015USD ($)investmentsubsidiaryCustomers	Sep. 30, 2014USD ($)	Sep. 30, 2013USD ($)
Accounting Policies [Line Items]
Number of subsidiaries | subsidiary	4
Number of customers (more than one million) | Customers	1,000,000
Number of investments that qualify as VIEs | investment	4
Pretax AFUDC Rate	4.12%	3.36%	5.43%
Composite depreciation and amortization rate	2.73%	2.77%	2.86%
PP&E, other percentage	91.20%	93.60%
Impairment loss	$ 5,625	$ 2,639	$ 2,600
Regulated revenue billing cycle	21 days
Duration of cost of gas recovered or refunded	12 months
Leasehold Improvements
Accounting Policies [Line Items]
Operating lease useful life	15 years
Washington Gas Light Company
Accounting Policies [Line Items]
Impairment loss	$ 0	2,639	2,600
WGL Energy Services
Accounting Policies [Line Items]
Indexed or fixed rate customer contracts terms	24 months
Washington Gas Resources
Accounting Policies [Line Items]
Impairment loss, cost-method investment	$ 5,600
Natural Gas Customers | WGL Energy Services
Accounting Policies [Line Items]
Number of customers | Customers	143,800
Abandoned LNG storage project
Accounting Policies [Line Items]
Impairment loss		1,900	500
Springfield Operations Center | Washington Gas Light Company
Accounting Policies [Line Items]
Impairment loss	$ 500	$ 800	$ 2,600
Firm Customer | Washington Gas Light Company
Accounting Policies [Line Items]
Percentage of total gas deliveries	77.20%
Interruptible Customers | Washington Gas Light Company
Accounting Policies [Line Items]
Percentage of total gas deliveries	13.60%
Electric Generation Customers | Washington Gas Light Company
Accounting Policies [Line Items]
Percentage of total gas deliveries	9.20%
Electricity Customers | WGL Energy Services
Accounting Policies [Line Items]
Number of customers | Customers	138,000

Accounting Policies - Property,

Accounting Policies - Property, Plant and Equipment at Original Cost (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Sep. 30, 2014
Accounting Policies [Line Items]
Total	$ 5,003,910	$ 4,582,764
PP&E, other percentage	91.20%	93.60%
WGL
Accounting Policies [Line Items]
Total	$ 5,003,900	$ 4,582,800
Total regulated and unregulated segments, percentage	100.00%	100.00%
Regulated Utility
Accounting Policies [Line Items]
Distribution, transmission and storage	$ 3,927,200	$ 3,635,300
General, miscellaneous and intangibles	424,800	448,300
Construction work in progress (CWIP)	210,400	203,900
Total regulated and unregulated segments	$ 4,562,400	$ 4,287,500
Distribution, transmission and storage, percentage	78.50%	79.30%
General, miscellaneous and intangibles percentage	8.50%	9.80%
Construction work in progress (CWIP), percentage	4.20%	4.50%
PP&E, other percentage	91.20%	93.60%
Unregulated Operation [Member]
Accounting Policies [Line Items]
Total regulated and unregulated segments	$ 441,500	$ 295,300
PP&E, other percentage	8.80%	6.40%

Accounting Policies - Lower-of-

Accounting Policies - Lower-of-Cost or Market Adjustments Pre-Tax Increase (Decrease) to Net Income (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Accounting Policies [Line Items]
Lower of cost or market adjustment	$ (22.8)	$ (3.2)	$ (10.1)
Operating Revenues Non Utility | WGL
Accounting Policies [Line Items]
Lower of cost or market adjustment	(21.5)	(3)	(10.1)
Utility Cost Of Gas | Washington Gas Light Company
Accounting Policies [Line Items]
Lower of cost or market adjustment	$ (1.3)	$ (0.2)	$ 0

Accounting Policies - Changes i

Accounting Policies - Changes in Asset Retirement Obligations (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset retirement obligation, current	$ 7	$ 6
WGL
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset retirement obligations at beginning of year	181.2	104
Liabilities incurred in the period	8.4	4.9
Liabilities settled in the period	(14.6)	(5.2)
Accretion expense	7.8	4.4
Revisions in estimated cash flows	24.9	73.1
Asset retirement obligations at the end of the year	207.7	181.2
Washington Gas Light Company
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset retirement obligations at beginning of year	179.8	102.7
Liabilities incurred in the period	8.1	4.9
Liabilities settled in the period	(14.6)	(5.2)
Accretion expense	7.7	4.3
Revisions in estimated cash flows	24.9	73.1
Asset retirement obligations at the end of the year	$ 205.9	$ 179.8

Regulated Operations (Details)

Regulated Operations (Details) - USD ($) $ in Thousands		Sep. 30, 2015	Sep. 30, 2014
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Current		$ 5,797	$ 3,752
Regulatory Assets, Noncurrent		80,018	71,638
Gas costs due from/to customers
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Current	[1]	1,700	0
Regulatory Liabilities, Current	[1]	22,600	16,200
Interruptible Sharing
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Current		3,300	3,400
Regulatory Liabilities, Current		2,600	0
Revenue normalization mechanisms for Maryland and Virginia
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Current		0	0
Regulatory Liabilities, Current		8,400	5,500
Plant Recovery Mechanisms
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Current		800	400
Regulatory Liabilities, Current		1,000	900
Total current
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Current		5,800	3,800
Regulatory Liabilities, Current		34,600	22,600
Accrued Asset Removal Costs
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		0	0
Regulatory Liability, Noncurrent		325,500	327,400
Deferred Gas Costs
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent	[1]	190,700	191,300
Regulatory Liability, Noncurrent		0	0
Other post-retirement benefit costs-trackers
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent	[2]	100	0
Regulatory Liability, Noncurrent		0	0
Deferred pension costs/income-trackers
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent	[2]	38,000	45,100
Regulatory Liability, Noncurrent		0	0
Unrecognized Pension Cost
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent	[1],[3]	173,900	147,900
Regulatory Liability, Noncurrent		0	0
Unrecognized Other Post Retirement Benefits
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent	[1],[3]	0	0
Regulatory Liability, Noncurrent	[1],[3]	104,400	86,400
Total pension and other post-retirement benefits
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		212,000	193,000
Regulatory Liability, Noncurrent		104,400	86,400
Income tax-related amounts due from/to customers(d)
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent	[4]	31,700	30,400
Regulatory Liability, Noncurrent	[4]	4,200	4,800
Losses/gains on issuance and extinguishments of debt and interest-rate derivative instruments(a)(e)
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent	[1],[5]	11,100	12,000
Regulatory Liability, Noncurrent	[1],[5]	1,600	1,700
Deferred gain on sale of assets(a)
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		0	0
Regulatory Liability, Noncurrent	[1]	1,400	1,400
Rights-of-way fees(a)
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent	[1]	1,600	1,500
Regulatory Liability, Noncurrent	[1]	0	0
Business process outsourcing and related costs (a)
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent	[1]	2,700	1,000
Regulatory Liability, Noncurrent		0	0
Nonretirement postemployment benefits(a)(f)
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent	[1],[6]	18,900	16,300
Regulatory Liability, Noncurrent		0	0
Deferred integrity management expenditures(a)(g)
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent	[1],[7]	5,100	2,700
Regulatory Liability, Noncurrent		0	0
Recoverable portion of abandoned LNG facility(a)
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent	[1]	5,000	5,600
Regulatory Liability, Noncurrent		0	0
Environmental response costs
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent	[1],[8]	1,800	600
Regulatory Liability, Noncurrent	[8]	0	0
Other regulatory expenses(a)
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent	[1]	2,100	1,500
Regulatory Liability, Noncurrent	[1]	9,900	9,700
Total other
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		80,000	71,600
Regulatory Liability, Noncurrent		17,100	17,600
Total deferred
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		482,700	455,900
Regulatory Liability, Noncurrent		447,000	431,400
Total
Public Utilities, General Disclosures [Line Items]
Regulatory Assets		488,500	459,700
Regulatory Liabilities		$ 481,600	$ 454,000
[1]	Washington Gas does not earn its overall rate of return on these assets. Washington Gas is allowed to recover and required to pay, using short-term interest rates, the carrying costs related to billed gas costs due from and to its customers in the District of Columbia and Virginia jurisdictions.
[2]	Relates to the District of Columbia jurisdiction.
[3]	Refer to Note 10-Pension and Other Post-Retirement Benefit Plans for a further discussion of these amounts.
[4]	This balance represents amounts due from customers for deferred tax liabilities related to tax benefits on deduction flowed directly to customers prior to the adoption of income tax normalization for ratemaking purposes.
[5]	The losses or gains on the issuance and extinguishment of debt and interest-rate derivative instruments include unamortized balances from transactions executed in prior fiscal years. These transactions create gains and losses that are amortized over the remaining life of the debt as prescribed by regulatory accounting requirements.
[6]	Represents the timing difference between the recognition of workers compensation and short-term disability costs in accordance with generally accepted accounting principles and the way these costs are recovered through rates.
[7]	This balance represents amounts for deferred expenditures associated with Washington Gas’ Distribution Integrity Management Program (DIMP) in Virginia.
[8]	This balance represents allowed remediation expenditures at Washington Gas sites to be recovered through rates for Maryland and the District of Columbia. The recovery period is over several years.

Accounts Payable and Other Ac56

Accounts Payable and Other Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Sep. 30, 2014
Accounts Payable and Accrued Liabilities [Line Items]
Accounts payable—trade	$ 277,300	$ 278,800
Employee benefits and payroll accruals	31,400	19,800
Other accrued liabilities	16,400	14,600
Accounts payable and other accrued liabilities	325,146	313,221
Washington Gas Light Company
Accounts Payable and Accrued Liabilities [Line Items]
Accounts payable—trade	122,200	146,400
Employee benefits and payroll accruals	29,500	18,200
Other accrued liabilities	7,600	11,900
Accounts payable and other accrued liabilities	$ 159,280	$ 176,467

Short-Term Debt (Details)

Short-Term Debt (Details) $ in Thousands		12 Months Ended
		Sep. 30, 2015USD ($)extension	Sep. 30, 2014USD ($)
Short Term Debt [Line Items]
Less: Commercial Paper		$ (332,000)	$ (453,500)
Committed credit
Short Term Debt [Line Items]
Unsecured revolving credit facility	[1]	800,000	800,000
Less: Commercial Paper		(332,000)	(453,500)
Net committed credit available		$ 468,000	$ 346,500
Short-term debt weighted average interest rate		0.26%	0.19%
Outstanding bank loans		$ 0
Maximum
Short Term Debt [Line Items]
Ratio of Indebtedness to Net Capital		1
Ratio Of Indebtedness To Net Capital Percentage		65.00%
Minimum
Short Term Debt [Line Items]
Ratio of Indebtedness to Net Capital		0.65
WGL
Short Term Debt [Line Items]
Revolving credit facility additional borrowings		$ 100,000
Revolving credit facility maximum borrowing capacity		$ 550,000
Ratio Of Indebtedness To Net Capital Percentage		51.00%
Debt Instrument, Number of Extension Options | extension		2
Term of extension option		1 year
WGL | Committed credit
Short Term Debt [Line Items]
Unsecured revolving credit facility	[1],[2]	$ 450,000	$ 450,000
Less: Commercial Paper	[2]	(243,000)	(364,500)
Net committed credit available	[2]	$ 207,000	$ 85,500
Short-term debt weighted average interest rate	[2]	0.30%	0.20%
Outstanding bank loans		$ 0	$ 0
Washington Gas Light Company
Short Term Debt [Line Items]
Less: Commercial Paper		(89,000)	(89,000)
Revolving credit facility additional borrowings		100,000
Revolving credit facility maximum borrowing capacity		$ 450,000
Ratio Of Indebtedness To Net Capital Percentage		42.00%
Debt Instrument, Number of Extension Options | extension		2
Term of extension option		1 year
Washington Gas Light Company | Committed credit
Short Term Debt [Line Items]
Unsecured revolving credit facility	[1]	$ 350,000	350,000
Less: Commercial Paper		(89,000)	(89,000)
Net committed credit available		$ 261,000	$ 261,000
Short-term debt weighted average interest rate		0.16%	0.13%
Outstanding bank loans		$ 0	$ 0
[1]	(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.
[2]	(b) WGL includes all subsidiaries other than Washington Gas.

Long Term Debt (Details)

Long Term Debt (Details) - USD ($)		12 Months Ended
		Sep. 30, 2015	Sep. 30, 2014
Long-Term Debt Maturities
Current maturities		$ 25,000,000	$ 20,000,000
Long-term debt		944,201,000	679,228,000
Unamortized discount		$ 1,799,000	$ 122,000
Total consolidated
Senior Notes, MTNs and Private Placement Notes Outstanding
Weighted Average Interest Rate		5.08%	5.65%
Long-term notes		$ 971,000,000	$ 691,000,000	[1]
Senior Notes, MTNs and Private Placement Issuances and Retirements
Principal	[2]	300,000,000
Maturities
Long-Term Debt Maturities
2,016	[3]	25,000,000
2,017	[3]	0
2,018	[3]	0
2,019	[3]	50,000,000
2,020	[3]	150,000,000
Thereafter	[3]	746,000,000
Total	[3]	971,000,000
Current maturities	[3]	25,000,000
Long-term debt	[3]	$ 946,000,000
WGL
Senior Notes, MTNs and Private Placement Notes Outstanding
Weighted Average Interest Rate	[4]	3.66%
Long-term notes	[4]	$ 250,000,000	$ 0	[1]
Long-Term Debt Maturities
Unamortized discount		1,700,000
WGL | Medium-term Notes [Member]
Long-Term Debt Maturities
2,016	[3],[5]	0
2,017	[3],[5]	0
2,018	[3],[5]	0
2,019	[3],[5]	0
2,020	[3],[5]	100,000,000
Thereafter	[3],[5]	150,000,000
Total	[3],[5]	250,000,000
Current maturities	[3],[5]	0
Long-term debt	[3],[5]	250,000,000
WGL | Total consolidated
Senior Notes, MTNs and Private Placement Notes Outstanding
Long-term notes	[2],[6]	250,000,000
WGL | November 1, 2019 [Member] | Issuances [Member]
Senior Notes, MTNs and Private Placement Issuances and Retirements
Principal	[2],[6]	$ 100,000,000
Interest Rate	[6]	2.25%
Effective Cost	[6],[7]	2.42%
Nominal Maturity Date	[6]	Nov. 1, 2019
WGL | November 1, 2044 [Member] | Issuances [Member]
Senior Notes, MTNs and Private Placement Issuances and Retirements
Principal	[2],[6]	$ 125,000,000
Interest Rate	[6]	4.60%
Effective Cost	[6],[7]	5.11%
Nominal Maturity Date	[6]	Nov. 1, 2044
WGL | November 1, 2044 [Member] | Issuances [Member]
Senior Notes, MTNs and Private Placement Issuances and Retirements
Principal	[2],[6]	$ 25,000,000
Interest Rate	[6]	4.60%
Effective Cost	[6],[7]	5.53%
Nominal Maturity Date	[6]	Nov. 1, 2044
Washington Gas Light Company
Senior Notes, MTNs and Private Placement Notes Outstanding
Weighted Average Interest Rate		5.58%	5.65%
Long-term notes		$ 721,000,000	$ 691,000,000	[1]
Long-Term Debt Maturities
Current maturities		25,000,000	20,000,000
Long-term debt		695,885,000	679,228,000
Unamortized discount		115,000	122,000
Washington Gas Light Company | Medium-term Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Unused Borrowing Capacity, Amount		600,000,000
Washington Gas Light Company | Other Long Term Debt [Member]
Long-Term Debt Maturities
2,016	[3]	25,000,000
2,017	[3]	0
2,018	[3]	0
2,019	[3]	50,000,000
2,020	[3]	50,000,000
Thereafter	[3]	596,000,000
Total	[3]	721,000,000
Current maturities	[3]	25,000,000
Long-term debt	[3]	696,000,000
Washington Gas Light Company | First Mortgage
Debt Instrument [Line Items]
Mortgage Debt Outstanding		0	0
Washington Gas Light Company | Retirements [Member]
Senior Notes, MTNs and Private Placement Notes Outstanding
Long-term notes	[2]	20,000,000	67,000,000
Washington Gas Light Company | Total consolidated
Senior Notes, MTNs and Private Placement Notes Outstanding
Long-term notes	[2]	50,000,000	175,000,000
Washington Gas Light Company | December 15, 2044 [Member] | Issuances [Member]
Senior Notes, MTNs and Private Placement Issuances and Retirements
Principal	[2]	$ 50,000,000
Interest Rate		4.24%
Effective Cost	[7]	4.41%
Washington Gas Light Company | December 15, 2043 [Member] | Issuances [Member]
Senior Notes, MTNs and Private Placement Issuances and Retirements
Principal	[2]		$ 75,000,000
Interest Rate			5.00%
Effective Cost	[7]		4.95%
Nominal Maturity Date			Dec. 15, 2043
Washington Gas Light Company | September 15, 2044 [Member] | Issuances [Member]
Senior Notes, MTNs and Private Placement Issuances and Retirements
Principal	[2]		$ 100,000,000
Interest Rate			4.22%
Effective Cost	[7]		4.27%
Nominal Maturity Date			Sep. 15, 2044
Washington Gas Light Company | August 9, 2015 [Member] | Retirements [Member]
Senior Notes, MTNs and Private Placement Issuances and Retirements
Principal	[2]	$ 20,000,000
Interest Rate		4.83%
Nominal Maturity Date		Aug. 9, 2015
Washington Gas Light Company | November 7, 2013 [Member] | Issuances [Member]
Senior Notes, MTNs and Private Placement Issuances and Retirements
Nominal Maturity Date		Dec. 15, 2044
Washington Gas Light Company | November 7, 2013 [Member] | Retirements [Member]
Senior Notes, MTNs and Private Placement Issuances and Retirements
Principal	[2]		$ 37,000,000
Interest Rate			4.88%
Nominal Maturity Date			Nov. 7, 2013
Washington Gas Light Company | September 10, 2014 [Member] | Retirements [Member]
Senior Notes, MTNs and Private Placement Issuances and Retirements
Principal	[2]		$ 30,000,000
Interest Rate			5.17%
Nominal Maturity Date			Sep. 10, 2014
[1]	Includes Senior Notes for WGL and both MTNs and private placement notes for Washington Gas. Represents face value including current maturities.
[2]	Represents face amount.
[3]	(a)Excludes unamortized discounts of $1.7 million and $0.1 million at September 30, 2015, for WGL and Washington Gas, respectively.
[4]	WGL includes WGL Holdings and all subsidiaries other than Washington Gas.
[5]	(b)WGL includes WGL Holdings and all subsidiaries other than Washington Gas.
[6]	WGL includes WGL Holdings and all subsidiaries other than Washington Gas.
[7]	The estimated effective cost of the issued notes, including consideration of issuance fees and hedge costs.

Common Stock (Details)

Common Stock (Details) - shares		12 Months Ended
		Sep. 30, 2015	Sep. 30, 2014
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Common stock outstanding (in shares)		49,728,662	50,656,553
Omnibus incentive compensation plan (in shares)	[1]	993,825
Dividend reinvestment and common stock purchase plan (in shares)		2,849,012
Employee savings plans (in shares)		637,196
Directors’ stock compensation plan (in shares)		81,555
Total common stock reserves (in shares)		4,561,588
Performance shares granted but not vested (in shares)		304,089
Performance shares issuable percentage upon vesting		200.00%
[1]	In March 2007, WGL adopted a shareholder-approved Omnibus Incentive Compensation Plan to replace on a prospective basis the 1999 Incentive Compensation Plan. Included are shares that may be issued upon the vesting of 304,089 performance shares that have been granted but not yet vested. Upon vesting, a number of shares equal to up to 200% of the number of performance shares granted may be issued, which would reduce the number of shares available for issuance under the Omnibus Incentive Compensation Plan. Refer to Note 11—Stock-Based Compensation for a discussion regarding our stock-based compensation plans.

Preferred Stock (Details)

Preferred Stock (Details) - $ / shares	Sep. 30, 2015	Sep. 30, 2014
Preferred Stock, Par or Stated Value Per Share (in dollars per share)	$ 0	$ 0
Washington Gas Light Company
Preferred Stock, Par or Stated Value Per Share (in dollars per share)	0	$ 0
Series One [Member] | Washington Gas Light Company
Preferred Stock, Par or Stated Value Per Share (in dollars per share)	$ 4.80
Preferred Stock, Shares Outstanding (in shares)	150,000
Preferred Stock, Liquidation Preference Per Share Involuntary (in dollars per share)	$ 100
Preferred Stock Liquidation Preference Voluntary (in dollars per share)	101
Preferred Stock, Redemption Price Per Share (in dollars per share)	101
Series Two [Member] | Washington Gas Light Company
Preferred Stock, Par or Stated Value Per Share (in dollars per share)	$ 4.25
Preferred Stock, Shares Outstanding (in shares)	70,600
Preferred Stock, Liquidation Preference Per Share Involuntary (in dollars per share)	$ 100
Preferred Stock Liquidation Preference Voluntary (in dollars per share)	105
Preferred Stock, Redemption Price Per Share (in dollars per share)	105
Series Three [Member] | Washington Gas Light Company
Preferred Stock, Par or Stated Value Per Share (in dollars per share)	$ 5
Preferred Stock, Shares Outstanding (in shares)	60,000
Preferred Stock, Liquidation Preference Per Share Involuntary (in dollars per share)	$ 100
Preferred Stock Liquidation Preference Voluntary (in dollars per share)	102
Preferred Stock, Redemption Price Per Share (in dollars per share)	$ 102

Earnings Per Share (Details)

Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Earnings Per Share [Abstract]
Net income (loss) applicable to common stock	$ 131,259	$ 105,940	$ 80,253
Basic (in shares)	49,794	51,759	51,697
Basic earnings per average common share	$ 2.64	$ 2.05	$ 1.55
Stock-based compensation plan	266	11	111
Total average common shares outstanding diluted (in shares)	50,060	51,770	51,808
Diluted earnings per average common share (in dollars per share)	$ 2.62	$ 2.05	$ 1.55

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Income Taxes [Line Items]
Regulatory asset, amortization period		5 years
Washington Gas Light Company
Income Taxes [Line Items]
Tax savings realized from tax sharing agreement	$ 0.5	$ 2.9	$ 1.3
Unrecognized tax benefits increase (decrease)	$ 6

Income Taxes (Components of Inc

Income Taxes (Components of Income Tax Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Deferred
Total deferred	$ 104,405	$ 25,795	$ 1,431
Total income tax expense	83,804	57,254	52,292
WGL
Current
Federal	(18,639)	29,976	41,425
State	2,977	5,149	11,258
Total current	(15,662)	35,125	52,683
Deferred
Total deferred	104,405	25,795	1,431
Amortization of investment tax credits	(4,939)	(3,666)	(1,822)
Total income tax expense	83,804	57,254	52,292
WGL | Accelerated Depreciation [Member]
Deferred
Federal	71,529	35,747	33,394
State	13,739	9,822	6,795
WGL | Other Federal [Member]
Deferred
Federal	17,726	(18,014)	(31,173)
State	1,411	(1,760)	(7,585)
Washington Gas Light Company
Current
Federal	(5,305)	37,098	40,492
State	907	4,262	7,515
Total current	(4,398)	41,360	48,007
Deferred
Total deferred	76,621	7,050	(2,915)
Amortization of investment tax credits	(832)	(876)	(895)
Total income tax expense	71,391	47,534	44,197
Washington Gas Light Company | Accelerated Depreciation [Member]
Deferred
Federal	71,046	34,833	34,518
State	13,701	9,540	6,770
Washington Gas Light Company | Other Federal [Member]
Deferred
Federal	(6,619)	(30,523)	(35,982)
State	$ (1,507)	$ (6,800)	$ (8,221)

Income Taxes (Tax Rate Reconcil

Income Taxes (Tax Rate Reconciliation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Income Taxes [Line Items]
Total income tax expense	$ 83,804	$ 57,254	$ 52,292
WGL
Income Taxes [Line Items]
Income taxes at statutory federal tax rate	75,760	57,580	46,853
Accelerated depreciation less amount deferred	1,187	1,875	2,106
Amortization of investment tax credits	(4,939)	(3,666)	(1,822)
Cost of removal	(2,721)	(4,902)	(2,356)
State income taxes-net of federal benefit	11,109	8,734	7,448
Medicare Part D adjustment	0	(3,621)	0
ASDHI impairment	1,969	0	0
Other items-net	1,439	1,254	63
Total income tax expense	$ 83,804	$ 57,254	$ 52,292
Statutory federal income tax rate (%)	35.00%	35.00%	35.00%
Accelerated depreciation less amount deferred (%)	0.55%	1.14%	1.57%
Amortization of investment tax credits (%)	(2.28%)	(2.23%)	(1.36%)
Cost of removal (%)	(1.26%)	(2.98%)	(1.76%)
State income taxes-net of federal benefit (%)	5.13%	5.31%	5.56%
Medicare Part D adjustment (%)	0.00%	(2.20%)	0.00%
ASDHI impairment (%)	0.91%	0.00%	0.00%
Other items-net (%)	0.66%	0.76%	0.05%
Effective Income Tax Rate, Continuing Operations, Total	38.71%	34.80%	39.06%
Washington Gas Light Company
Income Taxes [Line Items]
Income taxes at statutory federal tax rate	$ 63,024	$ 51,050	$ 40,782
Accelerated depreciation less amount deferred	2,108	1,875	2,106
Amortization of investment tax credits	(832)	(876)	(895)
Cost of removal	(2,721)	(4,902)	(2,356)
State income taxes-net of federal benefit	8,986	6,711	5,487
Consolidated tax sharing allocation	(533)	(2,862)	(1,290)
Medicare Part D adjustment	0	(3,621)	0
Other items-net	1,359	159	363
Total income tax expense	$ 71,391	$ 47,534	$ 44,197
Statutory federal income tax rate (%)	35.00%	35.00%	35.00%
Accelerated depreciation less amount deferred (%)	1.17%	1.29%	1.81%
Amortization of investment tax credits (%)	(0.46%)	(0.60%)	(0.77%)
Cost of removal (%)	(1.51%)	(3.36%)	(2.02%)
State income taxes-net of federal benefit (%)	4.99%	4.60%	4.71%
Consolidated tax sharing allocation (%)	(0.30%)	(1.96%)	(1.11%)
Medicare Part D adjustment (%)	0.00%	(2.48%)	0.00%
Other items-net (%)	0.76%	0.09%	0.31%
Effective Income Tax Rate, Continuing Operations, Total	39.65%	32.58%	37.93%

Income Taxes (Components of Def

Income Taxes (Components of Deferred Tax Assets) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Sep. 30, 2014
Current [Member]
Deferred Income Tax Assets:
Pensions	$ 0	$ 0
Uncollectible accounts	10,389	9,268
Inventory overheads	5,873	6,591
Employee compensation and benefits	4,733	6,306
Derivatives	8,580	6,503
Deferred gas costs	2,406	0
Solar grant/ investment tax credit	0	0
Tax credit carry forward	0	0
Other	861	814
Total assets	32,842	29,482
Deferred Income Tax Liabilities:
Other post-retirement benefits	0	0
Accelerated depreciation and other plant related items	0	0
Losses/gains on reacquired debt	0	0
Income taxes recoverable through future rates	0	0
Deferred gas costs	0	2,818
Partnership basis difference	0	0
Valuation allowances	0	0
Total liabilities	0	2,818
Net accumulated deferred income tax assets (liabilities)	32,842	26,664
Non-current [Member]
Deferred Income Tax Assets:
Pensions	44,468	24,349
Uncollectible accounts	0	0
Inventory overheads	0	0
Employee compensation and benefits	52,497	37,873
Derivatives	35,311	31,555
Deferred gas costs	0	4,218
Solar grant/ investment tax credit	53,067	39,184
Tax credit carry forward	55,040	0
Other	4,779	1,422
Total assets	245,162	138,601
Deferred Income Tax Liabilities:
Other post-retirement benefits	54,860	38,299
Accelerated depreciation and other plant related items	794,099	669,040
Losses/gains on reacquired debt	1,292	1,426
Income taxes recoverable through future rates	68,245	65,374
Deferred gas costs	815	0
Partnership basis difference	29,468	25,370
Valuation allowances	2,188	0
Total liabilities	950,967	799,509
Net accumulated deferred income tax assets (liabilities)	(705,805)	(660,908)
Washington Gas Light Company | Current [Member]
Deferred Income Tax Assets:
Pensions	0	0
Uncollectible accounts	7,637	7,618
Inventory overheads	5,873	6,591
Employee compensation and benefits	4,346	5,902
Derivatives	3,576	4,809
Deferred gas costs	2,406	0
Solar grant/ investment tax credit	0	0
Other	862	814
Total assets	24,700	25,734
Deferred Income Tax Liabilities:
Other post-retirement benefits	0	0
Accelerated depreciation and other plant related items	0	0
Losses/gains on reacquired debt	0	0
Income taxes recoverable through future rates	0	0
Deferred gas costs	0	2,818
Other	0	0
Total liabilities	0	2,818
Net accumulated deferred income tax assets (liabilities)	24,700	22,916
Washington Gas Light Company | Non-current [Member]
Deferred Income Tax Assets:
Pensions	43,748	23,738
Uncollectible accounts	0	0
Inventory overheads	0	0
Employee compensation and benefits	34,511	27,961
Derivatives	35,311	31,555
Deferred gas costs	0	4,218
Solar grant/ investment tax credit	0	312
Other	0	197
Total assets	113,570	87,981
Deferred Income Tax Liabilities:
Other post-retirement benefits	54,566	38,065
Accelerated depreciation and other plant related items	681,108	602,376
Losses/gains on reacquired debt	1,292	1,426
Income taxes recoverable through future rates	67,953	65,128
Deferred gas costs	815	0
Other	1,300	932
Total liabilities	807,034	707,927
Net accumulated deferred income tax assets (liabilities)	$ (693,464)	$ (619,946)

Income Taxes (Unrecognized Tax

Income Taxes (Unrecognized Tax Benefits) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Unrecognized Tax Benefits
Total unrecognized tax benefits, beginning balance	$ 32,613	$ 25,051	$ 22,082
Increases in tax positions relating to current year	12,848	10,512	5,251
Decreases in tax positions relating to prior year	(6,834)	(2,950)	(2,282)
Total unrecognized tax benefits, ending balance	$ 38,627	$ 32,613	$ 25,051

Pension and Other Post-retire67

Pension and Other Post-retirement Benefit Plans (Narrative) (Details) - USD ($)	Jan. 01, 2018	Sep. 30, 2015	Sep. 30, 2015		Sep. 30, 2014		Sep. 30, 2013	Sep. 30, 2021	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Defined Benefit Plan Disclosure [Line Items]
Total matching contributions			$ 4,600,000		$ 4,200,000		$ 4,300,000
Total supplemental contributions			2,100,000		1,600,000		800,000
Accumulated post-retirement benefit obligation, transition obligation							190,600,000
Prior service credit related to plan amendment		$ 26,100,000	$ (696,000)	[1]	(6,095,000)	[1]	1,671,000
Change in plan's funded status					$ 127,500,000
Percentage of prior years asset gains and losses recognized		20.00%	20.00%
Realized and unrealized gains and losses on equities prior year			80.00%
Realized and unrealized gains and losses on equities second prior year			60.00%
Realized and unrealized gains and losses on equities third prior year		40.00%	40.00%
Realized and unrealized gains and losses on equities fourth prior year		20.00%	20.00%
Defined Benefit Plan, Assumed Health Care Cost Trend Rates [Abstract]
Health Care Cost Trend Rates For Non Medicare Eligible Retirees		6.70%	6.70%		7.00%
Defined Benefit Plan Target Allocation Percentage [Abstract]
Asset Class Allocations Allowed Range Within Plus Or Minus		5.00%	5.00%
EGWP effect on post retirement benefits			$ 800,000		$ 500,000
Scenario, Forecast
Defined Benefit Plan, Assumed Health Care Cost Trend Rates [Abstract]
Future Healthcare Cost Trend Rates								5.00%	2.20%	3.20%	6.30%	0.00%
Post 2016 HRA Stipend Increase											3.00%
Union Eligible Employee
Defined Benefit Plan Target Allocation Percentage [Abstract]
US Large Cap Equities		50.00%	50.00%
Fixed Income And Cash		50.00%	50.00%
Management Employee
Defined Benefit Plan Target Allocation Percentage [Abstract]
US Large Cap Equities		60.00%	60.00%
Fixed Income And Cash		40.00%	40.00%
Aggregate Cost Limit Per Individual | Scenario, Forecast
Defined Benefit Plan Disclosure [Line Items]
Retiree Medical employer sponsored coverage limits under amendment	$ 11,850
Aggregate Cost Limit Per Family | Scenario, Forecast
Defined Benefit Plan Disclosure [Line Items]
Retiree Medical employer sponsored coverage limits under amendment	$ 30,950
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Prior service credit related to plan amendment			$ 300,000		300,000		1,000,000
The projected benefit obligation (PBO)		$ 892,200,000	892,200,000		865,200,000
Increase in PBO due to changes in mortality assumptions			$ 46,800,000
Defined Benefit Plan Target Allocation Percentage [Abstract]
US Large Cap Equities		32.50%	32.50%
US Small Mid Cap Equities		4.50%	4.50%
International Equities		8.00%	8.00%
Real Estate Investments		5.00%	5.00%
Fixed Income And Cash		50.00%	50.00%
Employer payment current fiscal year		$ 0	$ 0
Pension Plan | Scenario, Forecast
Defined Benefit Plan Target Allocation Percentage [Abstract]
Estimated future employer contributions in next fiscal year												$ 0
Other post-retirement benefits
Defined Benefit Plan Disclosure [Line Items]
Prior service credit related to plan amendment			(15,300,000)		(9,600,000)		$ (3,900,000)
Increase in PBO due to changes in mortality assumptions					15,300,000
Defined Benefit Plan Target Allocation Percentage [Abstract]
Employer payment current fiscal year		16,000,000	16,000,000
Other post-retirement benefits | Scenario, Forecast
Defined Benefit Plan Target Allocation Percentage [Abstract]
Estimated future employer contributions in next fiscal year												16,000,000
DB Restoration
Defined Benefit Plan Disclosure [Line Items]
The projected benefit obligation (PBO)		2,300,000	2,300,000		1,200,000
DB SERP
Defined Benefit Plan Disclosure [Line Items]
The projected benefit obligation (PBO)		53,000,000	53,000,000		$ 50,700,000
Defined Benefit Plan Target Allocation Percentage [Abstract]
Employer payment current fiscal year		$ 1,800,000	$ 1,800,000
DB SERP | Scenario, Forecast
Defined Benefit Plan Target Allocation Percentage [Abstract]
Estimated future employer contributions in next fiscal year												$ 4,800,000
Maximum
Defined Benefit Plan Disclosure [Line Items]
Percentage Of supplemental contribution			6.00%
Minimum
Defined Benefit Plan Disclosure [Line Items]
Percentage Of supplemental contribution			4.00%
[1]	(b) These accumulated other comprehensive income (loss) components are included in the computation of net periodic benefit cost. Refer to Note 10-Pension and other post-retirement benefit plans for additional details.

Pension and Other Post-retire68

Pension and Other Post-retirement Benefit Plans (Table 1) (Details) - USD ($) $ in Thousands		12 Months Ended
		Sep. 30, 2015		Sep. 30, 2014		Sep. 30, 2013
Change in plan assets
Fair Value of plan assets at beginning of year		$ 23,800		$ 21,100
Fair value of plan assets at end of year		27,700		23,800		$ 21,100
Total Recognized
Non-current asset		138,629		96,385
Non-current liability		(176,128)		(120,446)
Pension Plan
Change in projected benefit obligation
Benefit obligation at beginning of year	[1]	917,100		837,400
Service cost		15,500	[1]	14,000	[1]	17,000
Interest cost		39,100	[1]	40,400	[1]	36,600
Change in plan benefits	[1]	600		0
Actuarial loss (gain)	[1]	19,200		68,600
Retiree Contributions	[1]	0		0
Employer group waiver plan rebates	[1]	0		0
Benefits Paid	[1]	(44,000)		(43,300)
Projected benefit obligation at end of year	[1]	947,500		917,100		837,400
Change in plan assets
Fair Value of plan assets at beginning of year	[1]	804,700		745,200
Actual return on plan assets	[1]	19,900		103,300
Company contributions	[1]	1,800		1,700
Retiree Contributions and employer group waiver plan rebates	[1]	0		0
Expenses	[1]	(2,200)		(2,200)
Benefits Paid	[1]	(44,000)		(43,300)
Fair value of plan assets at end of year	[1]	780,200		804,700		745,200
Funded status at end of year	[1]	(167,300)		(112,400)
Total Recognized
Non-current asset	[1]	0		0
Current liability	[1]	(4,800)		(4,200)
Non-current liability	[1]	(162,500)		(108,200)
Total Recognized	[1]	(167,300)		(112,400)
Other post-retirement benefits
Change in projected benefit obligation
Benefit obligation at beginning of year		343,200	[2]	429,800
Service cost		7,100		7,600		9,600
Interest cost		14,700		18,700		18,800
Change in plan benefits		(26,100)		(136,500)
Actuarial loss (gain)		(23,700)		38,200
Retiree Contributions		2,000		4,400
Employer group waiver plan rebates		2,400		500
Benefits Paid		(19,700)		(19,500)
Projected benefit obligation at end of year		299,900	[2]	343,200	[2]	429,800
Change in plan assets
Fair Value of plan assets at beginning of year		439,600		380,900
Actual return on plan assets		(300)		57,800
Company contributions		16,000		16,000
Retiree Contributions and employer group waiver plan rebates		3,600		4,400
Expenses		(700)		0
Benefits Paid		(19,700)		(19,500)
Fair value of plan assets at end of year		438,500		439,600		$ 380,900
Funded status at end of year		138,600		96,400
Total Recognized
Non-current asset		138,600		96,400
Current liability		0		0
Non-current liability		0		0
Total Recognized		$ 138,600		$ 96,400
[1]	(a)The DB SERP and DB Restoration, included in pension benefits in the table above, have no assets.
[2]	(b)For the Health and Life Benefits, the change in projected benefit obligation represents the accumulated benefit obligation.

Pension and Other Post-retire69

Pension and Other Post-retirement Benefit Plans (Table2) (Details) - USD ($) $ in Millions	Sep. 30, 2015	Sep. 30, 2014
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	$ 892.2	$ 865.2
Accumulated benefit obligation	822.8	801.9
DB SERP
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	53	50.7
Accumulated benefit obligation	48.7	46.2
DB Restoration
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	2.3	1.2
Accumulated benefit obligation	$ 1.2	$ 0.7

Pension and Other Post-retire70

Pension and Other Post-retirement Benefit Plans (Table 3) (Details) - USD ($) $ in Thousands		12 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Unrecognized Costs/Income Recorded on the Balance Sheet
AOCI, tax expense (benefit)		$ 5,100	$ 4,900
Deferred Income Tax Benefit		104,405	25,795	$ 1,431
Pension Plan
Unrecognized Costs/Income Recorded on the Balance Sheet
Unrecognized actuarial net loss		190,100	162,600
Unrecognized prior service cost (credit)		1,500	1,200
Total		191,600	163,800
Regulatory asset	[1]	173,900	147,900
Pre-tax accumulated other comprehensive loss (gain)	[2]	17,700	15,900
Total		191,600	163,800
Deferred Income Tax Benefit		6,100	8,200
Other post-retirement benefits
Unrecognized Costs/Income Recorded on the Balance Sheet
Unrecognized actuarial net loss		43,800	50,100
Unrecognized prior service cost (credit)		(160,200)	(149,300)
Total		(116,400)	(99,200)
Regulatory asset	[1]	(110,500)	(94,600)
Pre-tax accumulated other comprehensive loss (gain)	[2]	(5,900)	(4,600)
Total		$ (116,400)	$ (99,200)
[1]	(a) The regulatory liability recorded on our balance sheets at September 30, 2015 and 2014 is net of a deferred income tax benefit of $6.1 million and $8.2 million, respectively.
[2]	(b)The total amount of accumulated other comprehensive loss recorded on our balance sheets at September 30, 2015 and 2014 is net of an income tax benefit of $5.1 million and $4.9 million, respectively.

Pension and Other Post-retire71

Pension and Other Post-retirement Benefit Plans (Table 4) (Details) $ in Millions	12 Months Ended
	Sep. 30, 2015USD ($)
Pension Plan | Regulatory Assets and Liabilities
Amounts Recognized During Fiscal Year
Actuarial net loss	$ 16.9
Prior service cost (credit)	0.3
Total	17.2
Amounts to be Recognized During Fiscal Year
Actuarial net loss	15.3
Prior service cost (credit)	0.2
Total	15.5
Pension Plan | Accumulated Other Comprehensive Loss
Amounts Recognized During Fiscal Year
Actuarial net loss	1.8
Prior service cost (credit)	0
Total	1.8
Amounts to be Recognized During Fiscal Year
Actuarial net loss	1.5
Prior service cost (credit)	0.1
Total	1.6
Health and Life Benefits | Regulatory Assets and Liabilities
Amounts Recognized During Fiscal Year
Actuarial net loss	4.2
Prior service cost (credit)	(14.6)
Total	(10.4)
Amounts to be Recognized During Fiscal Year
Actuarial net loss	1.2
Prior service cost (credit)	(16.8)
Total	(15.6)
Health and Life Benefits | Accumulated Other Comprehensive Loss
Amounts Recognized During Fiscal Year
Actuarial net loss	0.2
Prior service cost (credit)	(0.7)
Total	(0.5)
Amounts to be Recognized During Fiscal Year
Actuarial net loss	0.1
Prior service cost (credit)	(0.9)
Total	$ (0.8)

Pension and Other Post-retire72

Pension and Other Post-retirement Benefit Plans (Table 5) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Sep. 30, 2015		Sep. 30, 2014		Sep. 30, 2013
Defined Benefit Plan Disclosure [Line Items]
Recognized prior service cost (credit)	$ 26,100	$ (696)	[1]	$ (6,095)	[1]	$ 1,671
Recognized actuarial loss		1,195	[1]	(1,594)	[1]	(3,399)
Change in transition obligation		0		0		(238)
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost		15,500	[2]	14,000	[2]	17,000
Interest cost		39,100	[2]	40,400	[2]	36,600
Expected return on plan assets		(44,600)		(41,000)		(41,900)
Recognized prior service cost (credit)		300		300		1,000
Recognized actuarial loss		18,700		16,800		28,700
Change in transition obligation		0		0		0
Net periodic benefit cost		29,000		30,500		41,400
Amount allocated to construction projects		(4,600)		(4,300)		(5,700)
Amount deferred as regulatory asset (liability)-net		7,100		7,000		(3,700)
Amount charged (credited) to expense		31,500		33,200		32,000
Health and Life Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost		7,100		7,600		9,600
Interest cost		14,700		18,700		18,800
Expected return on plan assets		(20,800)		(19,300)		(18,300)
Recognized prior service cost (credit)		(15,300)		(9,600)		(3,900)
Recognized actuarial loss		4,400		5,000		9,200
Change in transition obligation		0		0		1,100
Net periodic benefit cost		(9,900)		2,400		16,500
Amount allocated to construction projects		1,900		(400)		(2,800)
Amount deferred as regulatory asset (liability)-net		(200)		(2,300)		2,400
Amount charged (credited) to expense		$ (8,200)		$ (300)		$ 16,100
[1]	(b) These accumulated other comprehensive income (loss) components are included in the computation of net periodic benefit cost. Refer to Note 10-Pension and other post-retirement benefit plans for additional details.
[2]	(a)The DB SERP and DB Restoration, included in pension benefits in the table above, have no assets.

Pension and Other Post-retire73

Pension and Other Post-retirement Benefit Plans (Table 6) (Details)		12 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Pension Plan
Net Periodic Benefit Cost Assumptions [Abstract]
Discount rate	[1]			4.00%
Expected long-term return on plan assets	[2]	6.75%	6.50%	6.75%
Pension Plan | Maximum
Benefit Obligations Assumptions [Abstract]
Discount rate		4.50%	4.40%
Rate of compensation increase		4.10%	4.10%
Net Periodic Benefit Cost Assumptions [Abstract]
Discount rate		4.40%	5.00%
Rate of compensation increase		4.10%	5.15%	5.15%
Pension Plan | Minimum
Benefit Obligations Assumptions [Abstract]
Discount rate		4.10%	4.00%
Rate of compensation increase		3.50%	3.50%
Net Periodic Benefit Cost Assumptions [Abstract]
Discount rate		4.00%	4.50%
Rate of compensation increase		3.50%	3.85%	3.85%
Health and Life Benefits
Benefit Obligations Assumptions [Abstract]
Discount rate		4.50%	4.40%
Rate of compensation increase		4.10%	4.10%
Net Periodic Benefit Cost Assumptions [Abstract]
Discount rate	[1]	4.40%		4.00%
Expected long-term return on plan assets	[2]	6.25%	6.25%	6.75%
Rate of compensation increase	[3]	4.10%	3.85%	3.85%
Assumed Income Tax Rate		45.60%
Health and Life Benefits | Maximum
Net Periodic Benefit Cost Assumptions [Abstract]
Discount rate			5.10%
Health and Life Benefits | Minimum
Net Periodic Benefit Cost Assumptions [Abstract]
Discount rate			4.60%
[1]	(a) The changes in the discount rates over the last three fiscal years primarily reflect the changes in long-term interest rates.
[2]	(b) For health and life benefits, the expected returns for certain funds may be lower due to certain portions of income that are subject to an assumed income tax rate of 45.6%.
[3]	(c) The changes in the rate of compensation reflects the best estimates of actual future compensation levels including consideration of general price levels, productivity, seniority, promotion, and other factors such as inflation rates.

Pension and Other Post-retire74

Pension and Other Post-retirement Benefit Plans (Table 7) (Details) $ in Millions	12 Months Ended
	Sep. 30, 2015USD ($)
Defined Benefit Plan, Assumed Health Care Cost Trend Rates [Abstract]
Increase one percentage point total service and interest cost components	$ 1.3
Decrease one percentage point total service and interest cost components	(1.1)
Increase one percentage point post-retirement benefit obligation	5.7
Decrease one percentage point post-retirement benefit obligation	$ (5.1)

Pension and Other Post-retire75

Pension and Other Post-retirement Benefit Plans (Table 8) (Details) - USD ($) $ in Millions		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets at end of year		$ 27.7	$ 23.8	$ 21.1
Pension Plan
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		781.9	803.7
Receivable (Payable)	[1]	(1.7)	1
Fair value of plan assets at end of year	[2]	$ 780.2	$ 804.7	745.2
Percentage of fair value of plan investments		100.20%	99.90%
Percent Receivable (Payable)	[1]	(0.20%)	0.10%
Total plan assets percent		100.00%	100.00%
Pension Plan | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		$ 29.5	$ 32.9
Pension Plan | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		724.7	747
Pension Plan | Level 3 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		27.7	23.8
Pension Plan | Cash and Cash Equivalents [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		$ 0.8	$ 0.6
Percentage of fair value of plan investments		0.10%	0.10%
Pension Plan | Cash and Cash Equivalents [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		$ 0.8	$ 0.6
Pension Plan | Cash and Cash Equivalents [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		0	0
Pension Plan | Cash and Cash Equivalents [Member] | Level 3 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		0	0
Pension Plan | Equity Securities US Small Cap [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		$ 28.7	$ 32.3
Percentage of fair value of plan investments		3.70%	4.00%
Pension Plan | Equity Securities US Small Cap [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		$ 28.7	$ 32.3
Pension Plan | Equity Securities US Small Cap [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		0	0
Pension Plan | Equity Securities US Small Cap [Member] | Level 3 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		0	0
Pension Plan | Equity Securities Preferred [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		$ 0.1	$ 0.1
Percentage of fair value of plan investments		0.00%	0.00%
Pension Plan | Equity Securities Preferred [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		$ 0	$ 0
Pension Plan | Equity Securities Preferred [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		0.1	0.1
Pension Plan | Equity Securities Preferred [Member] | Level 3 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		0	0
Pension Plan | US Treasury Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		$ 101.3	$ 110.6
Percentage of fair value of plan investments		13.00%	13.80%
Pension Plan | US Treasury Securities [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		$ 0	$ 0
Pension Plan | US Treasury Securities [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		101.3	110.6
Pension Plan | US Treasury Securities [Member] | Level 3 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		0	0
Pension Plan | Domestic Corporate Debt Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		$ 204.6	$ 108.4
Percentage of fair value of plan investments		26.20%	13.50%
Pension Plan | Domestic Corporate Debt Securities [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		$ 0	$ 0
Pension Plan | Domestic Corporate Debt Securities [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		204.6	108.4
Pension Plan | Domestic Corporate Debt Securities [Member] | Level 3 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		0	0
Pension Plan | U S Government Agencies And Sponsored Entities Debt Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		$ 23.9	$ 24.6
Percentage of fair value of plan investments		3.10%	3.00%
Pension Plan | U S Government Agencies And Sponsored Entities Debt Securities [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		$ 0	$ 0
Pension Plan | U S Government Agencies And Sponsored Entities Debt Securities [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		23.9	24.6
Pension Plan | U S Government Agencies And Sponsored Entities Debt Securities [Member] | Level 3 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		0	0
Pension Plan | Asset-backed Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		$ 1.7	$ 1.8
Percentage of fair value of plan investments		0.20%	0.20%
Pension Plan | Asset-backed Securities [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		$ 0	$ 0
Pension Plan | Asset-backed Securities [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		1.7	1.8
Pension Plan | Asset-backed Securities [Member] | Level 3 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		0	0
Pension Plan | Municipalities
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		$ 14	$ 9.2
Percentage of fair value of plan investments		1.80%	1.10%
Pension Plan | Municipalities | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		$ 0	$ 0
Pension Plan | Municipalities | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		14	9.2
Pension Plan | Municipalities | Level 3 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		0	0
Pension Plan | Foreign Corporate Debt Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		$ 37.1	$ 23.8
Percentage of fair value of plan investments		4.80%	3.00%
Pension Plan | Foreign Corporate Debt Securities [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		$ 0	$ 0
Pension Plan | Foreign Corporate Debt Securities [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		37.1	23.8
Pension Plan | Foreign Corporate Debt Securities [Member] | Level 3 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		0	0
Pension Plan | Repurchase Agreements [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments	[3]	$ 5.3	$ 2.5
Percentage of fair value of plan investments	[3]	0.70%	0.30%
Pension Plan | Repurchase Agreements [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments	[3]	$ 0	$ 0
Pension Plan | Repurchase Agreements [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments	[3]	5.3	2.5
Pension Plan | Repurchase Agreements [Member] | Level 3 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments	[3]	0	0
Pension Plan | Fixed Income Securities Other [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments	[4]	$ 4.7	$ 7
Percentage of fair value of plan investments	[4]	0.60%	0.80%
Pension Plan | Fixed Income Securities Other [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments	[4]	$ 0	$ 0
Pension Plan | Fixed Income Securities Other [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments	[4]	4.7	7
Pension Plan | Fixed Income Securities Other [Member] | Level 3 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments	[4]	0	0
Pension Plan | Mutual Funds [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments	[5]	$ 29.3	$ 112.4
Percentage of fair value of plan investments	[5]	3.70%	14.00%
Pension Plan | Mutual Funds [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments	[5]	$ 0	$ 0
Pension Plan | Mutual Funds [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments	[5]	29.3	112.4
Pension Plan | Mutual Funds [Member] | Level 3 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments	[5]	0	0
Pension Plan | Commingled Funds And Pooled Separate Accounts [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments	[6]	$ 302.5	$ 340
Percentage of fair value of plan investments	[6]	38.70%	42.30%
Pension Plan | Commingled Funds And Pooled Separate Accounts [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments	[6]	$ 0	$ 0
Pension Plan | Commingled Funds And Pooled Separate Accounts [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments	[6]	274.8	316.2
Pension Plan | Commingled Funds And Pooled Separate Accounts [Member] | Level 3 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments	[6]	27.7	23.8
Pension Plan | Private Equity / Limited Partnership
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments	[7]	$ 28	$ 30.5
Percentage of fair value of plan investments	[7]	3.60%	3.80%
Pension Plan | Private Equity / Limited Partnership | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments	[7]	$ 0	$ 0
Pension Plan | Private Equity / Limited Partnership | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments	[7]	28	30.5
Pension Plan | Private Equity / Limited Partnership | Level 3 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments	[7]	0	0
Pension Plan | Derivatives [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments	[8]	$ (0.1)	$ (0.1)
Percentage of fair value of plan investments	[8]	0.00%	0.00%
Pension Plan | Derivatives [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments	[8]	$ 0	$ 0
Pension Plan | Derivatives [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments	[8]	(0.1)	(0.1)
Pension Plan | Derivatives [Member] | Level 3 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments	[8]	0	0
Health and Life Benefits
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		437.8	439.8
Receivable (Payable)		0.7	(0.2)
Fair value of plan assets at end of year		$ 438.5	$ 439.6	$ 380.9
Percentage of fair value of plan investments		99.80%	100.00%
Percent Receivable (Payable)		0.20%	0.00%
Total plan assets percent		100.00%	100.00%
Health and Life Benefits | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		$ 1.9	$ 0.8
Health and Life Benefits | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		435.9	439
Health and Life Benefits | Level 3 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		0	0
Health and Life Benefits | Cash and Cash Equivalents [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		$ 0	$ 0.8
Percentage of fair value of plan investments		0.00%	0.20%
Health and Life Benefits | Cash and Cash Equivalents [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		$ 0	$ 0.8
Health and Life Benefits | Cash and Cash Equivalents [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		0	0
Health and Life Benefits | Cash and Cash Equivalents [Member] | Level 3 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		0	0
Health and Life Benefits | US Treasury Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		$ 27.7	$ 25.6
Percentage of fair value of plan investments		6.30%	5.80%
Health and Life Benefits | US Treasury Securities [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		$ 0	$ 0
Health and Life Benefits | US Treasury Securities [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		27.7	25.6
Health and Life Benefits | US Treasury Securities [Member] | Level 3 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		0	0
Health and Life Benefits | Domestic Corporate Debt Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		$ 33.5	$ 34
Percentage of fair value of plan investments		7.70%	7.70%
Health and Life Benefits | Domestic Corporate Debt Securities [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		$ 0	$ 0
Health and Life Benefits | Domestic Corporate Debt Securities [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		33.5	34
Health and Life Benefits | Domestic Corporate Debt Securities [Member] | Level 3 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		0	0
Health and Life Benefits | US Government Agencies Debt Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		$ 1.8	$ 2
Percentage of fair value of plan investments		0.40%	0.50%
Health and Life Benefits | US Government Agencies Debt Securities [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		$ 0	$ 0
Health and Life Benefits | US Government Agencies Debt Securities [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		1.8	2
Health and Life Benefits | US Government Agencies Debt Securities [Member] | Level 3 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		0	0
Health and Life Benefits | Municipalities
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		$ 4	$ 4.8
Percentage of fair value of plan investments		0.90%	1.10%
Health and Life Benefits | Municipalities | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		$ 0	$ 0
Health and Life Benefits | Municipalities | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		4	4.8
Health and Life Benefits | Municipalities | Level 3 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		0	0
Health and Life Benefits | Foreign Corporate Debt Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		$ 4.9	$ 5.7
Percentage of fair value of plan investments		1.10%	1.30%
Health and Life Benefits | Foreign Corporate Debt Securities [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		$ 0	$ 0
Health and Life Benefits | Foreign Corporate Debt Securities [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		4.9	5.7
Health and Life Benefits | Foreign Corporate Debt Securities [Member] | Level 3 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments		0	0
Health and Life Benefits | Fixed Income Securities Other [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments	[9]	$ 4.3	$ 5.3
Percentage of fair value of plan investments	[9]	1.00%	1.20%
Health and Life Benefits | Fixed Income Securities Other [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments	[9]	$ 0	$ 0
Health and Life Benefits | Fixed Income Securities Other [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments	[9]	4.3	5.3
Health and Life Benefits | Fixed Income Securities Other [Member] | Level 3 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments	[9]	0	0
Health and Life Benefits | Mutual Funds [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments	[10]	$ 1.9	$ 1.9
Percentage of fair value of plan investments	[10]	0.40%	0.40%
Health and Life Benefits | Mutual Funds [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments	[10]	$ 1.9	$ 0
Health and Life Benefits | Mutual Funds [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments	[10]	0	1.9
Health and Life Benefits | Mutual Funds [Member] | Level 3 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments	[10]	0	0
Health and Life Benefits | Commingled Funds [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments	[11]	$ 359.7	$ 359.7
Percentage of fair value of plan investments	[11]	82.00%	81.80%
Health and Life Benefits | Commingled Funds [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments	[11]	$ 0	$ 0
Health and Life Benefits | Commingled Funds [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments	[11]	359.7	359.7
Health and Life Benefits | Commingled Funds [Member] | Level 3 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan investments	[11]	$ 0	$ 0
[1]	At September 30, 2015, this payable represents a pending trade for investment purchases. At September 30, 2014, this receivable represents a pending trade for investment sales.
[2]	(a)The DB SERP and DB Restoration, included in pension benefits in the table above, have no assets.
[3]	This category includes Treasury Bills with a pre-commitment from the counterparty to repurchase the same securities on the next business day at an agreed-upon price.
[4]	This category primarily includes Yankee bonds and non-U.S. government bonds.
[5]	At September 30, 2015, investments in mutual funds consisited primarily of common stock of non-U.S. companies. At September 30, 2014, investments in mutual funds consisted primarily of corporate fixed income instruments.
[6]	At September 30, 2015, investments in commingled funds and pooled separate accounts consisted primarily of 80% common stock of large-cap U.S. companies; 18% income producing properties located in the United States; and 2% short-term money market investments. At September 30, 2014, investments in commingled funds and pooled separate accounts consisted primarily of 75% common stock of large-cap U.S. companies; 14% income producing properties located in the United States; 9% equity securities of non-U.S. companies; and 2% short-term money market investments.
[7]	(e) At September 30, 2015 and 2014, investments in private equity/limited partnership consisted of common stock of international companies.
[8]	At September 30, 2015, this category included long-term U.S. Treasury interest rate futures contracts, interest rate put options and credit default swap indexes. At September 30, 2014, this category included long-term U.S. Treasury interest rate futures contracts and interest rate put options.
[9]	At September 30, 2015 and 2014, this category consisted primarily of 76% non-U.S. government bonds and 24% Yankee bonds.
[10]	At September 30, 2015, investments in mutual funds consisted of a short-term money market fund valued at $1.00 per share. At September 30, 2014, investments in mutual funds consisted primarily of 63% short-term obligations consisting of certificates of deposit and time deposits, 23% high-quality commercial paper, 6% repurchase agreements, 4% corporate notes of U.S. and foreign corporations and 4% U.S. governmental and U.S. agency securities.
[11]	At September 30, 2015, investments in commingled funds consisted primarily of 68% common stock of large-cap U.S. companies,16% governmental fixed income securities and 16% corporate bonds. At September 30, 2014, investments in commingled funds consisted primarily of 66% common stock of large-cap U.S. companies, 17% U.S. agency obligations and government sponsored entities and 17% corporate bonds.

Pension and Other Post-retire76

Pension and Other Post-retirement Benefit Plans (Table 8-Footnotes) (Details)	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Large Cap U.S. Companies Common Stock [Member] | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Allocation of investments in comingled funds and pooled separate accounts	80.00%	75.00%
Large Cap U.S. Companies Common Stock [Member] | Health and Life Benefits
Defined Benefit Plan Disclosure [Line Items]
Allocation of investments in comingled funds	68.00%	66.00%
U.S. agency obligations and government sponsored entities [Member] | Health and Life Benefits
Defined Benefit Plan Disclosure [Line Items]
Allocation of investments in comingled funds	16.00%
Income Producing Properties [Member] | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Allocation of investments in comingled funds and pooled separate accounts	18.00%	14.00%
Foreign Company Stock [Member] | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Allocation of investments in comingled funds and pooled separate accounts		9.00%
Short-term money market investments [Member] | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Allocation of investments in comingled funds and pooled separate accounts	2.00%	2.00%
Certificates of deposit and time deposits [Member] | Health and Life Benefits
Defined Benefit Plan Disclosure [Line Items]
Allocation of investments in mutual funds		63.00%
High-quality commercial paper [Member] | Health and Life Benefits
Defined Benefit Plan Disclosure [Line Items]
Allocation of investments in mutual funds		23.00%
Repurchase Agreements [Member] | Health and Life Benefits
Defined Benefit Plan Disclosure [Line Items]
Allocation of investments in mutual funds		6.00%
Corporate notes of U.S. and foreign corporations [Member] | Health and Life Benefits
Defined Benefit Plan Disclosure [Line Items]
Allocation of investments in mutual funds		4.00%
U.S. governmental and U.S. agency securities [Member] | Health and Life Benefits
Defined Benefit Plan Disclosure [Line Items]
Allocation of investments in mutual funds		4.00%
Foreign Corporate Debt Securities [Member] | Health and Life Benefits
Defined Benefit Plan Disclosure [Line Items]
Allocation of investments in other securities	76.00%	76.00%
Yankee Bonds [Member] | Health and Life Benefits
Defined Benefit Plan Disclosure [Line Items]
Allocation of investments in other securities	24.00%	24.00%
U.S. agency obligations and government [Member] | Health and Life Benefits
Defined Benefit Plan Disclosure [Line Items]
Allocation of investments in comingled funds		17.00%
Corporate Bonds | Health and Life Benefits
Defined Benefit Plan Disclosure [Line Items]
Allocation of investments in comingled funds	16.00%	17.00%

Pension and Other Post-retire77

Pension and Other Post-retirement Benefit Plans (Table 9) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Fair Value of plan assets at beginning of year	$ 23.8	$ 21.1
Assets still held at year end	3.9	2.7
Fair value of plan assets at end of year	$ 27.7	$ 23.8

Pension and Other Post-retire78

Pension and Other Post-retirement Benefit Plans (Table 10) (Details) $ in Millions	Sep. 30, 2015USD ($)
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
2,016	$ 49.1
2,017	50.5
2,018	51.5
2,019	53.2
2,020	54.3
2021-2025	284.1
Health and Life Benefits
Defined Benefit Plan Disclosure [Line Items]
2,016	17.2
2,017	17.6
2,018	17.2
2,019	17.4
2,020	17.4
2021-2025	$ 86.9

Stock-Based Compensation (Narra

Stock-Based Compensation (Narrative) (Details) - USD ($)		12 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense recognized		$ 15,500,000	$ 3,400,000	$ 6,500,000
Unrecognized compensation expense		$ 11,400,000
Weighted-average period remaining to recognize unrecognized compensation expense		1 year 8 months
Tax benefit from compensation expense		$ 6,200,000	1,300,000	$ 2,600,000
Accounts payable and other accrued liabilities-other		16,400,000	14,600,000
Deferred Credits-other		$ 108,124,000	100,180,000
Performance Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period		3 years
Performances Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense		$ 4,400,000
Intrinsic Value Performance Shares Vested			2,200,000
Value of performance units vested		$ 0		$ 0
Volatility measurement period		3 years
Minimum percentage of performance shares issued		0.00%
Maximum percentage of performance shares issued		200.00%
Shares granted during the period	[1]	113,626
Weighted-average grant date fair value, vested		$ 0
Fair value of shares expected to vest		$ 12,900,000
Performance Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense		$ 7,000,000
Value of performance units vested		$ 1
Fair value of units expected to vest		$ 20,300,000
Cash To Settle Performance Unit Awards			2,000,000
Shares granted during the period		4,785,921
Liability for Equity Option Awards Outstanding		$ 13,300,000	2,400,000	$ 4,900,000
Accounts payable and other accrued liabilities-other		6,400,000		2,000,000
Deferred Credits-other		6,900,000	2,400,000	2,900,000
Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash received from stock options exercised		$ 200,000	700,000
Tax benefit realized from exercised stock options			100,000	$ 0
Stock options exercised		5,318		0
Stock options outstanding		0
Omnibus Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized for issue under plan		1,700,000
Directors Stock Compensation Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized for issue under plan		270,000
Compensation expense recognized		$ 800,000	700,000	$ 0
Tax benefit from compensation expense		$ 300,000	$ 300,000	$ 0
Shares granted during the period		15,100	17,000	16,600
Weighted-average grant date fair value, vested		$ 54.05	$ 40.06	$ 40.46
[1]	(a)The number of common shares issued related to performance shares may range from zero to 200 percent of the number of shares shown in the table above based on our achievement of performance goals for total shareholder return relative to a selected peer group of companies.

Stock-Based Compensation (Tab80

Stock-Based Compensation (Table 1) (Details) - $ / shares		12 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Performances Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Non-vested and outstanding, beginning of year	[1]	301,378
Granted	[1]	113,626
Vested	[1]	0
Cancelled/Forfeited	[1]	(110,915)
Non-vested and outstanding, end of year	[1]	304,089	301,378
Weighted-average grant date fair value, non-vested and outstanding, beginning of year		$ 40.57
Weighted-average grant date fair value, granted		44.44	$ 42.88	$ 39.73
Weighted-average grant date fair value, vested		0
Weighted-average grant date fair value, cancelled/forfeited		39.71
Weighted-average grant date fair value, non-vested and outstanding, end of year		$ 44.49	$ 40.57
Performance Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Non-vested and outstanding, beginning of year		12,268,921
Granted		4,785,921
Vested		0
Cancelled/Forfeited		(4,369,209)
Non-vested and outstanding, end of year		12,685,633	12,268,921
[1]	(a)The number of common shares issued related to performance shares may range from zero to 200 percent of the number of shares shown in the table above based on our achievement of performance goals for total shareholder return relative to a selected peer group of companies.

Stock-Based Compensation (Tab81

Stock-Based Compensation (Table 2) (Details) - $ / shares	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Performances Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected stock-price volatility	18.30%	19.10%	19.40%
Dividend yield	4.18%	3.93%	3.98%
Weighted-average grant date fair value, granted	$ 44.44	$ 42.88	$ 39.73
Performance Units [Member] | Grant 2014 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected stock-price volatility	20.20%
Performance Units [Member] | Grant 2013 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected stock-price volatility	20.80%

Environmental Matters (Narrativ

Environmental Matters (Narrative) (Details) $ in Thousands		12 Months Ended
		Sep. 30, 2015USD ($)site	Sep. 30, 2014USD ($)
Site Contingency [Line Items]
Regulatory Assets, Noncurrent		$ 80,018	$ 71,638
Environmental response costs
Site Contingency [Line Items]
Regulatory Assets, Noncurrent	[1],[2]	$ 1,800	600
District of Columbia
Site Contingency [Line Items]
Recovery of environmental response costs term		3 years
Washington Gas Light Company
Site Contingency [Line Items]
Number of sites | site		10
Estimated maximum liability		$ 17,200	19,300
Regulatory Assets, Noncurrent		$ 79,946	71,584
Washington Gas Light Company | Reserve for Environmental Costs [Member]
Site Contingency [Line Items]
Number of sites | site		4
Accrual for environmental loss contingencies		$ 6,600	8,500
Washington Gas Light Company | Environmental response costs
Site Contingency [Line Items]
Regulatory Assets, Noncurrent		$ 1,800	$ 600
[1]	This balance represents allowed remediation expenditures at Washington Gas sites to be recovered through rates for Maryland and the District of Columbia. The recovery period is over several years.
[2]	Washington Gas does not earn its overall rate of return on these assets. Washington Gas is allowed to recover and required to pay, using short-term interest rates, the carrying costs related to billed gas costs due from and to its customers in the District of Columbia and Virginia jurisdictions.

Commitments and Contingencies83

Commitments and Contingencies (Narrative) (Details) $ in Millions	12 Months Ended
	Sep. 30, 2015USD ($)company	Sep. 30, 2014USD ($)	Sep. 30, 2013USD ($)
Commitments And Contingencies [Line Items]
Rent expense	$ 6	$ 5.5	$ 5.6
Number Of Service Agreements With Pipeline Companies | company	4
WGL | Washington Gas Light Company | Guarantee on behalf of subsidiary
Commitments And Contingencies [Line Items]
Unrecorded Unconditional Purchase Obligation	$ 30.7
WGL | WGL Energy Services | Guarantee on behalf of subsidiary
Commitments And Contingencies [Line Items]
Unrecorded Unconditional Purchase Obligation	230.1
WGL | WGL Energy Systems | Guarantee on behalf of subsidiary
Commitments And Contingencies [Line Items]
Unrecorded Unconditional Purchase Obligation	8.5
WGL | WGL Midstream | Guarantee on behalf of subsidiary
Commitments And Contingencies [Line Items]
Unrecorded Unconditional Purchase Obligation	318.3
WGL | Other subsidiaries | Guarantee on behalf of subsidiary
Commitments And Contingencies [Line Items]
Unrecorded Unconditional Purchase Obligation	2
WGL | External Partners | Performance Guarantee
Commitments And Contingencies [Line Items]
Unrecorded Unconditional Purchase Obligation	$ 8.1

Committments and Contingencies

Committments and Contingencies - Tables (Details) $ in Millions	Sep. 30, 2015USD ($)
Minimum Payments Under Operating Leases
2,016	$ 6.4
2,017	5.8
2,018	5.9
2,019	2.7
2,020	2.8
Thereafter	23.1
Total	46.7
Washington Gas Light Company | Gas Purchase Committments
Contract Minimums
2,016	340.6	[1]
2,017	413.8	[1]
2,018	403.4	[1]
2,019	396.6	[1]
2,020	413.6	[1]
Thereafter	4,819	[1]
Total	6,787	[1]
Washington Gas Light Company | Pipeline Contracts
Contract Minimums
2,016	208.8	[2]
2,017	200.8	[2]
2,018	199.1	[2]
2,019	211.1	[2]
2,020	199.7	[2]
Thereafter	1,191.7	[2]
Total	2,211.2	[2]
WGL Energy Services | Gas Purchase Committments
Contract Minimums
2,016	156.4	[3]
2,017	67.8	[3]
2,018	9.7	[3]
2,019	0.5	[3]
2,020	0	[3]
Thereafter	0	[3]
Total	234.4	[3]
WGL Energy Services | Pipeline Contracts
Contract Minimums
2,016	3.2	[4]
2,017	2	[4]
2,018	1.4	[4]
2,019	0.8	[4]
2,020	0.5	[4]
Thereafter	1.2	[4]
Total	9.1	[4]
WGL Energy Services | Electric Purchase Commitments
Contract Minimums
2,016	477.4	[5]
2,017	215.8	[5]
2,018	56.3	[5]
2,019	6.2	[5]
2,020	1.1	[5]
Thereafter	0	[5]
Total	756.8	[5]
Commitments related to renewable energy credits	15.7
WGL Midstream | Gas Purchase Committments
Contract Minimums
2,016	252.9	[6]
2,017	348.6	[6]
2,018	1,082.6	[6]
2,019	1,650.9	[6]
2,020	1,866.4	[6]
Thereafter	32,117.1	[6]
Total	37,318.5	[6]
WGL Midstream | Pipeline Contracts
Contract Minimums
2,016	20.4	[4]
2,017	18.4	[4]
2,018	15.9	[4]
2,019	60.9	[4]
2,020	65	[4]
Thereafter	1,031.7	[4]
Total	1,212.3	[4]
Non Utility Total
Contract Minimums
2,016	910.3
2,017	652.6
2,018	1,165.9
2,019	1,719.3
2,020	1,933
Thereafter	33,150
Total	$ 39,531.1
[1]	Includes known and reasonably likely commitments to purchase natural gas. Cost estimates are based on forward market prices at September 30, 2015.
[2]	Represents minimum payments for natural gas transportation, storage and peaking contracts that have expiration dates through fiscal year 2034.
[3]	(a) Represents fixed price commitments with city gate equivalent deliveries.
[4]	(b) Represents minimum payments for natural gas transportation and storage contracts that have expiration dates through fiscal year 2044.
[5]	(c) Represents electric purchase commitments that are based on existing fixed price and fixed volume contracts. Includes $15.7 million of commitments related to renewable energy credits.
[6]	(d) Includes known and reasonably likely commitments to purchase natural gas. Cost estimates are based on forward market prices as of September 30, 2015. Certain of our gas purchase agreements have optionality, which may cause increases in these commitments.

Derivative and Weather Relate85

Derivative and Weather Related Instruments (Details) shares in Millions, kWh in Millions, MMBTU in Millions, $ in Millions		12 Months Ended
		Sep. 30, 2015USD ($)kWhMMBTUderivative	Sep. 30, 2014USD ($)kWhMMBTUshares	Sep. 30, 2013USD ($)
Asset Optimization [Abstract]
Gain (Loss) on Asset Optimization Transactions Net Pretax		$ 27.9	$ (35.4)	$ (33.2)
Unrealized Gains (Loss) On Asset Optimization Derivative Instruments Net Pretax		(6.3)	$ (66.2)	$ (45.4)
Absolute Notional Amounts of Open Positions on Derivative Instruments
Warrant Transaction Volume of Shares | shares			4.6
Balance Sheet Classification of Derivative Instruments
Netting of Collateral		10.2	$ 12
Total	[1]	(330.8)	(306.3)
Interest Rate Swap		125	150
Not Designated as Hedging Instrument [Member]
Balance Sheet Classification of Derivative Instruments
Gross Derivative Assets		74.5	72.6
Gross Derivative Liabilities		(412.1)	(389.2)
Designated as Hedging Instrument [Member]
Balance Sheet Classification of Derivative Instruments
Gross Derivative Assets		0	0
Gross Derivative Liabilities		(3.4)	(1.7)
Current assets- derivatives
Balance Sheet Classification of Derivative Instruments
Netting of Collateral		0	0
Total	[1]	22.9	18.3
Current assets- derivatives | Not Designated as Hedging Instrument [Member]
Balance Sheet Classification of Derivative Instruments
Gross Derivative Assets		29.7	20.8
Gross Derivative Liabilities		(6.8)	(2.5)
Current assets- derivatives | Designated as Hedging Instrument [Member]
Balance Sheet Classification of Derivative Instruments
Gross Derivative Assets		0	0
Gross Derivative Liabilities		0	0
Non current assets- derivatives
Balance Sheet Classification of Derivative Instruments
Netting of Collateral		0	0
Total	[1]	32.1	18.7
Non current assets- derivatives | Not Designated as Hedging Instrument [Member]
Balance Sheet Classification of Derivative Instruments
Gross Derivative Assets		32.3	18.7
Gross Derivative Liabilities		(0.2)	0
Non current assets- derivatives | Designated as Hedging Instrument [Member]
Balance Sheet Classification of Derivative Instruments
Gross Derivative Assets		0	0
Gross Derivative Liabilities		0	0
Current liabilities- Derivatives
Balance Sheet Classification of Derivative Instruments
Netting of Collateral		2.9	8
Total	[1]	(63.5)	(48.6)
Current liabilities- Derivatives | Not Designated as Hedging Instrument [Member]
Balance Sheet Classification of Derivative Instruments
Gross Derivative Assets		9.8	15.4
Gross Derivative Liabilities		(76.2)	(70.3)
Current liabilities- Derivatives | Designated as Hedging Instrument [Member]
Balance Sheet Classification of Derivative Instruments
Gross Derivative Assets		0	0
Gross Derivative Liabilities		0	(1.7)
Non current liabilities- derivatives
Balance Sheet Classification of Derivative Instruments
Netting of Collateral		7.3	4
Total	[1]	(322.3)	(294.7)
Non current liabilities- derivatives | Not Designated as Hedging Instrument [Member]
Balance Sheet Classification of Derivative Instruments
Gross Derivative Assets		2.7	17.7
Gross Derivative Liabilities		(328.9)	(316.4)
Non current liabilities- derivatives | Designated as Hedging Instrument [Member]
Balance Sheet Classification of Derivative Instruments
Gross Derivative Assets		0	0
Gross Derivative Liabilities		(3.4)	0
WGE Services
Derivative, Collateral [Abstract]
Right to Reclaim Cash		12.4	5.7
Collateral Already Posted Aggregate Fair Value		10.3	5.3
WGL Midstream
Derivative, Collateral [Abstract]
Right to Reclaim Cash		3.5	$ 11.4
Derivative, Collateral, Obligation to Return Cash		$ 0.4
Interest Rate Swap Derivative
Derivative, Collateral [Abstract]
Number of Interest Rate Derivatives Held | derivative		2
Derivative, Notional Amount		$ 125
Absolute Notional Amounts of Open Positions on Derivative Instruments
Interest Rate Swap Notional Principal Value		$ 125
Asset Optimization [Member]
Absolute Notional Amounts of Open Positions on Derivative Instruments
Natural Gas Derivative Transaction, Volume | MMBTU		2,082,920,000
Retail Sales [Member]
Absolute Notional Amounts of Open Positions on Derivative Instruments
Natural Gas Derivative Transaction, Volume | MMBTU		5,220,000	4,470,000
Electricity Derivative Transaction, Volume | kWh		4,292.7	3,831.4
Other Risk Management Activities [Member]
Absolute Notional Amounts of Open Positions on Derivative Instruments
Natural Gas Derivative Transaction, Volume | MMBTU		181,170,000	164,130,000
Electricity Derivative Transaction, Volume | kWh		19,965.7	16,734.1
WGL | Asset Optimization [Member]
Absolute Notional Amounts of Open Positions on Derivative Instruments
Natural Gas Derivative Transaction, Volume | MMBTU			2,059,330,000
Washington Gas Light Company
Derivative, Collateral [Abstract]
Right to Reclaim Cash		$ 3.5	$ 8.2
Derivative, Collateral, Obligation to Return Cash		3.8	$ 2.5
Absolute Notional Amounts of Open Positions on Derivative Instruments
Warrant Transaction Volume of Shares | shares			0
Balance Sheet Classification of Derivative Instruments
Gross Derivative Assets	[2]	20.4	$ 26.2
Gross Derivative Liabilities	[2]	(306.2)	(308.4)
Netting of Collateral	[2]	0	0.9
Total	[1],[2]	(285.8)	(281.3)
Interest Rate Swap		0	0
Washington Gas Light Company | Current assets- derivatives
Balance Sheet Classification of Derivative Instruments
Gross Derivative Assets	[2]	5.2	3.9
Gross Derivative Liabilities	[2]	(0.6)	0
Netting of Collateral	[2]	0	0
Total	[1],[2]	4.6	3.9
Washington Gas Light Company | Non current assets- derivatives
Balance Sheet Classification of Derivative Instruments
Gross Derivative Assets	[2]	13.3	9.5
Gross Derivative Liabilities	[2]	(0.1)	0
Netting of Collateral	[2]	0	0
Total	[1],[2]	13.2	9.5
Washington Gas Light Company | Current liabilities- Derivatives
Balance Sheet Classification of Derivative Instruments
Gross Derivative Assets	[2]	1.9	8.6
Gross Derivative Liabilities	[2]	(35.8)	(43.2)
Netting of Collateral	[2]	0	0.7
Total	[1],[2]	(33.9)	(33.9)
Washington Gas Light Company | Non current liabilities- derivatives
Balance Sheet Classification of Derivative Instruments
Gross Derivative Assets	[2]	0	4.2
Gross Derivative Liabilities	[2]	(269.7)	(265.2)
Netting of Collateral	[2]	0	0.2
Total	[1],[2]	$ (269.7)	$ (260.8)
Washington Gas Light Company | Asset Optimization [Member]
Absolute Notional Amounts of Open Positions on Derivative Instruments
Natural Gas Derivative Transaction, Volume | MMBTU		1,331,670,000	1,374,090,000
Washington Gas Light Company | Retail Sales [Member]
Absolute Notional Amounts of Open Positions on Derivative Instruments
Natural Gas Derivative Transaction, Volume | MMBTU		0	0
Electricity Derivative Transaction, Volume | kWh		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 | MMBTU		138,180,000	139,820,000
Electricity Derivative Transaction, Volume | kWh		0	0
[1]	(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.
[2]	(b) Washington Gas did not have any derivative instruments outstanding that were designated as hedging instruments at September 30, 2015 or 2014.

Derivative and Weather Relate86

Derivative and Weather Related Instruments (Gains and Losses) (Details) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
		Dec. 31, 2014	Sep. 30, 2015		Sep. 30, 2014		Sep. 30, 2013
Gains and (Losses) on Derivative Instruments
Amortization of amounts recorded to AOCI			$ (11,309)	[1]	$ (1,548)	[1]	$ 0
Gains (Losses) On Derivative Instruments			(17,200)		(244,900)		(173,100)
Ineffectiveness of cash flow hedge			(400)
Amortization that reclassified to interest expense		$ (200)
Effective portion of cash flow hedge			(11,500)
Operating Revenues Non Utility
Gains and (Losses) on Derivative Instruments
Recorded to income			71,300		(47,900)		(9,900)
Utility Cost Of Gas
Gains and (Losses) on Derivative Instruments
Recorded to income			(14,500)		(87,300)		(45,900)
Non Utility Cost Of Energy Related Sales
Gains and (Losses) on Derivative Instruments
Recorded to income			(43,700)		36,200		(2,400)
Other Income [Member]
Gains and (Losses) on Derivative Instruments
Recorded to income			0		(1,100)		200
Interest expense [Member]
Gains and (Losses) on Derivative Instruments
Recorded to income	[2]		(600)		(200)		0
Gas Costs [Member]
Gains and (Losses) on Derivative Instruments
Recorded to regulatory assets/liabilities			(18,400)		(143,300)		(115,100)
Other Regulatory Assets Liability [Member]
Gains and (Losses) on Derivative Instruments
Recorded to regulatory assets/liabilities			0		200		0
Other Comprehensive Income (Loss) [Member]
Gains and (Losses) on Derivative Instruments
Amortization of amounts recorded to AOCI	[3]		(11,300)		(1,500)		0
Washington Gas Light Company
Gains and (Losses) on Derivative Instruments
Gains (Losses) On Derivative Instruments			(32,900)		(230,400)		(161,000)
Washington Gas Light Company | Operating Revenues Non Utility
Gains and (Losses) on Derivative Instruments
Recorded to income			0		0		0
Washington Gas Light Company | Utility Cost Of Gas
Gains and (Losses) on Derivative Instruments
Recorded to income			(14,500)		(87,300)		(45,900)
Washington Gas Light Company | Non Utility Cost Of Energy Related Sales
Gains and (Losses) on Derivative Instruments
Recorded to income			0		0		0
Washington Gas Light Company | Other Income [Member]
Gains and (Losses) on Derivative Instruments
Recorded to income			0		0		0
Washington Gas Light Company | Interest expense [Member]
Gains and (Losses) on Derivative Instruments
Recorded to income	[2]		0		0		0
Washington Gas Light Company | Gas Costs [Member]
Gains and (Losses) on Derivative Instruments
Recorded to regulatory assets/liabilities			(18,400)		(143,300)		(115,100)
Washington Gas Light Company | Other Regulatory Assets Liability [Member]
Gains and (Losses) on Derivative Instruments
Recorded to regulatory assets/liabilities			0		200		0
Washington Gas Light Company | Other Comprehensive Income (Loss) [Member]
Gains and (Losses) on Derivative Instruments
Amortization of amounts recorded to AOCI	[3]		$ 0		$ 0		$ 0
[1]	(a) Cash flow hedging instruments represent interest rate swap agreements related to debt issuances. Refer to Note 14—Derivative and Weather-related Instruments for further discussion of the interest rate swap agreements.
[2]	(a) Fiscal year 2015 represents $(0.4) million of net ineffectiveness for our cash flow hedges and $(0.2) million of amortization of amounts previously recorded to Accumulated Other Comprehensive Income. Fiscal year 2014 amounts represent hedge ineffectiveness.
[3]	(b) Fiscal year 2015 represents the effective portion of our cash flow hedges of $(11.5) million less $(0.2) million of amortization that was reclassified to interest expense.

Derivative and Weather Relate87

Derivative and Weather Related Instruments (Details 2) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2013USD ($)	Sep. 30, 2015USD ($)Counterparties	Sep. 30, 2014USD ($)	Sep. 30, 2013USD ($)
WGE Services
Derivative [Line Items]
Number of Counterparties | Counterparties		1
Percentage Of Credit Exposure		10.00%
Obligation to counterparties		$ 0.7
WGE Services | Weather Instruments [Member]
Derivative [Line Items]
Gain (losses) on weather related instruments, pretax		$ 0.6	$ 3.4	$ (0.8)
WGL Midstream
Derivative [Line Items]
Number of Counterparties | Counterparties		2
Percentage Of Credit Exposure		10.00%
Obligation to counterparties		$ 17.4
WGL
Derivative [Line Items]
Derivative liabilities with credit-risk-contingent features		61.7	28.8
Maximum potential collateral requirements		54.6	16.5
Washington Gas Light Company
Derivative [Line Items]
Derivative liabilities with credit-risk-contingent features		18.9	20.6
Maximum potential collateral requirements		$ 18.8	$ 16.1
Number of Counterparties | Counterparties		1
Percentage Of Credit Exposure		10.00%
Obligation to counterparties		$ 17.5
Washington Gas Light Company | Weather Instruments [Member]
Derivative [Line Items]
Gain (losses) on weather related instruments, pretax	$ 0.8

Fair Value Measurements Under t

Fair Value Measurements Under the Fair Value Hierarchy (Details) - USD ($) $ in Millions	Sep. 30, 2015	Sep. 30, 2014
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Assets	$ 74.5	$ 72.6
Liabilities	(415.5)	(390.9)
Natural Gas Related Derivatives [Member]
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Assets	51.2	56.4
Liabilities	(372.1)	(368.2)
Electricity Related Derivatives [Member]
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Assets	23.3	16.2
Liabilities	(40)	(21)
Interest Rate Swap Derivative
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Liabilities	(3.4)	(1.7)
Level 1 [Member]
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Assets	0	0
Liabilities	0	0
Level 1 [Member] | Natural Gas Related Derivatives [Member]
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Assets	0	0
Liabilities	0	0
Level 1 [Member] | Electricity Related Derivatives [Member]
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Assets	0	0
Liabilities	0	0
Level 1 [Member] | Interest Rate Swap Derivative
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Liabilities	0	0
Level 2 [Member]
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Assets	24.7	23
Liabilities	(40)	(41.6)
Level 2 [Member] | Natural Gas Related Derivatives [Member]
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Assets	22.7	22.7
Liabilities	(33.9)	(39.8)
Level 2 [Member] | Electricity Related Derivatives [Member]
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Assets	2	0.3
Liabilities	(2.7)	(0.1)
Level 2 [Member] | Interest Rate Swap Derivative
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Liabilities	(3.4)	(1.7)
Level 3 [Member]
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Assets	49.8	49.6
Liabilities	(375.5)	(349.3)
Level 3 [Member] | Natural Gas Related Derivatives [Member]
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Assets	28.5	33.7
Liabilities	(338.2)	(328.4)
Level 3 [Member] | Electricity Related Derivatives [Member]
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Assets	21.3	15.9
Liabilities	(37.3)	(20.9)
Level 3 [Member] | Interest Rate Swap Derivative
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Liabilities	0	0
Washington Gas Light Company
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Assets	20.4	26.2
Liabilities	(306.2)	(308.4)
Washington Gas Light Company | Natural Gas Related Derivatives [Member]
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Assets	20.4	26.2
Liabilities	(306.2)	(308.4)
Washington Gas Light Company | Level 1 [Member]
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Assets	0	0
Liabilities	0	0
Washington Gas Light Company | Level 1 [Member] | 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 [Member]
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Assets	6.9	13.5
Liabilities	(11.6)	(25.1)
Washington Gas Light Company | Level 2 [Member] | Natural Gas Related Derivatives [Member]
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Assets	6.9	13.5
Liabilities	(11.6)	(25.1)
Washington Gas Light Company | Level 3 [Member]
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Assets	13.5	12.7
Liabilities	(294.6)	(283.3)
Washington Gas Light Company | Level 3 [Member] | Natural Gas Related Derivatives [Member]
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Assets	13.5	12.7
Liabilities	$ (294.6)	$ (283.3)

Fair Value Measurements (Quanti

Fair Value Measurements (Quantitative information WGLH) (Details) - USD ($)	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Fair Value Measurements Details [Line Items]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs	$ (325,700,000)	$ (299,700,000)	$ (151,700,000)
Natural Gas Related Derivatives [Member]
Fair Value Measurements Details [Line Items]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs	(309,700,000)	(294,700,000)	(155,200,000)
Electricity Related Derivatives [Member]
Fair Value Measurements Details [Line Items]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs	(16,000,000)	(5,000,000)	2,400,000
Washington Gas Light Company | Natural Gas Related Derivatives [Member]
Fair Value Measurements Details [Line Items]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs	(281,100,000)	(270,600,000)	$ (133,600,000)
Washington Gas Light Company | Natural Gas Related Derivatives [Member] | Discounted Cash Flow [Member] | Maximum | Natural Gas Basis Price [Member]
Fair Value Measurements Details [Line Items]
Input Price	3.500	6.154
Washington Gas Light Company | Natural Gas Related Derivatives [Member] | Discounted Cash Flow [Member] | Minimum | Natural Gas Basis Price [Member]
Fair Value Measurements Details [Line Items]
Input Price	(1.441)	(2.101)
WGL | Natural Gas Related Derivatives [Member] | Discounted Cash Flow [Member] | Maximum | Natural Gas Basis Price [Member]
Fair Value Measurements Details [Line Items]
Input Price	3.580	6.154
WGL | Natural Gas Related Derivatives [Member] | Discounted Cash Flow [Member] | Minimum | Natural Gas Basis Price [Member]
Fair Value Measurements Details [Line Items]
Input Price	(1.441)	(2.101)
WGL | Natural Gas Related Derivatives [Member] | Option Model [Member] | Maximum | Natural Gas Basis Price [Member]
Fair Value Measurements Details [Line Items]
Input Price	$ 2.950	$ 6.154
Option Volatility Percentage	867.00%	589.60%
WGL | Natural Gas Related Derivatives [Member] | Option Model [Member] | Minimum | Natural Gas Basis Price [Member]
Fair Value Measurements Details [Line Items]
Input Price	$ (1.283)	$ (1.675)
Option Volatility Percentage	22.50%	30.90%
WGL | Electricity Related Derivatives [Member] | Discounted Cash Flow [Member] | Maximum | Electricity Congestion Price [Member]
Fair Value Measurements Details [Line Items]
Input Price	$ 73.35	$ 90.95
WGL | Electricity Related Derivatives [Member] | Discounted Cash Flow [Member] | Minimum | Electricity Congestion Price [Member]
Fair Value Measurements Details [Line Items]
Input Price	$ (5.75)	$ (2.85)

Fair Value Measurements (Reconc

Fair Value Measurements (Reconciliation with Level 3 Inputs) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs	$ (325.7)	$ (299.7)	$ (151.7)
Realized and unrealized gains (losses)
Recorded to income	(63)	(79.4)	(94.8)
Recorded to Income	(63)	(79.4)
Recorded to regulatory assets - gas costs	(30.9)	(113.6)
Transfers into Level 3	5.4
Transfers out of Level 3	3.6	1.7
Purchases	10.5	5.2
Settlements	48.4	38.1
Weather Instruments [Member]
Realized and unrealized gains (losses)
Recorded to income	0	0	1.2
Natural Gas Related Derivatives [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs	(309.7)	(294.7)	(155.2)
Realized and unrealized gains (losses)
Recorded to income	(30.7)	(72.6)	(72.4)
Recorded to Income	(30.7)	(72.6)
Recorded to regulatory assets - gas costs	(30.9)	(113.6)
Transfers into Level 3	5.4
Transfers out of Level 3	3.6	1.7
Purchases	0	0
Settlements	37.6	45
Electricity Related Derivatives [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs	(16)	(5)	2.4
Realized and unrealized gains (losses)
Recorded to income	(32.3)	(5.7)	(23.8)
Recorded to Income	(32.3)	(5.7)
Recorded to regulatory assets - gas costs	0	0
Transfers into Level 3	0
Transfers out of Level 3	0	0
Purchases	10.5	5.2
Settlements	10.8	(6.9)
Warrant
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs	0	0	1.1
Realized and unrealized gains (losses)
Recorded to income	0	(1.1)	0.2
Recorded to Income	0	(1.1)
Recorded to regulatory assets - gas costs	0	0
Transfers into Level 3	0
Transfers out of Level 3	0	0
Purchases	0	0
Settlements	0	0
Washington Gas Light Company
Realized and unrealized gains (losses)
Recorded to income	(25)	(69.4)	(44.7)
Washington Gas Light Company | Weather Instruments [Member]
Realized and unrealized gains (losses)
Recorded to income	0	0	1.2
Washington Gas Light Company | Natural Gas Related Derivatives [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs	(281.1)	(270.6)	(133.6)
Realized and unrealized gains (losses)
Recorded to income	(25)	(69.4)	$ (45.9)
Recorded to Income	(25)	(69.4)
Recorded to regulatory assets - gas costs	(30.9)	(113.6)
Transfers into Level 3	5.4
Transfers out of Level 3	2.5	1.7
Settlements	$ 37.5	$ 44.3

Fair Value Measurements (Fair V

Fair Value Measurements (Fair Value of Financial Instruments) (Details) - USD ($) $ in Thousands		Sep. 30, 2015	Sep. 30, 2014
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Commercial Paper		$ 332,000	$ 453,500
Washington Gas Light Company
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Commercial Paper		89,000	89,000
Carrying Amount
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Money Market Funds	[1]	11,000	9,700
Other Short Term Investments	[1]	400	0
Commercial Paper	[2]	332,000	453,500
Long-term debt	[3]	944,200	679,200
Carrying Amount | Washington Gas Light Company
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Money Market Funds	[1]	4,300	4,300
Other Short Term Investments	[1]	400	0
Commercial Paper	[2]	89,000	89,000
Long-term debt	[3]	695,900	679,200
Fair Value
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Money Market Funds	[1]	11,000	9,700
Other Short Term Investments	[1]	400	0
Commercial Paper	[2]	332,000	453,500
Long-term debt	[3]	1,057,900	809,300
Fair Value | Washington Gas Light Company
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Money Market Funds	[1]	4,300	4,300
Other Short Term Investments	[1]	400	0
Commercial Paper	[2]	89,000	89,000
Long-term debt	[3]	$ 811,900	$ 809,300
[1]	(a) Balance located in cash and cash equivalents in the accompanying balance sheets. These amounts may be offset by outstanding checks.
[2]	(b) Balance is located in notes payable in the accompanying balance sheets.
[3]	(c)Less current maturities and unamortized discounts.

Fair Value Measurements (Realiz

Fair Value Measurements (Realized and Unrealized Gains and Losses with Level 3 Measurements) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income	$ (63)	$ (79.4)	$ (94.8)
Unrealized Gains (Losses) Attributable to derivative Assets and Liabilities Recorded for Level 3 Measurements
Recorded to regulatory assets - gas costs	(30.9)	(113.6)
Total Unrealized Gains (Losses)	(57.2)	(176.7)	(175.3)
Natural Gas Related Derivatives [Member]
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income	(30.7)	(72.6)	(72.4)
Unrealized Gains (Losses) Attributable to derivative Assets and Liabilities Recorded for Level 3 Measurements
Recorded to regulatory assets - gas costs	(30.9)	(113.6)
Total Unrealized Gains (Losses)	(40.6)	(171.8)	(181)
Electricity Related Derivatives [Member]
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income	(32.3)	(5.7)	(23.8)
Unrealized Gains (Losses) Attributable to derivative Assets and Liabilities Recorded for Level 3 Measurements
Recorded to regulatory assets - gas costs	0	0
Total Unrealized Gains (Losses)	(16.6)	(3.8)	5.5
Weather Instruments [Member]
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income	0	0	1.2
Warrant
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income	0	(1.1)	0.2
Unrealized Gains (Losses) Attributable to derivative Assets and Liabilities Recorded for Level 3 Measurements
Recorded to regulatory assets - gas costs	0	0
Total Unrealized Gains (Losses)	0	(1.1)	0.2
Operating Revenues Non Utility
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income	14.2	(24.4)	(36.1)
Unrealized Gains (Losses) Attributable to derivative Assets and Liabilities Recorded for Level 3 Measurements
Recorded to income	22.9	(38.8)	(18.7)
Operating Revenues Non Utility | Natural Gas Related Derivatives [Member]
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income	(5.7)	(2.3)	(27)
Unrealized Gains (Losses) Attributable to derivative Assets and Liabilities Recorded for Level 3 Measurements
Recorded to income	(2.2)	(5)	(25.3)
Operating Revenues Non Utility | Electricity Related Derivatives [Member]
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income	19.9	(22.1)	(9.1)
Unrealized Gains (Losses) Attributable to derivative Assets and Liabilities Recorded for Level 3 Measurements
Recorded to income	25.1	(33.8)	6.6
Operating Revenues Non Utility | Weather Instruments [Member]
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income	0	0	0
Operating Revenues Non Utility | Warrant
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income	0	0	0
Unrealized Gains (Losses) Attributable to derivative Assets and Liabilities Recorded for Level 3 Measurements
Recorded to income	0	0	0
Utility Cost Of Gas
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income	(25)	(69.4)	(45.8)
Unrealized Gains (Losses) Attributable to derivative Assets and Liabilities Recorded for Level 3 Measurements
Recorded to income	(15.8)	(60.6)	(44.3)
Utility Cost Of Gas | Natural Gas Related Derivatives [Member]
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income	(25)	(69.4)	(45.8)
Unrealized Gains (Losses) Attributable to derivative Assets and Liabilities Recorded for Level 3 Measurements
Recorded to income	(15.8)	(60.6)	(44.3)
Utility Cost Of Gas | Electricity Related Derivatives [Member]
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income	0	0	0
Unrealized Gains (Losses) Attributable to derivative Assets and Liabilities Recorded for Level 3 Measurements
Recorded to income	0	0	0
Utility Cost Of Gas | Weather Instruments [Member]
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income	0	0	0
Utility Cost Of Gas | Warrant
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income	0	0	0
Unrealized Gains (Losses) Attributable to derivative Assets and Liabilities Recorded for Level 3 Measurements
Recorded to income	0	0	0
Other income-net
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income		(1.1)	0.2
Unrealized Gains (Losses) Attributable to derivative Assets and Liabilities Recorded for Level 3 Measurements
Recorded to income		(1.1)	0.2
Other income-net | Natural Gas Related Derivatives [Member]
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income		0	0
Unrealized Gains (Losses) Attributable to derivative Assets and Liabilities Recorded for Level 3 Measurements
Recorded to income		0	0
Other income-net | Electricity Related Derivatives [Member]
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income		0	0
Unrealized Gains (Losses) Attributable to derivative Assets and Liabilities Recorded for Level 3 Measurements
Recorded to income		0	0
Other income-net | Weather Instruments [Member]
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income		0	0
Other income-net | Warrant
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income		(1.1)	0.2
Unrealized Gains (Losses) Attributable to derivative Assets and Liabilities Recorded for Level 3 Measurements
Recorded to income		(1.1)	0.2
Non Utility Cost Of Energy Related Sales
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income	(52.2)	15.5	(14.3)
Unrealized Gains (Losses) Attributable to derivative Assets and Liabilities Recorded for Level 3 Measurements
Recorded to income	(43.4)	33.7	(0.9)
Non Utility Cost Of Energy Related Sales | Natural Gas Related Derivatives [Member]
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income	0	(0.9)	0.4
Unrealized Gains (Losses) Attributable to derivative Assets and Liabilities Recorded for Level 3 Measurements
Recorded to income	(1.7)	3.7	0.2
Non Utility Cost Of Energy Related Sales | Electricity Related Derivatives [Member]
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income	(52.2)	16.4	(14.7)
Unrealized Gains (Losses) Attributable to derivative Assets and Liabilities Recorded for Level 3 Measurements
Recorded to income	(41.7)	30	(1.1)
Non Utility Cost Of Energy Related Sales | Weather Instruments [Member]
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income	0	0	0
Non Utility Cost Of Energy Related Sales | Warrant
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income	0	0	0
Unrealized Gains (Losses) Attributable to derivative Assets and Liabilities Recorded for Level 3 Measurements
Recorded to income	0	0	0
Operation And Maintenance Expense
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income			1.2
Operation And Maintenance Expense | Natural Gas Related Derivatives [Member]
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income			0
Operation And Maintenance Expense | Electricity Related Derivatives [Member]
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income			0
Operation And Maintenance Expense | Weather Instruments [Member]
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income			1.2
Operation And Maintenance Expense | Warrant
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income			0
Regulatory asset-gas costs member
Unrealized Gains (Losses) Attributable to derivative Assets and Liabilities Recorded for Level 3 Measurements
Recorded to income	(20.9)	(109.9)	(111.6)
Regulatory asset-gas costs member | Natural Gas Related Derivatives [Member]
Unrealized Gains (Losses) Attributable to derivative Assets and Liabilities Recorded for Level 3 Measurements
Recorded to income	(20.9)	(109.9)	(111.6)
Regulatory asset-gas costs member | Electricity Related Derivatives [Member]
Unrealized Gains (Losses) Attributable to derivative Assets and Liabilities Recorded for Level 3 Measurements
Recorded to income	0	0	0
Regulatory asset-gas costs member | Warrant
Unrealized Gains (Losses) Attributable to derivative Assets and Liabilities Recorded for Level 3 Measurements
Recorded to income	0	0	0
Washington Gas Light Company
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income	(25)	(69.4)	(44.7)
Washington Gas Light Company | Natural Gas Related Derivatives [Member]
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income	(25)	(69.4)	(45.9)
Unrealized Gains (Losses) Attributable to derivative Assets and Liabilities Recorded for Level 3 Measurements
Recorded to regulatory assets - gas costs	(30.9)	(113.6)
Total Unrealized Gains (Losses)	(36.7)	(170.5)	(155.9)
Washington Gas Light Company | Weather Instruments [Member]
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income	0	0	1.2
Washington Gas Light Company | Utility Cost Of Gas
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income	(25)	(69.4)	(45.9)
Washington Gas Light Company | Utility Cost Of Gas | Natural Gas Related Derivatives [Member]
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income	(25)	(69.4)	(45.9)
Unrealized Gains (Losses) Attributable to derivative Assets and Liabilities Recorded for Level 3 Measurements
Recorded to income	(15.8)	(60.6)	(44.3)
Washington Gas Light Company | Utility Cost Of Gas | Weather Instruments [Member]
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income	0	0	0
Washington Gas Light Company | Operation And Maintenance Expense
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income			1.2
Washington Gas Light Company | Operation And Maintenance Expense | Natural Gas Related Derivatives [Member]
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income			0
Washington Gas Light Company | Operation And Maintenance Expense | Weather Instruments [Member]
Realized and Unrealized Gains (Losses) Recorded to Income Statement Line Items for Level 3 Measurements
Recorded to income			1.2
Washington Gas Light Company | Regulatory asset-gas costs member | Natural Gas Related Derivatives [Member]
Unrealized Gains (Losses) Attributable to derivative Assets and Liabilities Recorded for Level 3 Measurements
Recorded to income	$ (20.9)	$ (109.9)	$ (111.6)

Fair Value Measurements (Nonrec

Fair Value Measurements (Nonrecurring Basis) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Fair Value Measurements [Line Items]
Impairment loss	$ 5,625	$ 2,639	$ 2,600
Washington Gas Light Company
Fair Value Measurements [Line Items]
Impairment loss	0	2,639	2,600
Washington Gas Light Company | Springfield Operations Center
Fair Value Measurements [Line Items]
Carrying Amount Of Long Lived Assets Held For Use		22,300	24,900
Fair Value Of Long Lived Assets Held For Use		21,500	22,300
Impairment loss	500	800	2,600
Washington Gas Light Company | Springfield Operations Center | Level 3 [Member]
Fair Value Measurements [Line Items]
Impairment loss			2,600
Washington Gas Light Company | Abandoned LNG Facility
Fair Value Measurements [Line Items]
Impairment loss		$ 1,900	$ 500
Washington Gas Resources
Fair Value Measurements [Line Items]
Impairment loss, cost-method investment	$ 5,600

Operating Segment Reporting (94

Operating Segment Reporting (Table 1) (Details) $ in Thousands		12 Months Ended
		Sep. 30, 2015USD ($)segment	Sep. 30, 2014USD ($)	Sep. 30, 2013USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | segment		4
Operating revenues	[1]	$ 2,659,830	$ 2,780,947	$ 2,466,138
Operating revenues, regulated utility		1,303,044	1,416,951	1,174,724
Operating revenues, non-utility		1,356,786	1,363,996	1,291,414
Depreciation and amortization, regulated utility		121,892	110,772	103,284
Depreciation and amortization, non-utility		121,892	110,772	103,284
Equity in earnings of unconsolidated affiliates		5,468	3,194	1,510
Total consolidated EBIT		266,894	202,252	169,876
Assets		5,294,201	4,856,499	4,260,060
Capital Expenditures		464,291	394,762	312,345
Equity Method Investments		136,884	94,902	61,897
Retail energy-marketing
Segment Reporting Information [Line Items]
Operating revenues, non-utility	[1]	1,306,758	1,310,279	1,279,364
Depreciation and amortization, non-utility		671	756	726
Equity in earnings of unconsolidated affiliates		0	1	0
Total consolidated EBIT		46,629	14,015	53,264
Assets		470,251	389,700	403,082
Capital Expenditures		28	76	730
Equity Method Investments		0	0	0
Commercial energy systems
Segment Reporting Information [Line Items]
Operating revenues, non-utility	[1]	51,813	40,679	35,217
Depreciation and amortization, non-utility		10,733	6,178	2,411
Equity in earnings of unconsolidated affiliates		2,095	1,953	1,070
Total consolidated EBIT		9,688	6,863	3,019
Assets		691,629	521,570	318,995
Capital Expenditures		136,749	108,363	83,667
Equity Method Investments		63,521	66,810	54,977
Midstream energy services
Segment Reporting Information [Line Items]
Operating revenues, non-utility	[1]	3,191	16,555	(20,390)
Depreciation and amortization, non-utility		129	124	124
Equity in earnings of unconsolidated affiliates		2,623	771	312
Total consolidated EBIT		(2,720)	8,412	(29,359)
Assets		237,839	211,824	231,368
Capital Expenditures		85	0	0
Equity Method Investments		73,363	28,076	6,507
Other Activities
Segment Reporting Information [Line Items]
Operating revenues, non-utility	[1]	0	0	0
Depreciation and amortization, non-utility		0	0	0
Equity in earnings of unconsolidated affiliates		750	469	128
Total consolidated EBIT		(9,667)	(11,539)	(8,669)
Assets		199,060	369,816	290,440
Capital Expenditures		0	0	0
Equity Method Investments		0	16	413
Eliminations
Segment Reporting Information [Line Items]
Operating revenues, non-utility	[1],[2]	(30,123)	(30,366)	(28,410)
Depreciation and amortization, non-utility	[2]	(57)	(350)	(415)
Equity in earnings of unconsolidated affiliates	[2]	0	0	0
Total consolidated EBIT	[2]	(1,013)	(167)	(2,026)
Assets	[2]	(558,130)	(615,933)	(470,121)
Capital Expenditures	[2]	0	0	0
Equity Method Investments	[2]	0	0	0
Regulated Utility
Segment Reporting Information [Line Items]
Operating revenues, regulated utility	[1]	1,328,191	1,443,800	1,200,357
Depreciation and amortization, regulated utility		110,416	104,064	100,438
Equity in earnings of unconsolidated affiliates		0	0	0
Total consolidated EBIT		223,977	184,668	153,647
Assets		4,253,552	3,979,522	3,486,296
Capital Expenditures		327,429	286,323	227,948
Equity Method Investments		$ 0	$ 0	$ 0
[1]	(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 public service commission fees, franchise fees and energy taxes. Operating revenue amounts in the “Eliminations” row 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]	(b) Intersegment eliminations include any mark-to market valuations associated with trading activities between WGL Midstream and WGL Energy Services, intercompany loans and a timing difference between Commercial Energy Systems’ recognition of revenue for the sale of Renewable Energy Credits (RECs) to Retail Energy-Marketing and Retail Energy-Marketing’s recognition of the associated expense. Retail Energy-Marketing has recorded a portion of the REC’s purchased as inventory to be used in future periods at which time they will be expensed.

Operating Segment Reporting (95

Operating Segment Reporting (Table 2) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Segment Reporting [Abstract]
Total consolidated EBIT	$ 266,894	$ 202,252	$ 169,876
Interest Expense	50,511	37,738	36,011
Income before income taxes	216,383	164,514	133,865
INCOME TAX EXPENSE (BENEFIT)	83,804	57,254	52,292
Net income	132,579	107,260	81,573
Dividends on Washington Gas Light Company preferred stock	1,320	1,320	1,320
Net income (loss) applicable to common stock	$ 131,259	$ 105,940	$ 80,253

Other Investments - Narratives

Other Investments - Narratives (Details) $ in Thousands	12 Months Ended
	Sep. 30, 2015USD ($)miledekathermsinvestment	Sep. 30, 2014USD ($)	Sep. 30, 2013USD ($)	Mar. 31, 2015dekatherms
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Number of investments that qualify as VIEs | investment	4
Equity in earnings of unconsolidated affiliates	$ 5,468	$ 3,194	$ 1,510
Direct Fiinancing Leases Receivable	42,900
Funding provided per agreement	4,151	0	$ 0
Investments in direct financing leases, capital leases	35,234	18,159
Investments in unconsolidated affiliates	136,884	100,528
Crab Run [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Equity in earnings of unconsolidated affiliates	700
WGL | Mountain Valley Pipeline [Member] | Guarantee on behalf of subsidiary
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Maximum exposure to loss	$ 20,000
Willams Partners L.P. | Constitution [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Equity Method Investment Ownership Percentage	41.00%
Cabot Oil And Gas Corporation | Constitution [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Equity Method Investment Ownership Percentage	25.00%
Piedmont Natural Gas | Constitution [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Equity Method Investment Ownership Percentage	24.00%
COG Holdings LLC [Member] | Meade [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Equity Method Investment Ownership Percentage	20.00%
Vega Midstream MPC LLC [Member] | Meade [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Equity Method Investment Ownership Percentage	15.00%
River Road Interests LLC [Member] | Meade [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Equity Method Investment Ownership Percentage	10.00%
WGL Midstream | Constitution [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Estimated Investment In Constitution	$ 83,400
Investment amount	$ 29,400
Equity Method Investment Ownership Percentage	10.00%
Investments in unconsolidated affiliates	$ 33,100
WGL Midstream | Constitution [Member] | Minimum
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Equity Method Investment Ownership Percentage	5.00%
WGL Midstream | Constitution [Member] | Maximum
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Equity Method Investment Ownership Percentage	50.00%
WGL Midstream | Meade [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Equity Method Investment Ownership Percentage	55.00%
Pipeline length in miles | mile	185
Transportation and delivery | dekatherms	1,700,000
VIE Maximum Loss Exposure	$ 59,400
Estimated Investment in Meade	410,600
Investments in unconsolidated affiliates	30,500	5,800
WGL Midstream | Mountain Valley Pipeline [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Equity Method Investment Ownership Percentage				7.00%
Transportation and delivery | dekatherms				2,000,000
Minimum funding requirement	14,000
Investments in unconsolidated affiliates	9,800
WGL Midstream | Mountain Valley Pipeline [Member] | Guarantee on behalf of subsidiary
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Funding provided per agreement	4,200
WGL Midstream | Mountain Valley Pipeline [Member] | Minimum
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Estimated Investment in Mountain Valley Pipeline	210,000
WGL Midstream | Mountain Valley Pipeline [Member] | Minimum | Guarantee on behalf of subsidiary
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Maximum exposure to loss	96,000
WGL Midstream | Mountain Valley Pipeline [Member] | Maximum
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Estimated Investment in Mountain Valley Pipeline	245,000
WGL Midstream | Mountain Valley Pipeline [Member] | Maximum | Guarantee on behalf of subsidiary
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Maximum exposure to loss	105,000
WGSW, Inc. [Member] | Sun Edison/Nextility [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Investments in direct financing leases, capital leases	37,200	19,900
Net Investment in Direct Financing Lease, Current	2,000	1,700
WGSW, Inc. [Member] | ASD Solar, LP [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Equity Method Investment Difference Between Carrying Amount and Underlying Equity	35,900
Investments in unconsolidated affiliates	63,500	66,800
Washington Gas Resources
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Impairment loss, cost-method investment	5,600
Washington Gas Resources | American Solar Direct Holdings Inc. (ASDHI)
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost Method Investments		$ 5,600
Impairment loss, cost-method investment	$ 5,600
Other External Partners [Member] | Mountain Valley Pipeline [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Equity Method Investment Ownership Percentage	3.00%

Other Investments - Financing L

Other Investments - Financing Leases Table (Details) - USD ($) $ in Millions	Sep. 30, 2015	Sep. 30, 2012
Capital Leases, Future Minimum Payments Receivable, Fiscal Year Maturity [Abstract]
2,016	$ 3.7
2,017	2.8
2,018	2.8
2,019	2.7
2,020	2.6
Thereafter	28.3
Total	42.9
Direct Financing Leases - Residual Value	9.5
Direct Financing Leases - Tax Credits	4.6
Direct Financing Leases - Unearned Income	$ 19.8
Direct Financing Leases - Initial Direct Costs		$ 0.7

Other Investments - Location Ta

Other Investments - Location Table (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2015		Sep. 30, 2014	Sep. 30, 2013
ASSETS
Investments in unconsolidated affiliates	$ 136,884		$ 100,528
Investments in direct financing leases, capital leases	35,234		18,159
INCOME STATEMENT
Equity in earnings of unconsolidated affiliates	5,468		3,194	$ 1,510
VIEs
ASSETS
Investments in unconsolidated affiliates	94,000		72,600
Investments in direct financing leases, capital leases	35,200		18,200
Net Investment in Direct Financing Lease, Current	2,000		1,700
Total assets	131,200		92,500
INCOME STATEMENT
Equity in earnings of unconsolidated affiliates	2,900		2,200	1,000
Depreciation and amortization	300		200	100
Other income - net	3,200		2,600	1,400
Net income	5,800		4,600	2,300
Non-VIEs
ASSETS
Investments in unconsolidated affiliates	42,900		27,900
Investments in direct financing leases, capital leases	0		0
Net Investment in Direct Financing Lease, Current	4,200	[1]	0
Total assets	47,100		27,900
INCOME STATEMENT
Equity in earnings of unconsolidated affiliates	2,600		1,000	500
Depreciation and amortization	0		0	0
Other income - net	(5,600)		0	0
Net income	(3,000)		1,000	500
Total
ASSETS
Investments in unconsolidated affiliates	136,900		100,500
Investments in direct financing leases, capital leases	35,200		18,200
Net Investment in Direct Financing Lease, Current	6,200		1,700
Total assets	178,300		120,400
INCOME STATEMENT
Equity in earnings of unconsolidated affiliates	5,500		3,200	1,500
Depreciation and amortization	300		200	100
Other income - net	(2,400)		2,600	1,400
Net income	$ 2,800		$ 5,600	$ 2,800
[1]	(a) Represents the financing provided to another partner in Mountain Valley to fund its capital commitment. Acquired ownership interest represents the collateral for repayment of the financing.

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Related Party Transaction [Line Items]
Gas balancing service charge	$ 25,100	$ 26,600	$ 25,000
Washington Gas Light Company
Related Party Transaction [Line Items]
Receivables from Associated Companies	3,176	4,821
Payables to Associated Companies	68,623	54,685
WGL Energy Services
Related Party Transaction [Line Items]
Related Party Gas Imbalance Payable	500
Related Party Gas Imbalance - Receivable		20
Related Party Purchased Receivables	$ 6,600	$ 7,700

Accumulated Other Comprehens100

Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Sep. 30, 2015		Sep. 30, 2014		Sep. 30, 2013
AOCI, Net of Tax [Roll Forward]
Beginning Balance		$ (7,961)		$ (11,048)
Qualified cash flow hedging instruments		(11,309)	[1]	(1,548)	[1]	$ 0
Change in prior service cost	$ (26,100)	696	[2]	6,095	[2]	(1,671)
Amortization of actuarial gain (loss)		(1,195)	[2]	1,594	[2]	3,399
Current-period other comprehensive income (loss)		(11,808)		6,141		1,966
Income tax expense related to other comprehensive income (loss)		(5,533)		3,054		813
Ending Balance	(14,236)	(14,236)		(7,961)		(11,048)
Washington Gas Light Company
AOCI, Net of Tax [Roll Forward]
Beginning Balance		(6,413)		(11,048)
Change in prior service cost		696	[3]	6,095	[3]	(1,671)
Amortization of actuarial gain (loss)		(1,195)	[3]	1,594	[3]	3,399
Current-period other comprehensive income (loss)		(499)		7,689
Income tax expense related to other comprehensive income (loss)		(200)		3,054		813
Ending Balance	$ (6,712)	$ (6,712)		$ (6,413)		$ (11,048)
[1]	(a) Cash flow hedging instruments represent interest rate swap agreements related to debt issuances. Refer to Note 14—Derivative and Weather-related Instruments for further discussion of the interest rate swap agreements.
[2]	(b) These accumulated other comprehensive income (loss) components are included in the computation of net periodic benefit cost. Refer to Note 10-Pension and other post-retirement benefit plans for additional details.
[3]	(a) These accumulated other comprehensive income (loss) components are included in the computation of net periodic benefit cost. Refer to Note 10-Pension and other post-retirement benefit plans for additional details.

Quarterly Financial Data - Tabl

Quarterly Financial Data - Table (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended														12 Months Ended
		Sep. 30, 2015	[2]	Jun. 30, 2015	[3]	Mar. 31, 2015	Dec. 31, 2014	[4]	Sep. 30, 2014	[2]	Jun. 30, 2014	[3]	Mar. 31, 2014	Dec. 31, 2013	[4]	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Operating revenues	[1]															$ 2,659,830	$ 2,780,947	$ 2,466,138
Operating income (loss)																260,773	197,522	165,818
Net income (loss) applicable to common stock																$ 131,259	$ 105,940	$ 80,253
Earnings (loss) per average share of common stock:
Basic																$ 2.64	$ 2.05	$ 1.55
Diluted																$ 2.62	$ 2.05	$ 1.55
WGL
Operating revenues		$ 467,687		$ 441,173		$ 1,001,733	$ 749,237		$ 458,900		$ 467,500		$ 1,174,250	$ 680,297
Operating income (loss)		13,612		(17,567)		142,886	121,842		69,566		(9,489)		104,733	32,712
Net income (loss) applicable to common stock		$ 1,606		$ (15,690)		$ 81,455	$ 63,888		$ 38,038		$ (11,940)		$ 61,213	$ 18,629
Earnings (loss) per average share of common stock:
Basic		$ 0.03		$ (0.32)		$ 1.64	$ 1.28		$ 0.74		$ (0.23)		$ 1.18	$ 0.36
Diluted		$ 0.03		$ (0.32)		$ 1.63	$ 1.28		$ 0.74		$ (0.23)		$ 1.18	$ 0.36
Washington Gas Light Company
Operating revenues		$ 134,959		$ 190,345		$ 615,694	$ 387,193		$ 138,825		$ 197,752		$ 716,808	$ 390,415		$ 1,328,191	$ 1,443,800	$ 1,200,357
Operating income (loss)		(15,454)		(6,729)		129,944	114,623		24,530		4,326		88,038	65,229		222,384	182,123	150,606
Net income (loss) applicable to common stock		$ (19,873)		$ (11,754)		$ 74,364	$ 64,621		$ 9,872		$ (521)		$ 49,176	$ 38,477		$ 107,358	$ 97,004	$ 71,002
[1]	(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 public service commission fees, franchise fees and energy taxes. Operating revenue amounts in the “Eliminations” row 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]	(c)During the fourth quarter of fiscal year 2015, Washington Gas recorded a one time adjustment of $2.4 million as a result of charges associated with a regulatory proceeding.
[3]	(b) During the third quarter of fiscal year 2015, WGL recorded a $3.0 million liability for un-recovered government contracting costs under the Small Business Administration Development 8(a) Program and Washington Gas recorded approximately $0.5 million in transaction fees related to the sale of its Springfield Operations Center. During the third quarter of fiscal year 2014, Washington Gas recorded a $1.9 million impairment charge on an abandoned LNG storage facility. Refer to Note 1—Accounting Policies of the Notes to Consolidated Financial Statements for further discussion of the impairments.
[4]	(a) During the first quarter of fiscal year 2015, WGL recorded an impairment charge of $5.6 million related to its investment in ASDHI. During the first quarter of fiscal year 2014, Washington Gas recorded an impairment charge of $0.8 million related to the Springfield Operations Center. Refer to Note 1—Accounting Policies of the Notes to Consolidated Financial Statements for further discussion of the impairments.

Quarterly Financial Information

Quarterly Financial Information - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Dec. 31, 2013
WGL
Un recovered government contracting costs		$ 3
WGL | American Solar Direct Holdings Inc [Member]
Impairment			$ 5.6
Washington Gas Light Company
Utilities Expense, Adjustment	$ 2.4
Abandoned LNG storage project | Washington Gas Light Company
Impairment				$ 1.9
Springfield Operations Center | Washington Gas Light Company
Impairment		$ 0.5			$ 0.8

Schedule II (Details)

Schedule II (Details) - USD ($) $ in Thousands		12 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Valuation and Qualifying Accounts Disclosure [Line Items]
Valuation Allowances and Reserves, Beginning Balance		$ 23,341	$ 20,433	$ 19,792
Valuation Allowances and Reserves, Charged to Cost and Expense		18,250	15,874	9,527
Valuation Allowances and Reserves, Charged to Other Accounts	[1]	4,789	4,341	4,217
Valuation Allowances and Reserves, Deductions	[2]	20,156	17,307	13,103
Valuation Allowances and Reserves, Ending Balance		26,224	23,341	20,433
Washington Gas Light Company
Valuation and Qualifying Accounts Disclosure [Line Items]
Valuation Allowances and Reserves, Beginning Balance		19,209	17,498	17,129
Valuation Allowances and Reserves, Charged to Cost and Expense		12,800	12,004	7,024
Valuation Allowances and Reserves, Charged to Other Accounts	[3]	4,686	4,198	3,978
Valuation Allowances and Reserves, Deductions	[4]	17,441	14,491	10,633
Valuation Allowances and Reserves, Ending Balance		$ 19,254	$ 19,209	$ 17,498
[1]	(a) Recoveries on receivables previously written off as uncollectible and unclaimed customer deposits, overpayments, etc., not refundable.
[2]	(b) Includes deductions for purposes for which reserves were provided or revisions made of estimated exposure.
[3]	(a) Recoveries on receivables previously written off as uncollectible and unclaimed customer deposits, overpayments, etc., not refundable.
[4]	(b) Includes deductions for purposes for which reserves were provided or revisions made of estimated exposure.