Consolidated Edison (ED) 10-K 15 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2017	Jan. 31, 2018	Jun. 30, 2017
Document Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Trading Symbol	ED
Entity Registrant Name	CONSOLIDATED EDISON INC
Entity Central Index Key	1,047,862
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		310,397,070
Entity Public Float			$ 24.7
CECONY
Document Information [Line Items]
Entity Registrant Name	CONSOLIDATED EDISON CO OF NEW YORK INC
Entity Central Index Key	23,632
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Non-accelerated Filer

Consolidated Income Statement

Consolidated Income Statement - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
OPERATING REVENUES
Electric	$ 8,612	$ 8,741	$ 8,832
Gas	2,133	1,692	1,709
Steam	595	551	629
Non-utility	693	1,091	1,384
TOTAL OPERATING REVENUES	12,033	12,075	12,554
OPERATING EXPENSES
Purchased power	1,601	2,439	2,973
Fuel	216	172	248
Gas purchased for resale	808	477	495
Other operations and maintenance	3,303	3,269	3,344
Depreciation and amortization	1,341	1,216	1,130
Taxes, other than income taxes	2,155	2,031	1,937
TOTAL OPERATING EXPENSES	9,424	9,604	10,127
Gain on sale of retail electric supply business and solar electric production projects	1	104	0
OPERATING INCOME	2,610	2,575	2,427
OTHER INCOME (DEDUCTIONS)
Investment income	79	47	0
Other income	47	44	35
Allowance for equity funds used during construction	11	10	5
Other deductions	(21)	(37)	(16)
TOTAL OTHER INCOME	116	64	24
INCOME BEFORE INTEREST AND INCOME TAX EXPENSE	2,726	2,639	2,451
INTEREST EXPENSE
Interest on long-term debt	726	678	632
Other interest	11	24	24
Allowance for borrowed funds used during construction	(8)	(6)	(3)
NET INTEREST EXPENSE	729	696	653
INCOME BEFORE INCOME TAX EXPENSE	1,997	1,943	1,798
INCOME TAX EXPENSE	472	698	605
NET INCOME	$ 1,525	$ 1,245	$ 1,193
Net income per common share — basic (dollars per share)	$ 4.97	$ 4.15	$ 4.07
Net income per common share — diluted (dollars per share)	4.94	4.12	4.05
DIVIDENDS DECLARED PER COMMON SHARE (dollars per share)	$ 2.76	$ 2.68	$ 2.60
AVERAGE NUMBER OF SHARES OUTSTANDING — BASIC	307.1	300.4	293
AVERAGE NUMBER OF SHARES OUTSTANDING — DILUTED	308.8	301.9	294.4
CECONY
OPERATING REVENUES
Electric	$ 7,972	$ 8,106	$ 8,172
Gas	1,901	1,508	1,527
Steam	595	551	629
TOTAL OPERATING REVENUES	10,468	10,165	10,328
OPERATING EXPENSES
Purchased power	1,415	1,568	1,719
Fuel	216	172	248
Gas purchased for resale	510	319	337
Other operations and maintenance	2,670	2,806	2,881
Depreciation and amortization	1,195	1,106	1,040
Taxes, other than income taxes	2,057	1,932	1,856
TOTAL OPERATING EXPENSES	8,063	7,903	8,081
OPERATING INCOME	2,405	2,262	2,247
OTHER INCOME (DEDUCTIONS)
Investment income	14	8	5
Allowance for equity funds used during construction	10	8	4
Other deductions	(17)	(16)	(14)
TOTAL OTHER INCOME	7	0	(5)
INCOME BEFORE INTEREST AND INCOME TAX EXPENSE	2,412	2,262	2,242
INTEREST EXPENSE
Interest on long-term debt	615	588	567
Other interest	14	19	19
Allowance for borrowed funds used during construction	(6)	(4)	(2)
NET INTEREST EXPENSE	623	603	584
INCOME BEFORE INCOME TAX EXPENSE	1,789	1,659	1,658
INCOME TAX EXPENSE	685	603	574
NET INCOME	$ 1,104	$ 1,056	$ 1,084

Consolidated Statement of Compr

Consolidated Statement of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
NET INCOME	$ 1,525	$ 1,245	$ 1,193
OTHER COMPREHENSIVE INCOME, NET OF TAXES
Pension and other postretirement benefit plan liability adjustments, net of taxes	1	7	11
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	1	7	11
COMPREHENSIVE INCOME	1,526	1,252	1,204
CECONY
NET INCOME	1,104	1,056	1,084
OTHER COMPREHENSIVE INCOME, NET OF TAXES
Pension and other postretirement benefit plan liability adjustments, net of taxes	1	2	2
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	1	2	2
COMPREHENSIVE INCOME	$ 1,105	$ 1,058	$ 1,086

Consolidated Statement of Cash

Consolidated Statement of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
OPERATING ACTIVITIES
Net income	$ 1,525	$ 1,245	$ 1,193
PRINCIPAL NON-CASH CHARGES/(CREDITS) TO INCOME
Depreciation and amortization	1,341	1,216	1,130
Deferred income taxes	485	783	653
Rate case amortization and accruals	(124)	(210)	(52)
Common equity component of allowance for funds used during construction	(11)	(10)	(5)
Net derivative (gains)/losses	(4)	(6)	3
Pre-tax gain on sale of retail electric supply business and solar electric production projects	(1)	(104)	0
Other non-cash items, net	(49)	142	77
CHANGES IN ASSETS AND LIABILITIES
Accounts receivable - customers	(6)	(69)	96
Materials and supplies, including fuel oil and gas in storage	5	13	22
Other receivables and other current assets	(44)	54	(27)
Taxes receivable	15	87	58
Prepayments	(19)	20	(14)
Accounts payable	95	29	(79)
Pensions and retiree benefits obligations, net	414	609	756
Pensions and retiree benefits contributions	(467)	(515)	(756)
Accrued taxes	44	2	(10)
Accrued interest	(7)	14	4
Superfund and environmental remediation costs, net	(14)	69	22
Distributions from equity investments	108	68	31
System benefit charge	101	244	38
Deferred charges, noncurrent assets and other regulatory assets	2,376	(97)	(111)
Deferred credits and other regulatory liabilities	(2,524)	(68)	182
Other current and noncurrent liabilities	128	(57)	66
NET CASH FLOWS FROM OPERATING ACTIVITIES	3,367	3,459	3,277
INVESTING ACTIVITIES
Utility construction expenditures	(3,028)	(2,835)	(2,562)
Cost of removal less salvage	(248)	(206)	(219)
Non-utility construction expenditures	(415)	(845)	(492)
Proceeds from sale of assets	34	252	0
Restricted cash	7	(17)	(13)
Proceeds from the transfer of assets to NY Transco	0	122	0
Other investing activities	37	31	(72)
NET CASH FLOWS USED IN INVESTING ACTIVITIES	(3,703)	(4,976)	(3,657)
FINANCING ACTIVITIES
Net (payment)/issuance of short-term debt	(477)	(475)	729
Issuance of long-term debt	1,697	2,590	1,147
Retirement of long-term debt	(434)	(735)	(500)
Debt issuance costs	(19)	(24)	(15)
Common stock dividends	(803)	(763)	(733)
Issuance of common shares - public offering	343	702	0
Issuance of common shares for stock plans, net of repurchases	51	51	1
Distribution to noncontrolling interest	(1)	(1)	0
NET CASH FLOWS FROM FINANCING ACTIVITIES	357	1,345	629
CASH AND TEMPORARY CASH INVESTMENTS:
NET CHANGE FOR THE PERIOD	21	(172)	249
BALANCE AT BEGINNING OF PERIOD	776	944	699
BALANCE AT END OF PERIOD	797	772	948
LESS: CHANGE IN CASH BALANCES HELD FOR SALE	0	(4)	4
BALANCE AT END OF PERIOD EXCLUDING HELD FOR SALE	797	776	944
Cash paid/(received) during the period for:
Interest	725	664	597
Income taxes	(29)	(180)	(36)
SUPPLEMENTAL DISCLOSURE OF NON-CASH INFORMATION
Construction expenditures in accounts payable	432	388	279
Issuance of common shares for dividend reinvestment	46	46	28
Debt assumed with business acquisitions	0	195	0
Electric and Gas Transmission Projects
INVESTING ACTIVITIES
Investments in/acquisitions of projects	(45)	(1,076)	0
Renewable Electric Production Projects
INVESTING ACTIVITIES
Investments in/acquisitions of projects	(45)	(402)	(299)
CECONY
OPERATING ACTIVITIES
Net income	1,104	1,056	1,084
PRINCIPAL NON-CASH CHARGES/(CREDITS) TO INCOME
Depreciation and amortization	1,195	1,106	1,040
Deferred income taxes	575	545	449
Rate case amortization and accruals	(142)	(227)	(74)
Common equity component of allowance for funds used during construction	(10)	(8)	(4)
Other non-cash items, net	(61)	(31)	(27)
CHANGES IN ASSETS AND LIABILITIES
Accounts receivable - customers	15	(23)	87
Materials and supplies, including fuel oil and gas in storage	(17)	18	24
Other receivables and other current assets	8	(11)	38
Accounts receivables from affiliated companies	45	81	(58)
Prepayments	(8)	13	13
Accounts payable	125	20	(51)
Accounts payable to affiliated companies	0	(2)	(11)
Pensions and retiree benefits obligations, net	370	579	714
Pensions and retiree benefits contributions	(420)	(476)	(703)
Accrued taxes	52	1	3
Accrued taxes to affiliated companies	(47)	117	(8)
Accrued interest	2	(7)	1
Superfund and environmental remediation costs, net	(12)	79	19
System benefit charge	85	221	38
Deferred charges, noncurrent assets and other regulatory assets	2,212	(172)	(150)
Deferred credits and other regulatory liabilities	(2,242)	179	379
Other current and noncurrent liabilities	37	(20)	16
NET CASH FLOWS FROM OPERATING ACTIVITIES	2,866	3,038	2,819
INVESTING ACTIVITIES
Utility construction expenditures	(2,840)	(2,672)	(2,410)
Cost of removal less salvage	(240)	(203)	(212)
Restricted cash	2	14	(16)
Proceeds from the transfer of assets to NY Transco	0	122	0
NET CASH FLOWS USED IN INVESTING ACTIVITIES	(3,078)	(2,739)	(2,638)
FINANCING ACTIVITIES
Net (payment)/issuance of short-term debt	(450)	(433)	583
Issuance of long-term debt	1,200	1,300	650
Retirement of long-term debt	0	(650)	(350)
Debt issuance costs	(15)	(13)	(7)
Capital contribution by parent	301	100	13
Dividend to parent	(796)	(744)	(872)
NET CASH FLOWS FROM FINANCING ACTIVITIES	240	(440)	17
CASH AND TEMPORARY CASH INVESTMENTS:
NET CHANGE FOR THE PERIOD	28	(141)	198
BALANCE AT BEGINNING OF PERIOD	702	843	645
BALANCE AT END OF PERIOD EXCLUDING HELD FOR SALE	730	702	843
Cash paid/(received) during the period for:
Interest	602	581	554
Income taxes	108	(162)	163
SUPPLEMENTAL DISCLOSURE OF NON-CASH INFORMATION
Construction expenditures in accounts payable	$ 351	$ 295	$ 210

Consolidated Balance Sheet

Consolidated Balance Sheet - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
CURRENT ASSETS
Cash and temporary cash investments	$ 797	$ 776
Accounts receivable - customers, less allowance for uncollectible accounts	1,103	1,106
Other receivables, less allowance for uncollectible accounts	160	195
Taxes receivable	64	79
Accrued unbilled revenue	598	447
Fuel oil, gas in storage, materials and supplies, at average cost	334	339
Prepayments	178	159
Regulatory assets	67	100
Restricted cash	47	54
Other current assets	189	151
TOTAL CURRENT ASSETS	3,537	3,406
INVESTMENTS	2,001	1,921
UTILITY PLANT, AT ORIGINAL COST
General	3,008	2,719
TOTAL	42,731	40,411
Less: Accumulated depreciation	9,063	8,541
Net	33,668	31,870
Construction work in progress	1,605	1,175
NET UTILITY PLANT	35,273	33,045
NON-UTILITY PLANT
Non-utility property, less accumulated depreciation	1,776	1,482
Construction work in progress	551	689
NET PLANT	37,600	35,216
OTHER NONCURRENT ASSETS
Goodwill	428	428
Intangible assets, less accumulated amortization of $15 and $6 in 2017 and 2016, respectively	131	124
Regulatory assets	4,266	7,024
Other deferred charges and noncurrent assets	148	136
TOTAL OTHER NONCURRENT ASSETS	4,973	7,712
TOTAL ASSETS	48,111	48,255
CURRENT LIABILITIES
Long-term debt due within one year	1,298	39
Notes payable	577	1,054
Accounts payable	1,286	1,147
Customer deposits	346	352
Accrued taxes	108	64
Accrued interest	143	150
Accrued wages	105	101
Fair value of derivative liabilities	17	77
Regulatory liabilities	101	128
System benefit charge	535	434
Other current liabilities	386	297
TOTAL CURRENT LIABILITIES	4,902	3,843
NONCURRENT LIABILITIES
Provision for injuries and damages	153	160
Pensions and retiree benefits	1,443	1,847
Superfund and other environmental costs	737	753
Asset retirement obligations	314	246
Fair value of derivative liabilities	38	40
Deferred income taxes and unamortized investment tax credits	5,495	10,205
Regulatory liabilities	4,577	1,905
Other deferred credits and noncurrent liabilities	296	215
TOTAL NONCURRENT LIABILITIES	13,053	15,371
LONG-TERM DEBT	14,731	14,735
EQUITY
Common shareholders’ equity	15,418	14,298
Noncontrolling interest	7	8
TOTAL EQUITY (See Statement of Equity)	15,425	14,306
TOTAL LIABILITIES AND EQUITY	48,111	48,255
Electric
UTILITY PLANT, AT ORIGINAL COST
Utility plant, at original cost	28,994	27,747
Gas
UTILITY PLANT, AT ORIGINAL COST
Utility plant, at original cost	8,256	7,524
Steam
UTILITY PLANT, AT ORIGINAL COST
Utility plant, at original cost	2,473	2,421
CECONY
CURRENT ASSETS
Cash and temporary cash investments	730	702
Accounts receivable - customers, less allowance for uncollectible accounts	1,009	1,032
Other receivables, less allowance for uncollectible accounts	92	81
Taxes receivable	19	0
Accrued unbilled revenue	454	399
Accounts receivable from affiliated companies	64	109
Fuel oil, gas in storage, materials and supplies, at average cost	287	270
Prepayments	108	100
Regulatory assets	62	90
Restricted cash	0	2
Other current assets	84	95
TOTAL CURRENT ASSETS	2,909	2,880
INVESTMENTS	383	315
UTILITY PLANT, AT ORIGINAL COST
General	2,753	2,490
TOTAL	40,024	37,847
Less: Accumulated depreciation	8,321	7,836
Net	31,703	30,011
Construction work in progress	1,502	1,104
NET UTILITY PLANT	33,205	31,115
NON-UTILITY PLANT
Non-utility property, less accumulated depreciation	4	4
NET PLANT	33,209	31,119
OTHER NONCURRENT ASSETS
Goodwill	245	245
Regulatory assets	3,863	6,473
Other deferred charges and noncurrent assets	87	69
TOTAL OTHER NONCURRENT ASSETS	3,950	6,542
TOTAL ASSETS	40,451	40,856
CURRENT LIABILITIES
Long-term debt due within one year	1,200	0
Notes payable	150	600
Accounts payable	1,057	876
Accounts payable to affiliated companies	10	10
Customer deposits	334	336
Accrued taxes	102	50
Accrued taxes to affiliated companies	72	119
Accrued interest	113	111
Accrued wages	95	91
Fair value of derivative liabilities	12	66
Regulatory liabilities	65	90
System benefit charge	483	398
Other current liabilities	245	242
TOTAL CURRENT LIABILITIES	3,938	2,989
NONCURRENT LIABILITIES
Provision for injuries and damages	147	154
Pensions and retiree benefits	1,140	1,544
Superfund and other environmental costs	637	655
Asset retirement obligations	287	227
Fair value of derivative liabilities	31	33
Deferred income taxes and unamortized investment tax credits	5,306	9,450
Regulatory liabilities	4,219	1,712
Other deferred credits and noncurrent liabilities	242	190
TOTAL NONCURRENT LIABILITIES	12,009	13,965
LONG-TERM DEBT	12,065	12,073
EQUITY
Common shareholders’ equity	12,439	11,829
TOTAL LIABILITIES AND EQUITY	40,451	40,856
CECONY | Electric
UTILITY PLANT, AT ORIGINAL COST
Utility plant, at original cost	27,299	26,122
CECONY | Gas
UTILITY PLANT, AT ORIGINAL COST
Utility plant, at original cost	7,499	6,814
CECONY | Steam
UTILITY PLANT, AT ORIGINAL COST
Utility plant, at original cost	$ 2,473	$ 2,421

Consolidated Balance Sheet (Par

Consolidated Balance Sheet (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Accounts receivable - customers, allowance for uncollectible accounts	$ 63	$ 69
Other receivables, allowance for uncollectible accounts	8	14
Non-utility property, accumulated depreciation	201	140
Intangible assets, accumulated amortization	15	6
CECONY
Accounts receivable - customers, allowance for uncollectible accounts	58	65
Other receivables, allowance for uncollectible accounts	7	13
Non-utility property, accumulated depreciation	$ 25	$ 25

Consolidated Statement of Equit

Consolidated Statement of Equity - USD ($) $ in Millions	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Treasury Stock	Capital Stock Expense	Accumulated Other Comprehensive Income/(Loss)	Noncontrolling Interest	CECONY	CECONYCommon Stock	CECONYAdditional Paid-In Capital	CECONYRetained Earnings	CECONYRepurchased Con Edison Stock	CECONYCapital Stock Expense	CECONYAccumulated Other Comprehensive Income/(Loss)
BALANCE AS OF BEGINNING OF PERIOD (in shares) at Dec. 31, 2014		293,000,000								235,000,000
BALANCE AS OF BEGINNING OF PERIOD at Dec. 31, 2014	$ 12,585	$ 32	$ 4,991	$ 8,691	$ (1,032)	$ (61)	$ (45)	$ 9							$ (11)
BALANCE AS OF BEGINNING OF PERIOD at Dec. 31, 2014									$ 11,188	$ 589	$ 4,234	$ 7,399	$ (962)	$ (61)	(11)
TREASURY STOCK, BALANCE AS OF BEGINNING OF PERIOD (in shares) at Dec. 31, 2014					23,000,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,193			1,193					1,084			1,084
Common stock dividends	(761)			(761)					(872)			(872)
Issuance of common shares for stock plans, net of repurchases (in shares)		0			0
Issuance of common shares for stock plans, net of repurchases	33		39		$ (6)
Capital contribution by parent									13		13
Other comprehensive income	11						11		2						2
Noncontrolling interest	0
BALANCE AS OF END OF PERIOD (in shares) at Dec. 31, 2015		293,000,000								235,000,000
BALANCE AS OF END OF PERIOD at Dec. 31, 2015	13,061	$ 32	5,030	9,123	$ (1,038)	(61)	(34)	9							(9)
BALANCE AS OF END OF PERIOD at Dec. 31, 2015									11,415	$ 589	4,247	7,611	(962)	(61)	(9)
TREASURY STOCK, BALANCE AS OF END OF PERIOD (in shares) at Dec. 31, 2015					23,000,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,245			1,245					1,056			1,056
Common stock dividends	(809)			(809)					(744)			(744)
Issuance of common shares - public offering (in shares)		10,000,000
Issuance of common shares - public offering	702	$ 1	723			(22)
Issuance of common shares for stock plans (in shares)		2,000,000
Issuance of common shares for stock plans	101		101
Capital contribution by parent									100		100
Other comprehensive income	7						7		2						2
Noncontrolling interest	(1)							(1)
BALANCE AS OF END OF PERIOD (in shares) at Dec. 31, 2016		305,000,000								235,000,000
BALANCE AS OF END OF PERIOD at Dec. 31, 2016	14,306	$ 33	5,854	9,559	$ (1,038)	(83)	(27)	8							(7)
BALANCE AS OF END OF PERIOD at Dec. 31, 2016	14,298								11,829	$ 589	4,347	7,923	(962)	(61)	(7)
TREASURY STOCK, BALANCE AS OF END OF PERIOD (in shares) at Dec. 31, 2016					23,000,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,525			1,525					1,104			1,104
Common stock dividends	(849)			(849)					(796)			(796)
Issuance of common shares - public offering (in shares)		5,000,000
Issuance of common shares - public offering	343	$ 1	344			(2)
Issuance of common shares for stock plans	100		100
Capital contribution by parent									301		302			(1)
Other comprehensive income	1						1		$ 1						1
Noncontrolling interest	(1)							(1)
BALANCE AS OF END OF PERIOD (in shares) at Dec. 31, 2017		310,000,000							21,976,200	235,000,000
BALANCE AS OF END OF PERIOD at Dec. 31, 2017	15,425	$ 34	$ 6,298	$ 10,235	$ (1,038)	$ (85)	$ (26)	$ 7							(6)
BALANCE AS OF END OF PERIOD at Dec. 31, 2017	$ 15,418								$ 12,439	$ 589	$ 4,649	$ 8,231	$ (962)	$ (62)	$ (6)
TREASURY STOCK, BALANCE AS OF END OF PERIOD (in shares) at Dec. 31, 2017					23,000,000

Consolidated Statement of Capit

Consolidated Statement of Capitalization - USD ($) shares in Millions, $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Schedule of Capitalization, Equity [Line Items]
TOTAL EQUITY BEFORE ACCUMULATED OTHER COMPREHENSIVE LOSS (in shares)	310	305
TOTAL EQUITY BEFORE ACCUMULATED OTHER COMPREHENSIVE LOSS	$ 15,444	$ 14,325
Pension plan liability adjustments, net of taxes	(23)	(24)
Unrealized losses on derivatives qualified as cash flow hedges, less reclassification adjustment for gains/(losses) included in net income and reclassification adjustment for unrealized losses included in regulatory assets, net of taxes	(3)	(3)
TOTAL ACCUMULATED OTHER COMPREHENSIVE LOSS, NET OF TAXES	(26)	(27)
Equity	15,418	14,298
Noncontrolling interest	7	8
TOTAL EQUITY (See Statement of Equity)	$ 15,425	$ 14,306
CECONY
Schedule of Capitalization, Equity [Line Items]
TOTAL EQUITY BEFORE ACCUMULATED OTHER COMPREHENSIVE LOSS (in shares)	235	235
TOTAL EQUITY BEFORE ACCUMULATED OTHER COMPREHENSIVE LOSS	$ 12,445	$ 11,836
Pension plan liability adjustments, net of taxes	(3)	(4)
Unrealized losses on derivatives qualified as cash flow hedges, less reclassification adjustment for gains/(losses) included in net income and reclassification adjustment for unrealized losses included in regulatory assets, net of taxes	(3)	(3)
TOTAL ACCUMULATED OTHER COMPREHENSIVE LOSS, NET OF TAXES	(6)	(7)
Equity	12,439	11,829
TOTAL SHAREHOLDER’S EQUITY (See Statement of Shareholder’s Equity)	$ 12,439	$ 11,829

Consolidated Statement of Capi9

Consolidated Statement of Capitalization - Long-term Debt - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016
Schedule of Capitalization, Long-term Debt [Line Items]
Other long-term debt		$ 310	$ 317
Unamortized debt expense		(113)	(107)
Unamortized debt discount		(29)	(27)
TOTAL		16,029	14,774
Long-term debt - Variable rate term loan		0	400
Less: Long-term debt due within one year		1,298	39
TOTAL LONG-TERM DEBT		14,731	14,735
TOTAL CAPITALIZATION		30,149	29,033
CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Unamortized debt expense		(94)	(87)
Unamortized debt discount		(27)	(26)
TOTAL		13,265	12,073
Less: Long-term debt due within one year		1,200	0
TOTAL LONG-TERM DEBT		12,065	12,073
TOTAL CAPITALIZATION		24,504	23,902
Coram
Schedule of Capitalization, Long-term Debt [Line Items]
TOTAL PROJECT DEBT		$ 170	180
Coram | Maximum
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		4.52%
Texas Solar 4
Schedule of Capitalization, Long-term Debt [Line Items]
TOTAL PROJECT DEBT		$ 61	64
Texas Solar 4 | Minimum
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		4.95%
Texas Solar 4 | Maximum
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		5.25%
California Solar 2
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		3.94%
TOTAL PROJECT DEBT		$ 110	114
California Solar 3
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		4.07%
TOTAL PROJECT DEBT		$ 93	95
Texas Solar 5
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		4.53%
TOTAL PROJECT DEBT		$ 155	158
Texas Solar 7
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		4.21%
TOTAL PROJECT DEBT		$ 214	218
Upton County Solar
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		4.45%
TOTAL PROJECT DEBT		$ 97	0
Other project debt
Schedule of Capitalization, Long-term Debt [Line Items]
TOTAL PROJECT DEBT		15	16
Project Debt
Schedule of Capitalization, Long-term Debt [Line Items]
TOTAL PROJECT DEBT		915	845
Debentures
Schedule of Capitalization, Long-term Debt [Line Items]
TOTAL		13,860	12,260
Debentures | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
TOTAL		$ 12,300	11,100
Debentures | Debenture Series 2008A, 5.85% Due 2018
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		5.85%
TOTAL		$ 600	600
Debentures | Debenture Series 2008A, 5.85% Due 2018 | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		5.85%
TOTAL		$ 600	600
Debentures | Debenture Series 2008A, 6.15% Due 2018
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		6.15%
TOTAL		$ 50	50
Debentures | Debenture Series 2008C, 7.125% Due 2018
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		7.125%
TOTAL		$ 600	600
Debentures | Debenture Series 2008C, 7.125% Due 2018 | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		7.125%
TOTAL		$ 600	600
Debentures | Debenture Series 2009A, 4.96% Due 2019
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		4.96%
TOTAL		$ 60	60
Debentures | Debenture Series 2009B, 6.65% Due 2019
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		6.65%
TOTAL		$ 475	475
Debentures | Debenture Series 2009B, 6.65% Due 2019 | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		6.65%
TOTAL		$ 475	475
Debentures | Debenture Series 2010A, 4.45% Due 2020
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		4.45%
TOTAL		$ 350	350
Debentures | Debenture Series 2010A, 4.45% Due 2020 | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		4.45%
TOTAL		$ 350	350
Debentures | Debenture Series 2017A, 2.00% Due 2020
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		2.00%
TOTAL		$ 400	0
Debentures | Debenture Series 2016A, 2.00% Due 2021
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		2.00%
TOTAL		$ 500	500
Debentures | Debenture Series 2014B, 3.30% Due 2024
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		3.30%
TOTAL		$ 250	250
Debentures | Debenture Series 2014B, 3.30% Due 2024 | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		3.30%
TOTAL		$ 250	250
Debentures | Debenture Series 2016B, 2.90% Due 2026
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		2.90%
TOTAL		$ 250	250
Debentures | Debenture Series 2016B, 2.90% Due 2026 | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		2.90%
TOTAL		$ 250	250
Debentures | Debenture Series 1997F, 6.50% Due 2027
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		6.50%
TOTAL		$ 80	80
Debentures | Debenture Series 2017B, 3.125% Due 2027
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		3.125%
TOTAL		$ 350	0
Debentures | Debenture Series 2017B, 3.125% Due 2027 | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		3.125%
TOTAL		$ 350	0
Debentures | Debenture Series 2003A, 5.875% Due 2033
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		5.875%
TOTAL		$ 175	175
Debentures | Debenture Series 2003A, 5.875% Due 2033 | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		5.875%
TOTAL		$ 175	175
Debentures | Debenture Series 2003C, 5.10% Due 2033
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		5.10%
TOTAL		$ 200	200
Debentures | Debenture Series 2003C, 5.10% Due 2033 | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		5.10%
TOTAL		$ 200	200
Debentures | Debenture Series 2004B, 5.70% Due 2034
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		5.70%
TOTAL		$ 200	200
Debentures | Debenture Series 2004B, 5.70% Due 2034 | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		5.70%
TOTAL		$ 200	200
Debentures | Debenture Series 2005A, 5.30% Due 2035
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		5.30%
TOTAL		$ 350	350
Debentures | Debenture Series 2005A, 5.30% Due 2035 | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		5.30%
TOTAL		$ 350	350
Debentures | Debenture Series 2005B, 5.25% Due 2035
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		5.25%
TOTAL		$ 125	125
Debentures | Debenture Series 2005B, 5.25% Due 2035 | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		5.25%
TOTAL		$ 125	125
Debentures | Debenture Series 2006A, 5.85% Due 2036
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		5.85%
TOTAL		$ 400	400
Debentures | Debenture Series 2006A, 5.85% Due 2036 | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		5.85%
TOTAL		$ 400	400
Debentures | Debenture Series 2006B, 6.20% Due 2036
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		6.20%
TOTAL		$ 400	400
Debentures | Debenture Series 2006B, 6.20% Due 2036 | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		6.20%
TOTAL		$ 400	400
Debentures | Debenture Series 2006E, 5.70% Due 2036
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		5.70%
TOTAL		$ 250	250
Debentures | Debenture Series 2006E, 5.70% Due 2036 | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		5.70%
TOTAL		$ 250	250
Debentures | Debenture Series 2007A, 6.30% Due 2037
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		6.30%
TOTAL		$ 525	525
Debentures | Debenture Series 2007A, 6.30% Due 2037 | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		6.30%
TOTAL		$ 525	525
Debentures | Debenture Series 2008B, 6.75% Due 2038
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		6.75%
TOTAL		$ 600	600
Debentures | Debenture Series 2008B, 6.75% Due 2038 | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		6.75%
TOTAL		$ 600	600
Debentures | Debenture Series 2009B, 6.00% Due 2039
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		6.00%
TOTAL		$ 60	60
Debentures | Debenture Series 2009C, 5.50% Due 2039
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		5.50%
TOTAL		$ 600	600
Debentures | Debenture Series 2009C, 5.50% Due 2039 | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		5.50%
TOTAL		$ 600	600
Debentures | Debenture Series 2010B, 5.70% Due 2040
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		5.70%
TOTAL		$ 350	350
Debentures | Debenture Series 2010B, 5.70% Due 2040 | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		5.70%
TOTAL		$ 350	350
Debentures | Debenture Series 2010B, 5.50% Due 2040
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		5.50%
TOTAL		$ 115	115
Debentures | Debenture Series 2012A, 4.20% Due 2042
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		4.20%
TOTAL		$ 400	400
Debentures | Debenture Series 2012A, 4.20% Due 2042 | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		4.20%
TOTAL		$ 400	400
Debentures | Debenture Series 2013A, 3.95% Due 2043
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		3.95%
TOTAL		$ 700	700
Debentures | Debenture Series 2013A, 3.95% Due 2043 | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		3.95%
TOTAL		$ 700	700
Debentures | Debenture Series 2014A, 4.45% Due 2044
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		4.45%
TOTAL		$ 850	850
Debentures | Debenture Series 2014A, 4.45% Due 2044 | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		4.45%
TOTAL		$ 850	850
Debentures | Debenture Series 2015A, 4.50% due 2045
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		4.50%
TOTAL		$ 650	650
Debentures | Debenture Series 2015A, 4.50% due 2045 | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		4.50%
TOTAL		$ 650	650
Debentures | Debenture Series 2015A, 4.95% due 2045
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		4.95%
TOTAL		$ 120	120
Debentures | Debenture Series 2015B, 4.69% due 2045
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		4.69%
TOTAL		$ 100	100
Debentures | Debenture Series 2016A, 3.85% Due 2046
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		3.85%
TOTAL		$ 550	550
Debentures | Debenture Series 2016A, 3.85% Due 2046 | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		3.85%
TOTAL		$ 550	550
Debentures | Debenture Series 2016A. 3.88% Due 2046
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		3.88%
TOTAL		$ 75	75
Debentures | Debenture Series 2017A, 3.875% Due 2047
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		3.875%
TOTAL		$ 500	0
Debentures | Debenture Series 2017A, 3.875% Due 2047 | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		3.875%
TOTAL		$ 500	0
Debentures | Debenture Series 2014C, 4.625% Due 2054
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		4.625%
TOTAL		$ 750	750
Debentures | Debenture Series 2014C, 4.625% Due 2054 | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		4.625%
TOTAL		$ 750	750
Debentures | Debenture Series 2016C, 4.30% Due 2056
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		4.30%
TOTAL		$ 500	500
Debentures | Debenture Series 2016C, 4.30% Due 2056 | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		4.30%
TOTAL		$ 500	500
Debentures | Debenture Series 2017C, 4.00% Due 2057
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		4.00%
TOTAL		$ 350
Debentures | Debenture Series 2017C, 4.00% Due 2057 | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		400.00%
TOTAL		$ 350	0
Tax-Exempt Debt
Schedule of Capitalization, Long-term Debt [Line Items]
TOTAL PROJECT DEBT	[1]	1,086	1,086
Tax-Exempt Debt | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
TOTAL		$ 1,086	1,086
Tax-Exempt Debt | Tax Exempt Debt Series 2004B Series 1, 2.45% Due 2032
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate	[1]	2.45%
TOTAL PROJECT DEBT	[1]	$ 127	127
Tax-Exempt Debt | Tax Exempt Debt Series 2004B Series 1, 2.45% Due 2032 | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		2.45%
TOTAL		$ 127	127
Tax-Exempt Debt | Tax Exempt Debt Series 1999A, 1.834% Due 2034
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate	[1]	1.834%
TOTAL PROJECT DEBT	[1]	$ 293	293
Tax-Exempt Debt | Tax Exempt Debt Series 1999A, 1.834% Due 2034 | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		1.834%
TOTAL		$ 293	293
Tax-Exempt Debt | Tax Exempt Debt Series 2004B Series 2, 1.68% Due 2035
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate	[1]	1.68%
TOTAL PROJECT DEBT	[1]	$ 20	20
Tax-Exempt Debt | Tax Exempt Debt Series 2004B Series 2, 1.68% Due 2035 | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		1.68%
TOTAL		$ 20	20
Tax-Exempt Debt | Tax Exempt Debt Series 2001B, 1.796% Due 2036
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate	[1]	1.796%
TOTAL PROJECT DEBT	[1]	$ 98	98
Tax-Exempt Debt | Tax Exempt Debt Series 2001B, 1.796% Due 2036 | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		1.796%
TOTAL		$ 98	98
Tax-Exempt Debt | Tax Exempt Debt Series 2010A, 1.715% Due 2036
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate	[1]	1.715%
TOTAL PROJECT DEBT	[1]	$ 225	225
Tax-Exempt Debt | Tax Exempt Debt Series 2010A, 1.715% Due 2036 | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		1.715%
TOTAL		$ 225	225
Tax-Exempt Debt | Tax Exempt Debt Series 2004A, 1.943% Due 2039
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate	[1]	1.943%
TOTAL PROJECT DEBT	[1]	$ 98	98
Tax-Exempt Debt | Tax Exempt Debt Series 2004A, 1.943% Due 2039 | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		1.943%
TOTAL		$ 98	98
Tax-Exempt Debt | Tax Exempt Debt Series 2004C, 1.663% Due 2039
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate	[1]	1.663%
TOTAL PROJECT DEBT	[1]	$ 99	99
Tax-Exempt Debt | Tax Exempt Debt Series 2004C, 1.663% Due 2039 | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		1.663%
TOTAL		$ 99	99
Tax-Exempt Debt | Tax-Exempt Debt Series 2005A, 1.627% Due 2039
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate	[1]	1.627%
TOTAL PROJECT DEBT	[1]	$ 126	126
Tax-Exempt Debt | Tax-Exempt Debt Series 2005A, 1.627% Due 2039 | CECONY
Schedule of Capitalization, Long-term Debt [Line Items]
Interest Rate		1.627%
TOTAL		$ 126	$ 126
[1]	Rates are to be reset weekly or by auction held every 35 days; December 31, 2017 rates shown.

General

General	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
General	General These combined notes accompany and form an integral part of the separate consolidated financial statements of each of the two separate registrants: Consolidated Edison, Inc. and its subsidiaries (Con Edison) and Consolidated Edison Company of New York, Inc. and its subsidiaries (CECONY). CECONY is a subsidiary of Con Edison and as such its financial condition and results of operations and cash flows, which are presented separately in the CECONY consolidated financial statements, are also consolidated, along with those of Orange and Rockland Utilities, Inc. (O&R), Con Edison Clean Energy Businesses, Inc. (together with its subsidiaries, the Clean Energy Businesses) and Con Edison Transmission, Inc. (together with its subsidiaries, Con Edison Transmission) in Con Edison’s consolidated financial statements. The term “Utilities” is used in these notes to refer to CECONY and O&R. As used in these notes, the term “Companies” refers to Con Edison and CECONY and, except as otherwise noted, the information in these combined notes relates to each of the Companies. However, CECONY makes no representation as to information relating to Con Edison or the subsidiaries of Con Edison other than itself. Con Edison has two regulated utility subsidiaries: CECONY and O&R. CECONY provides electric service and gas service in New York City and Westchester County. The company also provides steam service in parts of Manhattan. O&R, along with its regulated utility subsidiary, provides electric service in southeastern New York and northern New Jersey and gas service in southeastern New York. Con Edison Clean Energy Businesses, Inc. has three subsidiaries: Consolidated Edison Development, Inc. (Con Edison Development), a company that develops, owns and operates renewable and energy infrastructure projects; Consolidated Edison Energy, Inc. (Con Edison Energy), a company that provides energy-related products and services to wholesale customers; and Consolidated Edison Solutions, Inc. (Con Edison Solutions), a company that provides energy-related products and services to retail customers. Con Edison Transmission, Inc. invests in electric transmission facilities through its subsidiary, Consolidated Edison Transmission, LLC (CET Electric), and invests in gas pipeline and storage facilities through its subsidiary Con Edison Gas Pipeline and Storage, LLC (CET Gas). See Note U.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Principles of Consolidation The Companies’ consolidated financial statements include the accounts of their respective majority-owned subsidiaries, and variable interest entities (see Note Q), as required. All intercompany balances and transactions have been eliminated. Accounting Policies The accounting policies of Con Edison and its subsidiaries conform to generally accepted accounting principles in the United States of America (GAAP). For the Utilities, these accounting principles include the accounting rules for regulated operations and the accounting requirements of the Federal Energy Regulatory Commission (FERC) and the state regulators having jurisdiction. The accounting rules for regulated operations specify the economic effects that result from the causal relationship of costs and revenues in the rate-regulated environment and how these effects are to be accounted for by a regulated enterprise. Revenues intended to cover some costs may be recorded either before or after the costs are incurred. If regulation provides assurance that incurred costs will be recovered in the future, these costs would be recorded as deferred charges or “regulatory assets” under the accounting rules for regulated operations. If revenues are recorded for costs that are expected to be incurred in the future, these revenues would be recorded as deferred credits or “regulatory liabilities” under the accounting rules for regulated operations. The Utilities’ principal regulatory assets and liabilities are detailed in Note B. The Utilities are receiving or being credited with a return on all of their regulatory assets for which a cash outflow has been made, and are paying or being charged with a return on all of their regulatory liabilities for which a cash inflow has been received. The Utilities’ regulatory assets and liabilities will be recovered from customers, or applied for customer benefit, in accordance with rate provisions approved by the applicable state regulators. Other significant accounting policies of the Companies are referenced below in this Note A and in the notes that follow. Plant and Depreciation Utility Plant Utility plant is stated at original cost. The cost of repairs and maintenance is charged to expense and the cost of betterments is capitalized. The capitalized cost of additions to utility plant includes indirect costs such as engineering, supervision, payroll taxes, pensions, other benefits and an allowance for funds used during construction (AFUDC). The original cost of property is charged to expense over the estimated useful lives of the assets. Upon retirement, the original cost of property is charged to accumulated depreciation. See Note R. Rates used for AFUDC include the cost of borrowed funds and a reasonable rate of return on the Utilities’ own funds when so used, determined in accordance with regulations of the FERC or the state public utility regulatory authority having jurisdiction. The rate is compounded semiannually, and the amounts applicable to borrowed funds are treated as a reduction of interest charges, while the amounts applicable to the Utilities’ own funds are credited to other income (deductions). The AFUDC rates for CECONY were 5.5 percent , 4.7 percent and 4.4 percent for 2017 , 2016 and 2015 , respectively. The AFUDC rates for O&R were 2.5 percent , 3.5 percent and 0.4 percent for 2017 , 2016 and 2015 , respectively. The Utilities generally compute annual charges for depreciation using the straight-line method for financial statement purposes, with rates based on average service lives and net salvage factors. The average depreciation rates for CECONY were 3.1 percent for 2017 , 2016 and 2015 . The average depreciation rates for O&R were 2.9 percent for 2017 and 2016 and 3.0 percent for 2015 . The estimated lives for utility plant for CECONY range from 5 to 95 years for electric, 5 to 100 years for gas, 5 to 80 years for steam and 5 to 55 years for general plant. For O&R, the estimated lives for utility plant range from 5 to 75 years for electric and gas and 5 to 50 years for general plant. At December 31, 2017 and 2016 , the capitalized cost of the Companies’ utility plant, net of accumulated depreciation, was as follows: Con Edison CECONY (Millions of Dollars) 2017 2016 2017 2016 Electric Generation $544 $479 $544 $479 Transmission 3,210 3,184 2,990 2,963 Distribution 18,959 18,150 17,996 17,234 Gas (a) 6,976 6,285 6,403 5,749 Steam 1,798 1,882 1,798 1,882 General 2,105 1,816 1,905 1,639 Held for future use 76 74 67 65 Construction work in progress 1,605 1,175 1,502 1,104 Net Utility Plant $35,273 $33,045 $33,205 $31,115 (a) Primarily distribution. Under the Utilities’ rate plans, the aggregate annual depreciation allowance for the period ended December 31, 2017 was $1,253 million , including $1,184 million under CECONY’s electric, gas and steam rate plans that have been approved by the New York State Public Service Commission (NYSPSC). Non – Utility Plant Non-utility plant is stated at original cost. For Con Edison, non – utility plant consists primarily of the Clean Energy Businesses’ renewable electric production and gas storage. For the Utilities, non – utility plant consists of land and conduit for telecommunication use. Depreciation on these assets is computed using the straight-line method for financial statement purposes over their estimated useful lives, which range from 3 to 30 years . Goodwill Con Edison tests goodwill for impairment at least annually or whenever there is a triggering event. There is an option to first make a qualitative assessment of whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount before applying a two – step, quantitative goodwill impairment test. Con Edison has elected to perform the qualitative assessment for substantially all of its goodwill and, if needed, applies the two-step quantitative approach. The first step of the quantitative goodwill impairment test compares the estimated fair value of a reporting unit with its carrying value, including goodwill. If the estimated fair value of a reporting unit exceeds its carrying value, goodwill of the reporting unit is considered not impaired. If the carrying value exceeds the estimated fair value of the reporting unit, the second step is performed to measure the amount of impairment loss, if any. The second step requires a calculation of the implied fair value of goodwill. In 2017, Con Edison recorded no impairment charge on goodwill. See Note K. Long – Lived and Intangible Assets Con Edison evaluates the impairment of long-lived assets and intangible assets with definite lives, based on projections of undiscounted future cash flows, whenever events or changes in circumstances indicate that the carrying amounts of such assets may not be recoverable. In the event an evaluation indicates that such cash flows cannot be expected to be sufficient to fully recover the assets, the assets are written down to their estimated fair value. In 2015, Con Edison recorded a $5 million impairment charge on the assets held for sale of Pike County Light & Power Company (Pike), a former O&R subsidiary that was sold in August 2016 (see Note U). No impairment charges on long-lived assets were recognized in 2017 or 2016. No impairment charges on intangible assets with definite lives were recognized in 2017, 2016, or 2015. For information about the Companies' intangible assets, see Note K. Revenues The Utilities and Con Edison Solutions, until the sale of its retail electric supply business in September 2016 (see Note U), recognize revenues as energy is delivered to customers. The Utilities accrue and Con Edison Solutions accrued revenues at the end of each month for estimated energy not yet billed to customers. The Utilities defer over a 12 – month period net interruptible gas revenues, other than those authorized by the NYSPSC to be retained by the Utilities, for refund to firm gas sales and transportation customers. Con Edison Development recognizes revenue for the sale of energy from renewable electric production projects as energy is generated and billed to counterparties. Con Edison Development accrues revenues at the end of each month for energy not yet billed to counterparties. Con Edison Energy recognizes revenue as energy is delivered and services are provided for managing energy supply assets leased from others and managing the dispatch, fuel requirements and risk management activities for generating plants and merchant transmission in the northeastern United States. Con Edison Solutions recognizes revenue for providing energy-efficiency services to government and commercial customers, and Con Edison Development recognizes revenue for the engineering, procurement and construction of Upton 2, under the percentage-of-completion method of revenue recognition. Sales and profits on each percentage-of-completion contract are recorded based on the ratio of actual cumulative costs incurred to the total estimated costs at completion of the contract, multiplied by the total estimated contract revenue, less cumulative sales recognized in prior periods (the ‘‘cost-to-cost’’ method). The impact of revisions of contract estimates, which may result from contract modifications, performance or other reasons, are recognized on a cumulative catch-up basis in the period in which the revisions are made. Unbilled contract revenues were $58 million and $21 million as of December 31, 2017 and 2016, respectively, and represent accumulated incurred costs and earned profits on contracts (revenue arrangements), which have been recorded as revenues, but have not yet been billed to customers. Substantially all unbilled contract revenues are expected to be collected within one year. Unbilled contract revenues arise from the cost-to-cost method of revenue recognition. Unbilled contract revenues from fixed-price type contracts are converted to billed receivables when amounts are invoiced to customers according to contractual billing terms, which generally occur when deliveries or other performance milestones are completed. Unearned revenue, which reflects a liability for billings to customers in excess of earned revenue was $87 million and $2 million as of December 31, 2017 and 2016, respectively. Revenues recorded as energy is delivered, generated or services provided and billed to customers are recorded in accounts receivable – customers. Con Edison's and the Utilities' accounts receivable – customers balance also reflects the Utilities' purchase of receivables from energy service companies to support retail choice programs. Accrued revenues not yet billed to customers are recorded as accrued unbilled revenues. CECONY’s electric and gas rate plans and O&R’s New York electric and gas rate plans each contain a revenue decoupling mechanism under which the company’s actual energy delivery revenues are compared with the authorized delivery revenues and the difference accrued, with interest, for refund to, or recovery from, customers, as applicable. See “Rate Plans” in Note B. The NYSPSC requires utilities to record gross receipts tax revenues and expenses on a gross income statement presentation basis (i.e., included in both revenue and expense). The recovery of these taxes is generally provided for in the revenue requirement within each of the respective NYSPSC approved rate plans. Total excise taxes (inclusive of gross receipts taxes) recorded in operating revenues were as follows: For the Years Ended December 31, (Millions of Dollars) 2017 2016 2015 Con Edison $302 $336 $354 CECONY 292 316 331 For information about changes to the accounting rules for revenue recognition, see Note T. Recoverable Energy Costs The Utilities generally recover all of their prudently incurred fuel, purchased power and gas costs, including hedging gains and losses, in accordance with rate provisions approved by the applicable state public utility regulators. If the actual energy supply costs for a given month are more or less than the amounts billed to customers for that month, the difference in most cases is recoverable from or refundable to customers. Differences between actual and billed electric and steam supply costs and costs of its electric demand management programs are generally deferred for charge or refund to customers during the next billing cycle (normally within one or two months ). For the Utilities’ gas costs, differences between actual and billed gas costs during the 12 – month period ending each August are charged or refunded to customers during a subsequent 12 – month period. New York Independent System Operator (NYISO) The Utilities purchase electricity through the wholesale electricity market administered by the NYISO. The difference between purchased power and related costs initially billed to the Utilities by the NYISO and the actual cost of power subsequently calculated by the NYISO is refunded by the NYISO to the Utilities, or paid to the NYISO by the Utilities. The reconciliation payments or receipts are recoverable from or refundable to the Utilities’ customers. Certain other payments to or receipts from the NYISO are also subject to reconciliation, with shortfalls or amounts in excess of specified rate allowances recoverable from or refundable to customers. These include proceeds from the sale through the NYISO of transmission rights on CECONY’s transmission system (transmission congestion contracts or TCCs). Temporary Cash Investments Temporary cash investments are short-term, highly – liquid investments that generally have maturities of three months or less at the date of purchase. They are stated at cost, which approximates market. The Companies consider temporary cash investments to be cash equivalents. Investments Investments consist primarily of the investments of Con Edison Transmission and the Clean Energy Businesses that are accounted for under the equity method, and the fair value of the Utilities’ supplemental retirement income plan and deferred income plan assets. The following investment assets are included in the Companies' consolidated balance sheets at December 31, 2017 and 2016: Con Edison CECONY (Millions of Dollars) 2017 2016 2017 2016 CET Gas investment in Stagecoach Gas Services, LLC (a) $971 $992 $— $— Con Edison Development equity method investments (b) 467 488 — — Supplemental retirement income plan assets (c) 330 273 301 246 CET Gas investment in Mountain Valley Pipeline, LLC (a) 98 48 — — Deferred income plan assets 73 60 73 60 CET Electric investment in New York Transco, LLC (a) 53 51 — — Other 9 9 9 9 Total investments $2,001 $1,921 $383 $315 (a) See Note U. (b) See Note Q. (c) See Note E. Pension and Other Postretirement Benefits The accounting rules for retirement benefits require an employer to recognize an asset or liability for the overfunded or underfunded status of its pension and other postretirement benefit plans. For a pension plan, the asset or liability is the difference between the fair value of the plan’s assets and the projected benefit obligation. For any other postretirement benefit plan, the asset or liability is the difference between the fair value of the plan’s assets and the accumulated postretirement benefit obligation. The accounting rules generally require employers to recognize all unrecognized prior service costs and credits and unrecognized actuarial gains and losses in accumulated other comprehensive income/(loss) (OCI), net of tax. Such amounts will be adjusted as they are subsequently recognized as components of total periodic benefit cost or income pursuant to the current recognition and amortization provisions. For the Utilities’ pension and other postretirement benefit plans, regulatory accounting treatment is generally applied in accordance with the accounting rules for regulated operations. Unrecognized prior service costs or credits and unrecognized actuarial gains and losses are recorded to regulatory assets or liabilities, rather than OCI. See Notes E and F. The total periodic benefit costs are recognized in accordance with the accounting rules for retirement benefits. Investment gains and losses are recognized in expense over a 15 – year period and other actuarial gains and losses are recognized in expense over a 10 – year period, subject to the deferral provisions in the rate plans. In accordance with the Statement of Policy issued by the NYSPSC and its current electric, gas and steam rate plans, CECONY defers for payment to or recovery from customers the difference between such expenses and the amounts for such expenses reflected in rates. Generally, O&R also defers such difference pursuant to its rate plans. See Note B. The Companies calculate the expected return on pension and other postretirement benefit plan assets by multiplying the expected rate of return on plan assets by the market-related value (MRV) of plan assets at the beginning of the year, taking into consideration anticipated contributions and benefit payments that are to be made during the year. The accounting rules allow the MRV of plan assets to be either fair value or a calculated value that recognizes changes in fair value in a systematic and rational manner over not more than five years. The Companies use a calculated value when determining the MRV of the plan assets that adjusts for 20 percent of the difference between fair value and expected MRV of plan assets. This calculated value has the effect of stabilizing variability in assets to which the Companies apply the expected return. Federal Income Tax In accordance with accounting rules for income taxes, the Companies have recorded an accumulated deferred federal income tax liability at current tax rates for temporary differences between the book and tax basis of assets and liabilities. In accordance with rate plans, the Utilities have recovered amounts from customers for a portion of the tax liability they will pay in the future as a result of the reversal or “turn-around” of these temporary differences. As to the remaining deferred tax liability, the Utilities had established regulatory assets for the net revenue requirements to be recovered from customers for the related future tax expense pursuant to the NYSPSC's 1993 Policy Statement approving accounting procedures consistent with accounting rules for income taxes and providing assurances that these future increases in taxes will be recoverable in rates. Upon enactment of the Tax Cuts and Jobs Act of 2017 on December 22, 2017 (the TCJA), the Companies re-measured their deferred tax assets and liabilities based upon the 21 percent corporate income tax rate under the TCJA. As a result, Con Edison decreased its net deferred tax liabilities by $5,312 million (including $4,781 million for CECONY), recognized net income of $259 million , decreased its regulatory asset for future income tax by $1,250 million (including $1,182 million for CECONY), decreased its regulatory asset for revenue taxes by $90 million (including $86 million for CECONY), and accrued a regulatory liability for future income tax of $3,713 million (including $3,513 million for CECONY). See “Other Regulatory Matters” and “Regulatory Assets and Liabilities” in Note B and Note L. Accumulated deferred investment tax credits are amortized ratably over the lives of the related properties and applied as a reduction to future federal income tax expense. Con Edison and its subsidiaries file a consolidated federal income tax return. The consolidated income tax liability is allocated to each member of the consolidated group using the separate return method. Each member pays or receives an amount based on its own taxable income or loss in accordance with a consolidated tax allocation agreement. Tax loss and tax credit carryforwards are allocated among members in accordance with consolidated tax return regulations. State Income Tax Con Edison and its subsidiaries file a combined New York State Corporation Business Franchise Tax Return. Similar to a federal consolidated income tax return, the income of all entities in the combined group is subject to New York State taxation, after adjustments for differences between federal and New York law and apportionment of income among the states in which the company does business. Each member’s share of the New York State tax is based on its own New York State taxable income or loss. Research and Development Costs Research and development costs are charged to operating expenses as incurred. Research and development costs were as follows: For the Years Ended December 31, (Millions of Dollars) 2017 2016 2015 Con Edison $24 $24 $23 CECONY 23 22 22 Reclassification Certain prior year amounts have been reclassified to conform with the current year presentation. Earnings Per Common Share Con Edison presents basic and diluted earnings per share on the face of its consolidated income statement. Basic earnings per share (EPS) are calculated by dividing earnings available to common shareholders (“Net income” on Con Edison’s consolidated income statement) by the weighted average number of Con Edison common shares outstanding during the period. In the calculation of diluted EPS, weighted average shares outstanding are increased for additional shares that would be outstanding if potentially dilutive securities were converted to common stock. Potentially dilutive securities for Con Edison consist of restricted stock units and deferred stock units for which the average market price of the common shares for the period was greater than the exercise price. See Note M. Basic and diluted EPS for Con Edison are calculated as follows: For the Years Ended December 31, (Millions of Dollars, except per share amounts/Shares in Millions) 2017 2016 2015 Net income $1,525 $1,245 $1,193 Weighted average common shares outstanding – basic 307.1 300.4 293.0 Add: Incremental shares attributable to effect of potentially dilutive securities 1.7 1.5 1.4 Adjusted weighted average common shares outstanding – diluted 308.8 301.9 294.4 Net Income per common share – basic $4.97 $4.15 $4.07 Net Income per common share – diluted $4.94 $4.12 $4.05 Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Changes in Accumulated Other Comprehensive Income/(Loss) by Component Changes to accumulated other comprehensive income/(loss) (OCI) for Con Edison and CECONY are as follows: (Millions of Dollars) Con Edison CECONY Accumulated OCI, net of taxes, at December 31, 2014 (a) $(45) $(11) OCI before reclassifications, net of tax of $(3) for Con Edison 5 1 Amounts reclassified from accumulated OCI related to pension plan liabilities, net of tax of $(4) and $(1) for Con Edison and CECONY, respectively(a)(b) 6 1 Total OCI, net of taxes, at December 31, 2015 11 2 Accumulated OCI, net of taxes, at December 31, 2015 (a) $(34) $(9) OCI before reclassifications, net of tax of $(1) for Con Edison and CECONY 2 1 Amounts reclassified from accumulated OCI related to pension plan liabilities, net of tax of $(3) and $(1) for Con Edison and CECONY, respectively(a)(b) 5 1 Total OCI, net of taxes, at December 31, 2016 7 2 Accumulated OCI, net of taxes, at December 31, 2016 (a) $(27) $(7) OCI before reclassifications, net of tax of $3 and $1 for Con Edison and CECONY, respectively (4) — Amounts reclassified from accumulated OCI related to pension plan liabilities, net of tax of $(3) and $(1) for Con Edison and CECONY, respectively(a)(b) 5 1 Total OCI, net of taxes, at December 31, 2017 1 1 Accumulated OCI, net of taxes, at December 31, 2017 (a) $(26) $(6) (a) Tax reclassified from accumulated OCI is reported in the income tax expense line item of the consolidated income statement. (b) For the portion of unrecognized pension and other postretirement benefit costs relating to the Utilities, costs are recorded into, and amortized out of, regulatory assets instead of OCI. The net actuarial losses and prior service costs recognized during the period are included in the computation of total periodic pension and other postretirement benefit cost. See Notes E and F.

Regulatory Matters

Regulatory Matters	12 Months Ended
	Dec. 31, 2017
Regulated Operations [Abstract]
Regulatory Matters	Regulatory Matters Rate Plans The Utilities provide service to New York customers according to the terms of tariffs approved by the NYSPSC. Tariffs for service to customers of Rockland Electric Company (RECO), O&R’s New Jersey regulated utility subsidiary, are approved by the New Jersey Board of Public Utilities (NJBPU). The tariffs include schedules of rates for service that limit the rates charged by the Utilities to amounts that recover from their customers costs approved by the regulator, including capital costs, of providing service to customers as defined by the tariff. The tariffs implement rate plans adopted by state utility regulators in rate orders issued at the conclusion of rate proceedings. Pursuant to the Utilities’ rate plans, there generally can be no change to the charges to customers during the respective terms of the rate plans other than specified adjustments provided for in the rate plans. The Utilities’ rate plans each cover specified periods, but rates determined pursuant to a plan generally continue in effect until a new rate plan is approved by the state utility regulator. Common provisions of the Utilities’ New York rate plans include: Recoverable energy costs that allow the Utilities to recover on a current basis the costs for the energy they supply with no mark-up to their full-service customers. Cost reconciliations that reconcile pension and other postretirement benefit costs, environmental remediation costs, property taxes, variable rate tax-exempt debt and certain other costs to amounts reflected in delivery rates for such costs. In addition, changes in the Utilities' costs not reflected in rates, in excess of certain amounts, resulting from changes in tax or other law, rule, regulation, order, or other requirement or interpretation are deferred as a regulatory asset or regulatory liability to be reflected in the Utilities' next rate plan or in a manner to be determined by the NYSPSC. See "Other Regulatory Matters," below. Also, the Utilities generally retain the right to petition for recovery or accounting deferral of extraordinary and material cost increases and provision is sometimes made for the utility to retain a share of cost reductions, for example, property tax refunds. Revenue decoupling mechanisms that reconcile actual energy delivery revenues to the authorized delivery revenues approved by the NYSPSC. The difference is accrued with interest for refund to, or recovery from customers, as applicable. Earnings sharing that require the Utilities to defer for customer benefit a portion of earnings over specified rates of return on common equity. There is no symmetric mechanism for earnings below specified rates of return on common equity. Negative revenue adjustments for failure to meet certain performance standards relating to service, reliability, safety and other matters. Positive revenue adjustments for achievement of performance standards related to achievement of clean energy goals, safety and other matters. Net utility plant reconciliations that require deferral as a regulatory liability of the revenue requirement impact of the amount, if any, by which actual average net utility plant balances are less than amounts reflected in rates. There is generally no symmetric mechanism if actual average net utility plant balances are more than amounts reflected in rates. Rate base , as reflected in the rate plans, is, in general, the sum of the Utilities’ net plant, working capital and certain regulatory assets less deferred taxes and certain regulatory liabilities. For each rate plan, the NYSPSC uses a forecast of the average rate base for each year that new rates would be in effect (“rate year”). Weighted average cost of capital is determined based on the authorized common equity ratio, return on common equity, cost of long-term debt and customer deposits reflected in each rate plan. For each rate plan, the revenues designed to provide the utility a return on invested capital for each rate year are determined by multiplying each utility rate base by its pre – tax weighted average cost of capital. The Utilities’ actual return on common equity will reflect their actual operations for each rate year, and may be more or less than the authorized return on equity reflected in their rate plans (and if more, may be subject to earnings sharing). The following tables contain a summary of the Utilities’ rate plans: CECONY – Electric Effective period January 2014 – December 2016 January 2017 – December 2019 (b) Base rate changes Yr. 1 – $(76.2) million (a) Yr. 1 – $195 million (c) Amortizations to income of net regulatory (assets) and liabilities Yr. 1 and 2 – $(37) million (d) Yr. 1 – $84 million Other revenue sources Retention of $90 million of annual transmission congestion revenues. Retention of $75 million of annual transmission congestion revenues. Revenue decoupling mechanisms In 2014, 2015 and 2016, the company deferred for customer benefit $146 million, $98 million and $101 million of revenues, respectively. Continuation of reconciliation of actual to authorized electric delivery revenues. Recoverable energy costs (e) Current rate recovery of purchased power and fuel costs. Continuation of current rate recovery of purchased power and fuel costs. Negative revenue adjustments Potential penalties (up to $400 million annually) if certain performance targets are not met. In 2014, the company recorded a $5 million negative revenue adjustment. In 2015 and 2016, the company did not record any negative revenue adjustments. Potential penalties if certain performance targets relating to service, reliability, safety and other matters are not met: Cost reconciliations In 2014, 2015 and 2016, the company deferred $57 million, $26 million and $68 million of net regulatory liabilities, respectively (f). Continuation of reconciliation of expenses for pension and other postretirement benefits, variable-rate tax-exempt debt, major storms, property taxes (f), municipal infrastructure support costs (g), the impact of new laws and environmental site investigation and remediation to amounts reflected in rates (h). Net utility plant reconciliations Target levels reflected in rates were: Target levels reflected in rates: Average rate base Yr. 1 – $17,323 million Yr. 1 – $18,902 million Weighted average cost of capital (after-tax) Yr. 1 – 7.05 percent Yr. 1 – 6.82 percent Authorized return on common equity Yrs. 1 and 2 – 9.2 percent 9.0 percent Actual return on common equity Yr. 1 – 9.04 percent Yr. 1 – 9.3 percent Earnings sharing Most earnings above an annual earnings threshold of 9.8 percent for Yrs. 1 and 2 and 9.6 percent for Yr. 3 are to be applied to reduce regulatory assets for environmental remediation and other costs. In 2014 the company had no earnings above the threshold. Actual earnings were $44.4 million and $6.5 million above the threshold for 2015 and 2016, respectively. Most earnings above an annual earnings threshold of 9.5 percent are to be applied to reduce regulatory assets for environmental remediation and other costs accumulated in the rate year. Cost of long-term debt Yr. 1 – 5.17 percent Yr. 1 – 4.93 percent Common equity ratio 48 percent 48 percent (a) The impact of these base rate changes was deferred which resulted in a $30 million regulatory liability at December 31, 2015; this amount has been amortized to $0 at December 31, 2016. (b) In January 2017, the NYSPSC approved the September 2016 Joint Proposal for CECONY's electric rate plan for January 2017 through December 2019. If at the end of any year, Con Edison’s investments in its non-utility businesses exceed 15 percent of Con Edison’s total consolidated revenues, assets or cash flow, or if the ratio of holding company debt to total consolidated debt rises above 20 percent , CECONY is required to notify the NYSPSC and submit a ring-fencing plan or a demonstration why additional ring-fencing measures are not necessary. (c) The electric base rate increases are in addition to a $48 million increase resulting from the December 2016 expiration of a temporary credit under the prior rate plan. At the NYSPSC’s option, these increases are being implemented with increases of $199 million in each rate year. Base rates reflect recovery by the company of certain costs of its energy efficiency, system peak reduction and electric vehicle programs (Yr. 1 - $20.5 million ; Yr. 2 - $49 million ; and Yr. 3 - $107.5 million ) over a ten -year period, including the overall pre-tax rate of return on such costs. (d) Amounts reflect annual amortization of $107 million of the regulatory asset for deferred Superstorm Sandy and other major storm costs. The costs recoverable from customers were reduced by $4 million . The costs are no longer subject to NYSPSC staff review and the recovery of the costs is no longer subject to refund. In 2016, an additional $123 million of net regulatory liabilities were amortized to income. (e) For transmission service provided pursuant to the open access transmission tariff of PJM Interconnection LLC (PJM), unless and until changed by the NYSPSC, the company will recover all charges incurred associated with the transmission service. Starting in January 2014, PJM submitted to the FERC a series of requests that substantially increase the charges for the transmission service. CECONY has challenged each of these requests. To date, FERC has rejected all but one of CECONY’s protests. In June 2015 and May 2016, CECONY filed appeals of certain FERC decisions with the U.S. Court of Appeals. In April 2017, the transmission service terminated because CECONY did not exercise its option to continue the service. (f) Deferrals for property taxes are limited to 90 percent of the difference from amounts reflected in rates, subject to an annual maximum for the remaining difference of not more than a maximum number of basis points ( 5.0 , 7.5 or 10.0 basis points , depending on the year). (g) In general, if actual expenses for municipal infrastructure support (other than company labor) are below the amounts reflected in rates the company will defer the difference for credit to customers, and if the actual expenses are above the amount reflected in rates the company will defer for recovery from customers 80 percent of the difference subject to a maximum deferral of 30 percent of the amount reflected in rates. (h) In addition, amounts reflected in rates relating to the regulatory asset for future income tax and the excess deferred federal income tax liability are subject to reconciliation. The NYSPSC staff is to audit the regulatory asset and the tax liability. Differences resulting from the NYSPSC staff review will be deferred for NYSPSC determination of any amounts to be refunded or collected from customers. See "Other Regulatory Matters," below. CECONY – Gas Effective period January 2014 – December 2016 January 2017 - December 2019 (b) Base rate changes Yr. 1 – $(54.6) million (a) Yr. 1 – $(5) million (b) Amortizations to income of net regulatory (assets) and liabilities $4 million over three years Yr. 1 – $39 million Other revenue sources Retention of revenues from non-firm customers of up to $65 million and 15 percent of any such revenues above $65 million. The company retained $70 million, $66 million and $65 million of such revenues in 2014, 2015 and 2016, respectively. Retention of annual revenues from non-firm customers of up to $65 million and 15 percent of any such revenues above $65 million. Revenue decoupling mechanisms In 2014, 2015 and 2016, the company deferred $28 million, $54 million and $71 million of regulatory liabilities, respectively. Continuation of reconciliation of actual to authorized gas delivery revenues. Recoverable energy costs Current rate recovery of purchased gas costs. Continuation of current rate recovery of purchased gas costs. Negative revenue adjustments Potential penalties (up to $33 million in 2014, $44 million in 2015, and $56 million in 2016) if certain gas performance targets are not met. In 2014, 2015 and 2016, the company did not record any negative revenue adjustments. Potential penalties if performance targets relating to service, safety and other matters are not met: Cost reconciliations In 2014, 2015 and 2016, the company deferred $38 million, $11 million, and $32 million of net regulatory liabilities, respectively. (c) Continuation of reconciliation of expenses for pension and other postretirement benefits, variable-rate tax-exempt debt, major storms, property taxes, municipal infrastructure support costs, the impact of new laws and environmental site investigation and remediation to amounts reflected in rates. (d) Net utility plant reconciliations Target levels reflected in rates were: Target levels reflected in rates: Average rate base Yr. 1 – $3,521 million Yr. 1 – $4,841 million Weighted average cost of capital Yr. 1 – 7.10 percent Yr. 1 – 6.82 percent Authorized return on common equity 9.3 percent 9.0 percent Actual return on common equity Yr. 1 – 8.02 percent Yr. 1 – 9.22 percent Earnings sharing Most earnings above an annual earnings threshold of 9.9 percent are to be applied to reduce regulatory assets for environmental remediation and other costs. In 2014, 2015 and 2016, the company had no earnings above the threshold. Most earnings above an annual earnings threshold of 9.5 percent are to be applied to reduce regulatory assets for environmental remediation and other costs accumulated in the rate year. Cost of long-term debt Yr. 1 – 5.17 percent Yr. 1 – 4.93 percent Common equity ratio 48 percent 48 percent (a) The impact of these base rate changes was deferred which resulted in a $32 million regulatory liability at December 31, 2016. (b) In January 2017, the NYSPSC approved the September 2016 Joint Proposal for CECONY's gas rate plan for January 2017 through December 2019. The gas base rate decrease is offset by a $41 million increase resulting from the December 2016 expiration of a temporary credit under the prior rate plan. (c) Deferrals for property taxes are limited to 90 percent of the difference from amounts reflected in rates, subject to an annual maximum for the remaining difference of not more than a 10 basis point impact on return on common equity (d) See footnotes (e), (f), (g) and (h) to the table under "CECONY - Electric" above. CECONY – Steam Effective period January 2014 – December 2016 (a) Base rate changes Yr. 1 – $(22.4) million (b) Amortizations to income of net regulatory (assets) and liabilities $37 million over three years Recoverable energy costs Current rate recovery of purchased power and fuel costs. Negative revenue adjustments Potential penalties (up to $1 million annually) if certain steam performance targets are not met. In 2014, 2015, 2016 and 2017, the company did not record any negative revenue adjustments. Cost reconciliations (c) In 2014, 2015, 2016 and 2017, the company deferred $42 million of net regulatory liabilities, $17 million of net regulatory assets, $8 million and $14 million of net regulatory liabilities, respectively. Net utility plant reconciliations Target levels reflected in rates were: Average rate base Yr. 1 – $1,511 million Weighted average cost of capital (after-tax) Yr. 1 – 7.10 percent Authorized return on common equity 9.3 percent Actual return on common equity Yr. 1 – 9.82 percent Earnings sharing Weather normalized earnings above an annual earnings threshold of 9.9 percent are to be applied to reduce regulatory assets for environmental remediation and other costs. Cost of long-term debt Yr. 1 – 5.17 percent Common equity ratio 48 percent (a) Rates determined pursuant to this rate plan continue in effect until a new rate plan is approved by the NYSPSC. (b) The impact of these base rate changes was deferred which resulted in an $8 million regulatory liability at December 31, 2016. (c) Deferrals for property taxes are limited to 90 percent of the difference from amounts reflected in rates, subject to an annual maximum for the remaining difference of not more than a 10 basis point impact on return on common equity. O&R New York – Electric Effective period July 2012 – October 2015 November 2015 - October 2017 (a) Base rate changes Yr. 1 – $19.4 million Yr. 1 – $9.3 million – $8.8 million Amortizations to income of net regulatory (assets) and liabilities $(32.2) million over three years Yr. 1 – $(8.5) million (b) – $(9.4) million (b) Revenue decoupling mechanisms In 2012, 2013 and 2014, the company deferred for the customer’s benefit $2.6 million, $3.2 million and $(3.4) million, respectively. In 2015, 2016 and 2017, the company deferred for the customer’s benefit an immaterial amount, $6.3 million as regulatory liabilities and $11.2 million as regulatory asset, respectively. Recoverable energy costs Current rate recovery of purchased power and fuel costs. Continuation of current rate recovery of purchased power costs. Negative revenue adjustments Potential penalties (up to $3 million annually) if certain customer service and system reliability performance targets are not met. In 2012, 2013 and 2014, the company did not record any negative revenue adjustments. Potential penalties (up to $4 million annually) if certain performance targets are not met. In 2015 the company recorded $1.25 million in negative revenue adjustments. In 2016 and 2017, the company did not record any negative revenue adjustments. Cost reconciliations In 2012, 2013 and 2014, the company deferred $7.8 million, $4.1 million and $(0.2) million as a net increase/(decrease) to regulatory assets, respectively. In 2015, 2016 and 2017, the company deferred $0.3 million, $7.4 million and $3.2 million as net decreases to regulatory assets, respectively. Net utility plant reconciliations Target levels reflected in rates were: Target levels reflected in rates are: – $928 million (c) – $970 million (c) The company increased/(reduced) its regulatory asset by $2.2 million, $(1.9) million and $(1.9) million in 2015, 2016 and 2017, respectively. Average rate base Yr. 1 – $671 million Yr. 1 – $763 million – $805 million Weighted average cost of capital (after-tax) Yr. 1 – 7.61 percent Yr. 1 – 7.10 percent – 7.06 percent Authorized return on common equity Yr. 1 – 9.4 percent 9.0 percent Actual return on common equity Yr. 1 – 12.9 percent Yr. 1 – 10.8 percent Earnings sharing The company recorded a regulatory liability of $1 million for earnings above the sharing threshold under the rate plan as of December 31, 2014. Most earnings above an annual earnings threshold of 9.6 percent are to be applied to reduce regulatory assets. In 2015, earnings did not exceed the earnings threshold. Actual earnings were $6.1 million and $0.3 million above the threshold for 2016 and 2017, respectively. Cost of long-term debt Yr. 1 – 6.07 percent Yr. 1 – 5.42 percent – 5.35 percent Common equity ratio 48 percent 48 percent (a) Rates determined pursuant to this rate plan continue in effect until a new rate plan is approved by the NYSPSC. (b) $59.3 million of the regulatory asset for deferred storm costs is to be recovered from customers over a five year period, including $11.85 million in each of years 1 and 2, $1 million of the regulatory asset for such costs will not be recovered from customers, and all outstanding issues related to Superstorm Sandy and other past major storms prior to November 2014 are resolved. Approximately $4 million of regulatory assets for property tax and interest rate reconciliations will not be recovered from customers. Amounts that will not be recovered from customers were charged-off in June 2015. (c) Excludes electric AMI as to which the company will be required to defer as a regulatory liability the revenue requirement impact of the amount, if any, by which actual average net utility plant balances are less than amounts reflected in rates: $1 million in year 1 and $9 million in year 2. I n January 2018, O&R filed a request with the NYSPSC for an increase in the rates it charges for electric service rendered in New York, effective January 1, 2019, of $20.3 million . The filing reflects a return on common equity of 9.75 percent and a common equity ratio of 48 percent . The filing proposes continuation of the provisions with respect to recovery from customers of the cost of purchased power, and the reconciliation of actual expenses allocable to the electric business to the amounts for such costs reflected in electric rates for storm costs, pension and other postretirement benefit costs, environmental remediation and property taxes. O&R New York – Gas Effective period November 2009 – October 2015 November 2015 – October 2018 Base rate changes Yr. 1 – $9 million Yr. 1 – $16.4 million – $16.4 million – $5.8 million – $10.6 million collected through a surcharge Amortization to income of net regulatory (assets) and liabilities $(2) million over three years Yr. 1 – $(1.7) million (a) – $(2.1) million (a) – $(2.5) million (a) Revenue decoupling mechanisms In 2012, 2013 and 2014, the company deferred $4.7 million, $0.7 million and $(0.1) million of regulatory liabilities, respectively. In 2015 and 2016, the company deferred $0.8 million regulatory assets and $6.2 million of regulatory liabilities, respectively. In 2017, the company deferred $1.7 million in regulatory liabilities. Recoverable energy costs Current rate recovery of purchased gas costs. Current rate recovery of purchased gas costs. Negative revenue adjustments Potential penalties (up to $1.4 million annually) if certain operations and customer service requirements are not met. In 2012, 2013 and 2014, the company did not record any negative revenue adjustments. Potential penalties (up to $3.7 million in Yr. 1, $4.7 million in Yr. 2 and $4.9 million in Yr. 3) if certain performance targets are not met. In 2015, 2016 and 2017, the company did not record any negative revenue adjustments. Cost reconciliations In 2012, 2013 and 2014, the company deferred $0.7 million, $8.3 million and $8.3 million as net regulatory assets, respectively. In 2015 and 2016, the company deferred $4.5 million and $6.6 million as net regulatory liabilities and assets, respectively. In 2017, the company deferred $3.5 million as net regulatory liabilities. Net utility plant reconciliations The company deferred $0.7 million in 2012 as a regulatory asset and no deferrals were recorded for 2013 or 2014. Target levels reflected in rates are: – $492 million (b) – $518 million (b) – $546 million (b) No deferral was recorded for 2015 and immaterial amounts were recorded as regulatory liabilities in 2016 and 2017. Average rate base Yr. 1 – $280 million Yr. 1 – $366 million – $391 million – $417 million Weighted average cost of capital (after-tax) 8.49 percent Yr. 1 – 7.10 percent – 7.06 percent – 7.06 percent Authorized return on common equity 10.4 percent 9.0 percent Actual return on common equity Yr. 1 – 10.2 percent Yr. 1 – 11.2 percent Earnings sharing Earnings above an annual earnings threshold of 11.4 percent are to be applied to reduce regulatory assets. In 2012, 2013 and 2014, earnings did not exceed the earnings threshold. Most earnings above an annual earnings threshold of 9.6 percent are to be applied to reduce regulatory assets. In 2015, earnings did not exceed the earnings threshold. Actual earnings were $4 million and $0.2 million above the threshold for 2016 and 2017, respectively. Cost of long-term debt 6.81 percent Yr. 1 – 5.42 percent – 5.35 percent – 5.35 percent Common equity ratio 48 percent 48 percent (a) Reflects that the company will not recover from customers a total of approximately $14 million of regulatory assets for property tax and interest rate reconciliations. Amounts that will not be recovered from customers were charged-off in June 2015. (b) Excludes gas AMI as to which the company will be required to defer as a regulatory liability the revenue requirement impact of the amount, if any, by which actual average net utility plant balances are less than amounts reflected in rates: $0.5 million in year 1, $4.2 million in year 2 and $7.2 million in year 3. In January 2018, O&R filed a request with the NYSPSC for an increase in the rates it charges for gas service rendered in New York, effective January 1, 2019, of $4.5 million . The filing reflects a return on common equity of 9.75 percent and a common equity ratio of 48 percent . The filing proposes continuation of the provisions with respect to recovery from customers of the cost of purchased gas, and the reconciliation of actual expenses allocable to the gas business to the amounts for such costs reflected in gas rates for pension and other postretirement benefit costs, environmental remediation and property taxes. RECO Effective period August 2014 – February 2017 March 2017 (a) Base rate changes Yr. 1 – $13.0 million Yr. 1 – $1.7 million Amortization to income of net regulatory (assets) and liabilities $0.4 million over three years and $(25.6) million of deferred storm costs over four years $0.2 million over three years and continuation of $(25.6) million of deferred storm costs over four years expiring July 31, 2018 (b) Recoverable energy costs Current rate recovery of purchased power costs. Current rate recovery of purchased power costs. Cost reconciliations None None Average rate base $172.2 million Yr. 1 – $178.7 million Weighted average cost of capital (after-tax) 7.83 percent 7.47 percent Authorized return on common equity 9.75 percent 9.6 percent Actual return on common equity Yr. 1 – 9.2 percent (c) Cost of long-term debt 5.89 percent 5.37 percent Common equity ratio 50 percent 49.7 percent (a) Effective until a new rate plan approved by the NJBPU goes into effect. (b) In January 2016, the NJBPU approved RECO’s plan to spend $15.7 million in capital over three years to harden its electric system against storms, the costs of which RECO, beginning in 2017, is collecting through a customer surcharge. (c) Actual return on common equity for first rate year of current rate plan not determinable until March 31, 2018 end of rate year. In November 2017, FERC approved a September 2017 settlement agreement among RECO, the New Jersey Division of Rate Counsel and the NJBPU that increases RECO's annual transmission revenue requirement from $11.8 million to $17.7 million , effective April 2017. The revenue requirement reflects a return on common equity of 10.0 percent . Other Regulatory Matters In August and November 2017, the NYSPSC issued orders in its proceeding investigating an April 21, 2017 Metropolitan Transportation Authority (MTA) subway power outage. The orders indicated that the investigation determined that the outage was caused by a failure of CECONY’s electricity supply to a subway station, which led to a loss of the subway signals, and that one of the secondary services to the MTA facility had been improperly rerouted and was not properly documented by the company. The orders also indicated that the loss of power to the subway station affected multiple subway lines and caused widespread delays across the subway system. Pursuant to the orders, the company is required to take certain actions, including inspecting, repairing and installing certain electrical equipment that serves the subway system, analyzing power supply and power quality events affecting the MTA’s signaling services, and filing monthly reports with the NYSPSC on all of the company's activities related to the subway system. In July 2017, the Chairman of the NYSPSC notified the company that the April 21, 2017 subway power outage incident will likely result in a prudence review of the reasonableness of CECONY's actions and conduct. The orders did not commence a prudence review. The company incurred costs related to this matter in 2017 of $65 million . Included in this amount is $15 million in capital and operating and maintenance costs reflected in the company's electric rate plan and $50 million deferred as a regulatory asset pursuant to the rate plan. The company, which plans to complete the required actions in 2018, expects to incur costs related to this matter in 2018 of $137 million . Included in this amount is $10 million in expected capital and operating and maintenance costs reflected in the rate plan and $127 million expected to be deferred as a regulatory asset pursuant to the rate plan. In December 2017, the NYSPSC issued an order initiating a proceeding to study the potential effects of the TCJA on the tax expenses and liabilities of New York State utilities and the regulatory treatment to preserve the resulting benefits for customers. In January 2018, the NJBPU issued an order initiating a proceeding to consider the TCJA. Upon enactment of the TCJA, CECONY, O&R and RECO re-measured their deferred tax assets and liabilities based upon the 21 percent corporate income tax rate under the TCJA. As a result, CECONY, O&R and RECO, decreased their net deferred tax liabilities by $4,781 million , $216 million and $45 million , respectively, decreased their regulatory asset for future income tax by $1,182 million , $51 million and $17 million , respectively, decreased their regulatory asset for revenue taxes by $86 million , $4 million and $0 million , respectively, and accrued regulatory liabilities for future income tax of $3,513 million , $161 million and $28 million , respectively. See Note L. In January 2018, the NYSPSC issued an order initiating a focused operations audit of the income tax accounting of certain utilities, including CECONY and O&R. See footnote (h) to the table under "CECONY – Electric," above. Regulatory Assets and Liabilities Regulatory assets and liabilities at December 31, 2017 and 2016 were comprised of the following items: Con Edison CECONY (Millions of Dollars) 2017 2016 2017 2016 Regulatory assets Unrecognized pension and other postretirement costs $2,526 $2,874 $2,376 $2,730 Future income tax* — 2,439 — 2,325 Environmental remediation costs 793 823 677 711 Revenue taxes 260 295 248 280 Pension and other postretirement benefits deferrals 79 38 58 7 Recoverable energy costs 60 42 52 38 Municipal infrastructure support costs 56 44 56 44 Property tax reconciliation 51 37 25 — MTA power reliability deferral 50 — 50 — Deferred derivative losses 44 48 37 42 Deferred storm costs 38 56 — 3 Brooklyn Queens demand management program 37 29 37 29 Unamortized loss on reacquired debt 37 43 35 41 Indian Point Energy Center program costs 29 50 29 50 Preferred stock redemption 24 25 24 25 Workers’ compensation 10 13 10 13 Net electric deferrals 9 24 9 24 O&R transition bond charges 9 15 — — Surcharge for New York State assessment 2 28 2 26 Other 152 101 138 85 Regulatory assets – noncurrent 4,266 7,024 3,863 6,473 Deferred derivative losses 40 91 37 86 Recoverable energy costs 27 9 25 4 Regulatory assets – current 67 100 62 90 Total Regulatory Assets $4,333 $7,124 $3,925 $6,563 Regulatory liabilities Future income tax* $2,545 $— $2,390 $— Allowance for cost of removal less salvage 846 755 719 641 Pension and other postretirement benefit deferrals 207 193 181 162 Net unbilled revenue deferrals 183 145 183 145 Energy efficiency portfolio standard unencumbered funds 127 — 122 — Property tax reconciliation 107 178 107 178 Unrecognized other postretirement costs 92 60 92 60 Settlement of prudence proceeding 66 95 66 95 Property tax refunds 44 1 44 1 Carrying charges on repair allowance and bonus depreciation 43 68 42 67 New York State income tax rate change 36 61 35 60 Variable-rate tax-exempt debt - cost rate reconciliation 30 55 26 48 Earnings sharing - electric, gas and steam 29 39 19 28 Settlement of gas proceedings 27 27 27 27 Base rate change deferrals 21 40 21 40 Net utility plant reconciliations 12 16 8 15 Other 162 172 137 145 Regulatory liabilities – noncurrent 4,577 1,905 4,219 1,712 Refundable energy costs 41 29 16 5 Deferred derivative gains 31 28 28 24 Revenue decoupling mechanism 29 71 21 61 Regulatory liabilities—current 101 128 65 90 Total Regulatory Liabilities $4,678 $2,033 $4,284 $1,802 ` * See "Federal Income Tax" in Note A, "Other Regulatory Matters," above, and Note L . Unrecognized pension and other postretirement costs represent the net regulatory asset associated with the accounting rules for retirement benefits. See Note A. Revenue taxes represent the timing difference between taxes collected and paid by the Utilities to fund mass transportation. Deferred storm costs represent response and restoration costs, other than capital expenditures, in connection with Superstorm Sandy and other major storms that were deferred by the Utilities. Net electric deferrals represent the remaining unamortized balance of certain regulatory assets and liabilities of CECONY that were combined effecti

Capitalization

Capitalization	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Capitalization	Capitalization Common Stock At December 31, 2017 and 2016 , Con Edison owned all of the issued and outstanding shares of common stock of the Utilities, the Clean Energy Businesses and Con Edison Transmission. CECONY owns 21,976,200 shares of Con Edison stock, which it purchased prior to 2001 in connection with Con Edison’s stock repurchase plan. CECONY presents in the financial statements the cost of the Con Edison stock it owns as a reduction of common shareholder’s equity. Capitalization of Con Edison The outstanding capitalization for each of the Companies is shown on its Consolidated Statement of Capitalization, and for Con Edison includes outstanding debt of the Utilities and the Clean Energy Businesses. Dividends In accordance with NYSPSC requirements, the dividends that the Utilities generally pay are limited to not more than 100 percent of their respective income available for dividends calculated on a two – year rolling average basis. Excluded from the calculation of “income available for dividends” are non-cash charges to income resulting from accounting changes or charges to income resulting from significant unanticipated events. The restriction also does not apply to dividends paid in order to transfer to Con Edison proceeds from major transactions, such as asset sales, or to dividends reducing each utility subsidiary’s equity ratio to a level appropriate to its business risk. Long-term Debt Long-term debt maturing in the period 2018 - 2022 is as follows: (Millions of Dollars) Con Edison CECONY 2018 $1,298 $1,200 2019 578 475 2020 791 350 2021 544 — 2022 335 — CECONY has issued $450 million of tax – exempt debt through the New York State Energy Research and Development Authority (NYSERDA) that currently bear interest at a rate determined weekly and is subject to tender by bondholders for purchase by the company. The carrying amounts and fair values of long-term debt at December 31, 2017 and 2016 are: (Millions of Dollars) 2017 2016 Long-Term Debt (including current portion) (a) Carrying Amount Fair Value Carrying Amount Fair Value Con Edison $16,029 $18,147 $14,774 $16,093 CECONY $13,265 $15,163 $12,073 $13,268 (a) Amounts shown are net of unamortized debt expense and unamortized debt discount of $142 million and $121 million for Con Edison and CECONY, respectively, as of December 31, 2017 and $134 million and $113 million for Con Edison and CECONY, respectively, as of December 31, 2016 . Fair values of long-term debt have been estimated primarily using available market information. For Con Edison, $17,511 million and $636 million of the fair value of long-term debt at December 31, 2017 are classified as Level 2 and Level 3, respectively. For CECONY, $14,527 million and $636 million of the fair value of long-term debt at December 31, 2017 are classified as Level 2 and Level 3, respectively (see Note P). The $636 million of long-term debt classified as Level 3 is CECONY’s tax-exempt, auction-rate securities for which the market is highly illiquid and there is a lack of observable inputs. At December 31, 2017 and 2016 , long – term debt of Con Edison included $915 million and $845 million , respectively, of non-recourse debt secured by the pledge of the applicable renewable energy production projects of the Clean Energy Businesses. At December 31, 2017 and 2016 , long-term debt of Con Edison included $7 million and $11 million , respectively, of Transition Bonds issued in 2004 by O&R’s New Jersey utility subsidiary through a special purpose entity. Significant Debt Covenants The significant debt covenants under the financing arrangements for the Companies' debentures and Con Edison's notes include obligations to pay principal and interest when due and covenants not to consolidate with or merge into any other corporation unless certain conditions are met. In addition, Con Edison's notes include covenants that the company shall continue its utility business in New York City and shall not permit its ratio of consolidated debt to consolidated capital to exceed 0.675 to 1 and include cross default provisions with respect to other indebtedness of the company or its material subsidiaries having a then outstanding principal balance in excess of $100 million . The Companies' debentures have no cross default provisions. The tax – exempt financing arrangements of CECONY are subject to covenants for the debentures discussed above and the covenants discussed below. The Companies were in compliance with their significant debt covenants at December 31, 2017 . The tax-exempt financing arrangements involved the issuance of uncollateralized promissory notes of CECONY to NYSERDA in exchange for the net proceeds of a like amount of tax – exempt bonds with substantially the same terms sold to the public by NYSERDA. The tax-exempt financing arrangements include covenants with respect to the tax – exempt status of the financing, including covenants with respect to the use of the facilities financed. The arrangements include provisions for the maintenance of liquidity and credit facilities, the failure to comply with which would, except as otherwise provided, constitute an event of default for the debt to which such provisions applied. The failure to comply with debt covenants would, except as otherwise provided, constitute an event of default for the debt to which such provisions applied. If an event of default were to occur, the principal and accrued interest on the debt to which such event of default applied and, in the case of the Con Edison notes, a make-whole premium might and, in the case of certain events of default would, become due and payable immediately. The liquidity and credit facilities currently in effect for the tax – exempt financing include covenants that the ratio of debt to total capital of CECONY will not at any time exceed 0.65 to 1 and that, subject to certain exceptions, CECONY will not mortgage, lien, pledge or otherwise encumber its assets. Certain of the facilities also include as events of default, defaults in payments of other debt obligations in excess of specified levels ( $150 million or $100 million , depending on the facility)

Short-Term Borrowing

Short-Term Borrowing	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Short-Term Borrowing	Short-Term Borrowing In December 2016, Con Edison and the Utilities entered into a credit agreement (Credit Agreement), under which banks are committed to provide loans and letters of credit on a revolving credit basis. The Credit Agreement expires in December 2022. There is a maximum of $2,250 million of credit available. The full amount is available to CECONY and $1,000 million (subject to increase up to $1,500 million ) is available to Con Edison, including up to $1,200 million of letters of credit. The Credit Agreement supports the Companies’ commercial paper programs. The Companies have not borrowed under the Credit Agreement. At December 31, 2017 , Con Edison had $577 million of commercial paper outstanding, of which $150 million was outstanding under CECONY’s program. The weighted average interest rate at December 31, 2017 was 1.8 percent for both Con Edison and CECONY. At December 31, 2016 , Con Edison had $1,054 million of commercial paper outstanding of which $600 million was outstanding under CECONY’s program. The weighted average interest rate at December 31, 2016 was 1.0 percent for both Con Edison and CECONY. At December 31, 2017 and 2016 , no loans were outstanding under the credit agreement (Credit Agreement). An immaterial amount and $2 million (including $2 million for CECONY) of letters of credit were outstanding under the Credit Agreement as of December 31, 2017 and 2016 , respectively. The banks’ commitments under the Credit Agreement are subject to certain conditions, including that there be no event of default. The commitments are not subject to maintenance of credit rating levels or the absence of a material adverse change. Upon a change of control of, or upon an event of default by one of the Companies, the banks may terminate their commitments with respect to that company, declare any amounts owed by that company under the Credit Agreement immediately due and payable and require that company to provide cash collateral relating to the letters of credit issued for it under the Credit Agreement. Events of default include the exceeding at any time of a ratio of consolidated debt to consolidated total capital of 0.65 to 1 (at December 31, 2017 this ratio was 0.51 to 1 for Con Edison and 0.52 to 1 for CECONY); having liens on its assets in an aggregate amount exceeding five percent of its consolidated total capital, subject to certain exceptions; and the failure, following any applicable notice period, to meet certain other customary covenants. Interest and fees charged for the revolving credit facilities and any loans made or letters of credit issued under the Credit Agreement reflect the Companies’ respective credit ratings. The Companies were in compliance with their covenants at December 31, 2017 . See Note S for information about short-term borrowing between related parties.

Pension Benefits

Pension Benefits	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Pension Benefits	Pension Benefits Con Edison maintains a tax-qualified, non-contributory pension plan that covers substantially all employees of CECONY, O&R, Con Edison Transmission and certain employees of the Clean Energy Businesses. The plan is designed to comply with the Internal Revenue Code and the Employee Retirement Income Security Act of 1974. In addition, Con Edison maintains additional non – qualified supplemental pension plans. Total Periodic Benefit Cost The components of the Companies’ total periodic benefit costs for 2017 , 2016 and 2015 were as follows: Con Edison CECONY (Millions of Dollars) 2017 2016 2015 2017 2016 2015 Service cost – including administrative expenses $263 $275 $297 $246 $258 $279 Interest cost on projected benefit obligation 591 596 575 554 559 538 Expected return on plan assets (968) (947) (886) (917) (898) (840) Recognition of net actuarial loss 595 596 775 563 565 734 Recognition of prior service costs (17) 4 4 (19) 2 2 NET PERIODIC BENEFIT COST $464 $524 $765 $427 $486 $713 Amortization of regulatory asset (a) — — 1 — — 1 TOTAL PERIODIC BENEFIT COST $464 $524 $766 $427 $486 $714 Cost capitalized (181) (214) (301) (169) (203) (285) Reconciliation to rate level (34) 54 (74) (41) 58 (74) Cost charged to operating expenses $249 $364 $391 $217 $341 $355 (a) Relates to an increase in CECONY’s pension obligation of $45 million from a 1999 special retirement program. Funded Status The funded status at December 31, 2017 , 2016 and 2015 was as follows: Con Edison CECONY (Millions of Dollars) 2017 2016 2015 2017 2016 2015 CHANGE IN PROJECTED BENEFIT OBLIGATION Projected benefit obligation at beginning of year $14,095 $14,377 $15,081 $13,203 $13,482 $14,137 Service cost – excluding administrative expenses 259 271 293 241 254 274 Interest cost on projected benefit obligation 591 596 575 554 559 538 Net actuarial loss/(gain) 1,231 (302) (996) 1,171 (282) (931) Plan amendments 6 (256) — — (259) — Benefits paid (646) (591) (576) (602) (551) (536) PROJECTED BENEFIT OBLIGATION AT END OF YEAR $15,536 $14,095 $14,377 $14,567 $13,203 $13,482 CHANGE IN PLAN ASSETS Fair value of plan assets at beginning of year $12,472 $11,759 $11,495 $11,815 $11,141 $10,897 Actual return on plan assets 2,041 829 126 1,935 787 118 Employer contributions 450 508 750 412 469 697 Benefits paid (646) (591) (576) (602) (551) (536) Administrative expenses (43) (33) (36) (41) (31) (35) FAIR VALUE OF PLAN ASSETS AT END OF YEAR $14,274 $12,472 $11,759 $13,519 $11,815 $11,141 FUNDED STATUS $(1,262) $(1,623) $(2,618) $(1,048) $(1,388) $(2,341) Unrecognized net loss $2,760 $3,157 $3,909 $2,624 $2,995 $3,704 Unrecognized prior service costs (223) (244) 16 (242) (258) 3 Accumulated benefit obligation 13,897 12,655 12,909 12,972 11,806 12,055 The increase in the pension plan’s fair value of plan assets was the primary cause of the decreased pension liability at Con Edison and CECONY of $361 million and $340 million , respectively, compared with December 31, 2016 . For Con Edison, this decrease in pension liability corresponds with a decrease to regulatory assets of $368 million for unrecognized net losses and unrecognized prior service costs associated with the Utilities consistent with the accounting rules for regulated operations, a credit to OCI of $4 million (net of taxes) for the unrecognized net losses, and an immaterial change to OCI (net of taxes) for the unrecognized prior service costs associated with the Clean Energy Businesses, Con Edison Transmission, and RECO. For CECONY, the decrease in pension liability corresponds with a decrease to regulatory assets of $353 million for unrecognized net losses and unrecognized prior service costs consistent with the accounting rules for regulated operations, a credit to OCI of $1 million (net of taxes) for unrecognized net losses, and an immaterial change to OCI (net of taxes) for the unrecognized prior service costs associated with the Clean Energy Businesses and Con Edison Transmission. A portion of the unrecognized net loss and prior service cost for the pension plan, equal to $689 million and $(17) million , respectively, will be recognized from accumulated OCI and the regulatory asset into net periodic benefit cost over the next year for Con Edison. Included in these amounts are $654 million and $(19) million , respectively, for CECONY. At December 31, 2017 and 2016 , Con Edison’s investments include $330 million and $273 million , respectively, held in external trust accounts for benefit payments pursuant to the supplemental retirement plans. Included in these amounts for CECONY were $301 million and $246 million , respectively. See Note P. The accumulated benefit obligations for the supplemental retirement plans for Con Edison and CECONY were $331 million and $297 million as of December 31, 2017 and $303 million and $268 million as of December 31, 2016 , respectively. Assumptions The actuarial assumptions were as follows: 2017 2016 2015 Weighted-average assumptions used to determine benefit obligations at December 31: Discount rate 3.70 % 4.25 % 4.25 % Rate of compensation increase CECONY 4.25 % 4.25 % 4.25 % O&R 4.00 % 4.00 % 4.00 % Weighted-average assumptions used to determine net periodic benefit cost for the years ended December 31: Discount rate 4.25 % 4.25 % 3.90 % Expected return on plan assets 7.50 % 7.80 % 7.80 % Rate of compensation increase CECONY 4.25 % 4.25 % 4.25 % O&R 4.00 % 4.00 % 4.00 % The expected return assumption reflects anticipated returns on the plan’s current and future assets. The Companies’ expected return was based on an evaluation of the current environment, market and economic outlook, relationships between the economy and asset class performance patterns, and recent and long-term trends in asset class performance. The projections were based on the plan’s target asset allocation. Discount Rate Assumption To determine the assumed discount rate, the Companies use a model that produces a yield curve based on yields on selected highly rated (Aa or higher by either Moody’s or Standard & Poor’s) corporate bonds. Bonds with insufficient liquidity, bonds with questionable pricing information and bonds that are not representative of the overall market are excluded from consideration. For example, the bonds used in the model cannot be callable (with the exception of "make whole" callable bonds), and the amount of the bond issue outstanding must be in excess of $50 million . The spot rates defined by the yield curve and the plan’s projected benefit payments are used to develop a weighted average discount rate. Expected Benefit Payments Based on current assumptions, the Companies expect to make the following benefit payments over the next ten years : (Millions of Dollars) 2018 2019 2020 2021 2022 2023-2027 Con Edison $728 $738 $753 $765 $778 $4,083 CECONY 677 686 700 712 724 3,804 Expected Contributions Based on estimates as of December 31, 2017 , the Companies expect to make contributions to the pension plans during 2018 of $473 million (of which $435 million is to be contributed by CECONY). The Companies’ policy is to fund the total periodic benefit cost of the qualified plan to the extent tax deductible and to also contribute to the non-qualified supplemental plans. Plan Assets The asset allocations for the pension plan at the end of 2017 , 2016 and 2015 , and the target allocation for 2018 are as follows: Target Allocation Range Plan Assets at December 31, Asset Category 2018 2017 2016 2015 Equity Securities 53% - 63% 58 % 58 % 57 % Debt Securities 28% - 38% 33 % 33 % 33 % Real Estate 7% -11% 9 % 9 % 10 % Total 100% 100 % 100 % 100 % Con Edison has established a pension trust for the investment of assets to be used for the exclusive purpose of providing retirement benefits to participants and beneficiaries and payment of plan expenses. Pursuant to resolutions adopted by Con Edison’s Board of Directors, the Management Development and Compensation Committee of the Board of Directors (the Committee) has general oversight responsibility for Con Edison’s pension and other employee benefit plans. The pension plan’s named fiduciaries have been granted the authority to control and manage the operation and administration of the plans, including overall responsibility for the investment of assets in the trust and the power to appoint and terminate investment managers. The investment objectives of the Con Edison pension plan are to maintain a level and form of assets adequate to meet benefit obligations to participants, to achieve the expected long-term total return on the trust assets within a prudent level of risk and maintain a level of volatility that is not expected to have a material impact on the company’s expected contribution and expense or the company’s ability to meet plan obligations. The assets of the plan have no significant concentration of risk in one country (other than the United States), industry or entity. The strategic asset allocation is intended to meet the objectives of the pension plan by diversifying its funds across asset classes, investment styles and fund managers. An asset/liability study typically is conducted every few years to determine whether the current strategic asset allocation continues to represent the appropriate balance of expected risk and reward for the plan to meet expected liabilities. Each study considers the investment risk of the asset allocation and determines the optimal asset allocation for the plan. The target asset allocation for 2018 reflects the results of such a study conducted in 2016. Individual fund managers operate under written guidelines provided by Con Edison, which cover such areas as investment objectives, performance measurement, permissible investments, investment restrictions, trading and execution, and communication and reporting requirements. Con Edison management regularly monitors, and the named fiduciaries review and report to the Committee regarding, asset class performance, total fund performance, and compliance with asset allocation guidelines. Management changes fund managers and rebalances the portfolio as appropriate. At the direction of the named fiduciaries, such changes are reported to the Committee. Assets measured at fair value on a recurring basis are summarized below as defined by the accounting rules for fair value measurements (see Note P). The fair values of the pension plan assets at December 31, 2017 by asset category are as follows: (Millions of Dollars) Level 1 Level 2 Total Investments within the fair value hierarchy U.S. Equity (a) $3,872 $28 $3,900 International Equity (b) 4,132 — 4,132 U.S. Government Issued Debt (c) — 1,786 1,786 Corporate Bonds Debt (d) — 2,450 2,450 Structured Assets Debt (e) — 3 3 Other Fixed Income Debt (f) — 125 125 Cash and Cash Equivalents (g) 124 352 476 Futures (h) 308 — 308 Total investments within the fair value hierarchy $8,436 $4,744 $13,180 Investments measured at NAV per share (n) Private Equity (i) 336 Real Estate (j) 1,214 Hedge Funds (k) 251 Total investments valued using NAV per share $1,801 Funds for retiree health benefits (l) (168) (94) (262) Funds for retiree health benefits measured at NAV per share (l)(n) (36) Total funds for retiree health benefits $(298) Investments (excluding funds for retiree health benefits) $8,268 $4,650 $14,683 Pending activities (m) (409) Total fair value of plan net assets $14,274 (a) U.S. Equity includes both actively- and passively-managed assets with investments in domestic equity index funds and actively-managed small-capitalization equities. (b) International Equity includes international equity index funds and actively-managed international equities. (c) U.S. Government Issued Debt includes agency and treasury securities. (d) Corporate Bonds Debt consists of debt issued by various corporations. (e) Structured Assets Debt includes commercial-mortgage-backed securities and collateralized mortgage obligations. (f) Other Fixed Income Debt includes municipal bonds, sovereign debt and regional governments. (g) Cash and Cash Equivalents include short term investments, money markets, foreign currency and cash collateral. (h) Futures consist of exchange-traded financial contracts encompassing U.S. Equity, International Equity and U.S. Government indices. (i) Private Equity consists of global equity funds that are not exchange-traded. (j) Real Estate investments include real estate funds based on appraised values that are broadly diversified by geography and property type. (k) Hedge Funds are within a commingled structure which invests in various hedge fund managers who can invest in all financial instruments. (l) The Companies set aside funds for retiree health benefits through a separate account within the pension trust, as permitted under Section 401(h) of the Internal Revenue Code of 1986, as amended. In accordance with the Code, the plan’s investments in the 401(h) account may not be used for, or diverted to, any purpose other than providing health benefits for retirees. The net assets held in the 401(h) account are calculated based on a pro-rata percentage allocation of the net assets in the pension plan. The related obligations for health benefits are not included in the pension plan’s obligations and are included in the Companies’ other postretirement benefit obligation. See Note F. (m) Pending activities include security purchases and sales that have not settled, interest and dividends that have not been received and reflects adjustments for available estimates at year end. (n) In accordance with ASU 2015-07, Fair Value Measurements (Topic 820): Disclosures for Investments in Certain Entities That Calculate Net Asset Value per Share (or its equivalent), certain investments that are measured at fair value using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. The fair values of the pension plan assets at December 31, 2016 by asset category are as follows: (Millions of Dollars) Level 1 Level 2 Total Investments within the fair value hierarchy U.S. Equity (a) $3,466 $— $3,466 International Equity (b) 3,187 371 3,558 U.S. Government Issued Debt (c) — 1,337 1,337 Corporate Bonds Debt (d) — 2,140 2,140 Structured Assets Debt (e) — 1 1 Other Fixed Income Debt (f) — 200 200 Cash and Cash Equivalents (g) 147 389 536 Futures (h) 296 68 364 Total investments within the fair value hierarchy $7,096 $4,506 $11,602 Investments measured at NAV per share (n) Private Equity (i) 247 Real Estate (j) 1,139 Hedge Funds (k) 229 Total investments valued using NAV per share $1,615 Funds for retiree health benefits (l) (165) (105) (270) Funds for retiree health benefits measured at NAV per share (l)(n) (37) Total funds for retiree health benefits $(307) Investments (excluding funds for retiree health benefits) $6,931 $4,401 $12,910 Pending activities (m) (438) Total fair value of plan net assets $12,472 (a) - (n) Reference is made to footnotes (a) through (n) in the above table of pension plan assets at December 31, 2017 by asset category. The Companies also offer a defined contribution savings plan that covers substantially all employees and made contributions to the plan as follows: For the Years Ended December 31, (Millions of Dollars) 2017 2016 2015 Con Edison $40 $36 $34 CECONY 35 32 29

Other Postretirement Benefits

Other Postretirement Benefits	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Other Postretirement Benefits	Other Postretirement Benefits The Utilities and Con Edison Transmission currently have contributory comprehensive hospital, medical and prescription drug programs for eligible retirees, their dependents and surviving spouses. CECONY also has a contributory life insurance program for bargaining unit employees and provides basic life insurance benefits up to a specified maximum at no cost to certain retired management employees. O&R has a non-contributory life insurance program for retirees. Certain employees of the Clean Energy Businesses and Con Edison Transmission are eligible to receive benefits under these programs. Total Periodic Benefit Cost The components of the Companies’ total periodic postretirement benefit costs for 2017 , 2016 and 2015 were as follows: Con Edison CECONY (Millions of Dollars) 2017 2016 2015 2017 2016 2015 Service cost $20 $18 $20 $13 $13 $15 Interest cost on accumulated other postretirement benefit obligation 46 48 51 38 40 43 Expected return on plan assets (69) (77) (78) (61) (67) (68) Recognition of net actuarial loss 2 5 31 (3) 3 28 Recognition of prior service cost (17) (20) (20) (11) (14) (14) TOTAL PERIODIC POSTRETIREMENT BENEFIT COST $(18) $(26) $4 $(24) $(25) $4 Cost capitalized 8 11 (2) 10 10 (2) Reconciliation to rate level (4) 22 14 (2) 22 6 Cost charged to operating expenses $(14) $7 $16 $(16) $7 $8 Funded Status The funded status of the programs at December 31, 2017 , 2016 and 2015 were as follows: Con Edison CECONY (Millions of Dollars) 2017 2016 2015 2017 2016 2015 CHANGE IN BENEFIT OBLIGATION Benefit obligation at beginning of year $1,198 $1,287 $1,411 $1,007 $1,093 $1,203 Service cost 20 18 20 13 13 15 Interest cost on accumulated postretirement benefit obligation 46 48 51 38 40 43 Amendments — — — — — — Net actuarial loss/(gain) 53 (57) (103) 16 (52) (85) Benefits paid and administrative expenses (134) (134) (127) (124) (122) (117) Participant contributions 36 36 35 35 35 34 BENEFIT OBLIGATION AT END OF YEAR $1,219 $1,198 $1,287 $985 $1,007 $1,093 CHANGE IN PLAN ASSETS Fair value of plan assets at beginning of year $975 $994 $1,084 $851 $870 $950 Actual return on plan assets 150 60 (6) 130 52 (4) Employer contributions 17 7 6 8 7 6 EGWP payments 34 35 28 30 33 26 Participant contributions 35 36 35 35 35 34 Benefits paid (172) (157) (153) (161) (146) (142) FAIR VALUE OF PLAN ASSETS AT END OF YEAR $1,039 $975 $994 $893 $851 $870 FUNDED STATUS $(180) $(223) $(293) $(92) $(156) $(223) Unrecognized net loss/(gain) $(47) $(24) $28 $(85) $(42) $4 Unrecognized prior service costs (14) (31) (51) (7) (18) (32) The increase in the fair value of plan assets was the primary cause of the decreased liability for other postretirement benefits at Con Edison and CECONY of $43 million and $64 million , respectively, compared with December 31, 2016 . For Con Edison, this decreased liability corresponds with an increase to regulatory liabilities of $11 million for unrecognized net losses and unrecognized prior service costs associated with the Utilities consistent with the accounting rules for regulated operations, a debit to OCI of $3 million (net of taxes) for the unrecognized net losses and an immaterial change to OCI (net of taxes) for the unrecognized prior service costs associated with the Clean Energy Businesses, Con Edison Transmission, and RECO. For CECONY, the decrease in liability corresponds with an increase to regulatory liabilities of $32 million for unrecognized net losses and unrecognized prior service costs associated with the company consistent with the accounting rules for regulated operations, and an immaterial change to OCI (net of taxes) for the unrecognized net losses and unrecognized prior service costs associated with the Clean Energy Businesses and Con Edison Transmission. A portion of the unrecognized net losses and prior service costs for the other postretirement benefits, equal to $8 million and $(6) million , respectively, will be recognized from accumulated OCI and the regulatory asset into net periodic benefit cost over the next year for Con Edison. Included in these amounts are $1 million and $(2) million , respectively, for CECONY. Assumptions The actuarial assumptions were as follows: 2017 2016 2015 Weighted-average assumptions used to determine benefit obligations at December 31: Discount Rate CECONY 3.55 % 4.00 % 4.05 % O&R 3.70 % 4.20 % 4.20 % Weighted-average assumptions used to determine net periodic benefit cost for the years ended December 31: Discount Rate CECONY 4.00 % 4.05 % 3.75 % O&R 4.20 % 4.20 % 3.85 % Expected Return on Plan Assets 7.50 % 7.00 % 7.75 % Refer to Note E for descriptions of the basis for determining the expected return on assets, investment policies and strategies and the assumed discount rate. The health care cost trend rate used to determine net periodic benefit cost for the year ended December 31, 2017 was 5.80 percent , which is assumed to decrease gradually to 4.50 percent by 2024 and remain at that level thereafter. The health care cost trend rate used to determine benefit obligations as of December 31, 2017 was 5.60 percent , which is assumed to decrease gradually to 4.50 percent by 2024 and remain at that level thereafter. A one-percentage point change in the assumed health care cost trend rate would have the following effects at December 31, 2017 : Con Edison CECONY 1-Percentage-Point (Millions of Dollars) Increase Decrease Increase Decrease Effect on accumulated other postretirement benefit obligation $13 $11 $(20) $35 Effect on service cost and interest cost components for 2017 2 — (1) 1 Expected Benefit Payments Based on current assumptions, the Companies expect to make the following benefit payments over the next ten years , net of receipt of governmental subsidies: (Millions of Dollars) 2018 2019 2020 2021 2022 2023-2027 Con Edison $83 $81 $78 $76 $75 $363 CECONY 73 70 67 65 64 303 Expected Contributions Based on estimates as of December 31, 2017 , Con Edison and CECONY expect to make a contribution of $7 million (substantially all of which is to be contributed by CECONY) to the other postretirement benefit plans in 2018 . The Companies’ policy is to fund the total periodic benefit cost of the plans to the extent tax deductible. Plan Assets The asset allocations for CECONY’s other postretirement benefit plans at the end of 2017 , 2016 and 2015 , and the target allocation for 2018 are as follows: Target Allocation Range Plan Assets at December 31, Asset Category 2018 2017 2016 2015 Equity Securities 50%-80% 60 % 60 % 59 % Debt Securities 20%-50% 40 % 40 % 41 % Total 100% 100 % 100 % 100 % Con Edison has established postretirement health and life insurance benefit plan trusts for the investment of assets to be used for the exclusive purpose of providing other postretirement benefits to participants and beneficiaries. Refer to Note E for a discussion of Con Edison’s investment policy for its benefit plans. The fair values of the plan assets at December 31, 2017 by asset category as defined by the accounting rules for fair value measurements (see Note P) are as follows: (Millions of Dollars) Level 1 Level 2 Total Equity (a) $— $420 $420 Other Fixed Income Debt (b) — 286 286 Cash and Cash Equivalents (c) — 16 16 Total investments $— $722 $722 Funds for retiree health benefits (d) 168 94 262 Investments (including funds for retiree health benefits) $168 $816 $984 Funds for retiree health benefits measured at net asset value (d)(e) 36 Pending activities (f) 19 Total fair value of plan net assets $1,039 (a) Equity includes a passively managed commingled index fund benchmarked to the MSCI All Country World Index. (b) Other Fixed Income Debt includes a passively managed commingled index fund benchmarked to the Barclays Capital Aggregate Index. (c) Cash and Cash Equivalents include short term investments and money markets. (d) The Companies set aside funds for retiree health benefits through a separate account within the pension trust, as permitted under Section 401(h) of the Internal Revenue Code of 1986, as amended. In accordance with the Code, the plan’s investments in the 401(h) account may not be used for, or diverted to, any purpose other than providing health benefits for retirees. The net assets held in the 401(h) account are calculated based on a pro-rata percentage allocation of the net assets in the pension plan. The related obligations for health benefits are not included in the pension plan’s obligations and are included in the Companies’ other postretirement benefit obligation. See Note E. (e) In accordance with ASU 2015-07, Fair Value Measurements (Topic 820): Disclosures for Investments in Certain Entities That Calculate Net Asset Value per Share (or its equivalent), certain investments that are measured at fair value using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. (f) Pending activities include security purchases and sales that have not settled, interest and dividends that have not been received, and reflects adjustments for available estimates at year end. The fair values of the plan assets at December 31, 2016 by asset category (see Note P) are as follows: (Millions of Dollars) Level 1 Level 2 Total Equity (a) $— $391 $391 Other Fixed Income Debt (b) — 250 250 Cash and Cash Equivalents (c) — 13 13 Total investments $— $654 $654 Funds for retiree health benefits (d) 165 105 270 Investments (including funds for retiree health benefits) $165 $759 $924 Funds for retiree health benefits measured at net asset value (d)(e) 37 Pending activities (f) 14 Total fair value of plan net assets $975 (a) - (f) Reference is made to footnotes (a) through (f) in the above table of other postretirement benefit plan assets at December 31, 2017 by asset category.

Environmental Matters

Environmental Matters	12 Months Ended
	Dec. 31, 2017
Environmental Remediation Obligations [Abstract]
Environmental Matters	Environmental Matters Superfund Sites Hazardous substances, such as asbestos, polychlorinated biphenyls (PCBs) and coal tar, have been used or generated in the course of operations of the Utilities and their predecessors and are present at sites and in facilities and equipment they currently or previously owned, including sites at which gas was manufactured or stored. The Federal Comprehensive Environmental Response, Compensation and Liability Act of 1980 and similar state statutes (Superfund) impose joint and several liability, regardless of fault, upon generators of hazardous substances for investigation and remediation costs (which include costs of demolition, removal, disposal, storage, replacement, containment and monitoring) and natural resource damages. Liability under these laws can be material and may be imposed for contamination from past acts, even though such past acts may have been lawful at the time they occurred. The sites at which the Utilities have been asserted to have liability under these laws, including their manufactured gas plant sites and any neighboring areas to which contamination may have migrated, are referred to herein as “Superfund Sites.” For Superfund Sites where there are other potentially responsible parties and the Utilities are not managing the site investigation and remediation, the accrued liability represents an estimate of the amount the Utilities will need to pay to investigate and, where determinable, discharge their related obligations. For Superfund Sites (including the manufactured gas plant sites) for which one of the Utilities is managing the investigation and remediation, the accrued liability represents an estimate of the company’s share of the undiscounted cost to investigate the sites and, for sites that have been investigated in whole or in part, the cost to remediate the sites, if remediation is necessary and if a reasonable estimate of such cost can be made. Remediation costs are estimated in light of the information available, applicable remediation standards and experience with similar sites. The accrued liabilities and regulatory assets related to Superfund Sites at December 31, 2017 and 2016 were as follows: Con Edison CECONY (Millions of Dollars) 2017 2016 2017 2016 Accrued Liabilities: Manufactured gas plant sites $651 $664 $551 $567 Other Superfund Sites 86 89 86 88 Total $737 $753 $637 $655 Regulatory assets $793 $823 $677 $711 Most of the accrued Superfund Site liability relates to sites that have been investigated, in whole or in part. However, for some of the sites, the extent and associated cost of the required remediation has not yet been determined. As investigations progress and information pertaining to the required remediation becomes available, the Utilities expect that additional liability may be accrued, the amount of which is not presently determinable but may be material. The Utilities are permitted to recover or defer as regulatory assets (for subsequent recovery through rates) prudently incurred site investigation and remediation costs. Environmental remediation costs incurred related to Superfund Sites at December 31, 2017 and 2016 were as follows: Con Edison CECONY (Millions of Dollars) 2017 2016 2017 2016 Remediation costs incurred $24 $34 $19 $21 Insurance and other third party recoveries received by Con Edison or CECONY were immaterial in 2017. Con Edison and CECONY received $1 million in insurance and other third party recoveries in 2016. Con Edison and CECONY estimate that in 2018 they will incur costs for remediation of approximately $47 million and $34 million , respectively. The Companies are unable to estimate the time period over which the remaining accrued liability will be incurred because, among other things, the required remediation has not been determined for some of the sites. In 2017 , Con Edison and CECONY estimated that for their manufactured gas plant sites (including CECONY’s Astoria site), the aggregate undiscounted potential liability for the investigation and remediation of coal tar and/or other environmental contaminants could range up to $2.7 billion and $2.5 billion , respectively. These estimates were based on the assumption that there is contamination at all sites, including those that have not yet been fully investigated and additional assumptions about the extent of the contamination and the type and extent of the remediation that may be required. Actual experience may be materially different. Asbestos Proceedings Suits have been brought in New York State and federal courts against the Utilities and many other defendants, wherein a large number of plaintiffs sought large amounts of compensatory and punitive damages for deaths and injuries allegedly caused by exposure to asbestos at various premises of the Utilities. The suits that have been resolved, which are many, have been resolved without any payment by the Utilities, or for amounts that were not, in the aggregate, material to them. The amounts specified in all the remaining thousands of suits total billions of dollars; however, the Utilities believe that these amounts are greatly exaggerated, based on the disposition of previous claims. At December 31, 2017 , Con Edison and CECONY have accrued their estimated aggregate undiscounted potential liabilities for these suits and additional suits that may be brought over the next 15 years as shown in the following table. These estimates were based upon a combination of modeling, historical data analysis and risk factor assessment. Courts have begun, and unless otherwise determined on appeal may continue, to apply different standards for determining liability in asbestos suits than the standard that applied historically. As a result, the Companies currently believe that there is a reasonable possibility of an exposure to loss in excess of the liability accrued for the suits. The Companies are unable to estimate the amount or range of such loss. In addition, certain current and former employees have claimed or are claiming workers’ compensation benefits based on alleged disability from exposure to asbestos. CECONY is permitted to defer as regulatory assets (for subsequent recovery through rates) costs incurred for its asbestos lawsuits and workers’ compensation claims. The accrued liability for asbestos suits and workers’ compensation proceedings (including those related to asbestos exposure) and the amounts deferred as regulatory assets for the Companies at December 31, 2017 and 2016 were as follows: Con Edison CECONY (Millions of Dollars) 2017 2016 2017 2016 Accrued liability – asbestos suits $8 $8 $7 $7 Regulatory assets – asbestos suits $8 $8 $7 $7 Accrued liability – workers’ compensation $84 $88 $80 $83 Regulatory assets – workers’ compensation $10 $13 $10 $13

Other Material Contingencies

Other Material Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Other Material Contingencies	10 years Total (Millions of Dollars) Con Edison Transmission $643 $404 $— $1,047 Energy transactions 431 27 211 669 Renewable electric production projects 210 — 24 234 Other 123 — — 123 Total $1,407 $431 $235 $2,073 Con Edison Transmission – Con Edison has guaranteed payment by CET Electric of the contributions CET Electric agreed to make to New York Transco LLC (NY Transco). CET Electric acquired a 45.7 percent interest in NY Transco when it was formed in 2014. In May 2016, the transmission owners transferred certain projects to NY Transco, for which CET Electric made its required contributions. NY Transco has proposed other transmission projects in the New York Independent System Operator's competitive bidding process. These other projects are subject to certain authorizations from the NYSPSC, the FERC and, as applicable, other federal, state and local agencies. Guarantee amount shown is for the maximum possible required amount of CET Electric's contributions for these other projects as calculated based on the assumptions that the projects are completed at 175 percent of their estimated costs and NY Transco does not use any debt financing for the projects. Guarantee term shown is assumed as the selection of the projects and resulting timing of the contributions is not certain. Also included within the table above is a guarantee for $25 million from Con Edison on behalf of CET Gas in relation to a proposed gas transmission project in West Virginia and Virginia. See Note U. Energy Transactions — Con Edison guarantees payments on behalf of the Clean Energy Businesses in order to facilitate physical and financial transactions in electricity, gas, pipeline capacity, transportation, oil, renewable energy credits and energy services. To the extent that liabilities exist under the contracts subject to these guarantees, such liabilities are included in Con Edison’s consolidated balance sheet. Renewable Electric Production Projects – Con Edison, Con Edison Development and Con Edison Solutions guarantee payments on behalf of their wholly-owned subsidiaries associated with their investment in, or development for others of, solar and wind energy facilities. Other – Other guarantees include $70 million in guarantees provided by Con Edison to Travelers Insurance Company for indemnity agreements for surety bonds in connection with operation of solar energy facilities and energy service projects of Con Edison Development and Con Edison Solutions, respectively. Other guarantees also include Con Edison's guarantee (subject to a $53 million maximum amount) of certain obligations of Con Edison Solutions under the agreement pursuant to which it sold its retail electric supply business. See Note U." id="sjs-B4">Other Material Contingencies Manhattan Explosion and Fire On March 12, 2014, two multi-use five-story tall buildings located on Park Avenue between 116th and 117th Streets in Manhattan were destroyed by an explosion and fire. CECONY had delivered gas to the buildings through service lines from a distribution main located below ground on Park Avenue. Eight people died and more than 50 people were injured. Additional buildings were also damaged. The National Transportation Safety Board (NTSB) investigated. The parties to the investigation included the company, the City of New York, the Pipeline and Hazardous Materials Safety Administration and the NYSPSC. In June 2015, the NTSB issued a final report concerning the incident, its probable cause and safety recommendations. The NTSB determined that the probable cause of the incident was (1) the failure of a defective fusion joint at a service tee (which joined a plastic service line to a plastic distribution main) installed by the company that allowed gas to leak from the distribution main and migrate into a building where it ignited and (2) a breach in a City sewer line that allowed groundwater and soil to flow into the sewer, resulting in a loss of support for the distribution main, which caused it to sag and overstressed the defective fusion joint. The NTSB also made safety recommendations, including recommendations to the company that addressed its procedures for the preparation and examination of plastic fusions, training of its staff on conditions for notifications to the City’s Fire Department and extension of its gas main isolation valve installation program. In February 2017, the NYSPSC approved a settlement agreement with the company related to the NYSPSC's investigations of the incident and the practices of qualifying persons to perform plastic fusions. Pursuant to the agreement, the company will provide $27 million of future benefits to customers (for which it has accrued a regulatory liability, see Note B) and will not recover from customers $126 million of costs for gas emergency response activities that it had previously incurred and expensed. Approximately eighty suits are pending against the company seeking generally unspecified damages and, in some cases, punitive damages, for wrongful death, personal injury, property damage and business interruption. The company has notified its insurers of the incident and believes that the policies in force at the time of the incident will cover the company’s costs, in excess of a required retention (the amount of which is not material), to satisfy any liability it may have for damages in connection with the incident. The company is unable to estimate the amount or range of its possible loss for damages related to the incident. At December 31, 2017 , the company had not accrued a liability for damages related to the incident. Other Contingencies See “Other Regulatory Matters” in Note B and "Uncertain Tax Positions" in Note L. Guarantees Con Edison and its subsidiaries enter into various agreements providing financial or performance assurance primarily to third parties on behalf of their subsidiaries. Maximum amounts guaranteed by Con Edison totaled $2,073 million and $2,370 million at December 31, 2017 and 2016 , respectively. A summary, by type and term, of Con Edison’s total guarantees at December 31, 2017 is as follows: Guarantee Type 0 – 3 years 4 – 10 years > 10 years Total (Millions of Dollars) Con Edison Transmission $643 $404 $— $1,047 Energy transactions 431 27 211 669 Renewable electric production projects 210 — 24 234 Other 123 — — 123 Total $1,407 $431 $235 $2,073 Con Edison Transmission – Con Edison has guaranteed payment by CET Electric of the contributions CET Electric agreed to make to New York Transco LLC (NY Transco). CET Electric acquired a 45.7 percent interest in NY Transco when it was formed in 2014. In May 2016, the transmission owners transferred certain projects to NY Transco, for which CET Electric made its required contributions. NY Transco has proposed other transmission projects in the New York Independent System Operator's competitive bidding process. These other projects are subject to certain authorizations from the NYSPSC, the FERC and, as applicable, other federal, state and local agencies. Guarantee amount shown is for the maximum possible required amount of CET Electric's contributions for these other projects as calculated based on the assumptions that the projects are completed at 175 percent of their estimated costs and NY Transco does not use any debt financing for the projects. Guarantee term shown is assumed as the selection of the projects and resulting timing of the contributions is not certain. Also included within the table above is a guarantee for $25 million from Con Edison on behalf of CET Gas in relation to a proposed gas transmission project in West Virginia and Virginia. See Note U. Energy Transactions — Con Edison guarantees payments on behalf of the Clean Energy Businesses in order to facilitate physical and financial transactions in electricity, gas, pipeline capacity, transportation, oil, renewable energy credits and energy services. To the extent that liabilities exist under the contracts subject to these guarantees, such liabilities are included in Con Edison’s consolidated balance sheet. Renewable Electric Production Projects – Con Edison, Con Edison Development and Con Edison Solutions guarantee payments on behalf of their wholly-owned subsidiaries associated with their investment in, or development for others of, solar and wind energy facilities. Other – Other guarantees include $70 million in guarantees provided by Con Edison to Travelers Insurance Company for indemnity agreements for surety bonds in connection with operation of solar energy facilities and energy service projects of Con Edison Development and Con Edison Solutions, respectively. Other guarantees also include Con Edison's guarantee (subject to a $53 million maximum amount) of certain obligations of Con Edison Solutions under the agreement pursuant to which it sold its retail electric supply business. See Note U.

Electricity Purchase Agreements

Electricity Purchase Agreements	12 Months Ended
	Dec. 31, 2017
Regulated Operations [Abstract]
Electricity Purchase Agreements	Regulatory Matters Rate Plans The Utilities provide service to New York customers according to the terms of tariffs approved by the NYSPSC. Tariffs for service to customers of Rockland Electric Company (RECO), O&R’s New Jersey regulated utility subsidiary, are approved by the New Jersey Board of Public Utilities (NJBPU). The tariffs include schedules of rates for service that limit the rates charged by the Utilities to amounts that recover from their customers costs approved by the regulator, including capital costs, of providing service to customers as defined by the tariff. The tariffs implement rate plans adopted by state utility regulators in rate orders issued at the conclusion of rate proceedings. Pursuant to the Utilities’ rate plans, there generally can be no change to the charges to customers during the respective terms of the rate plans other than specified adjustments provided for in the rate plans. The Utilities’ rate plans each cover specified periods, but rates determined pursuant to a plan generally continue in effect until a new rate plan is approved by the state utility regulator. Common provisions of the Utilities’ New York rate plans include: Recoverable energy costs that allow the Utilities to recover on a current basis the costs for the energy they supply with no mark-up to their full-service customers. Cost reconciliations that reconcile pension and other postretirement benefit costs, environmental remediation costs, property taxes, variable rate tax-exempt debt and certain other costs to amounts reflected in delivery rates for such costs. In addition, changes in the Utilities' costs not reflected in rates, in excess of certain amounts, resulting from changes in tax or other law, rule, regulation, order, or other requirement or interpretation are deferred as a regulatory asset or regulatory liability to be reflected in the Utilities' next rate plan or in a manner to be determined by the NYSPSC. See "Other Regulatory Matters," below. Also, the Utilities generally retain the right to petition for recovery or accounting deferral of extraordinary and material cost increases and provision is sometimes made for the utility to retain a share of cost reductions, for example, property tax refunds. Revenue decoupling mechanisms that reconcile actual energy delivery revenues to the authorized delivery revenues approved by the NYSPSC. The difference is accrued with interest for refund to, or recovery from customers, as applicable. Earnings sharing that require the Utilities to defer for customer benefit a portion of earnings over specified rates of return on common equity. There is no symmetric mechanism for earnings below specified rates of return on common equity. Negative revenue adjustments for failure to meet certain performance standards relating to service, reliability, safety and other matters. Positive revenue adjustments for achievement of performance standards related to achievement of clean energy goals, safety and other matters. Net utility plant reconciliations that require deferral as a regulatory liability of the revenue requirement impact of the amount, if any, by which actual average net utility plant balances are less than amounts reflected in rates. There is generally no symmetric mechanism if actual average net utility plant balances are more than amounts reflected in rates. Rate base , as reflected in the rate plans, is, in general, the sum of the Utilities’ net plant, working capital and certain regulatory assets less deferred taxes and certain regulatory liabilities. For each rate plan, the NYSPSC uses a forecast of the average rate base for each year that new rates would be in effect (“rate year”). Weighted average cost of capital is determined based on the authorized common equity ratio, return on common equity, cost of long-term debt and customer deposits reflected in each rate plan. For each rate plan, the revenues designed to provide the utility a return on invested capital for each rate year are determined by multiplying each utility rate base by its pre – tax weighted average cost of capital. The Utilities’ actual return on common equity will reflect their actual operations for each rate year, and may be more or less than the authorized return on equity reflected in their rate plans (and if more, may be subject to earnings sharing). The following tables contain a summary of the Utilities’ rate plans: CECONY – Electric Effective period January 2014 – December 2016 January 2017 – December 2019 (b) Base rate changes Yr. 1 – $(76.2) million (a) Yr. 1 – $195 million (c) Amortizations to income of net regulatory (assets) and liabilities Yr. 1 and 2 – $(37) million (d) Yr. 1 – $84 million Other revenue sources Retention of $90 million of annual transmission congestion revenues. Retention of $75 million of annual transmission congestion revenues. Revenue decoupling mechanisms In 2014, 2015 and 2016, the company deferred for customer benefit $146 million, $98 million and $101 million of revenues, respectively. Continuation of reconciliation of actual to authorized electric delivery revenues. Recoverable energy costs (e) Current rate recovery of purchased power and fuel costs. Continuation of current rate recovery of purchased power and fuel costs. Negative revenue adjustments Potential penalties (up to $400 million annually) if certain performance targets are not met. In 2014, the company recorded a $5 million negative revenue adjustment. In 2015 and 2016, the company did not record any negative revenue adjustments. Potential penalties if certain performance targets relating to service, reliability, safety and other matters are not met: Cost reconciliations In 2014, 2015 and 2016, the company deferred $57 million, $26 million and $68 million of net regulatory liabilities, respectively (f). Continuation of reconciliation of expenses for pension and other postretirement benefits, variable-rate tax-exempt debt, major storms, property taxes (f), municipal infrastructure support costs (g), the impact of new laws and environmental site investigation and remediation to amounts reflected in rates (h). Net utility plant reconciliations Target levels reflected in rates were: Target levels reflected in rates: Average rate base Yr. 1 – $17,323 million Yr. 1 – $18,902 million Weighted average cost of capital (after-tax) Yr. 1 – 7.05 percent Yr. 1 – 6.82 percent Authorized return on common equity Yrs. 1 and 2 – 9.2 percent 9.0 percent Actual return on common equity Yr. 1 – 9.04 percent Yr. 1 – 9.3 percent Earnings sharing Most earnings above an annual earnings threshold of 9.8 percent for Yrs. 1 and 2 and 9.6 percent for Yr. 3 are to be applied to reduce regulatory assets for environmental remediation and other costs. In 2014 the company had no earnings above the threshold. Actual earnings were $44.4 million and $6.5 million above the threshold for 2015 and 2016, respectively. Most earnings above an annual earnings threshold of 9.5 percent are to be applied to reduce regulatory assets for environmental remediation and other costs accumulated in the rate year. Cost of long-term debt Yr. 1 – 5.17 percent Yr. 1 – 4.93 percent Common equity ratio 48 percent 48 percent (a) The impact of these base rate changes was deferred which resulted in a $30 million regulatory liability at December 31, 2015; this amount has been amortized to $0 at December 31, 2016. (b) In January 2017, the NYSPSC approved the September 2016 Joint Proposal for CECONY's electric rate plan for January 2017 through December 2019. If at the end of any year, Con Edison’s investments in its non-utility businesses exceed 15 percent of Con Edison’s total consolidated revenues, assets or cash flow, or if the ratio of holding company debt to total consolidated debt rises above 20 percent , CECONY is required to notify the NYSPSC and submit a ring-fencing plan or a demonstration why additional ring-fencing measures are not necessary. (c) The electric base rate increases are in addition to a $48 million increase resulting from the December 2016 expiration of a temporary credit under the prior rate plan. At the NYSPSC’s option, these increases are being implemented with increases of $199 million in each rate year. Base rates reflect recovery by the company of certain costs of its energy efficiency, system peak reduction and electric vehicle programs (Yr. 1 - $20.5 million ; Yr. 2 - $49 million ; and Yr. 3 - $107.5 million ) over a ten -year period, including the overall pre-tax rate of return on such costs. (d) Amounts reflect annual amortization of $107 million of the regulatory asset for deferred Superstorm Sandy and other major storm costs. The costs recoverable from customers were reduced by $4 million . The costs are no longer subject to NYSPSC staff review and the recovery of the costs is no longer subject to refund. In 2016, an additional $123 million of net regulatory liabilities were amortized to income. (e) For transmission service provided pursuant to the open access transmission tariff of PJM Interconnection LLC (PJM), unless and until changed by the NYSPSC, the company will recover all charges incurred associated with the transmission service. Starting in January 2014, PJM submitted to the FERC a series of requests that substantially increase the charges for the transmission service. CECONY has challenged each of these requests. To date, FERC has rejected all but one of CECONY’s protests. In June 2015 and May 2016, CECONY filed appeals of certain FERC decisions with the U.S. Court of Appeals. In April 2017, the transmission service terminated because CECONY did not exercise its option to continue the service. (f) Deferrals for property taxes are limited to 90 percent of the difference from amounts reflected in rates, subject to an annual maximum for the remaining difference of not more than a maximum number of basis points ( 5.0 , 7.5 or 10.0 basis points , depending on the year). (g) In general, if actual expenses for municipal infrastructure support (other than company labor) are below the amounts reflected in rates the company will defer the difference for credit to customers, and if the actual expenses are above the amount reflected in rates the company will defer for recovery from customers 80 percent of the difference subject to a maximum deferral of 30 percent of the amount reflected in rates. (h) In addition, amounts reflected in rates relating to the regulatory asset for future income tax and the excess deferred federal income tax liability are subject to reconciliation. The NYSPSC staff is to audit the regulatory asset and the tax liability. Differences resulting from the NYSPSC staff review will be deferred for NYSPSC determination of any amounts to be refunded or collected from customers. See "Other Regulatory Matters," below. CECONY – Gas Effective period January 2014 – December 2016 January 2017 - December 2019 (b) Base rate changes Yr. 1 – $(54.6) million (a) Yr. 1 – $(5) million (b) Amortizations to income of net regulatory (assets) and liabilities $4 million over three years Yr. 1 – $39 million Other revenue sources Retention of revenues from non-firm customers of up to $65 million and 15 percent of any such revenues above $65 million. The company retained $70 million, $66 million and $65 million of such revenues in 2014, 2015 and 2016, respectively. Retention of annual revenues from non-firm customers of up to $65 million and 15 percent of any such revenues above $65 million. Revenue decoupling mechanisms In 2014, 2015 and 2016, the company deferred $28 million, $54 million and $71 million of regulatory liabilities, respectively. Continuation of reconciliation of actual to authorized gas delivery revenues. Recoverable energy costs Current rate recovery of purchased gas costs. Continuation of current rate recovery of purchased gas costs. Negative revenue adjustments Potential penalties (up to $33 million in 2014, $44 million in 2015, and $56 million in 2016) if certain gas performance targets are not met. In 2014, 2015 and 2016, the company did not record any negative revenue adjustments. Potential penalties if performance targets relating to service, safety and other matters are not met: Cost reconciliations In 2014, 2015 and 2016, the company deferred $38 million, $11 million, and $32 million of net regulatory liabilities, respectively. (c) Continuation of reconciliation of expenses for pension and other postretirement benefits, variable-rate tax-exempt debt, major storms, property taxes, municipal infrastructure support costs, the impact of new laws and environmental site investigation and remediation to amounts reflected in rates. (d) Net utility plant reconciliations Target levels reflected in rates were: Target levels reflected in rates: Average rate base Yr. 1 – $3,521 million Yr. 1 – $4,841 million Weighted average cost of capital Yr. 1 – 7.10 percent Yr. 1 – 6.82 percent Authorized return on common equity 9.3 percent 9.0 percent Actual return on common equity Yr. 1 – 8.02 percent Yr. 1 – 9.22 percent Earnings sharing Most earnings above an annual earnings threshold of 9.9 percent are to be applied to reduce regulatory assets for environmental remediation and other costs. In 2014, 2015 and 2016, the company had no earnings above the threshold. Most earnings above an annual earnings threshold of 9.5 percent are to be applied to reduce regulatory assets for environmental remediation and other costs accumulated in the rate year. Cost of long-term debt Yr. 1 – 5.17 percent Yr. 1 – 4.93 percent Common equity ratio 48 percent 48 percent (a) The impact of these base rate changes was deferred which resulted in a $32 million regulatory liability at December 31, 2016. (b) In January 2017, the NYSPSC approved the September 2016 Joint Proposal for CECONY's gas rate plan for January 2017 through December 2019. The gas base rate decrease is offset by a $41 million increase resulting from the December 2016 expiration of a temporary credit under the prior rate plan. (c) Deferrals for property taxes are limited to 90 percent of the difference from amounts reflected in rates, subject to an annual maximum for the remaining difference of not more than a 10 basis point impact on return on common equity (d) See footnotes (e), (f), (g) and (h) to the table under "CECONY - Electric" above. CECONY – Steam Effective period January 2014 – December 2016 (a) Base rate changes Yr. 1 – $(22.4) million (b) Amortizations to income of net regulatory (assets) and liabilities $37 million over three years Recoverable energy costs Current rate recovery of purchased power and fuel costs. Negative revenue adjustments Potential penalties (up to $1 million annually) if certain steam performance targets are not met. In 2014, 2015, 2016 and 2017, the company did not record any negative revenue adjustments. Cost reconciliations (c) In 2014, 2015, 2016 and 2017, the company deferred $42 million of net regulatory liabilities, $17 million of net regulatory assets, $8 million and $14 million of net regulatory liabilities, respectively. Net utility plant reconciliations Target levels reflected in rates were: Average rate base Yr. 1 – $1,511 million Weighted average cost of capital (after-tax) Yr. 1 – 7.10 percent Authorized return on common equity 9.3 percent Actual return on common equity Yr. 1 – 9.82 percent Earnings sharing Weather normalized earnings above an annual earnings threshold of 9.9 percent are to be applied to reduce regulatory assets for environmental remediation and other costs. Cost of long-term debt Yr. 1 – 5.17 percent Common equity ratio 48 percent (a) Rates determined pursuant to this rate plan continue in effect until a new rate plan is approved by the NYSPSC. (b) The impact of these base rate changes was deferred which resulted in an $8 million regulatory liability at December 31, 2016. (c) Deferrals for property taxes are limited to 90 percent of the difference from amounts reflected in rates, subject to an annual maximum for the remaining difference of not more than a 10 basis point impact on return on common equity. O&R New York – Electric Effective period July 2012 – October 2015 November 2015 - October 2017 (a) Base rate changes Yr. 1 – $19.4 million Yr. 1 – $9.3 million – $8.8 million Amortizations to income of net regulatory (assets) and liabilities $(32.2) million over three years Yr. 1 – $(8.5) million (b) – $(9.4) million (b) Revenue decoupling mechanisms In 2012, 2013 and 2014, the company deferred for the customer’s benefit $2.6 million, $3.2 million and $(3.4) million, respectively. In 2015, 2016 and 2017, the company deferred for the customer’s benefit an immaterial amount, $6.3 million as regulatory liabilities and $11.2 million as regulatory asset, respectively. Recoverable energy costs Current rate recovery of purchased power and fuel costs. Continuation of current rate recovery of purchased power costs. Negative revenue adjustments Potential penalties (up to $3 million annually) if certain customer service and system reliability performance targets are not met. In 2012, 2013 and 2014, the company did not record any negative revenue adjustments. Potential penalties (up to $4 million annually) if certain performance targets are not met. In 2015 the company recorded $1.25 million in negative revenue adjustments. In 2016 and 2017, the company did not record any negative revenue adjustments. Cost reconciliations In 2012, 2013 and 2014, the company deferred $7.8 million, $4.1 million and $(0.2) million as a net increase/(decrease) to regulatory assets, respectively. In 2015, 2016 and 2017, the company deferred $0.3 million, $7.4 million and $3.2 million as net decreases to regulatory assets, respectively. Net utility plant reconciliations Target levels reflected in rates were: Target levels reflected in rates are: – $928 million (c) – $970 million (c) The company increased/(reduced) its regulatory asset by $2.2 million, $(1.9) million and $(1.9) million in 2015, 2016 and 2017, respectively. Average rate base Yr. 1 – $671 million Yr. 1 – $763 million – $805 million Weighted average cost of capital (after-tax) Yr. 1 – 7.61 percent Yr. 1 – 7.10 percent – 7.06 percent Authorized return on common equity Yr. 1 – 9.4 percent 9.0 percent Actual return on common equity Yr. 1 – 12.9 percent Yr. 1 – 10.8 percent Earnings sharing The company recorded a regulatory liability of $1 million for earnings above the sharing threshold under the rate plan as of December 31, 2014. Most earnings above an annual earnings threshold of 9.6 percent are to be applied to reduce regulatory assets. In 2015, earnings did not exceed the earnings threshold. Actual earnings were $6.1 million and $0.3 million above the threshold for 2016 and 2017, respectively. Cost of long-term debt Yr. 1 – 6.07 percent Yr. 1 – 5.42 percent – 5.35 percent Common equity ratio 48 percent 48 percent (a) Rates determined pursuant to this rate plan continue in effect until a new rate plan is approved by the NYSPSC. (b) $59.3 million of the regulatory asset for deferred storm costs is to be recovered from customers over a five year period, including $11.85 million in each of years 1 and 2, $1 million of the regulatory asset for such costs will not be recovered from customers, and all outstanding issues related to Superstorm Sandy and other past major storms prior to November 2014 are resolved. Approximately $4 million of regulatory assets for property tax and interest rate reconciliations will not be recovered from customers. Amounts that will not be recovered from customers were charged-off in June 2015. (c) Excludes electric AMI as to which the company will be required to defer as a regulatory liability the revenue requirement impact of the amount, if any, by which actual average net utility plant balances are less than amounts reflected in rates: $1 million in year 1 and $9 million in year 2. I n January 2018, O&R filed a request with the NYSPSC for an increase in the rates it charges for electric service rendered in New York, effective January 1, 2019, of $20.3 million . The filing reflects a return on common equity of 9.75 percent and a common equity ratio of 48 percent . The filing proposes continuation of the provisions with respect to recovery from customers of the cost of purchased power, and the reconciliation of actual expenses allocable to the electric business to the amounts for such costs reflected in electric rates for storm costs, pension and other postretirement benefit costs, environmental remediation and property taxes. O&R New York – Gas Effective period November 2009 – October 2015 November 2015 – October 2018 Base rate changes Yr. 1 – $9 million Yr. 1 – $16.4 million – $16.4 million – $5.8 million – $10.6 million collected through a surcharge Amortization to income of net regulatory (assets) and liabilities $(2) million over three years Yr. 1 – $(1.7) million (a) – $(2.1) million (a) – $(2.5) million (a) Revenue decoupling mechanisms In 2012, 2013 and 2014, the company deferred $4.7 million, $0.7 million and $(0.1) million of regulatory liabilities, respectively. In 2015 and 2016, the company deferred $0.8 million regulatory assets and $6.2 million of regulatory liabilities, respectively. In 2017, the company deferred $1.7 million in regulatory liabilities. Recoverable energy costs Current rate recovery of purchased gas costs. Current rate recovery of purchased gas costs. Negative revenue adjustments Potential penalties (up to $1.4 million annually) if certain operations and customer service requirements are not met. In 2012, 2013 and 2014, the company did not record any negative revenue adjustments. Potential penalties (up to $3.7 million in Yr. 1, $4.7 million in Yr. 2 and $4.9 million in Yr. 3) if certain performance targets are not met. In 2015, 2016 and 2017, the company did not record any negative revenue adjustments. Cost reconciliations In 2012, 2013 and 2014, the company deferred $0.7 million, $8.3 million and $8.3 million as net regulatory assets, respectively. In 2015 and 2016, the company deferred $4.5 million and $6.6 million as net regulatory liabilities and assets, respectively. In 2017, the company deferred $3.5 million as net regulatory liabilities. Net utility plant reconciliations The company deferred $0.7 million in 2012 as a regulatory asset and no deferrals were recorded for 2013 or 2014. Target levels reflected in rates are: – $492 million (b) – $518 million (b) – $546 million (b) No deferral was recorded for 2015 and immaterial amounts were recorded as regulatory liabilities in 2016 and 2017. Average rate base Yr. 1 – $280 million Yr. 1 – $366 million – $391 million – $417 million Weighted average cost of capital (after-tax) 8.49 percent Yr. 1 – 7.10 percent – 7.06 percent – 7.06 percent Authorized return on common equity 10.4 percent 9.0 percent Actual return on common equity Yr. 1 – 10.2 percent Yr. 1 – 11.2 percent Earnings sharing Earnings above an annual earnings threshold of 11.4 percent are to be applied to reduce regulatory assets. In 2012, 2013 and 2014, earnings did not exceed the earnings threshold. Most earnings above an annual earnings threshold of 9.6 percent are to be applied to reduce regulatory assets. In 2015, earnings did not exceed the earnings threshold. Actual earnings were $4 million and $0.2 million above the threshold for 2016 and 2017, respectively. Cost of long-term debt 6.81 percent Yr. 1 – 5.42 percent – 5.35 percent – 5.35 percent Common equity ratio 48 percent 48 percent (a) Reflects that the company will not recover from customers a total of approximately $14 million of regulatory assets for property tax and interest rate reconciliations. Amounts that will not be recovered from customers were charged-off in June 2015. (b) Excludes gas AMI as to which the company will be required to defer as a regulatory liability the revenue requirement impact of the amount, if any, by which actual average net utility plant balances are less than amounts reflected in rates: $0.5 million in year 1, $4.2 million in year 2 and $7.2 million in year 3. In January 2018, O&R filed a request with the NYSPSC for an increase in the rates it charges for gas service rendered in New York, effective January 1, 2019, of $4.5 million . The filing reflects a return on common equity of 9.75 percent and a common equity ratio of 48 percent . The filing proposes continuation of the provisions with respect to recovery from customers of the cost of purchased gas, and the reconciliation of actual expenses allocable to the gas business to the amounts for such costs reflected in gas rates for pension and other postretirement benefit costs, environmental remediation and property taxes. RECO Effective period August 2014 – February 2017 March 2017 (a) Base rate changes Yr. 1 – $13.0 million Yr. 1 – $1.7 million Amortization to income of net regulatory (assets) and liabilities $0.4 million over three years and $(25.6) million of deferred storm costs over four years $0.2 million over three years and continuation of $(25.6) million of deferred storm costs over four years expiring July 31, 2018 (b) Recoverable energy costs Current rate recovery of purchased power costs. Current rate recovery of purchased power costs. Cost reconciliations None None Average rate base $172.2 million Yr. 1 – $178.7 million Weighted average cost of capital (after-tax) 7.83 percent 7.47 percent Authorized return on common equity 9.75 percent 9.6 percent Actual return on common equity Yr. 1 – 9.2 percent (c) Cost of long-term debt 5.89 percent 5.37 percent Common equity ratio 50 percent 49.7 percent (a) Effective until a new rate plan approved by the NJBPU goes into effect. (b) In January 2016, the NJBPU approved RECO’s plan to spend $15.7 million in capital over three years to harden its electric system against storms, the costs of which RECO, beginning in 2017, is collecting through a customer surcharge. (c) Actual return on common equity for first rate year of current rate plan not determinable until March 31, 2018 end of rate year. In November 2017, FERC approved a September 2017 settlement agreement among RECO, the New Jersey Division of Rate Counsel and the NJBPU that increases RECO's annual transmission revenue requirement from $11.8 million to $17.7 million , effective April 2017. The revenue requirement reflects a return on common equity of 10.0 percent . Other Regulatory Matters In August and November 2017, the NYSPSC issued orders in its proceeding investigating an April 21, 2017 Metropolitan Transportation Authority (MTA) subway power outage. The orders indicated that the investigation determined that the outage was caused by a failure of CECONY’s electricity supply to a subway station, which led to a loss of the subway signals, and that one of the secondary services to the MTA facility had been improperly rerouted and was not properly documented by the company. The orders also indicated that the loss of power to the subway station affected multiple subway lines and caused widespread delays across the subway system. Pursuant to the orders, the company is required to take certain actions, including inspecting, repairing and installing certain electrical equipment that serves the subway system, analyzing power supply and power quality events affecting the MTA’s signaling services, and filing monthly reports with the NYSPSC on all of the company's activities related to the subway system. In July 2017, the Chairman of the NYSPSC notified the company that the April 21, 2017 subway power outage incident will likely result in a prudence review of the reasonableness of CECONY's actions and conduct. The orders did not commence a prudence review. The company incurred costs related to this matter in 2017 of $65 million . Included in this amount is $15 million in capital and operating and maintenance costs reflected in the company's electric rate plan and $50 million deferred as a regulatory asset pursuant to the rate plan. The company, which plans to complete the required actions in 2018, expects to incur costs related to this matter in 2018 of $137 million . Included in this amount is $10 million in expected capital and operating and maintenance costs reflected in the rate plan and $127 million expected to be deferred as a regulatory asset pursuant to the rate plan. In December 2017, the NYSPSC issued an order initiating a proceeding to study the potential effects of the TCJA on the tax expenses and liabilities of New York State utilities and the regulatory treatment to preserve the resulting benefits for customers. In January 2018, the NJBPU issued an order initiating a proceeding to consider the TCJA. Upon enactment of the TCJA, CECONY, O&R and RECO re-measured their deferred tax assets and liabilities based upon the 21 percent corporate income tax rate under the TCJA. As a result, CECONY, O&R and RECO, decreased their net deferred tax liabilities by $4,781 million , $216 million and $45 million , respectively, decreased their regulatory asset for future income tax by $1,182 million , $51 million and $17 million , respectively, decreased their regulatory asset for revenue taxes by $86 million , $4 million and $0 million , respectively, and accrued regulatory liabilities for future income tax of $3,513 million , $161 million and $28 million , respectively. See Note L. In January 2018, the NYSPSC issued an order initiating a focused operations audit of the income tax accounting of certain utilities, including CECONY and O&R. See footnote (h) to the table under "CECONY – Electric," above. Regulatory Assets and Liabilities Regulatory assets and liabilities at December 31, 2017 and 2016 were comprised of the following items: Con Edison CECONY (Millions of Dollars) 2017 2016 2017 2016 Regulatory assets Unrecognized pension and other postretirement costs $2,526 $2,874 $2,376 $2,730 Future income tax* — 2,439 — 2,325 Environmental remediation costs 793 823 677 711 Revenue taxes 260 295 248 280 Pension and other postretirement benefits deferrals 79 38 58 7 Recoverable energy costs 60 42 52 38 Municipal infrastructure support costs 56 44 56 44 Property tax reconciliation 51 37 25 — MTA power reliability deferral 50 — 50 — Deferred derivative losses 44 48 37 42 Deferred storm costs 38 56 — 3 Brooklyn Queens demand management program 37 29 37 29 Unamortized loss on reacquired debt 37 43 35 41 Indian Point Energy Center program costs 29 50 29 50 Preferred stock redemption 24 25 24 25 Workers’ compensation 10 13 10 13 Net electric deferrals 9 24 9 24 O&R transition bond charges 9 15 — — Surcharge for New York State assessment 2 28 2 26 Other 152 101 138 85 Regulatory assets – noncurrent 4,266 7,024 3,863 6,473 Deferred derivative losses 40 91 37 86 Recoverable energy costs 27 9 25 4 Regulatory assets – current 67 100 62 90 Total Regulatory Assets $4,333 $7,124 $3,925 $6,563 Regulatory liabilities Future income tax* $2,545 $— $2,390 $— Allowance for cost of removal less salvage 846 755 719 641 Pension and other postretirement benefit deferrals 207 193 181 162 Net unbilled revenue deferrals 183 145 183 145 Energy efficiency portfolio standard unencumbered funds 127 — 122 — Property tax reconciliation 107 178 107 178 Unrecognized other postretirement costs 92 60 92 60 Settlement of prudence proceeding 66 95 66 95 Property tax refunds 44 1 44 1 Carrying charges on repair allowance and bonus depreciation 43 68 42 67 New York State income tax rate change 36 61 35 60 Variable-rate tax-exempt debt - cost rate reconciliation 30 55 26 48 Earnings sharing - electric, gas and steam 29 39 19 28 Settlement of gas proceedings 27 27 27 27 Base rate change deferrals 21 40 21 40 Net utility plant reconciliations 12 16 8 15 Other 162 172 137 145 Regulatory liabilities – noncurrent 4,577 1,905 4,219 1,712 Refundable energy costs 41 29 16 5 Deferred derivative gains 31 28 28 24 Revenue decoupling mechanism 29 71 21 61 Regulatory liabilities—current 101 128 65 90 Total Regulatory Liabilities $4,678 $2,033 $4,284 $1,802 ` * See "Federal Income Tax" in Note A, "Other Regulatory Matters," above, and Note L . Unrecognized pension and other postretirement costs represent the net regulatory asset associated with the accounting rules for retirement benefits. See Note A. Revenue taxes represent the timing difference between taxes collected and paid by the Utilities to fund mass transportation. Deferred storm costs represent response and restoration costs, other than capital expenditures, in connection with Superstorm Sandy and other major storms that were deferred by the Utilities. Net electric deferrals represent the remaining unamortized balance of certain regulatory assets and liabilities of CECONY that were combined effecti

Leases

Leases	12 Months Ended
	Dec. 31, 2017
Leases [Abstract]
Leases	Leases Con Edison’s subsidiaries lease electric transmission facilities, gas distribution facilities, land, office buildings and equipment. In accordance with the accounting rules for leases, these leases are classified as either capital leases or operating leases. Most of the operating leases provide the option to renew at the fair rental value for future periods. Generally, it is expected that leases will be renewed or replaced in the normal course of business. Capital leases: For ratemaking purposes capital leases are treated as operating leases; therefore, in accordance with the accounting rules for regulated operations, the amortization of the leased asset is based on the rental payments recovered from customers. The following assets under capital leases are included in the Companies’ consolidated balance sheets at December 31, 2017 and 2016 : Con Edison CECONY (Millions of Dollars) 2017 2016 2017 2016 UTILITY PLANT Common $2 $3 $1 $2 The accumulated amortization of the capital leases for Con Edison and CECONY was $3 million and $2 million , respectively at December 31, 2017 , and $3 million and $1 million , respectively at December 31, 2016 . Operating leases: The future minimum lease commitments under the Companies’ operating lease agreements that are not cancellable by the Companies are as follows: (Millions of Dollars) Con Edison CECONY 2018 $63 $55 2019 63 56 2020 63 55 2021 62 54 2022 59 53 All years thereafter 746 645 Total $1,056 $918 Substantially all of the amounts shown in the above table are estimated amounts payable under CECONY’s revocable consent agreement with New York City for the use of streets and public places for installation and operation of transformers and associated vaults and equipment. Under the agreement, payments by CECONY increase 2.18 percent annually and are subject to decrease if CECONY’s transformer installations decrease by ½ of 1 percent or more from the prior year. For information about changes to the accounting rules for leases, see Note T.

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangible Assets	Goodwill and Other Intangible Assets In 2017, Con Edison elected to perform the optional qualitative assessment for goodwill related to the O&R merger and the gas storage company, and the first step of the quantitative test for the residential solar company. In 2016 Con Edison performed the first step of the quantitative analysis for the goodwill related to the O&R merger, the gas storage company, and the residential solar company and deemed that the second step assessment was not required. In 2017 and 2016 , Con Edison completed impairment tests for its goodwill of $406 million related to the O&R merger, and determined that it was not impaired. For the impairment test, $245 million and $161 million of goodwill were allocated to CECONY and O&R, respectively. In 2017 and 2016 , Con Edison completed impairment tests for goodwill of $8 million related to a gas storage company acquired by CET Gas from Con Edison Development and determined that it was not impaired. In 2016, Con Edison completed impairment tests for goodwill of $15 million related to two energy services companies owned by the Clean Energy Businesses and determined that goodwill was impaired and, upon calculating the implied fair value of goodwill using fair values based primarily on discounted cash flows, recorded a corresponding impairment charge of $15 million ( $12 million , net of tax). Additionally, in 2016, the Clean Energy Businesses acquired a residential solar company and recorded $14 million of goodwill as part of the preliminary purchase price allocation. In 2017, Con Edison determined that goodwill related to the residential solar company was not impaired. Estimates of future cash flows, projected growth rates, and discount rates inherent in the cash flow estimates for Con Edison subsidiaries other than the Utilities may vary significantly from actual results, which could result in a future impairment of goodwill. For information about changes to the accounting rules for goodwill, see Note T. Con Edison's other intangible assets consist primarily of power purchase agreements, which were identified as part of purchase price allocations associated with acquisitions made by Con Edison Development in 2016. At December 31, 2017 and 2016, intangible assets arising from power purchase agreements were $131 million and $119 million , net of accumulated amortization of $9 million and $1 million , respectively, and are being amortized over the life of each agreement. Excluding power purchase agreements, Con Edison’s other intangible assets were an immaterial amount and $5 million , net of accumulated amortization of $6 million and $5 million , at December 31, 2017 and 2016, respectively. CECONY’s other intangible assets were immaterial at December 31, 2017 and 2016. Con Edison recorded amortization expense related to its intangible assets of $9 million in 2017, $2 million in 2016 and an immaterial amount in 2015. Con Edison expects amortization expense to be $9 million per year over the next five years.

Income Tax

Income Tax	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Tax	Income Tax The components of income tax are as follows: Con Edison CECONY (Millions of Dollars) 2017 2016 2015 2017 2016 2015 State Current $(2) $(42) $38 $37 $(1) $48 Deferred 103 188 93 75 114 82 Federal Current (11) (43) (86) 73 59 77 Deferred 391 604 569 504 435 372 Amortization of investment tax credits (9) (9) (9) (4) (4) (5) Total income tax expense $472 $698 $605 $685 $603 $574 The tax effects of temporary differences, which gave rise to deferred tax assets and liabilities, are as follows: Con Edison CECONY (Millions of Dollars) 2017 2016 2017 2016 Deferred tax liabilities: Property basis differences $6,555 $9,446 $5,968 $8,620 Regulatory assets: Unrecognized pension and other postretirement costs 697 1,162 656 1,104 Future income tax — 986 — 940 Environmental remediation costs 219 333 187 287 Deferred storm costs 11 23 — 1 Other regulatory assets 269 371 241 321 Equity investments 263 363 — — Total deferred tax liabilities $8,014 $12,684 $7,052 $11,273 Deferred tax assets: Accrued pension and other postretirement costs $264 $581 $187 $467 Regulatory liabilities: Future income tax 698 — 660 — Other regulatory liabilities 593 822 524 728 Superfund and other environmental costs 203 304 176 265 Asset retirement obligations 86 99 79 92 Loss carryforwards 95 59 — — Tax credits carryforward 658 498 — — Valuation allowance (33) (16) — — Other 112 303 148 312 Total deferred tax assets 2,676 2,650 1,774 1,864 Net deferred tax liabilities $5,338 $10,034 $5,278 $9,409 Unamortized investment tax credits 157 171 28 41 Net deferred tax liabilities and unamortized investment tax credits $5,495 $10,205 $5,306 $9,450 The TCJA includes significant changes affecting the taxation of regulated public utilities, such as CECONY and O&R, and Con Edison’s other businesses. Substantially all of the provisions of the TCJA are effective for taxable years beginning after December 31, 2017. The TCJA reduces the corporate federal income tax rate from 35 percent to 21 percent . The specific provisions related to regulated public utilities in the TCJA generally allow for the continued deductibility of interest expense, do not allow for full expensing for tax purposes of certain property acquired after September 27, 2017, and continue certain rate normalization requirements for accelerated depreciation benefits. For other businesses, TCJA provides for full expensing of property acquired after September 27, 2017 and limits a deduction for interest expense to 30 percent of adjusted taxable income (which resembles earnings before interest, taxes, depreciation and amortization or “EBITDA”). In accordance with the accounting rules for income taxes (see “Federal Income Tax” in Note A), the tax effects of changes in tax laws are to be recognized in the period in which the law is enacted and deferred tax assets and liabilities are to be re-measured at the enacted tax rate expected to apply when temporary differences are to be realized or settled. For CECONY and O&R, in accordance with their New York rate plans and the accounting rules for regulated operations the change in deferred taxes was recorded as either an offset to a regulatory asset or a regulatory liability. See “Accounting Policies” in Note A and “Rate Plans” in Note B. For Con Edison’s other businesses, the change in deferred taxes was reflected as a decrease in income tax expense, which increased Con Edison's net income. Upon enactment of the TCJA, the Companies re-measured their deferred tax assets and liabilities based upon the TCJA’s 21 percent corporate federal income tax rate. As a result, Con Edison, decreased its net deferred tax liabilities by $5,312 million (including $4,781 million for CECONY), recognized $259 million in net income, decreased its regulatory asset for future income tax by $1,250 million (including $1,182 million for CECONY), decreased the regulatory asset for revenue taxes by $90 million (including $86 million for CECONY), and accrued a regulatory liability for future income tax of $3,713 million (including $3,513 million for CECONY). Since the Companies are in a net regulatory liability position with respect to these income tax matters, the Companies netted the regulatory asset for future income tax against the regulatory liability for future income tax. Under the rate normalization requirements continued by the TCJA, $2,684 million of the net regulatory liability (including $2,542 million for CECONY) related to certain accelerated tax depreciation benefits is to be amortized over the remaining lives of the related assets. The remainder of the net regulatory liability is to be refunded (or credited) to customers as determined by the NYSPSC or NJBPU, as applicable. See “Other Regulatory Matters” in Note B. The amount recognized in net income included $269 million for the Clean Energy Businesses, $11 million for Con Edison Transmission and $(21) million for the parent company. The re-measurement had no impact on the Companies’ cash flows for 2017. SEC Staff Accounting Bulletin 118 (SAB 118), issued when the TCJA was enacted, clarifies accounting for income taxes if information is not yet available or complete and provides for up to a one year period in which to complete the required analyses and accounting. SAB 118 describes three scenarios associated with a company’s status of accounting for income tax reform: (1) a company is complete with its accounting for certain effects of tax reform, (2) a company is able to determine a reasonable estimate for certain effects of tax reform and records that estimate as a provisional amount, or (3) a company is not able to determine a reasonable estimate and therefore continues to apply the accounting rules for income taxes, based on the provisions of the tax laws that were in effect immediately prior to the TCJA being enacted. The Companies have completed the required analysis and accounting for substantially all the effects of the TCJA’s enactment and have made a reasonable estimate as to the other effects, and have reflected the measurement and accounting of the effects in their 2017 consolidated financial statements. The items reflected as provisional amounts include tax depreciation and amortization and other book/tax differences. The Companies have accounted for these items based on its interpretation of the TCJA. Further interpretive guidance on the TCJA from the IRS, U.S. Treasury Department, or the Joint Committee on Taxation may require adjustments to the Companies’ accounting. In accordance with SAB 118, adjustments, if any, will be recorded in 2018. The Companies did not identify any effects of the TCJA for which they were not able to either complete the required analysis or make a reasonable estimate. Reconciliation of the difference between income tax expense and the amount computed by applying the prevailing statutory income tax rate to income before income taxes is as follows: Con Edison CECONY (% of Pre-tax income) 2017 2016 2015 2017 2016 2015 STATUTORY TAX RATE Federal 35 % 35 % 35 % 35 % 35 % 35 % Changes in computed taxes resulting from: State income tax 4 4 5 4 4 5 Cost of removal 1 (1 ) (5 ) 1 (1 ) (5 ) Other plant-related items (1 ) — — (1 ) (1 ) — TCJA tax rate reduction (13 ) — — — — — Renewable energy credits (1 ) (1 ) (1 ) — — — Research and development credits — (1 ) — — (1 ) — Other (2 ) — — (1 ) — — Effective tax rate 23 % 36 % 34 % 38 % 36 % 35 % In 2017, Con Edison had a federal net operating loss of approximately $121 million , due primarily to bonus depreciation. Con Edison expects to carryback approximately $53 million of its 2017 net operating loss to 2007, which will result in recovery of $19 million of income tax. The remaining 2017 federal net operating loss of $68 million will be carried forward to future years and will not expire until 2037. General business tax credits that were generated in 2017 ( $176 million ) will be carried forward to future years. Con Edison has $658 million in general business tax credit (primarily renewable energy tax credits), which if unused will begin to expire in 2032. A deferred tax asset for these tax attribute carryforwards was recorded, and no valuation allowance has been provided, as it is more likely than not that the deferred tax asset will be realized. For New York State income tax purposes, Con Edison has a net operating loss carryforward available from 2017 of $137 million , primarily as a result of accelerated tax deductions on renewable energy projects. A deferred tax asset has been recognized for this New York State net operating loss that will not expire until 2037. A valuation allowance has not been provided; as it is more likely than not that the deferred tax asset will be realized. Con Edison recorded a full valuation allowance of $3 million in 2015 against its charitable contribution carryforward from 2011. Due to the expiration of this charitable contribution carryforward in 2016, Con Edison wrote off the deferred tax asset and corresponding valuation allowance. Charitable contributions carryforward of $5 million , $5 million and $4 million for 2015, 2016 and 2017, respectively, that will expire in 2020, 2021 and 2022, respectively, were recorded as a deferred tax asset and no valuation allowance has been provided, as it is more likely than not that the deferred tax asset will be realized. In addition, a $21 million valuation allowance for New York City net operating loss carryforward and a $12 million valuation allowance for state net operating losses carryforward has been provided; as it is not more likely than not that the deferred tax asset will be realized. The Protecting Americans from Tax Hikes Act of 2015 extended bonus depreciation for property acquired and placed in service during 2015 through 2019. The bonus depreciation percentage is 50 percent for property placed in service during 2015, 2016 and 2017 and phases down to 40 percent in 2018, and 30 percent in 2019. As a result of the extension of bonus depreciation to 2015, Con Edison, in February 2016, received a refund of 2015 estimated taxes paid in the amount of $160 million ( $143 million for CECONY). The TCJA does not allow bonus depreciation for property acquired and placed into service by regulated public utilities after September 27, 2017, but provides for full expensing for Con Edison's other businesses. Uncertain Tax Positions Under the accounting rules for income taxes, the Companies are not permitted to recognize the tax benefit attributable to a tax position unless such position is more likely than not to be sustained upon examination by taxing authorities, including resolution of any related appeals and litigation processes, based solely on the technical merits of the position. A reconciliation of the beginning and ending amounts of unrecognized tax benefits for Con Edison and CECONY follows: Con Edison CECONY (Millions of Dollars) 2017 2016 2015 2017 2016 2015 Balance at January 1, $42 $34 $34 $21 $2 $2 Additions based on tax positions related to the current year 1 2 — 1 2 — Additions based on tax positions of prior years 1 19 1 1 19 — Reductions for tax positions of prior years (24) (13) — (18) (2) — Reductions from expiration of statute of limitations (2) — (1) — — — Settlements (6) — — — — — Balance at December 31, $12 $42 $34 $5 $21 $2 In 2017, Con Edison reached a settlement with New York State on tax years 2006 through 2009 and on two significant items through 2015 and reversed $30 million in uncertain tax positions. Of this amount, $6 million ( $4 million , net of federal taxes) reduced Con Edison’s effective tax rate. The amount related to CECONY was $18 million ( $12 million , net of federal taxes), all of which reduced CECONY’s unamortized state investment tax credits. Current and prior year additions in 2017 are for tax credits. As of December 31, 2017 , Con Edison reasonably expects to resolve within the next twelve months approximately $8 million ( $7 million , net of federal taxes) of various federal and state uncertainties due to the expected completion of ongoing tax examinations and expiration of statute of limitations, of which the entire amount, if recognized, would reduce Con Edison’s effective tax rate. The amount related to CECONY is approximately $4 million , of which the entire amount, if recognized, would reduce CECONY’s effective tax rate. The Companies recognize interest on liabilities for uncertain tax positions in interest expense and would recognize penalties, if any, in operating expenses in the Companies’ consolidated income statements. In 2017 , 2016 and 2015 , the Companies recognized an immaterial amount of interest and no penalties for uncertain tax positions in their consolidated income statements. At December 31, 2017 and 2016 , the Companies reflected an immaterial amount of interest and no penalties in their consolidated balance sheets. At December 31, 2017 , the total amount of unrecognized tax benefits that, if recognized, would reduce the Companies’ effective tax rate is $12 million ( $11 million , net of federal taxes) with $5 million attributable to CECONY. Federal tax returns for 2012 through 2016 remain under examination, with tax refunds for tax years 2012 through 2015 waiting for approval by the Joint Committee on Taxation. State income tax returns remain open for examination in New York for tax years 2010 through 2016 and in New Jersey for tax years 2008 through 2016.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	Stock-Based Compensation The Companies may compensate employees and directors with, among other things, stock options, stock units, restricted stock units and contributions to the stock purchase plan. The Long Term Incentive Plan, which was approved by Con Edison’s shareholders in 2003 (2003 LTIP), and the Long Term Incentive Plan, which was approved by Con Edison’s shareholders in 2013 (2013 LTIP), are collectively referred to herein as the LTIP. The LTIP provides for, among other things, awards to employees of restricted stock units and stock options and, to Con Edison’s non-employee directors, stock units. Existing awards under the 2003 LTIP continue in effect, however no new awards may be issued under the 2003 LTIP. The 2013 LTIP provides for awards for up to five million shares of common stock. Shares of Con Edison common stock used to satisfy the Companies’ obligations with respect to stock-based compensation may be new (authorized, but unissued) shares, treasury shares or shares purchased in the open market. The shares used during the year ended December 31, 2017 were new shares. The Companies intend to use new shares to fulfill their stock-based compensation obligations for 2018 . The Companies recognized stock-based compensation expense using a fair value measurement method. The following table summarizes stock-based compensation expense recognized by the Companies in the years ended December 31, 2017 , 2016 and 2015 : Con Edison CECONY (Millions of Dollars) 2017 2016 2015 2017 2016 2015 Performance-based restricted stock $53 $42 $27 $45 $36 $23 Time-based restricted stock 2 2 1 2 2 1 Non-employee director deferred stock compensation 2 2 2 2 2 2 Stock purchase plan 6 4 4 6 4 3 Total $63 $50 $34 $55 $44 $29 Income tax benefit $25 $20 $14 $22 $18 $12 Stock Options The Companies last granted stock options in 2006. The stock options generally vested over a three -year period and had a term of 10 years . Options were granted at an exercise price equal to the fair market value of a common share when the option was granted. The Companies generally recognized compensation expense (based on the fair value of stock option awards) over the vesting period. At December 31, 2017 and 2016 , there were no outstanding options. The aggregate intrinsic value of options exercised in 2016 for Con Edison and CECONY was $2 million . Aggregate intrinsic value represents the changes in the fair value of all outstanding options from their grant dates to December 31, 2016. Cash received by Con Edison for payment of the exercise price for Con Edison and CECONY options in 2016 was $3 million . No options were exercised in 2017. The income tax benefit Con Edison realized from stock options exercised in the years ended December 31, 2016 and 2015 was $1 million . Restricted Stock and Stock Units Restricted stock and stock unit awards under the LTIP have been made as follows: (i) awards that provide for adjustment of the number of units (performance-restricted stock units or Performance RSUs) to certain officers and employees; (ii) time-based awards to certain employees; and (iii) awards to non-employee directors. Restricted stock and stock units awarded represents the right to receive, upon vesting, shares of Con Edison common stock, or, except for units awarded under the directors’ plan, the cash value of shares or a combination thereof. The number of units in each annual Performance RSU award is subject to adjustment as follows: (i) 50 percent of the units awarded will be multiplied by a factor that may range from 0 to 200 percent , based on Con Edison’s total shareholder return relative to a specified peer group during a specified performance period (the TSR portion); and (ii) 50 percent of the units awarded will be multiplied by factors that may range from 0 to 200 percent, based on determinations made in connection with the Companies’ annual incentive plans or, for certain executive officers, actual performance as compared to certain performance measures during a specified performance period (the non-TSR portion). Performance RSU awards generally vest upon completion of the performance period. Performance against the established targets is recomputed each reporting period as of the earlier of the reporting date and the vesting date. The TSR portion applies a Monte Carlo simulation model, and the non-TSR portion is the product of the market price at the end of the period and the average non-TSR determination over the vesting period. Performance RSUs are “liability awards” because each Performance RSU represents the right to receive, upon vesting, one share of Con Edison common stock, the cash value of a share or a combination thereof. As such, changes in the fair value of the Performance RSUs are reflected in net income. The assumptions used to calculate the fair value of the awards were as follows: 2017 2016 2015 Risk-free interest rate (a) 1.76% - 1.89% 0.85% - 1.20% 0.64% - 3.28% Expected term (b) 3 years 3 years 3 years Expected share price volatility (c) 11.01% - 14.70% 17.72% - 18.22% 15.82% (a) The risk-free rate is based on the U.S. Treasury zero-coupon yield curve. (b) The expected term of the Performance RSUs equals the vesting period. The Companies do not expect significant forfeitures to occur. (c) Based on historical experience. A summary of changes in the status of the Performance RSUs’ TSR and non-TSR portions during the year ended December 31, 2017 is as follows: Con Edison CECONY Weighted Average Grant Date Fair Value (a) Weighted Average Grant Date Fair Value (a) Units TSR Portion (b) Non-TSR Portion (c) Units TSR Portion (b) Non-TSR Portion (c) Non-vested at December 31, 2016 1,087,137 $55.45 $63.03 848,342 $54.92 $63.00 Granted 368,150 73.13 74.54 277,318 72.78 74.72 Vested (375,684) 25.36 53.66 (293,842) 25.32 53.66 Forfeited (50,671) 76.29 72.23 (46,226) 76.41 72.31 Transferred (d) — — — (1,426) 53.01 72.52 Non-vested at December 31, 2017 1,028,932 $71.74 $70.11 784,166 $71.06 $70.08 (a) The TSR and non-TSR Portions each account for 50 percent of the awards’ value. (b) Fair value is determined using the Monte Carlo simulation described above. Weighted average grant date fair value does not reflect any accrual or payment of dividends prior to vesting. (c) Fair value is determined using the market price of one share of Con Edison common stock on the grant date. The market price has not been discounted to reflect that dividends do not accrue and are not payable on Performance RSUs until vesting. (d) Represents allocation to another Con Edison subsidiary of a portion of the Performance RSUs that had been awarded to a CECONY officer who transferred to the other subsidiary. The total expense to be recognized by Con Edison in future periods for unvested Performance RSUs outstanding at December 31, 2017 is $38 million , including $31 million for CECONY, and is expected to be recognized over a weighted average period of one year for both Con Edison and CECONY. In accordance with the accounting rules for stock compensation, for time-based awards, the Companies are accruing a liability and recognizing compensation expense based on the market value of a common share throughout the vesting period. The vesting period for awards is three years and is based on the employee’s continuous service to Con Edison. Prior to vesting, the awards are subject to forfeiture in whole or in part under certain circumstances. The awards are “liability awards” because each restricted stock unit represents the right to receive, upon vesting, one share of Con Edison common stock, the cash value of a share or a combination thereof. As such, prior to vesting, changes in the fair value of the units are reflected in net income. A summary of changes in the status of time-based awards during the year ended December 31, 2017 is as follows: Con Edison CECONY Units Weighted Average Grant Date Fair Value Units Weighted Average Grant Date Fair Value Non-vested at December 31, 2016 65,980 $64.04 62,580 $64.03 Granted 23,000 77.66 21,800 77.66 Vested (21,359) 53.77 (20,359) 53.77 Forfeited (2,751) 71.62 (2,601) 71.93 Non-vested at December 31, 2017 64,870 $71.93 61,420 $71.93 The total expense to be recognized by Con Edison in future periods for unvested time-based awards outstanding at December 31, 2017 for Con Edison and CECONY was $2 million and is expected to be recognized over a weighted average period of one year . Under the LTIP, each non-employee director receives stock units, which are deferred until the director’s separation from service or another date specified by the director. Each director may also elect to defer all or a portion of their cash compensation into additional stock units, which are deferred until the director’s termination of service or another date specified by the director. Non-employee directors’ stock units issued under the LTIP are considered “equity awards,” because they may only be settled in shares. Directors immediately vest in units issued to them. The fair value of the units is determined using the closing price of Con Edison’s common stock on the business day immediately preceding the date of issue. In the year ended December 31, 2017 , approximately 28,100 units were issued at a weighted average grant date price of $81.15 . Stock Purchase Plan The Stock Purchase Plan, which was approved by shareholders in 2004 and 2014, provides for the Companies to contribute up to $1 for each $9 invested by their directors, officers or employees to purchase Con Edison common stock under the plan. Eligible participants may invest up to $25,000 during any calendar year (subject to an additional limitation for officers and employees of not more than 20 percent of their pay). Dividends paid on shares held under the plan are reinvested in additional shares unless otherwise directed by the participant. Participants in the plan immediately vest in shares purchased by them under the plan. The fair value of the shares of Con Edison common stock purchased under the plan was calculated using the average of the high and low composite sale prices at which shares were traded at the New York Stock Exchange on the trading day immediately preceding such purchase dates. During 2017 , 2016 and 2015 , 719,125 , 720,268 and 761,784 shares were purchased under the Stock Purchase Plan at a weighted average price of $79.57 , $72.67 and $62.75 per share, respectively.

Financial Information by Busine

Financial Information by Business Segment	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Financial Information by Business Segment	Financial Information by Business Segment The business segments of each of the Companies, which are its operating segments, were determined based on management’s reporting and decision-making requirements in accordance with the accounting rules for segment reporting. Con Edison’s principal business segments are CECONY’s regulated utility activities, O&R’s regulated utility activities, the Clean Energy Businesses and Con Edison Transmission. CECONY’s principal business segments are its regulated electric, gas and steam utility activities. Con Edison Transmission, which had begun investing in electric transmission and gas pipeline and storage assets (see Note U), was added in June 2016 as a separate reportable segment based on management’s reporting and decision-making, including performance evaluation and resource allocation. For comparison purposes, the previously reported financial information by business segments was reclassified to reflect the current business segment presentation. All revenues of these business segments are from customers located in the United States of America. Also, all assets of the business segments are located in the United States of America. The accounting policies of the segments are the same as those described in Note A. Common services shared by the business segments are assigned directly or allocated based on various cost factors, depending on the nature of the service provided. The financial data for the business segments are as follows: As of and for the Year Ended December 31, 2017 (Millions of Dollars) Operating revenues Inter- segment revenues Depreciation and amortization Operating income Other Income (deductions) Interest charges Income taxes on operating income (a) Total assets Capital expenditures CECONY Electric $7,972 $16 $925 $1,862 $7 $472 $511 $29,661 $1,905 Gas 1,901 6 185 472 — 113 152 8,387 909 Steam 595 75 85 71 — 38 25 2,403 90 Consolidation adjustments — (97) — — — — — — — Total CECONY $10,468 $— $1,195 $2,405 $7 $623 $688 $40,451 $2,904 O&R Electric $642 $— $51 $100 $1 $24 $30 $1,949 $128 Gas 232 — 20 41 — 12 12 824 61 Other — — — — — — — — — Total O&R $874 $— $71 $141 $1 $36 $42 $2,773 $189 Clean Energy Businesses $694 $— $74 $69 $33 $43 $(273) $2,735 $447 Con Edison Transmission 2 — 1 (8) 80 16 (11) 1,222 66 Other (b) (5) — — 3 (5) 11 13 930 — Total Con Edison $12,033 $— $1,341 $2,610 $116 $729 $459 $48,111 $3,606 As of and for the Year Ended December 31, 2016 (Millions of Dollars) Operating revenues Inter- segment revenues Depreciation and amortization Operating income Other Income (deductions) Interest charges Income taxes on operating income (a) Total assets Capital expenditures CECONY Electric $8,106 $17 $865 $1,847 $2 $459 $495 $30,708 $1,819 Gas 1,508 6 159 357 (1) 105 92 7,553 811 Steam 551 88 82 58 (1) 39 30 2,595 126 Consolidation adjustments — (111) — — — — — — — Total CECONY $10,165 $— $1,106 $2,262 $— $603 $617 $40,856 $2,756 O&R Electric $637 $— $49 $95 $1 $24 $30 $1,949 $114 Gas 184 — 18 35 — 12 10 809 52 Other — — — — — — — — — Total O&R $821 $— $67 $130 $1 $36 $40 $2,758 $166 Clean Energy Businesses $1,091 $7 $42 $183 $21 $34 $53 $2,551 $1,235 Con Edison Transmission — — — (3) 43 6 — 1,150 1,078 Other (b) (2) (7) 1 3 (1) 17 4 940 — Total Con Edison $12,075 $— $1,216 $2,575 $64 $696 $714 $48,255 $5,235 As of and for the Year Ended December 31, 2015 (Millions of Dollars) Operating revenues Inter- segment revenues Depreciation and amortization Operating income Other Income (deductions) Interest charges Income taxes on operating income (a) Total assets Capital expenditures CECONY Electric $8,172 $18 $820 $1,798 $(2) $447 $447 $30,603 $1,658 Gas 1,527 6 142 356 (2) 96 100 6,974 671 Steam 629 86 78 93 (1) 41 41 2,653 106 Consolidation adjustments — (110) — — — — — — — Total CECONY $10,328 $— $1,040 $2,247 $(5) $584 $588 $40,230 $2,435 O&R Electric $663 $— $50 $103 $(2) $23 $31 $2,140 $114 Gas 182 — 18 18 (2) 12 2 579 46 Other — — — — — — — — — Total O&R $845 $— $68 $121 $(4) $35 $33 $2,719 $160 Clean Energy Businesses $1,383 $(2) $22 $58 $35 $11 $22 $1,680 $823 Con Edison Transmission — — — — — — — 3 — Other (b) (2) 2 — 1 (2) 23 1 1,010 — Total Con Edison $12,554 $— $1,130 $2,427 $24 $653 $644 $45,642 $3,418 (a) For Con Edison, the income tax expense/(benefit) on non-operating income was $13 million , $(16) million and $(40) million in 2017 , 2016 and 2015 , respectively. For CECONY, the income tax expense/(benefit) on non-operating income was $(3) million , $(14) million and $(14) million in 2017 , 2016 and 2015 , respectively. At December 31, 2017, Con Edison re-measured its deferred tax assets and liabilities based upon the 21 percent corporate income tax rate under the TCJA. As a result, Con Edison, decreased its federal income tax expense by $259 million ( $269 million , $11 million and $(21) million , respectively, for Clean Energy Businesses, Con Edison Transmission and the parent company). See “Other Regulatory Matters” in Note B and Note L to the financial statements in Item 8. (b) Parent company and consolidation adjustments. Other does not represent a business segment.

Derivative Instruments and Hedg

Derivative Instruments and Hedging Activities	12 Months Ended
	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments and Hedging Activities	Derivative Instruments and Hedging Activities Commodity Derivatives Con Edison’s subsidiaries hedge market price fluctuations associated with physical purchases and sales of electricity, natural gas, steam and, to a lesser extent, refined fuels by using derivative instruments including futures, forwards, basis swaps, options, transmission congestion contracts and financial transmission rights contracts. Derivatives are recognized on the consolidated balance sheet at fair value (see Note P), unless an exception is available under the accounting rules for derivatives and hedging. Qualifying derivative contracts that have been designated as normal purchases or normal sales contracts are not reported at fair value under the accounting rules. The fair values of the Companies’ commodity derivatives including the offsetting of assets and liabilities on the consolidated balance sheet at December 31, 2017 and 2016 were: (Millions of Dollars) 2017 2016 Balance Sheet Location Gross Amounts of Recognized Assets/ (Liabilities) Gross Amounts Offset Net Amounts of Assets/(Liabilities) (a) Gross Amounts of Recognized Assets/ (Liabilities) Gross Amounts Offset Net Amounts of Assets/(Liabilities) (a) Con Edison Fair value of derivative assets Current $83 $(51) $32 (b) $81 $(64) $17 (b) Noncurrent 10 (4) 6 49 (43) 6 Total fair value of derivative assets $93 $(55) $38 $130 $(107) $23 Fair value of derivative liabilities Current $(67) $50 $(17) $(138) $61 $(77) Noncurrent (43) 5 (38) (91) 52 (39) (c) Total fair value of derivative liabilities $(110) $55 $(55) $(229) $113 $(116) Net fair value derivative assets/(liabilities) $(17) $— $(17) (b) $(99) $6 $(93) (b)(c) CECONY Fair value of derivative assets Current $39 $(15) $24 (b) $52 $(45) $7 (b) Noncurrent 9 (4) 5 41 (35) 6 Total fair value of derivative assets $48 $(19) $29 $93 $(80) $13 Fair value of derivative liabilities Current $(26) $14 $(12) $(111) $45 $(66) Noncurrent (36) 4 (32) (77) 44 (33) Total fair value of derivative liabilities $(62) $18 $(44) $(188) $89 $(99) Net fair value derivative assets/(liabilities) $(14) $(1) $(15) (b) $(95) $9 $(86) (b) (a) Derivative instruments and collateral were offset on the consolidated balance sheet as applicable under the accounting rules. The Companies enter into master agreements for their commodity derivatives. These agreements typically provide offset in the event of contract termination. In such case, generally the non-defaulting party’s payable will be offset by the defaulting party’s payable. The non-defaulting party will customarily notify the defaulting party within a specific time period and come to an agreement on the early termination amount. (b) At December 31, 2017 and 2016 , margin deposits for Con Edison ( $12 million and $7 million , respectively) and CECONY ( $11 million and $7 million , respectively) were classified as derivative assets on the consolidated balance sheet, but not included in the table. Margin is collateral, typically cash, that the holder of a derivative instrument is required to deposit in order to transact on an exchange and to cover its potential losses with its broker or the exchange. (c) Does not include ($1) million for interest rate swap (see below). The Utilities generally recover their prudently incurred fuel, purchased power and gas costs, including hedging gains and losses, in accordance with rate provisions approved by the applicable state utility regulators. See "Recoverable Energy Costs" in Note A. In accordance with the accounting rules for regulated operations, the Utilities record a regulatory asset or liability to defer recognition of unrealized gains and losses on their electric and gas derivatives. As gains and losses are realized in future periods, they will be recognized as purchased power, gas and fuel costs in the Companies’ consolidated income statements. The Clean Energy Businesses record realized and unrealized gains and losses on their derivative contracts in purchased power, gas purchased for resale and non-utility revenue in the reporting period in which they occur. Management believes that these derivative instruments represent economic hedges that mitigate exposure to fluctuations in commodity prices. The following table presents the realized and unrealized gains or losses on commodity derivatives that have been deferred or recognized in earnings for the years ended December 31, 2017 and 2016 : Con Edison CECONY (Millions of Dollars) Balance Sheet Location 2017 2016 2017 2016 Pre-tax gains/(losses) deferred in accordance with accounting rules for regulated operations: Current Deferred derivative gains $3 $23 $4 $18 Noncurrent Deferred derivative gains — 1 — 2 Total deferred gains/(losses) $3 $24 $4 $20 Current Deferred derivative losses $51 $22 $49 $18 Current Recoverable energy costs (154) (212) (144) (194) Noncurrent Deferred derivative losses 4 2 5 4 Total deferred gains/(losses) $(99) $(188) $(90) $(172) Net deferred gains/(losses) $(96) $(164) $(86) $(152) Income Statement Location Pre-tax gain/(loss) recognized in income Purchased power expense $— $(101) (b) $— $— Gas purchased for resale 3 (112) — — Non-utility revenue 5 (a) 9 (b) — — Other operations and maintenance expense — 1 (c) — 1 (c) Total pre-tax gain/(loss) recognized in income $8 $(203) $— $1 (a) For the year ended December 31, 2017 , Con Edison recorded an immaterial unrealized pre-tax gain in non-utility operating revenue. (b) For the year ended December 31, 2016 , Con Edison recorded unrealized pre-tax gains and losses in non-utility operating revenue ( $5 million loss) and purchased power expense ( $11 million gain). (c) For the year ended December 31, 2016 , Con Edison and CECONY recorded an unrealized gain in other operations and maintenance expense ( $1 million ). The following table presents the hedged volume of Con Edison’s and CECONY’s derivative transactions at December 31, 2017 : Electric Energy (MWh) (a)(b) Capacity (MW) (a) Natural Gas (Dt) (a)(b) Refined Fuels (gallons) Con Edison 31,741,652 10,275 177,433,144 3,780,000 CECONY 29,696,600 5,100 169,790,000 3,780,000 (a) Volumes are reported net of long and short positions, except natural gas collars where the volumes of long positions are reported. (b) Excludes electric congestion and gas basis swap contracts which are associated with electric and gas contracts and hedged volumes. The Companies are exposed to credit risk related to transactions entered into primarily for the various energy supply and hedging activities by the Utilities and the Clean Energy Businesses. Credit risk relates to the loss that may result from a counterparty’s nonperformance. The Companies use credit policies to manage this risk, including an established credit approval process, monitoring of counterparty limits, netting provisions within agreements, collateral or prepayment arrangements, credit insurance and credit default swaps. The Companies measure credit risk exposure as the replacement cost for open energy commodity and derivative positions plus amounts owed from counterparties for settled transactions. The replacement cost of open positions represents unrealized gains, net of any unrealized losses where the Companies have a legally enforceable right to offset. At December 31, 2017 , Con Edison and CECONY had $103 million and $28 million of credit exposure in connection with energy supply and hedging activities, net of collateral, respectively. Con Edison’s net credit exposure consisted of $39 million with investment-grade counterparties, $29 million with independent system operators, $22 million with commodity exchange brokers, and $13 million with non-investment grade/non-rated counterparties. CECONY’s net credit exposure consisted of $17 million with investment-grade counterparties and $11 million with commodity exchange brokers. The collateral requirements associated with, and settlement of, derivative transactions are included in net cash flows from operating activities in the Companies’ consolidated statement of cash flows. Most derivative instrument contracts contain provisions that may require a party to provide collateral on its derivative instruments that are in a net liability position. The amount of collateral to be provided will depend on the fair value of the derivative instruments and the party’s credit ratings. The following table presents the aggregate fair value of the Companies’ derivative instruments with credit-risk-related contingent features that are in a net liability position, the collateral posted for such positions and the additional collateral that would have been required to be posted had the lowest applicable credit rating been reduced one level and to below investment grade at December 31, 2017 : (Millions of Dollars) Con Edison (a) CECONY (a) Aggregate fair value – net liabilities $39 $31 Collateral posted 68 63 Additional collateral (b) (downgrade one level from current ratings) — — Additional collateral (b)(c) (downgrade to below investment grade from current ratings) 29 22 (a) Non-derivative transactions for the purchase and sale of electricity and gas and qualifying derivative instruments, which have been designated as normal purchases or normal sales, are excluded from the table. These transactions primarily include purchases of electricity from independent system operators. In the event the Utilities and the Clean Energy Businesses were no longer extended unsecured credit for such purchases, the Companies would be required to post additional collateral of $8 million at December 31, 2017 . For certain other such non-derivative transactions, the Companies could be required to post collateral under certain circumstances, including in the event counterparties had reasonable grounds for insecurity. (b) The Companies measure the collateral requirements by taking into consideration the fair value amounts of derivative instruments that contain credit-risk-related contingent features that are in a net liabilities position plus amounts owed to counterparties for settled transactions and amounts required by counterparties for minimum financial security. The fair value amounts represent unrealized losses, net of any unrealized gains where the Companies have a legally enforceable right to offset. (c) Derivative instruments that are net assets have been excluded from the table. At December 31, 2017 , if Con Edison had been downgraded to below investment grade, it would have been required to post additional collateral for such derivative instruments of $18 million . Interest Rate Swap In December 2016, the Clean Energy Businesses acquired Coram Wind which holds an interest rate swap that terminates in June 2024, pursuant to which it pays a fixed-rate of 2.0855 percent and receives a LIBOR-based variable rate. The fair value of this interest rate swap was immaterial as of December 31, 2017 and a liability of $1 million as of December 31, 2016 on Con Edison’s consolidated balance sheet.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The accounting rules for fair value measurements and disclosures define fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date in a principal or most advantageous market. Fair value is a market-based measurement that is determined based on inputs, which refer broadly to assumptions that market participants use in pricing assets or liabilities. These inputs can be readily observable, market corroborated, or generally unobservable firm inputs. The Companies often make certain assumptions that market participants would use in pricing the asset or liability, including assumptions about risk, and the risks inherent in the inputs to valuation techniques. The Companies use valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs. The accounting rules for fair value measurements and disclosures established a fair value hierarchy, which prioritizes the inputs to valuation techniques used to measure fair value in three broad levels. The rules require that assets and liabilities be classified in their entirety based on the level of input that is significant to the fair value measurement. Assessing the significance of a particular input may require judgment considering factors specific to the asset or liability, and may affect the valuation of the asset or liability and their placement within the fair value hierarchy. The Companies classify fair value balances based on the fair value hierarchy defined by the accounting rules for fair value measurements and disclosures as follows: • Level 1 – Consists of assets or liabilities whose value is based on unadjusted quoted prices in active markets at the measurement date. An active market is one in which transactions for assets or liabilities occur with sufficient frequency and volume to provide pricing information on an ongoing basis. This category includes contracts traded on active exchange markets valued using unadjusted prices quoted directly from the exchange. • Level 2 – Consists of assets or liabilities valued using industry standard models and based on prices, other than quoted prices within Level 1, that are either directly or indirectly observable as of the measurement date. The industry standard models consider observable assumptions including time value, volatility factors and current market and contractual prices for the underlying commodities, in addition to other economic measures. This category includes contracts traded on active exchanges or in over-the-counter markets priced with industry standard models. • Level 3 – Consists of assets or liabilities whose fair value is estimated based on internally developed models or methodologies using inputs that are generally less readily observable and supported by little, if any, market activity at the measurement date. Unobservable inputs are developed based on the best available information and subject to cost benefit constraints. This category includes contracts priced using models that are internally developed and contracts placed in illiquid markets. It also includes contracts that expire after the period of time for which quoted prices are available and internal models are used to determine a significant portion of the value. Assets and liabilities measured at fair value on a recurring basis for the years ended December 31, 2017 and 2016 are summarized below. 2017 2016 (Millions of Dollars) Level 1 Level 2 Level 3 Netting Adjustment (e) Total Level 1 Level 2 Level 3 Netting Adjustment (e) Total Con Edison Derivative assets: Commodity (a)(b)(c) $5 $77 $7 $(39) $50 $14 $33 $7 $(24) $30 Other (a)(b)(d) 283 120 — — 403 222 111 — — 333 Total assets $288 $197 $7 $(39) $453 $236 $144 $7 $(24) $363 Derivative liabilities: Commodity (a)(b)(c) $8 $93 $6 $(52) $55 $4 $144 $6 $(38) $116 Interest Rate Swap (a)(b)(c)(f) — — — — — — 1 — — 1 Total liabilities $8 $93 $6 $(52) $55 $4 $145 $6 $(38) $117 CECONY Derivative assets: Commodity (a)(b)(c) $3 $40 $4 $(7) $40 $10 $19 $1 $(10) $20 Other (a)(b)(d) 260 114 — — 374 200 106 — — 306 Total assets $263 $154 $4 $(7) $414 $210 $125 $1 $(10) $326 Derivative liabilities: Commodity (a)(b)(c) $5 $57 $— $(18) $44 $1 $124 $— $(26) $99 (a) The Companies’ policy is to review the fair value hierarchy and recognize transfers into and transfers out of the levels at the end of each reporting period. Con Edison and CECONY had $11 million and $10 million , respectively, of commodity derivative liabilities transferred from level 3 to level 2 during the year ended December 31, 2017 because of availability of observable market data due to the decrease in the terms of certain contracts from beyond three years as of September 30, 2017 to less than three years as of December 31, 2017 . There were no transfers between levels 1 , 2 and 3 for the year ended December 31, 2016 . (b) Level 2 assets and liabilities include investments held in the deferred compensation plan and/or non-qualified retirement plans, exchange-traded contracts where there is insufficient market liquidity to warrant inclusion in Level 1, certain over-the-counter derivative instruments for electricity, refined products and natural gas. Derivative instruments classified as Level 2 are valued using industry standard models that incorporate corroborated observable inputs; such as pricing services or prices from similar instruments that trade in liquid markets, time value and volatility factors. (c) The accounting rules for fair value measurements and disclosures require consideration of the impact of nonperformance risk (including credit risk) from a market participant perspective in the measurement of the fair value of assets and liabilities. At December 31, 2017 and 2016 , the Companies determined that nonperformance risk would have no material impact on their financial position or results of operations. (d) Other assets are comprised of assets such as life insurance contracts within the deferred compensation plan and non-qualified retirement plans. (e) Amounts represent the impact of legally-enforceable master netting agreements that allow the Companies to net gain and loss positions and cash collateral held or placed with the same counterparties. (f) See Note O. The employees in the Companies’ risk management group develop and maintain the Companies’ valuation policies and procedures for, and verify pricing and fair value valuation of, commodity derivatives. Under the Companies’ policies and procedures, multiple independent sources of information are obtained for forward price curves used to value commodity derivatives. Fair value and changes in fair value of commodity derivatives are reported on a monthly basis to the Companies’ risk committees, comprised of officers and employees of the Companies that oversee energy hedging at the Utilities and the Clean Energy Businesses. The risk management group reports to the Companies’ Vice President and Treasurer. Fair Value of Level 3 at December 31, 2017 (Millions of Dollars) Valuation Techniques Unobservable Inputs Range Con Edison — Commodity Electricity $(1) Discounted Cash Flow Forward energy prices (a) $15.52-$115.00 per MWh Discounted Cash Flow Forward capacity prices (a) $1.50-$12.50 per kW-month Transmission Congestion Contracts $2 Discounted Cash Flow Inter-zonal forward price curves adjusted for historical zonal losses (b) $0.19-$3.57 per MWh Total Con Edison — Commodity $1 CECONY — Commodity Electricity $3 Discounted Cash Flow Forward capacity prices (a) $2.35-$12.50 per kW-month Transmission Congestion Contracts $1 Discounted Cash Flow Inter-zonal forward price curves adjusted for historical zonal losses (b) $0.51-$3.00 per MWh Total CECONY — Commodity $4 (a) Generally, increases/(decreases) in this input in isolation would result in a higher/(lower) fair value measurement. (b) Generally, increases/(decreases) in this input in isolation would result in a lower/(higher) fair value measurement. The table listed below provides a reconciliation of the beginning and ending net balances for assets and liabilities measured at fair value for the years ended December 31, 2017 and 2016 and classified as Level 3 in the fair value hierarchy: Con Edison CECONY (Millions of Dollars) 2017 2016 2017 2016 Beginning balance as of January 1, $1 $6 $1 $8 Included in earnings 8 (7) 2 (1) Included in regulatory assets and liabilities (13) (6) (7) (6) Purchases 2 4 1 2 Sales — 4 — — Settlements (8) — (3) (2) Transfer out of level 3 11 — 10 — Ending balance as of December 31, $1 $1 $4 $1 For the Utilities, realized gains and losses on Level 3 commodity derivative assets and liabilities are reported as part of purchased power, gas and fuel costs. The Utilities generally recover these costs in accordance with rate provisions approved by the applicable state public utilities regulators. See Note A. Unrealized gains and losses for commodity derivatives are generally deferred on the consolidated balance sheet in accordance with the accounting rules for regulated operations. For the Clean Energy Businesses, realized and unrealized gains and losses on Level 3 commodity derivative assets and liabilities are reported in non-utility revenues ( $2 million gain and immaterial ) and purchased power costs (immaterial and $6 million loss) on the consolidated income statement for the years ended December 31, 2017 and 2016 , respectively. The change in fair value relating to Level 3 commodity derivative assets and liabilities held at December 31, 2017 and 2016 is included in non-utility revenues ( $2 million gain and immaterial) and purchased power costs (immaterial and $1 million loss) on the consolidated income statement for the years ended December 31, 2017 and 2016 , respectively.

Variable Interest Entities

Variable Interest Entities	12 Months Ended
	Dec. 31, 2017
Equity Method Investments and Joint Ventures [Abstract]
Variable Interest Entities	Variable Interest Entities The accounting rules for consolidation address the consolidation of a variable interest entity (VIE) by a business enterprise that is the primary beneficiary. A VIE is an entity that does not have a sufficient equity investment at risk to permit it to finance its activities without additional subordinated financial support, or whose equity investors lack the characteristics of a controlling financial interest. The primary beneficiary is the business enterprise that has the power to direct the activities of the VIE that most significantly impact the VIE’s economic performance and either absorbs a significant amount of the VIE’s losses or has the right to receive benefits that could be significant to the VIE. The Companies enter into arrangements including leases, partnerships and electricity purchase agreements, with various entities. As a result of these arrangements, the Companies retain or may retain a variable interest in these entities. CECONY CECONY has an ongoing long-term electricity purchase agreement with Brooklyn Navy Yard Cogeneration Partners, LP, a potential VIE. In April 2017 , CECONY's long-term electricity purchase agreement with Cogen Technologies Linden Venture, LP, another potential VIE, expired. In 2017 , requests were made of these counterparties for information necessary to determine whether the entity was a VIE and whether CECONY is the primary beneficiary; however, the information was not made available. See Note I for information on these electricity purchase agreements, the payments pursuant to which constitute CECONY's maximum exposure to loss with respect to the potential VIEs. Con Edison Development Con Edison has a variable interest in OCI Solar San Antonio 4 LLC (Texas Solar 4), which is a consolidated entity in which Con Edison Development has an 80 percent membership interest. Con Edison is the primary beneficiary since the power to direct the activities that most significantly impact the economics of Texas Solar 4 is held by Con Edison Development. Texas Solar 4 owns a project company that developed a 40 MW (AC) solar electric production project in Texas. Electricity generated by the project is sold to the City of San Antonio pursuant to a long-term power purchase agreement. At December 31, 2017 and 2016 , Con Edison’s consolidated balance sheet includes $26 million and $54 million in net assets (as detailed in the table below) respectively and the noncontrolling interest of the third party of $7 million related to Texas Solar 4. Earnings for the years ended December 31, 2017 and 2016 were immaterial. (Millions of Dollars) 2017 2016 Restricted cash $5 $8 Non-utility property, less accumulated depreciation of $12 and $9, respectively 101 104 Other assets 8 43 Total assets (a) $114 $155 Long-term debt due within one year $2 $3 Other liabilities 28 38 Long-term debt 58 60 Total liabilities (b) $88 $101 (a) The assets of Texas Solar 4 represent assets of a consolidated VIE that can be used only to settle obligations of the consolidated VIE. (b) The liabilities of Texas Solar 4 represent liabilities of a consolidated VIE for which creditors do not have recourse to the general credit of the primary beneficiary. The following table summarizes the VIEs in which Con Edison Development has entered into as of December 31, 2017 : Project Name (a) Generating Capacity (b) (MW AC) Power Purchase Agreement Term in Years Year of Initial Investment Location Maximum Millions of Dollars ) (c) Copper Mountain Solar 3 128 20 2014 Nevada $175 Mesquite Solar 1 83 20 2013 Arizona 103 Copper Mountain Solar 2 75 25 2013 Nevada 82 California Solar 55 25 2012 California 63 Broken Bow II 38 25 2014 Nebraska 44 Texas Solar 4 32 25 2014 Texas 19 (a) With the exception of Texas Solar 4, Con Edison’s ownership interest is 50 percent and these projects are accounted for using the equity method of accounting. With the exception of Texas Solar 4, Con Edison is not the primary beneficiary since the power to direct the activities that most significantly impact the economics of the entities are shared equally between Con Edison Development and third parties. Con Edison’s ownership interest in Texas Solar 4 is 80 percent and is consolidated in the financial statements. Con Edison is the primary beneficiary since the power to direct the activities that most significantly impact the economics of Texas Solar 4 is held by Con Edison Development. (b) Represents Con Edison Development’s ownership interest in the project. (c) For investments accounted for under the equity method, maximum exposure is equal to the carrying value of the investment on the consolidated balance sheet. For consolidated investments, such as Texas Solar 4, maximum exposure is equal to the net assets of the project on the consolidated balance sheet less any applicable noncontrolling interest ( $7 million for Texas Solar 4). Con Edison did not provide any financial or other support during the year that was not previously contractually required.

Asset Retirement Obligations

Asset Retirement Obligations	12 Months Ended
	Dec. 31, 2017
Asset Retirement Obligation Disclosure [Abstract]
Asset Retirement Obligations	Asset Retirement Obligations The Companies recognize a liability at fair value for legal obligations associated with the retirement of long-lived assets in the period in which they are incurred, or when sufficient information becomes available to reasonably estimate the fair value of such legal obligations. When the liability is initially recorded, asset retirement costs are capitalized by increasing the carrying amount of the related asset. The liability is accreted to its present value each period and the capitalized cost is depreciated over the useful life of the related asset. The fair value of the asset retirement obligation liability is measured using expected future cash flows discounted at credit-adjusted risk-free rates, historical information, and where available, quoted prices from outside contractors. The Companies evaluate these assumptions underlying the asset retirement obligation liability on an annual basis or as frequently as needed. The Companies recorded asset retirement obligations associated with the removal of asbestos and asbestos-containing material in their buildings (other than the structures enclosing generating stations and substations), electric equipment and steam and gas distribution systems. The Companies also recorded asset retirement obligations relating to gas and oil pipelines abandoned in place and municipal infrastructure support. The Companies did not record an asset retirement obligation for the removal of asbestos associated with the structures enclosing generating stations and substations. For these building structures, the Companies were unable to reasonably estimate their asset retirement obligations because the Companies were unable to estimate the undiscounted retirement costs or the retirement dates and settlement dates. The amount of the undiscounted retirement costs could vary considerably depending on the disposition method for the building structures, and the method has not been determined. The Companies anticipate continuing to use these building structures in their businesses for an indefinite period, and so the retirement dates and settlement dates are not determinable. Con Edison recorded asset retirement obligations for the removal of the Clean Energy Businesses’ solar and wind equipment related to projects located on property that is not owned by them and the term of the arrangement is finite including any renewal options. Con Edison did not record asset retirement obligations for the Clean Energy Businesses’ projects that are located on property that is owned by them because they expect that the equipment will continue to generate electricity at these facilities long past the manufacturer’s warranty at minimal operating expense. Therefore, Con Edison was unable to reasonably estimate the retirement date of this equipment. The Utilities include in depreciation rates the estimated removal costs, less salvage, for utility plant assets. The amounts related to removal costs that are associated with asset retirement obligations are classified as an asset retirement liability. Pursuant to accounting rules for regulated operations, future removal costs that do not represent legal asset retirement obligations are recorded as regulatory liabilities. Accretion and depreciation expenses related to removal costs that represent legal asset retirement obligations are applied against the Companies’ regulatory liabilities. Asset retirement costs that are recoverable from customers are recorded as regulatory liabilities to reflect the timing difference between costs recovered through the rate-making process and recognition of costs. At December 31, 2017 , the liabilities for asset retirement obligations of Con Edison and CECONY were $314 million and $287 million , respectively. At December 31, 2016 , the liabilities for asset retirement obligations of Con Edison and CECONY were $246 million and $227 million , respectively. The change in liabilities at December 31, 2017 was due to changes in estimated cash flows of $98 million and $91 million for Con Edison and CECONY, respectively, and accretion expense of $10 million and $9 million for Con Edison and CECONY, respectively. The changes were offset by liabilities settled of $40 million for both Con Edison and CECONY. Con Edison and CECONY also recorded reductions of $36 million and $37 million during the years ended December 31, 2017 and 2016 , respectively, to the regulatory liability associated with cost of removal to reflect depreciation and interest expense.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions CECONY provides administrative and other services to, and receives such services from, Con Edison and its other subsidiaries pursuant to cost allocation procedures approved by the NYSPSC. The costs of administrative and other services provided by CECONY to, and received by it from, Con Edison and its other subsidiaries for the years ended December 31, 2017 , 2016 and 2015 were as follows: CECONY (Millions of Dollars) 2017 2016 2015 Cost of services provided $111 $108 $99 Cost of services received 64 64 60 In addition, CECONY and O&R have joint gas supply arrangements, in connection with which CECONY sold to O&R $66 million , $47 million and $54 million of natural gas for the years ended December 31, 2017 , 2016 and 2015 , respectively. These amounts are net of the effect of related hedging transactions. The Utilities perform work and incur expenses on behalf of NY Transco, a company in which CET Electric has a 45.7 percent equity interest. The Utilities bill NY Transco for such work and expenses in accordance with established policies. For the year ended December 31, 2017 and 2016, the amounts billed by the Utilities to NY Transco were immaterial. In May 2016, CECONY transferred certain electric transmission projects to NY Transco. See Note U. CECONY has storage and wheeling service contracts with Stagecoach Gas Services LLC (Stagecoach), a joint venture formed by a subsidiary of CET Gas and a subsidiary of Crestwood Equity Partners LP (Crestwood). In addition, CECONY is the replacement shipper on one of Crestwood’s firm transportation agreements with Tennessee Gas Pipeline Company LLC. From the inception of the joint venture in June 2016 through December 31, 2017 , the amount of storage and wheeling services received by CECONY from Stagecoach was $49 million . In addition, the Clean Energy Businesses entered into two electricity sales agreements with Stagecoach under which the amounts received in 2017 and 2016 were immaterial. CECONY has a 20 -year transportation contract with Mountain Valley Pipeline, LLC (MVP) for 250,000 dekatherms per day of capacity. CET Gas holds a 12.5 percent equity interest in MVP. In October 2017, the Environmental Defense Fund and the Natural Resource Defense Council requested the NYSPSC to prohibit CECONY from recovering costs under its MVP contract. For the year ended December 31, 2017, CECONY incurred no costs under the contract. CECONY had a financial electric capacity contract with Con Edison Energy for the period May 2016 through April 2017. For the years ended December 31, 2017 and 2016, Con Edison Energy's realized gains under this contract were $3 million and immaterial, respectively. FERC has authorized CECONY through 2019 to lend funds to O&R from time to time, for periods of not more than 12 months , in amounts not to exceed $250 million outstanding at any time, at prevailing market rates. There were no outstanding loans to O&R at December 31, 2017 and 2016 .

New Financial Accounting Standa

New Financial Accounting Standards	12 Months Ended
	Dec. 31, 2017
Accounting Changes and Error Corrections [Abstract]
New Financial Accounting Standards	New Financial Accounting Standards In January 2018, the Companies adopted Accounting Standards Update (ASU) No. 2014-09, “Revenue from Contracts with Customers (Topic 606),” including the amendments thereto, (the New Standard) using the modified retrospective approach the New Standard permitted. The New Standard supersedes the revenue recognition requirements within Accounting Standards Codification Topic 605, “Revenue Recognition,” and most industry-specific guidance (the Superseded Standard). The purpose of the New Standard is to create a consistent framework for revenue recognition. The New Standard clarifies how to measure and recognize revenue arising from customer contracts to depict the transfer of goods or services in an amount that reflects the consideration the entity expects to receive. The New Standard also clarifies key areas including principal/agent considerations, performance obligations, licensing, sales taxes, noncash consideration, and contracts. The majority of Con Edison’s’ revenues and substantially all of CECONY’s revenues are derived from the provision of electric, gas, and steam service to customers pursuant to the terms of tariffs approved by the NYSPSC or NJBPU. For such service, the Companies expect that the revenue from contracts with customers for a period that will be recorded under the New Standard will be equivalent to the revenue for the period that would have been recorded under the Superseded Standard. Most of Con Edison’s other revenues are derived from the Clean Energy Businesses’ sale of energy-related products and services, operation of renewable and energy infrastructure projects, and sale of renewable energy credits. For such businesses, Con Edison expects that the revenue from contracts with customers for a period that will be recorded under the New Standard will not be materially different from the revenue for the period that would have been recorded under the Superseded Standard. Under the modified retrospective method of adoption, prior year reported results are not restated and a cumulative-effect adjustment, if applicable, is recorded to retained earnings at January 1, 2018. As of January 1, 2018, the cumulative-effect adjustment was not material to the Companies. The Companies also plan to use certain practical expedients including applying this guidance to open contracts at the date of adoption and recognizing revenues for certain contracts under the invoice practical expedient. Such expedients allow revenue recognition to be consistent with invoiced amounts (including estimated billings) provided certain criteria are met, including consideration of whether the invoiced amounts reasonably represent the value provided to customers. The adoption of the New Standard will not have a material impact on the Companies’ financial statements, results of operations, and liquidity, including the presentation of revenues in their consolidated income statements. The adoption of the New Standard will not require a change in the Companies’ internal control over financial reporting that is reasonably likely to materially affect their internal control over financial reporting. In February 2016, the FASB issued amendments on financial reporting of leasing transactions through ASU No. 2016-02, “Leases (Topic 842)." The amendments require lessees to recognize assets and liabilities on the balance sheet and disclose key information about leasing arrangements. Lessees will need to recognize a right-of-use asset and a lease liability for virtually all of their leases (other than leases that meet the definition of a short-term lease). Lessor accounting is similar to the current model, but updated to align with certain changes to the lessee model. For income statement purposes, the pattern of expense recognition will depend on whether transactions are designated as operating leases or finance leases. In January 2018, the FASB issued amendments on the lease standard’s application to land easements through ASU No. 2018-01, “Leases (Topic 842): Land Easement Practical Expedient for Transition to Topic 842.” The amendments allow an entity to not evaluate under Topic 842 land easements that exist or expired before the entity’s adoption of Topic 842 and that were not previously accounted for as leases under the current lease standard. The amendments are effective for reporting periods beginning after December 15, 2018. Early adoption is permitted. The amendments must be adopted using a modified retrospective transition and provide for certain practical expedients. Based on the existing portfolio of leases at implementation, for leases currently classified as operating leases, the Companies expect to recognize on the statements of financial position right-of-use assets and lease liabilities. The Companies are in the process of evaluating the potential impact of the new guidance on the Companies’ results of operations and liquidity. In January 2017, the FASB issued amendments to the guidance for Business Combinations through ASU 2017-01, “Business Combinations (Topic 805): Clarifying the Definition of a Business.” The amendments in this update clarify the definition of a business and provide guidance on evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. For public entities, the amendments are effective for reporting periods beginning after December 15, 2017. The application of this guidance is not expected to have a material impact on the Companies’ financial position, results of operations and liquidity. In January 2017, the FASB issued amendments to the guidance for the subsequent measurement of goodwill through ASU 2017-04, “Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment.” The amendments in this update simplify goodwill impairment testing by eliminating Step 2 of the goodwill impairment test wherein an entity has to compute the implied fair value of goodwill by performing procedures to determine the fair value of its assets and liabilities. Under the new guidance, an entity should recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value up to the total amount of goodwill allocated to that reporting unit. For public entities, the amendments are effective for reporting periods beginning after December 15, 2019. Early adoption is permitted. The application of this guidance is not expected to have a material impact on the Companies’ financial position, results of operations and liquidity. In February 2017, the FASB issued amendments to the guidance for other income through ASU 2017-05, “Other Income-Gains and Losses from the Derecognition of Nonfinancial Assets (Subtopic 610-20): Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Nonfinancial Assets.” The amendments in this update clarify the scope of assets within Subtopic 610-20 and add guidance for partial sales of nonfinancial assets. The amendments are effective upon the adoption of ASU 2014-09, and therefore will be effective for reporting periods beginning after December 15, 2017. The application of this guidance is not expected to have a material impact on the Companies’ financial position, results of operations and liquidity. In March 2017, the FASB issued amendments to the guidance for retirement benefits through ASU 2017-07, “Compensation-Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost.” The amendments in this update modify the presentation of net benefit cost, where the service component must be disaggregated from the other components of net benefit cost and be presented in the same line item as current employee compensation costs. The remaining components of the net benefit cost should be presented outside of income from operations. Additionally, the update allows only the service cost component to be eligible for capitalization. For public entities, the amendments are effective for reporting periods beginning after December 15, 2017. The guidance allows a practical expedient that permits the use of amounts disclosed in prior-period financial statements as appropriate estimates when applying the presentation requirements retrospectively. The Companies have elected to use the practical expedient under ASU 2017-07. The application of this guidance is not expected to have a material impact on the Companies’ financial position, results of operations and liquidity. In March 2017, the FASB issued amendments to the guidance for debt securities through ASU 2017-08, “Receivables-Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities.” The amendments in this update shorten the amortization period for certain callable debt securities held at a premium. The amendments do not require an accounting change for securities held at a discount; the discount continues to be amortized to maturity. For public entities, the amendments are effective for reporting periods beginning after December 15, 2018. Early adoption is permitted. The application of this guidance is not expected to have a material impact on the Companies’ financial position, results of operations and liquidity. In May 2017, the FASB issued amendments to the guidance for stock compensation through ASU 2017-09, “Compensation-Stock Compensation (Topic 718): Scope of Modification Accounting.” The amendments in this update specify that changes to value, vesting conditions, or classification of an existing share-based payment award require application of modification accounting in Topic 718. For public entities, the amendments are effective for reporting periods beginning after December 15, 2017.The application of this guidance is not expected to have a material impact on the Companies’ financial position, results of operations and liquidity. In August 2017, the FASB issued amendments to the guidance for derivatives and hedging through ASU 2017-12, “Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities.” The amendments in this update provide greater clarification on hedge accounting for risk components, presentation and disclosure of hedging instruments, and overall targeted improvements to simplify hedge accounting. For public entities, the amendments are effective for reporting periods beginning after December 15, 2018. Early adoption is permitted. The Companies are in the process of evaluating the potential impact of the new guidance on the Companies’ financial position, results of operations and liquidity. In February 2018, the FASB issued amendments to the guidance for reporting comprehensive income through ASU 2018-02, “Income Statement-Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income.” The amendments allow a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the TCJA. For public entities, the amendments are effective for reporting periods beginning after December 15, 2018. Early adoption is permitted. The Companies are in the process of evaluating the potential impact of the new guidance on the Companies’ financial position, results of operations and liquidity.

Acquisitions, Investments and D

Acquisitions, Investments and Dispositions	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Acquisitions, Investments and Dispositions	Acquisitions, Investments and Dispositions Acquisitions and Investments Texas Solar 7 In January 2016, Con Edison Development acquired a 100 percent equity interest in a company that is the owner of a 106 MW (AC) solar electric production project in Texas (Texas Solar 7) for $227 million , as to which $218 million was recorded as non-utility construction work in progress and the remaining $9 million was recorded as other receivables. The project commenced commercial operation in the third quarter of 2016. The project has been financed, in part, by debt secured by the project. Electricity generated by this project is to be purchased by the City of San Antonio pursuant to a long-term power purchase agreement. At December 31, 2017 and 2016, net assets of the project were approximately $137 million and $127 million , respectively, (including $41 million for an intangible asset pertaining to the value of the power purchase agreement). Con Edison's equity interest in Texas Solar 7 is consolidated in the financial statements. Mountain Valley Pipeline In January 2016, CET Gas acquired a 12.5 percent equity interest in MVP, a company developing a proposed gas transmission project in West Virginia and Virginia. The company's initial contribution to MVP was $18 million . At December 31, 2017 and 2016 , CET Gas' investment in MVP was $98 million and $48 million , respectively. MVP has indicated that the project has an estimated total cost of $3,000 million to $3,500 million and is targeted to be fully in-service during the fourth quarter of 2018. Con Edison is accounting for its equity interest in MVP as an equity method investment. NY Transco In May 2016, CECONY transferred certain electric transmission projects to NY Transco, a company in which CET Electric has a 45.7 percent equity interest, for a purchase price of $122 million and an $8 million payment for associated easement rights. At December 31, 2017 and 2016 , CET Electric's investment in NY Transco was $53 million and $51 million , respectively. Con Edison is accounting for its equity interest in NY Transco as an equity method investment. Stagecoach Gas Services In April 2016, a CET Gas subsidiary agreed with a subsidiary of Crestwood to form a joint venture to own, operate and further develop existing gas pipeline and storage businesses located in northern Pennsylvania and southern New York. The transaction was substantially completed in June 2016, and the remainder was completed in November 2016. Crestwood contributed businesses to a new entity, Stagecoach, and the CET Gas subsidiary contributed $974 million for a 50 percent equity interest in Stagecoach. At December 31, 2017 and 2016 , CET Gas' investment in Stagecoach was $971 million and $992 million , respectively. Con Edison is accounting for its equity interest in Stagecoach as an equity method investment. Pilesgrove In June 2016, Con Edison Development recorded an $8 million ( $5 million , net of taxes) impairment charge on its 50 percent equity interest in Pilesgrove Solar, LLC (Pilesgrove), which owns an 18 MW (AC) solar electric production project in New Jersey. In August 2016, Con Edison Development acquired the remaining 50 percent equity interest in Pilesgrove for a purchase price of approximately $16 million and recorded a bargain purchase gain of $8 million ( $5 million , net of taxes); $45 million was recorded as non-utility property and the remaining $3 million was recorded as current assets. The impairment charge and bargain purchase gain are included in Investment and other income on Con Edison’s consolidated income statement. At December 31, 2017 and 2016 , net assets of the project were approximately $45 million . Con Edison's equity interest in Pilesgrove is consolidated in the financial statements. Panoche Valley In October 2016, Con Edison Development, which owned a 50 percent equity interest, acquired the remaining 50 percent equity interest in Panoche Holdings, LLC (Panoche), which is developing a 240 MW (AC) solar electric production project in California, for cash consideration of $28 million and the release of Panoche from its obligation under a $242 million note payable to Con Edison Development. At the time of acquisition, $290 million was recorded as non-utility construction work in process, $22 million was recorded as other assets and $14 million was recorded as current liabilities. A part of the project commenced commercial operation in December 2017. At December 31, 2017 and 2016 , net assets of the project were approximately $435 million and $388 million , respectively. Con Edison's equity interest in Panoche is consolidated in the financial statements. Coram Wind In December 2016, Con Edison Development acquired a 100 percent equity interest in Coram California Development, LP (Coram), which owns a 102 MW (AC) wind electric production project in California for $97 million , as to which $191 million was recorded as non-utility property, $78 million was recorded as an intangible asset, $8 million of restricted cash was recorded as other current assets, and $180 million was recorded as long term debt. In December 2017, an increase of $22 million was recorded to the intangible asset and a corresponding decrease was recorded to non-utility property. The intangible asset pertains to the value of the project's power purchase agreement, relative to current market rates, and is being amortized over the life of the agreement. The project commenced commercial operation in March 2012. At December 31, 2017 and 2016 , net assets of the project were approximately $87 million and $96 million , respectively. Con Edison's equity interest in Coram is consolidated in the financial statements. Dispositions Pike County Light & Power Company (Pike) In October 2015, O&R entered into an agreement to sell Pike to Corning Natural Gas Holding Corporation (Corning). In August 2016, the sale was completed. O&R received cash consideration of $15 million for the sale. O&R has agreed to provide transition services to Corning for operations and customer support for a period of up to 18 months subsequent to the sale. In addition, O&R will continue to purchase and sell to Pike electric and gas commodity for three years . Pike has an option to extend the commodity procurement service for up to an additional three years . At September 30, 2015, O&R recorded an impairment charge of $5 million ( $3 million , net of taxes), representing the difference between the carrying amount of Pike’s assets and the estimated sales proceeds. Con Edison Solutions' Retail Electric Supply Business In July 2016, Con Edison Solutions entered into an agreement to sell the assets of its retail electric supply business (including retail contracts, related derivative instruments, information systems, and accounts receivable) to a subsidiary of Exelon Corporation (Exelon). In September 2016, the sale was completed for cash consideration of $235 million , subject to working capital adjustments. The sale resulted in a gain of $104 million ( $56 million , net of taxes), inclusive of a $65 million ( $42 million , net of taxes) gain on derivative instruments. The tax effect of the sale included $16 million ( $10 million , net of federal tax) of state taxes related to a change in the apportionment of state income taxes. Con Edison Solutions provided transition services to the Exelon subsidiary for operations and customer support through January 2018 during a portion of which period certain guarantees or other credit support provided by Con Edison in connection with the retail electric supply business continued in effect. See Note H. Upton 2 In May 2017, Con Edison Development sold Upton 2, a development stage solar electric production project, for $11 million to Vistra Asset Co. and recorded a $1 million gain on sale ( $0.7 million , net of taxes). In addition, Con Edison Development agreed to perform the engineering, procurement and construction for the 180 MW (AC) project, which is expected to be substantially completed in 2018.

Schedule I - Condensed Financia

Schedule I - Condensed Financial Information	12 Months Ended
	Dec. 31, 2017
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Schedule I - Condensed Financial Information	Schedule I Condensed Financial Information of Consolidated Edison, Inc. (a) Condensed Statement of Income and Comprehensive Income (Parent Company Only) For the Years Ended December 31, (Millions of Dollars, except per share amounts) 2017 2016 2015 Equity in earnings of subsidiaries $1,544 $1,254 $1,195 Other income (deductions), net of taxes 31 32 27 Interest expense (50) (41) (29) Net Income $1,525 $1,245 $1,193 Comprehensive Income $1,526 $1,252 $1,204 Net Income Per Share – Basic $4.97 $4.15 $4.07 Net Income Per Share – Diluted $4.94 $4.12 $4.05 Dividends Declared Per Share $2.76 $2.68 $2.60 Average Number Of Shares Outstanding—Basic (In Millions) 307.1 300.4 293.0 Average Number Of Shares Outstanding—Diluted (In Millions) 308.8 301.9 294.4 (a) These financial statements, in which Con Edison’s subsidiaries have been included using the equity method, should be read together with its consolidated financial statements and the notes thereto appearing above. Condensed Financial Information of Consolidated Edison, Inc. (a) Condensed Statement of Cash Flows (Parent Company Only) For the Years Ended December 31, (Millions of Dollars) 2017 2016 2015 Net Income $1,525 $1,245 $1,193 Equity in earnings of subsidiaries (1,544) (1,254) (1,195) Dividends received from: CECONY 796 744 872 O&R 44 43 81 Clean Energy Businesses 12 10 8 Con Edison Transmission 8 — — Change in Assets: Special deposits — — — Income taxes receivable 34 87 58 Other – net 21 (152) (382) Net Cash Flows from Operating Activities 896 723 635 Investing Activities Contributions to subsidiaries (434) (691) (15) Long term debt receivable from affiliated companies — (900) — Net Cash Flows Used in Investing Activities (434) (1,591) (15) Financing Activities Net proceeds of short-term debt (53) (53) 162 Issuance of long-term debt 400 900 — Retirement of long-term debt (402) (2) (2) Debt issuance costs (2) (5) — Issuance of common shares for stock plans, net of repurchases 51 51 1 Issuance of common shares - public offering 343 702 — Common stock dividends (803) (763) (733) Net Cash Flows Used in Financing Activities (466) 830 (572) Net Change for the Period (4) (38) 48 Balance at Beginning of Period 13 51 3 Balance at End of Period $9 $13 $51 (a) These financial statements, in which Con Edison’s subsidiaries have been included using the equity method, should be read together with its consolidated financial statements and the notes thereto appearing above. Condensed Financial Information of Consolidated Edison, Inc. (a) Condensed Balance Sheet (Parent Company Only) December 31, (Millions of Dollars) 2017 2016 Assets Current Assets Cash and temporary cash investments $9 $13 Income taxes receivable 45 79 Accounts receivable from affiliated companies 687 702 Prepayments 36 24 Other current assets 18 19 Total Current Assets 795 837 Investments in subsidiaries 15,110 13,991 Goodwill 406 406 Deferred income tax 18 42 Long term debt receivable from affiliated companies 900 900 Other noncurrent assets 2 16 Total Assets $17,231 $16,192 Liabilities and Shareholders’ Equity Current Liabilities Long-term debt due within one year $2 $2 Notes payable 331 384 Accounts payable to affiliated companies 274 288 Other current liabilities 10 22 Total Current Liabilities 617 696 Total Liabilities 617 696 Long-term debt 1,195 1,198 Shareholders’ Equity Common stock, including additional paid-in capital 6,331 5,887 Retained earnings 9,088 8,411 Total Shareholders’ Equity 15,419 14,298 Total Liabilities and Shareholders’ Equity $17,231 $16,192 (a) These financial statements, in which Con Edison’s subsidiaries have been included using the equity method, should be read together with its consolidated financial statements and the notes thereto appearing above.

Schedule II - Valuation and Qua

Schedule II - Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2017
Valuation and Qualifying Accounts [Abstract]
Schedule II - Valuation and Qualifying Accounts	Schedule II Valuation and Qualifying Accounts For the Years Ended December 31, 2017 , 2016 and 2015 COLUMN C Additions Company (Millions of Dollars) COLUMN A Description COLUMN B Balance at Beginning of Period (1) Charged To Costs And Expenses (2) Charged To Other Accounts COLUMN D Deductions (b) COLUMN E Balance At End of Period Con Edison Allowance for uncollectible accounts (a): 2017 $83 $64 $— $77 $70 2016 $96 $63 $— $76 $83 2015 $106 $77 $— $87 $96 CECONY Allowance for uncollectible accounts (a): 2017 $78 $60 $— $73 $65 2016 $91 $57 $— $70 $78 2015 $98 $69 $— $76 $91 (a) This is a valuation account deducted in the balance sheet from the assets (Accounts receivable - customers and Other receivables) to which they apply. (b) Accounts written off less cash collections, miscellaneous adjustments and amounts reinstated as receivables previously written off.

Summary of Significant Accoun34

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation The Companies’ consolidated financial statements include the accounts of their respective majority-owned subsidiaries, and variable interest entities (see Note Q), as required. All intercompany balances and transactions have been eliminated.
Accounting Policies	Accounting Policies The accounting policies of Con Edison and its subsidiaries conform to generally accepted accounting principles in the United States of America (GAAP). For the Utilities, these accounting principles include the accounting rules for regulated operations and the accounting requirements of the Federal Energy Regulatory Commission (FERC) and the state regulators having jurisdiction. The accounting rules for regulated operations specify the economic effects that result from the causal relationship of costs and revenues in the rate-regulated environment and how these effects are to be accounted for by a regulated enterprise. Revenues intended to cover some costs may be recorded either before or after the costs are incurred. If regulation provides assurance that incurred costs will be recovered in the future, these costs would be recorded as deferred charges or “regulatory assets” under the accounting rules for regulated operations. If revenues are recorded for costs that are expected to be incurred in the future, these revenues would be recorded as deferred credits or “regulatory liabilities” under the accounting rules for regulated operations. The Utilities’ principal regulatory assets and liabilities are detailed in Note B. The Utilities are receiving or being credited with a return on all of their regulatory assets for which a cash outflow has been made, and are paying or being charged with a return on all of their regulatory liabilities for which a cash inflow has been received. The Utilities’ regulatory assets and liabilities will be recovered from customers, or applied for customer benefit, in accordance with rate provisions approved by the applicable state regulators.
Plant and Depreciation	Non – Utility Plant Non-utility plant is stated at original cost. For Con Edison, non – utility plant consists primarily of the Clean Energy Businesses’ renewable electric production and gas storage. For the Utilities, non – utility plant consists of land and conduit for telecommunication use. Depreciation on these assets is computed using the straight-line method for financial statement purposes over their estimated useful lives, which range from 3 to 30 years . Plant and Depreciation Utility Plant Utility plant is stated at original cost. The cost of repairs and maintenance is charged to expense and the cost of betterments is capitalized. The capitalized cost of additions to utility plant includes indirect costs such as engineering, supervision, payroll taxes, pensions, other benefits and an allowance for funds used during construction (AFUDC). The original cost of property is charged to expense over the estimated useful lives of the assets. Upon retirement, the original cost of property is charged to accumulated depreciation. See Note R. Rates used for AFUDC include the cost of borrowed funds and a reasonable rate of return on the Utilities’ own funds when so used, determined in accordance with regulations of the FERC or the state public utility regulatory authority having jurisdiction. The rate is compounded semiannually, and the amounts applicable to borrowed funds are treated as a reduction of interest charges, while the amounts applicable to the Utilities’ own funds are credited to other income (deductions). The AFUDC rates for CECONY were 5.5 percent , 4.7 percent and 4.4 percent for 2017 , 2016 and 2015 , respectively. The AFUDC rates for O&R were 2.5 percent , 3.5 percent and 0.4 percent for 2017 , 2016 and 2015 , respectively. The Utilities generally compute annual charges for depreciation using the straight-line method for financial statement purposes, with rates based on average service lives and net salvage factors. The average depreciation rates for CECONY were 3.1 percent for 2017 , 2016 and 2015 . The average depreciation rates for O&R were 2.9 percent for 2017 and 2016 and 3.0 percent for 2015 . The estimated lives for utility plant for CECONY range from 5 to 95 years for electric, 5 to 100 years for gas, 5 to 80 years for steam and 5 to 55 years for general plant. For O&R, the estimated lives for utility plant range from 5 to 75 years for electric and gas and 5 to 50 years for general plant.
Goodwill	Goodwill Con Edison tests goodwill for impairment at least annually or whenever there is a triggering event. There is an option to first make a qualitative assessment of whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount before applying a two – step, quantitative goodwill impairment test. Con Edison has elected to perform the qualitative assessment for substantially all of its goodwill and, if needed, applies the two-step quantitative approach. The first step of the quantitative goodwill impairment test compares the estimated fair value of a reporting unit with its carrying value, including goodwill. If the estimated fair value of a reporting unit exceeds its carrying value, goodwill of the reporting unit is considered not impaired. If the carrying value exceeds the estimated fair value of the reporting unit, the second step is performed to measure the amount of impairment loss, if any. The second step requires a calculation of the implied fair value of goodwill.
Long-Lived and Intangible Assets	Long – Lived and Intangible Assets Con Edison evaluates the impairment of long-lived assets and intangible assets with definite lives, based on projections of undiscounted future cash flows, whenever events or changes in circumstances indicate that the carrying amounts of such assets may not be recoverable. In the event an evaluation indicates that such cash flows cannot be expected to be sufficient to fully recover the assets, the assets are written down to their estimated fair value.
Revenues	Revenues The Utilities and Con Edison Solutions, until the sale of its retail electric supply business in September 2016 (see Note U), recognize revenues as energy is delivered to customers. The Utilities accrue and Con Edison Solutions accrued revenues at the end of each month for estimated energy not yet billed to customers. The Utilities defer over a 12 – month period net interruptible gas revenues, other than those authorized by the NYSPSC to be retained by the Utilities, for refund to firm gas sales and transportation customers. Con Edison Development recognizes revenue for the sale of energy from renewable electric production projects as energy is generated and billed to counterparties. Con Edison Development accrues revenues at the end of each month for energy not yet billed to counterparties. Con Edison Energy recognizes revenue as energy is delivered and services are provided for managing energy supply assets leased from others and managing the dispatch, fuel requirements and risk management activities for generating plants and merchant transmission in the northeastern United States. Con Edison Solutions recognizes revenue for providing energy-efficiency services to government and commercial customers, and Con Edison Development recognizes revenue for the engineering, procurement and construction of Upton 2, under the percentage-of-completion method of revenue recognition. Sales and profits on each percentage-of-completion contract are recorded based on the ratio of actual cumulative costs incurred to the total estimated costs at completion of the contract, multiplied by the total estimated contract revenue, less cumulative sales recognized in prior periods (the ‘‘cost-to-cost’’ method). The impact of revisions of contract estimates, which may result from contract modifications, performance or other reasons, are recognized on a cumulative catch-up basis in the period in which the revisions are made. Unbilled contract revenues were $58 million and $21 million as of December 31, 2017 and 2016, respectively, and represent accumulated incurred costs and earned profits on contracts (revenue arrangements), which have been recorded as revenues, but have not yet been billed to customers. Substantially all unbilled contract revenues are expected to be collected within one year. Unbilled contract revenues arise from the cost-to-cost method of revenue recognition. Unbilled contract revenues from fixed-price type contracts are converted to billed receivables when amounts are invoiced to customers according to contractual billing terms, which generally occur when deliveries or other performance milestones are completed. Unearned revenue, which reflects a liability for billings to customers in excess of earned revenue was $87 million and $2 million as of December 31, 2017 and 2016, respectively. Revenues recorded as energy is delivered, generated or services provided and billed to customers are recorded in accounts receivable – customers. Con Edison's and the Utilities' accounts receivable – customers balance also reflects the Utilities' purchase of receivables from energy service companies to support retail choice programs. Accrued revenues not yet billed to customers are recorded as accrued unbilled revenues. CECONY’s electric and gas rate plans and O&R’s New York electric and gas rate plans each contain a revenue decoupling mechanism under which the company’s actual energy delivery revenues are compared with the authorized delivery revenues and the difference accrued, with interest, for refund to, or recovery from, customers, as applicable. See “Rate Plans” in Note B. The NYSPSC requires utilities to record gross receipts tax revenues and expenses on a gross income statement presentation basis (i.e., included in both revenue and expense). The recovery of these taxes is generally provided for in the revenue requirement within each of the respective NYSPSC approved rate plans.
Recoverable Energy Costs/New York Independent System Operator (NYISO)	Recoverable Energy Costs The Utilities generally recover all of their prudently incurred fuel, purchased power and gas costs, including hedging gains and losses, in accordance with rate provisions approved by the applicable state public utility regulators. If the actual energy supply costs for a given month are more or less than the amounts billed to customers for that month, the difference in most cases is recoverable from or refundable to customers. Differences between actual and billed electric and steam supply costs and costs of its electric demand management programs are generally deferred for charge or refund to customers during the next billing cycle (normally within one or two months ). For the Utilities’ gas costs, differences between actual and billed gas costs during the 12 – month period ending each August are charged or refunded to customers during a subsequent 12 – month period. New York Independent System Operator (NYISO) The Utilities purchase electricity through the wholesale electricity market administered by the NYISO. The difference between purchased power and related costs initially billed to the Utilities by the NYISO and the actual cost of power subsequently calculated by the NYISO is refunded by the NYISO to the Utilities, or paid to the NYISO by the Utilities. The reconciliation payments or receipts are recoverable from or refundable to the Utilities’ customers. Certain other payments to or receipts from the NYISO are also subject to reconciliation, with shortfalls or amounts in excess of specified rate allowances recoverable from or refundable to customers. These include proceeds from the sale through the NYISO of transmission rights on CECONY’s transmission system (transmission congestion contracts or TCCs).
Temporary Cash Investments	Temporary Cash Investments Temporary cash investments are short-term, highly – liquid investments that generally have maturities of three months or less at the date of purchase. They are stated at cost, which approximates market. The Companies consider temporary cash investments to be cash equivalents.
Investments	Investments Investments consist primarily of the investments of Con Edison Transmission and the Clean Energy Businesses that are accounted for under the equity method, and the fair value of the Utilities’ supplemental retirement income plan and deferred income plan assets.
Pension and Other Postretirement Benefits	Pension and Other Postretirement Benefits The accounting rules for retirement benefits require an employer to recognize an asset or liability for the overfunded or underfunded status of its pension and other postretirement benefit plans. For a pension plan, the asset or liability is the difference between the fair value of the plan’s assets and the projected benefit obligation. For any other postretirement benefit plan, the asset or liability is the difference between the fair value of the plan’s assets and the accumulated postretirement benefit obligation. The accounting rules generally require employers to recognize all unrecognized prior service costs and credits and unrecognized actuarial gains and losses in accumulated other comprehensive income/(loss) (OCI), net of tax. Such amounts will be adjusted as they are subsequently recognized as components of total periodic benefit cost or income pursuant to the current recognition and amortization provisions. For the Utilities’ pension and other postretirement benefit plans, regulatory accounting treatment is generally applied in accordance with the accounting rules for regulated operations. Unrecognized prior service costs or credits and unrecognized actuarial gains and losses are recorded to regulatory assets or liabilities, rather than OCI. See Notes E and F. The total periodic benefit costs are recognized in accordance with the accounting rules for retirement benefits. Investment gains and losses are recognized in expense over a 15 – year period and other actuarial gains and losses are recognized in expense over a 10 – year period, subject to the deferral provisions in the rate plans. In accordance with the Statement of Policy issued by the NYSPSC and its current electric, gas and steam rate plans, CECONY defers for payment to or recovery from customers the difference between such expenses and the amounts for such expenses reflected in rates. Generally, O&R also defers such difference pursuant to its rate plans. See Note B. The Companies calculate the expected return on pension and other postretirement benefit plan assets by multiplying the expected rate of return on plan assets by the market-related value (MRV) of plan assets at the beginning of the year, taking into consideration anticipated contributions and benefit payments that are to be made during the year. The accounting rules allow the MRV of plan assets to be either fair value or a calculated value that recognizes changes in fair value in a systematic and rational manner over not more than five years. The Companies use a calculated value when determining the MRV of the plan assets that adjusts for 20 percent of the difference between fair value and expected MRV of plan assets. This calculated value has the effect of stabilizing variability in assets to which the Companies apply the expected return.
Federal Income Tax/State Income Tax	Federal Income Tax In accordance with accounting rules for income taxes, the Companies have recorded an accumulated deferred federal income tax liability at current tax rates for temporary differences between the book and tax basis of assets and liabilities. In accordance with rate plans, the Utilities have recovered amounts from customers for a portion of the tax liability they will pay in the future as a result of the reversal or “turn-around” of these temporary differences. As to the remaining deferred tax liability, the Utilities had established regulatory assets for the net revenue requirements to be recovered from customers for the related future tax expense pursuant to the NYSPSC's 1993 Policy Statement approving accounting procedures consistent with accounting rules for income taxes and providing assurances that these future increases in taxes will be recoverable in rates. Upon enactment of the Tax Cuts and Jobs Act of 2017 on December 22, 2017 (the TCJA), the Companies re-measured their deferred tax assets and liabilities based upon the 21 percent corporate income tax rate under the TCJA. As a result, Con Edison decreased its net deferred tax liabilities by $5,312 million (including $4,781 million for CECONY), recognized net income of $259 million , decreased its regulatory asset for future income tax by $1,250 million (including $1,182 million for CECONY), decreased its regulatory asset for revenue taxes by $90 million (including $86 million for CECONY), and accrued a regulatory liability for future income tax of $3,713 million (including $3,513 million for CECONY). See “Other Regulatory Matters” and “Regulatory Assets and Liabilities” in Note B and Note L. Accumulated deferred investment tax credits are amortized ratably over the lives of the related properties and applied as a reduction to future federal income tax expense. Con Edison and its subsidiaries file a consolidated federal income tax return. The consolidated income tax liability is allocated to each member of the consolidated group using the separate return method. Each member pays or receives an amount based on its own taxable income or loss in accordance with a consolidated tax allocation agreement. Tax loss and tax credit carryforwards are allocated among members in accordance with consolidated tax return regulations. State Income Tax Con Edison and its subsidiaries file a combined New York State Corporation Business Franchise Tax Return. Similar to a federal consolidated income tax return, the income of all entities in the combined group is subject to New York State taxation, after adjustments for differences between federal and New York law and apportionment of income among the states in which the company does business. Each member’s share of the New York State tax is based on its own New York State taxable income or loss.
Research and Development Costs	Research and Development Costs Research and development costs are charged to operating expenses as incurred.
Reclassification	Reclassification Certain prior year amounts have been reclassified to conform with the current year presentation.
Earnings Per Common Share	Earnings Per Common Share Con Edison presents basic and diluted earnings per share on the face of its consolidated income statement. Basic earnings per share (EPS) are calculated by dividing earnings available to common shareholders (“Net income” on Con Edison’s consolidated income statement) by the weighted average number of Con Edison common shares outstanding during the period. In the calculation of diluted EPS, weighted average shares outstanding are increased for additional shares that would be outstanding if potentially dilutive securities were converted to common stock. Potentially dilutive securities for Con Edison consist of restricted stock units and deferred stock units for which the average market price of the common shares for the period was greater than the exercise price.
Estimates	Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
New Financial Accounting Standards	New Financial Accounting Standards In January 2018, the Companies adopted Accounting Standards Update (ASU) No. 2014-09, “Revenue from Contracts with Customers (Topic 606),” including the amendments thereto, (the New Standard) using the modified retrospective approach the New Standard permitted. The New Standard supersedes the revenue recognition requirements within Accounting Standards Codification Topic 605, “Revenue Recognition,” and most industry-specific guidance (the Superseded Standard). The purpose of the New Standard is to create a consistent framework for revenue recognition. The New Standard clarifies how to measure and recognize revenue arising from customer contracts to depict the transfer of goods or services in an amount that reflects the consideration the entity expects to receive. The New Standard also clarifies key areas including principal/agent considerations, performance obligations, licensing, sales taxes, noncash consideration, and contracts. The majority of Con Edison’s’ revenues and substantially all of CECONY’s revenues are derived from the provision of electric, gas, and steam service to customers pursuant to the terms of tariffs approved by the NYSPSC or NJBPU. For such service, the Companies expect that the revenue from contracts with customers for a period that will be recorded under the New Standard will be equivalent to the revenue for the period that would have been recorded under the Superseded Standard. Most of Con Edison’s other revenues are derived from the Clean Energy Businesses’ sale of energy-related products and services, operation of renewable and energy infrastructure projects, and sale of renewable energy credits. For such businesses, Con Edison expects that the revenue from contracts with customers for a period that will be recorded under the New Standard will not be materially different from the revenue for the period that would have been recorded under the Superseded Standard. Under the modified retrospective method of adoption, prior year reported results are not restated and a cumulative-effect adjustment, if applicable, is recorded to retained earnings at January 1, 2018. As of January 1, 2018, the cumulative-effect adjustment was not material to the Companies. The Companies also plan to use certain practical expedients including applying this guidance to open contracts at the date of adoption and recognizing revenues for certain contracts under the invoice practical expedient. Such expedients allow revenue recognition to be consistent with invoiced amounts (including estimated billings) provided certain criteria are met, including consideration of whether the invoiced amounts reasonably represent the value provided to customers. The adoption of the New Standard will not have a material impact on the Companies’ financial statements, results of operations, and liquidity, including the presentation of revenues in their consolidated income statements. The adoption of the New Standard will not require a change in the Companies’ internal control over financial reporting that is reasonably likely to materially affect their internal control over financial reporting. In February 2016, the FASB issued amendments on financial reporting of leasing transactions through ASU No. 2016-02, “Leases (Topic 842)." The amendments require lessees to recognize assets and liabilities on the balance sheet and disclose key information about leasing arrangements. Lessees will need to recognize a right-of-use asset and a lease liability for virtually all of their leases (other than leases that meet the definition of a short-term lease). Lessor accounting is similar to the current model, but updated to align with certain changes to the lessee model. For income statement purposes, the pattern of expense recognition will depend on whether transactions are designated as operating leases or finance leases. In January 2018, the FASB issued amendments on the lease standard’s application to land easements through ASU No. 2018-01, “Leases (Topic 842): Land Easement Practical Expedient for Transition to Topic 842.” The amendments allow an entity to not evaluate under Topic 842 land easements that exist or expired before the entity’s adoption of Topic 842 and that were not previously accounted for as leases under the current lease standard. The amendments are effective for reporting periods beginning after December 15, 2018. Early adoption is permitted. The amendments must be adopted using a modified retrospective transition and provide for certain practical expedients. Based on the existing portfolio of leases at implementation, for leases currently classified as operating leases, the Companies expect to recognize on the statements of financial position right-of-use assets and lease liabilities. The Companies are in the process of evaluating the potential impact of the new guidance on the Companies’ results of operations and liquidity. In January 2017, the FASB issued amendments to the guidance for Business Combinations through ASU 2017-01, “Business Combinations (Topic 805): Clarifying the Definition of a Business.” The amendments in this update clarify the definition of a business and provide guidance on evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. For public entities, the amendments are effective for reporting periods beginning after December 15, 2017. The application of this guidance is not expected to have a material impact on the Companies’ financial position, results of operations and liquidity. In January 2017, the FASB issued amendments to the guidance for the subsequent measurement of goodwill through ASU 2017-04, “Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment.” The amendments in this update simplify goodwill impairment testing by eliminating Step 2 of the goodwill impairment test wherein an entity has to compute the implied fair value of goodwill by performing procedures to determine the fair value of its assets and liabilities. Under the new guidance, an entity should recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value up to the total amount of goodwill allocated to that reporting unit. For public entities, the amendments are effective for reporting periods beginning after December 15, 2019. Early adoption is permitted. The application of this guidance is not expected to have a material impact on the Companies’ financial position, results of operations and liquidity. In February 2017, the FASB issued amendments to the guidance for other income through ASU 2017-05, “Other Income-Gains and Losses from the Derecognition of Nonfinancial Assets (Subtopic 610-20): Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Nonfinancial Assets.” The amendments in this update clarify the scope of assets within Subtopic 610-20 and add guidance for partial sales of nonfinancial assets. The amendments are effective upon the adoption of ASU 2014-09, and therefore will be effective for reporting periods beginning after December 15, 2017. The application of this guidance is not expected to have a material impact on the Companies’ financial position, results of operations and liquidity. In March 2017, the FASB issued amendments to the guidance for retirement benefits through ASU 2017-07, “Compensation-Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost.” The amendments in this update modify the presentation of net benefit cost, where the service component must be disaggregated from the other components of net benefit cost and be presented in the same line item as current employee compensation costs. The remaining components of the net benefit cost should be presented outside of income from operations. Additionally, the update allows only the service cost component to be eligible for capitalization. For public entities, the amendments are effective for reporting periods beginning after December 15, 2017. The guidance allows a practical expedient that permits the use of amounts disclosed in prior-period financial statements as appropriate estimates when applying the presentation requirements retrospectively. The Companies have elected to use the practical expedient under ASU 2017-07. The application of this guidance is not expected to have a material impact on the Companies’ financial position, results of operations and liquidity. In March 2017, the FASB issued amendments to the guidance for debt securities through ASU 2017-08, “Receivables-Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities.” The amendments in this update shorten the amortization period for certain callable debt securities held at a premium. The amendments do not require an accounting change for securities held at a discount; the discount continues to be amortized to maturity. For public entities, the amendments are effective for reporting periods beginning after December 15, 2018. Early adoption is permitted. The application of this guidance is not expected to have a material impact on the Companies’ financial position, results of operations and liquidity. In May 2017, the FASB issued amendments to the guidance for stock compensation through ASU 2017-09, “Compensation-Stock Compensation (Topic 718): Scope of Modification Accounting.” The amendments in this update specify that changes to value, vesting conditions, or classification of an existing share-based payment award require application of modification accounting in Topic 718. For public entities, the amendments are effective for reporting periods beginning after December 15, 2017.The application of this guidance is not expected to have a material impact on the Companies’ financial position, results of operations and liquidity. In August 2017, the FASB issued amendments to the guidance for derivatives and hedging through ASU 2017-12, “Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities.” The amendments in this update provide greater clarification on hedge accounting for risk components, presentation and disclosure of hedging instruments, and overall targeted improvements to simplify hedge accounting. For public entities, the amendments are effective for reporting periods beginning after December 15, 2018. Early adoption is permitted. The Companies are in the process of evaluating the potential impact of the new guidance on the Companies’ financial position, results of operations and liquidity. In February 2018, the FASB issued amendments to the guidance for reporting comprehensive income through ASU 2018-02, “Income Statement-Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income.” The amendments allow a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the TCJA. For public entities, the amendments are effective for reporting periods beginning after December 15, 2018. Early adoption is permitted. The Companies are in the process of evaluating the potential impact of the new guidance on the Companies’ financial position, results of operations and liquidity.

Summary of Significant Accoun35

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Capitalized Cost of Utility Plant	At December 31, 2017 and 2016 , the capitalized cost of the Companies’ utility plant, net of accumulated depreciation, was as follows: Con Edison CECONY (Millions of Dollars) 2017 2016 2017 2016 Electric Generation $544 $479 $544 $479 Transmission 3,210 3,184 2,990 2,963 Distribution 18,959 18,150 17,996 17,234 Gas (a) 6,976 6,285 6,403 5,749 Steam 1,798 1,882 1,798 1,882 General 2,105 1,816 1,905 1,639 Held for future use 76 74 67 65 Construction work in progress 1,605 1,175 1,502 1,104 Net Utility Plant $35,273 $33,045 $33,205 $31,115 (a) Primarily distribution.
Schedule of Total Excise Taxes Recorded in Operating Revenues	Total excise taxes (inclusive of gross receipts taxes) recorded in operating revenues were as follows: For the Years Ended December 31, (Millions of Dollars) 2017 2016 2015 Con Edison $302 $336 $354 CECONY 292 316 331
Schedule of Investment Assets	The following investment assets are included in the Companies' consolidated balance sheets at December 31, 2017 and 2016: Con Edison CECONY (Millions of Dollars) 2017 2016 2017 2016 CET Gas investment in Stagecoach Gas Services, LLC (a) $971 $992 $— $— Con Edison Development equity method investments (b) 467 488 — — Supplemental retirement income plan assets (c) 330 273 301 246 CET Gas investment in Mountain Valley Pipeline, LLC (a) 98 48 — — Deferred income plan assets 73 60 73 60 CET Electric investment in New York Transco, LLC (a) 53 51 — — Other 9 9 9 9 Total investments $2,001 $1,921 $383 $315 (a) See Note U. (b) See Note Q. (c) See Note E.
Research and Development Costs	Research and development costs were as follows: For the Years Ended December 31, (Millions of Dollars) 2017 2016 2015 Con Edison $24 $24 $23 CECONY 23 22 22
Basic and Diluted EPS	Basic and diluted EPS for Con Edison are calculated as follows: For the Years Ended December 31, (Millions of Dollars, except per share amounts/Shares in Millions) 2017 2016 2015 Net income $1,525 $1,245 $1,193 Weighted average common shares outstanding – basic 307.1 300.4 293.0 Add: Incremental shares attributable to effect of potentially dilutive securities 1.7 1.5 1.4 Adjusted weighted average common shares outstanding – diluted 308.8 301.9 294.4 Net Income per common share – basic $4.97 $4.15 $4.07 Net Income per common share – diluted $4.94 $4.12 $4.05
Changes in Accumulated Other Comprehensive Income/(Loss)	Changes to accumulated other comprehensive income/(loss) (OCI) for Con Edison and CECONY are as follows: (Millions of Dollars) Con Edison CECONY Accumulated OCI, net of taxes, at December 31, 2014 (a) $(45) $(11) OCI before reclassifications, net of tax of $(3) for Con Edison 5 1 Amounts reclassified from accumulated OCI related to pension plan liabilities, net of tax of $(4) and $(1) for Con Edison and CECONY, respectively(a)(b) 6 1 Total OCI, net of taxes, at December 31, 2015 11 2 Accumulated OCI, net of taxes, at December 31, 2015 (a) $(34) $(9) OCI before reclassifications, net of tax of $(1) for Con Edison and CECONY 2 1 Amounts reclassified from accumulated OCI related to pension plan liabilities, net of tax of $(3) and $(1) for Con Edison and CECONY, respectively(a)(b) 5 1 Total OCI, net of taxes, at December 31, 2016 7 2 Accumulated OCI, net of taxes, at December 31, 2016 (a) $(27) $(7) OCI before reclassifications, net of tax of $3 and $1 for Con Edison and CECONY, respectively (4) — Amounts reclassified from accumulated OCI related to pension plan liabilities, net of tax of $(3) and $(1) for Con Edison and CECONY, respectively(a)(b) 5 1 Total OCI, net of taxes, at December 31, 2017 1 1 Accumulated OCI, net of taxes, at December 31, 2017 (a) $(26) $(6) (a) Tax reclassified from accumulated OCI is reported in the income tax expense line item of the consolidated income statement. (b) For the portion of unrecognized pension and other postretirement benefit costs relating to the Utilities, costs are recorded into, and amortized out of, regulatory assets instead of OCI. The net actuarial losses and prior service costs recognized during the period are included in the computation of total periodic pension and other postretirement benefit cost. See Notes E and F.

Regulatory Matters (Tables)

Regulatory Matters (Tables)	12 Months Ended
	Dec. 31, 2017
Regulated Operations [Abstract]
Summary of Utilities Rate Plans	RECO Effective period August 2014 – February 2017 March 2017 (a) Base rate changes Yr. 1 – $13.0 million Yr. 1 – $1.7 million Amortization to income of net regulatory (assets) and liabilities $0.4 million over three years and $(25.6) million of deferred storm costs over four years $0.2 million over three years and continuation of $(25.6) million of deferred storm costs over four years expiring July 31, 2018 (b) Recoverable energy costs Current rate recovery of purchased power costs. Current rate recovery of purchased power costs. Cost reconciliations None None Average rate base $172.2 million Yr. 1 – $178.7 million Weighted average cost of capital (after-tax) 7.83 percent 7.47 percent Authorized return on common equity 9.75 percent 9.6 percent Actual return on common equity Yr. 1 – 9.2 percent (c) Cost of long-term debt 5.89 percent 5.37 percent Common equity ratio 50 percent 49.7 percent (a) Effective until a new rate plan approved by the NJBPU goes into effect. (b) In January 2016, the NJBPU approved RECO’s plan to spend $15.7 million in capital over three years to harden its electric system against storms, the costs of which RECO, beginning in 2017, is collecting through a customer surcharge. The following tables contain a summary of the Utilities’ rate plans: CECONY – Electric Effective period January 2014 – December 2016 January 2017 – December 2019 (b) Base rate changes Yr. 1 – $(76.2) million (a) Yr. 1 – $195 million (c) Amortizations to income of net regulatory (assets) and liabilities Yr. 1 and 2 – $(37) million (d) Yr. 1 – $84 million Other revenue sources Retention of $90 million of annual transmission congestion revenues. Retention of $75 million of annual transmission congestion revenues. Revenue decoupling mechanisms In 2014, 2015 and 2016, the company deferred for customer benefit $146 million, $98 million and $101 million of revenues, respectively. Continuation of reconciliation of actual to authorized electric delivery revenues. Recoverable energy costs (e) Current rate recovery of purchased power and fuel costs. Continuation of current rate recovery of purchased power and fuel costs. Negative revenue adjustments Potential penalties (up to $400 million annually) if certain performance targets are not met. In 2014, the company recorded a $5 million negative revenue adjustment. In 2015 and 2016, the company did not record any negative revenue adjustments. Potential penalties if certain performance targets relating to service, reliability, safety and other matters are not met: Cost reconciliations In 2014, 2015 and 2016, the company deferred $57 million, $26 million and $68 million of net regulatory liabilities, respectively (f). Continuation of reconciliation of expenses for pension and other postretirement benefits, variable-rate tax-exempt debt, major storms, property taxes (f), municipal infrastructure support costs (g), the impact of new laws and environmental site investigation and remediation to amounts reflected in rates (h). Net utility plant reconciliations Target levels reflected in rates were: Target levels reflected in rates: Average rate base Yr. 1 – $17,323 million Yr. 1 – $18,902 million Weighted average cost of capital (after-tax) Yr. 1 – 7.05 percent Yr. 1 – 6.82 percent Authorized return on common equity Yrs. 1 and 2 – 9.2 percent 9.0 percent Actual return on common equity Yr. 1 – 9.04 percent Yr. 1 – 9.3 percent Earnings sharing Most earnings above an annual earnings threshold of 9.8 percent for Yrs. 1 and 2 and 9.6 percent for Yr. 3 are to be applied to reduce regulatory assets for environmental remediation and other costs. In 2014 the company had no earnings above the threshold. Actual earnings were $44.4 million and $6.5 million above the threshold for 2015 and 2016, respectively. Most earnings above an annual earnings threshold of 9.5 percent are to be applied to reduce regulatory assets for environmental remediation and other costs accumulated in the rate year. Cost of long-term debt Yr. 1 – 5.17 percent Yr. 1 – 4.93 percent Common equity ratio 48 percent 48 percent (a) The impact of these base rate changes was deferred which resulted in a $30 million regulatory liability at December 31, 2015; this amount has been amortized to $0 at December 31, 2016. (b) In January 2017, the NYSPSC approved the September 2016 Joint Proposal for CECONY's electric rate plan for January 2017 through December 2019. If at the end of any year, Con Edison’s investments in its non-utility businesses exceed 15 percent of Con Edison’s total consolidated revenues, assets or cash flow, or if the ratio of holding company debt to total consolidated debt rises above 20 percent , CECONY is required to notify the NYSPSC and submit a ring-fencing plan or a demonstration why additional ring-fencing measures are not necessary. (c) The electric base rate increases are in addition to a $48 million increase resulting from the December 2016 expiration of a temporary credit under the prior rate plan. At the NYSPSC’s option, these increases are being implemented with increases of $199 million in each rate year. Base rates reflect recovery by the company of certain costs of its energy efficiency, system peak reduction and electric vehicle programs (Yr. 1 - $20.5 million ; Yr. 2 - $49 million ; and Yr. 3 - $107.5 million ) over a ten -year period, including the overall pre-tax rate of return on such costs. (d) Amounts reflect annual amortization of $107 million of the regulatory asset for deferred Superstorm Sandy and other major storm costs. The costs recoverable from customers were reduced by $4 million . The costs are no longer subject to NYSPSC staff review and the recovery of the costs is no longer subject to refund. In 2016, an additional $123 million of net regulatory liabilities were amortized to income. (e) For transmission service provided pursuant to the open access transmission tariff of PJM Interconnection LLC (PJM), unless and until changed by the NYSPSC, the company will recover all charges incurred associated with the transmission service. Starting in January 2014, PJM submitted to the FERC a series of requests that substantially increase the charges for the transmission service. CECONY has challenged each of these requests. To date, FERC has rejected all but one of CECONY’s protests. In June 2015 and May 2016, CECONY filed appeals of certain FERC decisions with the U.S. Court of Appeals. In April 2017, the transmission service terminated because CECONY did not exercise its option to continue the service. (f) Deferrals for property taxes are limited to 90 percent of the difference from amounts reflected in rates, subject to an annual maximum for the remaining difference of not more than a maximum number of basis points ( 5.0 , 7.5 or 10.0 basis points , depending on the year). (g) In general, if actual expenses for municipal infrastructure support (other than company labor) are below the amounts reflected in rates the company will defer the difference for credit to customers, and if the actual expenses are above the amount reflected in rates the company will defer for recovery from customers 80 percent of the difference subject to a maximum deferral of 30 percent of the amount reflected in rates. (h) In addition, amounts reflected in rates relating to the regulatory asset for future income tax and the excess deferred federal income tax liability are subject to reconciliation. The NYSPSC staff is to audit the regulatory asset and the tax liability. Differences resulting from the NYSPSC staff review will be deferred for NYSPSC determination of any amounts to be refunded or collected from customers. See "Other Regulatory Matters," below. CECONY – Gas Effective period January 2014 – December 2016 January 2017 - December 2019 (b) Base rate changes Yr. 1 – $(54.6) million (a) Yr. 1 – $(5) million (b) Amortizations to income of net regulatory (assets) and liabilities $4 million over three years Yr. 1 – $39 million Other revenue sources Retention of revenues from non-firm customers of up to $65 million and 15 percent of any such revenues above $65 million. The company retained $70 million, $66 million and $65 million of such revenues in 2014, 2015 and 2016, respectively. Retention of annual revenues from non-firm customers of up to $65 million and 15 percent of any such revenues above $65 million. Revenue decoupling mechanisms In 2014, 2015 and 2016, the company deferred $28 million, $54 million and $71 million of regulatory liabilities, respectively. Continuation of reconciliation of actual to authorized gas delivery revenues. Recoverable energy costs Current rate recovery of purchased gas costs. Continuation of current rate recovery of purchased gas costs. Negative revenue adjustments Potential penalties (up to $33 million in 2014, $44 million in 2015, and $56 million in 2016) if certain gas performance targets are not met. In 2014, 2015 and 2016, the company did not record any negative revenue adjustments. Potential penalties if performance targets relating to service, safety and other matters are not met: Cost reconciliations In 2014, 2015 and 2016, the company deferred $38 million, $11 million, and $32 million of net regulatory liabilities, respectively. (c) Continuation of reconciliation of expenses for pension and other postretirement benefits, variable-rate tax-exempt debt, major storms, property taxes, municipal infrastructure support costs, the impact of new laws and environmental site investigation and remediation to amounts reflected in rates. (d) Net utility plant reconciliations Target levels reflected in rates were: Target levels reflected in rates: Average rate base Yr. 1 – $3,521 million Yr. 1 – $4,841 million Weighted average cost of capital Yr. 1 – 7.10 percent Yr. 1 – 6.82 percent Authorized return on common equity 9.3 percent 9.0 percent Actual return on common equity Yr. 1 – 8.02 percent Yr. 1 – 9.22 percent Earnings sharing Most earnings above an annual earnings threshold of 9.9 percent are to be applied to reduce regulatory assets for environmental remediation and other costs. In 2014, 2015 and 2016, the company had no earnings above the threshold. Most earnings above an annual earnings threshold of 9.5 percent are to be applied to reduce regulatory assets for environmental remediation and other costs accumulated in the rate year. Cost of long-term debt Yr. 1 – 5.17 percent Yr. 1 – 4.93 percent Common equity ratio 48 percent 48 percent (a) The impact of these base rate changes was deferred which resulted in a $32 million regulatory liability at December 31, 2016. (b) In January 2017, the NYSPSC approved the September 2016 Joint Proposal for CECONY's gas rate plan for January 2017 through December 2019. The gas base rate decrease is offset by a $41 million increase resulting from the December 2016 expiration of a temporary credit under the prior rate plan. (c) Deferrals for property taxes are limited to 90 percent of the difference from amounts reflected in rates, subject to an annual maximum for the remaining difference of not more than a 10 basis point impact on return on common equity (d) See footnotes (e), (f), (g) and (h) to the table under "CECONY - Electric" above. CECONY – Steam Effective period January 2014 – December 2016 (a) Base rate changes Yr. 1 – $(22.4) million (b) Amortizations to income of net regulatory (assets) and liabilities $37 million over three years Recoverable energy costs Current rate recovery of purchased power and fuel costs. Negative revenue adjustments Potential penalties (up to $1 million annually) if certain steam performance targets are not met. In 2014, 2015, 2016 and 2017, the company did not record any negative revenue adjustments. Cost reconciliations (c) In 2014, 2015, 2016 and 2017, the company deferred $42 million of net regulatory liabilities, $17 million of net regulatory assets, $8 million and $14 million of net regulatory liabilities, respectively. Net utility plant reconciliations Target levels reflected in rates were: Average rate base Yr. 1 – $1,511 million Weighted average cost of capital (after-tax) Yr. 1 – 7.10 percent Authorized return on common equity 9.3 percent Actual return on common equity Yr. 1 – 9.82 percent Earnings sharing Weather normalized earnings above an annual earnings threshold of 9.9 percent are to be applied to reduce regulatory assets for environmental remediation and other costs. Cost of long-term debt Yr. 1 – 5.17 percent Common equity ratio 48 percent (a) Rates determined pursuant to this rate plan continue in effect until a new rate plan is approved by the NYSPSC. (b) The impact of these base rate changes was deferred which resulted in an $8 million regulatory liability at December 31, 2016. (c) Deferrals for property taxes are limited to 90 percent of the difference from amounts reflected in rates, subject to an annual maximum for the remaining difference of not more than a 10 basis point impact on return on common equity. O&R New York – Electric Effective period July 2012 – October 2015 November 2015 - October 2017 (a) Base rate changes Yr. 1 – $19.4 million Yr. 1 – $9.3 million – $8.8 million Amortizations to income of net regulatory (assets) and liabilities $(32.2) million over three years Yr. 1 – $(8.5) million (b) – $(9.4) million (b) Revenue decoupling mechanisms In 2012, 2013 and 2014, the company deferred for the customer’s benefit $2.6 million, $3.2 million and $(3.4) million, respectively. In 2015, 2016 and 2017, the company deferred for the customer’s benefit an immaterial amount, $6.3 million as regulatory liabilities and $11.2 million as regulatory asset, respectively. Recoverable energy costs Current rate recovery of purchased power and fuel costs. Continuation of current rate recovery of purchased power costs. Negative revenue adjustments Potential penalties (up to $3 million annually) if certain customer service and system reliability performance targets are not met. In 2012, 2013 and 2014, the company did not record any negative revenue adjustments. Potential penalties (up to $4 million annually) if certain performance targets are not met. In 2015 the company recorded $1.25 million in negative revenue adjustments. In 2016 and 2017, the company did not record any negative revenue adjustments. Cost reconciliations In 2012, 2013 and 2014, the company deferred $7.8 million, $4.1 million and $(0.2) million as a net increase/(decrease) to regulatory assets, respectively. In 2015, 2016 and 2017, the company deferred $0.3 million, $7.4 million and $3.2 million as net decreases to regulatory assets, respectively. Net utility plant reconciliations Target levels reflected in rates were: Target levels reflected in rates are: – $928 million (c) – $970 million (c) The company increased/(reduced) its regulatory asset by $2.2 million, $(1.9) million and $(1.9) million in 2015, 2016 and 2017, respectively. Average rate base Yr. 1 – $671 million Yr. 1 – $763 million – $805 million Weighted average cost of capital (after-tax) Yr. 1 – 7.61 percent Yr. 1 – 7.10 percent – 7.06 percent Authorized return on common equity Yr. 1 – 9.4 percent 9.0 percent Actual return on common equity Yr. 1 – 12.9 percent Yr. 1 – 10.8 percent Earnings sharing The company recorded a regulatory liability of $1 million for earnings above the sharing threshold under the rate plan as of December 31, 2014. Most earnings above an annual earnings threshold of 9.6 percent are to be applied to reduce regulatory assets. In 2015, earnings did not exceed the earnings threshold. Actual earnings were $6.1 million and $0.3 million above the threshold for 2016 and 2017, respectively. Cost of long-term debt Yr. 1 – 6.07 percent Yr. 1 – 5.42 percent – 5.35 percent Common equity ratio 48 percent 48 percent (a) Rates determined pursuant to this rate plan continue in effect until a new rate plan is approved by the NYSPSC. (b) $59.3 million of the regulatory asset for deferred storm costs is to be recovered from customers over a five year period, including $11.85 million in each of years 1 and 2, $1 million of the regulatory asset for such costs will not be recovered from customers, and all outstanding issues related to Superstorm Sandy and other past major storms prior to November 2014 are resolved. Approximately $4 million of regulatory assets for property tax and interest rate reconciliations will not be recovered from customers. Amounts that will not be recovered from customers were charged-off in June 2015. (c) Excludes electric AMI as to which the company will be required to defer as a regulatory liability the revenue requirement impact of the amount, if any, by which actual average net utility plant balances are less than amounts reflected in rates: $1 million in year 1 and $9 million in year 2. O&R New York – Gas Effective period November 2009 – October 2015 November 2015 – October 2018 Base rate changes Yr. 1 – $9 million Yr. 1 – $16.4 million – $16.4 million – $5.8 million – $10.6 million collected through a surcharge Amortization to income of net regulatory (assets) and liabilities $(2) million over three years Yr. 1 – $(1.7) million (a) – $(2.1) million (a) – $(2.5) million (a) Revenue decoupling mechanisms In 2012, 2013 and 2014, the company deferred $4.7 million, $0.7 million and $(0.1) million of regulatory liabilities, respectively. In 2015 and 2016, the company deferred $0.8 million regulatory assets and $6.2 million of regulatory liabilities, respectively. In 2017, the company deferred $1.7 million in regulatory liabilities. Recoverable energy costs Current rate recovery of purchased gas costs. Current rate recovery of purchased gas costs. Negative revenue adjustments Potential penalties (up to $1.4 million annually) if certain operations and customer service requirements are not met. In 2012, 2013 and 2014, the company did not record any negative revenue adjustments. Potential penalties (up to $3.7 million in Yr. 1, $4.7 million in Yr. 2 and $4.9 million in Yr. 3) if certain performance targets are not met. In 2015, 2016 and 2017, the company did not record any negative revenue adjustments. Cost reconciliations In 2012, 2013 and 2014, the company deferred $0.7 million, $8.3 million and $8.3 million as net regulatory assets, respectively. In 2015 and 2016, the company deferred $4.5 million and $6.6 million as net regulatory liabilities and assets, respectively. In 2017, the company deferred $3.5 million as net regulatory liabilities. Net utility plant reconciliations The company deferred $0.7 million in 2012 as a regulatory asset and no deferrals were recorded for 2013 or 2014. Target levels reflected in rates are: – $492 million (b) – $518 million (b) – $546 million (b) No deferral was recorded for 2015 and immaterial amounts were recorded as regulatory liabilities in 2016 and 2017. Average rate base Yr. 1 – $280 million Yr. 1 – $366 million – $391 million – $417 million Weighted average cost of capital (after-tax) 8.49 percent Yr. 1 – 7.10 percent – 7.06 percent – 7.06 percent Authorized return on common equity 10.4 percent 9.0 percent Actual return on common equity Yr. 1 – 10.2 percent Yr. 1 – 11.2 percent Earnings sharing Earnings above an annual earnings threshold of 11.4 percent are to be applied to reduce regulatory assets. In 2012, 2013 and 2014, earnings did not exceed the earnings threshold. Most earnings above an annual earnings threshold of 9.6 percent are to be applied to reduce regulatory assets. In 2015, earnings did not exceed the earnings threshold. Actual earnings were $4 million and $0.2 million above the threshold for 2016 and 2017, respectively. Cost of long-term debt 6.81 percent Yr. 1 – 5.42 percent – 5.35 percent – 5.35 percent Common equity ratio 48 percent 48 percent (a) Reflects that the company will not recover from customers a total of approximately $14 million of regulatory assets for property tax and interest rate reconciliations. Amounts that will not be recovered from customers were charged-off in June 2015. (b) Excludes gas AMI as to which the company will be required to defer as a regulatory liability the revenue requirement impact of the amount, if any, by which actual average net utility plant balances are less than amounts reflected in rates: $0.5 million in year 1, $4.2 million in year 2 and $7.2 million in year 3.
Schedule of Regulatory Assets	Regulatory assets and liabilities at December 31, 2017 and 2016 were comprised of the following items: Con Edison CECONY (Millions of Dollars) 2017 2016 2017 2016 Regulatory assets Unrecognized pension and other postretirement costs $2,526 $2,874 $2,376 $2,730 Future income tax* — 2,439 — 2,325 Environmental remediation costs 793 823 677 711 Revenue taxes 260 295 248 280 Pension and other postretirement benefits deferrals 79 38 58 7 Recoverable energy costs 60 42 52 38 Municipal infrastructure support costs 56 44 56 44 Property tax reconciliation 51 37 25 — MTA power reliability deferral 50 — 50 — Deferred derivative losses 44 48 37 42 Deferred storm costs 38 56 — 3 Brooklyn Queens demand management program 37 29 37 29 Unamortized loss on reacquired debt 37 43 35 41 Indian Point Energy Center program costs 29 50 29 50 Preferred stock redemption 24 25 24 25 Workers’ compensation 10 13 10 13 Net electric deferrals 9 24 9 24 O&R transition bond charges 9 15 — — Surcharge for New York State assessment 2 28 2 26 Other 152 101 138 85 Regulatory assets – noncurrent 4,266 7,024 3,863 6,473 Deferred derivative losses 40 91 37 86 Recoverable energy costs 27 9 25 4 Regulatory assets – current 67 100 62 90 Total Regulatory Assets $4,333 $7,124 $3,925 $6,563 Regulatory liabilities Future income tax* $2,545 $— $2,390 $— Allowance for cost of removal less salvage 846 755 719 641 Pension and other postretirement benefit deferrals 207 193 181 162 Net unbilled revenue deferrals 183 145 183 145 Energy efficiency portfolio standard unencumbered funds 127 — 122 — Property tax reconciliation 107 178 107 178 Unrecognized other postretirement costs 92 60 92 60 Settlement of prudence proceeding 66 95 66 95 Property tax refunds 44 1 44 1 Carrying charges on repair allowance and bonus depreciation 43 68 42 67 New York State income tax rate change 36 61 35 60 Variable-rate tax-exempt debt - cost rate reconciliation 30 55 26 48 Earnings sharing - electric, gas and steam 29 39 19 28 Settlement of gas proceedings 27 27 27 27 Base rate change deferrals 21 40 21 40 Net utility plant reconciliations 12 16 8 15 Other 162 172 137 145 Regulatory liabilities – noncurrent 4,577 1,905 4,219 1,712 Refundable energy costs 41 29 16 5 Deferred derivative gains 31 28 28 24 Revenue decoupling mechanism 29 71 21 61 Regulatory liabilities—current 101 128 65 90 Total Regulatory Liabilities $4,678 $2,033 $4,284 $1,802 ` * See "Federal Income Tax" in Note A, "Other Regulatory Matters," above, and Note L .
Schedule of Regulatory Liabilities	Regulatory assets and liabilities at December 31, 2017 and 2016 were comprised of the following items: Con Edison CECONY (Millions of Dollars) 2017 2016 2017 2016 Regulatory assets Unrecognized pension and other postretirement costs $2,526 $2,874 $2,376 $2,730 Future income tax* — 2,439 — 2,325 Environmental remediation costs 793 823 677 711 Revenue taxes 260 295 248 280 Pension and other postretirement benefits deferrals 79 38 58 7 Recoverable energy costs 60 42 52 38 Municipal infrastructure support costs 56 44 56 44 Property tax reconciliation 51 37 25 — MTA power reliability deferral 50 — 50 — Deferred derivative losses 44 48 37 42 Deferred storm costs 38 56 — 3 Brooklyn Queens demand management program 37 29 37 29 Unamortized loss on reacquired debt 37 43 35 41 Indian Point Energy Center program costs 29 50 29 50 Preferred stock redemption 24 25 24 25 Workers’ compensation 10 13 10 13 Net electric deferrals 9 24 9 24 O&R transition bond charges 9 15 — — Surcharge for New York State assessment 2 28 2 26 Other 152 101 138 85 Regulatory assets – noncurrent 4,266 7,024 3,863 6,473 Deferred derivative losses 40 91 37 86 Recoverable energy costs 27 9 25 4 Regulatory assets – current 67 100 62 90 Total Regulatory Assets $4,333 $7,124 $3,925 $6,563 Regulatory liabilities Future income tax* $2,545 $— $2,390 $— Allowance for cost of removal less salvage 846 755 719 641 Pension and other postretirement benefit deferrals 207 193 181 162 Net unbilled revenue deferrals 183 145 183 145 Energy efficiency portfolio standard unencumbered funds 127 — 122 — Property tax reconciliation 107 178 107 178 Unrecognized other postretirement costs 92 60 92 60 Settlement of prudence proceeding 66 95 66 95 Property tax refunds 44 1 44 1 Carrying charges on repair allowance and bonus depreciation 43 68 42 67 New York State income tax rate change 36 61 35 60 Variable-rate tax-exempt debt - cost rate reconciliation 30 55 26 48 Earnings sharing - electric, gas and steam 29 39 19 28 Settlement of gas proceedings 27 27 27 27 Base rate change deferrals 21 40 21 40 Net utility plant reconciliations 12 16 8 15 Other 162 172 137 145 Regulatory liabilities – noncurrent 4,577 1,905 4,219 1,712 Refundable energy costs 41 29 16 5 Deferred derivative gains 31 28 28 24 Revenue decoupling mechanism 29 71 21 61 Regulatory liabilities—current 101 128 65 90 Total Regulatory Liabilities $4,678 $2,033 $4,284 $1,802

Capitalization (Tables)

Capitalization (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Schedule of Long-Term Debt Maturities	Long-term debt maturing in the period 2018 - 2022 is as follows: (Millions of Dollars) Con Edison CECONY 2018 $1,298 $1,200 2019 578 475 2020 791 350 2021 544 — 2022 335 —
Carrying Amounts and Fair Values of Long-Term Debt	The carrying amounts and fair values of long-term debt at December 31, 2017 and 2016 are: (Millions of Dollars) 2017 2016 Long-Term Debt (including current portion) (a) Carrying Amount Fair Value Carrying Amount Fair Value Con Edison $16,029 $18,147 $14,774 $16,093 CECONY $13,265 $15,163 $12,073 $13,268 (a) Amounts shown are net of unamortized debt expense and unamortized debt discount of $142 million and $121 million for Con Edison and CECONY, respectively, as of December 31, 2017 and $134 million and $113 million for Con Edison and CECONY, respectively, as of December 31, 2016 .

Pension Benefits (Tables)

Pension Benefits (Tables)	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Total Periodic Benefit Costs	The components of the Companies’ total periodic benefit costs for 2017 , 2016 and 2015 were as follows: Con Edison CECONY (Millions of Dollars) 2017 2016 2015 2017 2016 2015 Service cost – including administrative expenses $263 $275 $297 $246 $258 $279 Interest cost on projected benefit obligation 591 596 575 554 559 538 Expected return on plan assets (968) (947) (886) (917) (898) (840) Recognition of net actuarial loss 595 596 775 563 565 734 Recognition of prior service costs (17) 4 4 (19) 2 2 NET PERIODIC BENEFIT COST $464 $524 $765 $427 $486 $713 Amortization of regulatory asset (a) — — 1 — — 1 TOTAL PERIODIC BENEFIT COST $464 $524 $766 $427 $486 $714 Cost capitalized (181) (214) (301) (169) (203) (285) Reconciliation to rate level (34) 54 (74) (41) 58 (74) Cost charged to operating expenses $249 $364 $391 $217 $341 $355 (a) Relates to an increase in CECONY’s pension obligation of $45 million from a 1999 special retirement program. The components of the Companies’ total periodic postretirement benefit costs for 2017 , 2016 and 2015 were as follows: Con Edison CECONY (Millions of Dollars) 2017 2016 2015 2017 2016 2015 Service cost $20 $18 $20 $13 $13 $15 Interest cost on accumulated other postretirement benefit obligation 46 48 51 38 40 43 Expected return on plan assets (69) (77) (78) (61) (67) (68) Recognition of net actuarial loss 2 5 31 (3) 3 28 Recognition of prior service cost (17) (20) (20) (11) (14) (14) TOTAL PERIODIC POSTRETIREMENT BENEFIT COST $(18) $(26) $4 $(24) $(25) $4 Cost capitalized 8 11 (2) 10 10 (2) Reconciliation to rate level (4) 22 14 (2) 22 6 Cost charged to operating expenses $(14) $7 $16 $(16) $7 $8
Schedule of Funded Status	The funded status at December 31, 2017 , 2016 and 2015 was as follows: Con Edison CECONY (Millions of Dollars) 2017 2016 2015 2017 2016 2015 CHANGE IN PROJECTED BENEFIT OBLIGATION Projected benefit obligation at beginning of year $14,095 $14,377 $15,081 $13,203 $13,482 $14,137 Service cost – excluding administrative expenses 259 271 293 241 254 274 Interest cost on projected benefit obligation 591 596 575 554 559 538 Net actuarial loss/(gain) 1,231 (302) (996) 1,171 (282) (931) Plan amendments 6 (256) — — (259) — Benefits paid (646) (591) (576) (602) (551) (536) PROJECTED BENEFIT OBLIGATION AT END OF YEAR $15,536 $14,095 $14,377 $14,567 $13,203 $13,482 CHANGE IN PLAN ASSETS Fair value of plan assets at beginning of year $12,472 $11,759 $11,495 $11,815 $11,141 $10,897 Actual return on plan assets 2,041 829 126 1,935 787 118 Employer contributions 450 508 750 412 469 697 Benefits paid (646) (591) (576) (602) (551) (536) Administrative expenses (43) (33) (36) (41) (31) (35) FAIR VALUE OF PLAN ASSETS AT END OF YEAR $14,274 $12,472 $11,759 $13,519 $11,815 $11,141 FUNDED STATUS $(1,262) $(1,623) $(2,618) $(1,048) $(1,388) $(2,341) Unrecognized net loss $2,760 $3,157 $3,909 $2,624 $2,995 $3,704 Unrecognized prior service costs (223) (244) 16 (242) (258) 3 Accumulated benefit obligation 13,897 12,655 12,909 12,972 11,806 12,055 The funded status of the programs at December 31, 2017 , 2016 and 2015 were as follows: Con Edison CECONY (Millions of Dollars) 2017 2016 2015 2017 2016 2015 CHANGE IN BENEFIT OBLIGATION Benefit obligation at beginning of year $1,198 $1,287 $1,411 $1,007 $1,093 $1,203 Service cost 20 18 20 13 13 15 Interest cost on accumulated postretirement benefit obligation 46 48 51 38 40 43 Amendments — — — — — — Net actuarial loss/(gain) 53 (57) (103) 16 (52) (85) Benefits paid and administrative expenses (134) (134) (127) (124) (122) (117) Participant contributions 36 36 35 35 35 34 BENEFIT OBLIGATION AT END OF YEAR $1,219 $1,198 $1,287 $985 $1,007 $1,093 CHANGE IN PLAN ASSETS Fair value of plan assets at beginning of year $975 $994 $1,084 $851 $870 $950 Actual return on plan assets 150 60 (6) 130 52 (4) Employer contributions 17 7 6 8 7 6 EGWP payments 34 35 28 30 33 26 Participant contributions 35 36 35 35 35 34 Benefits paid (172) (157) (153) (161) (146) (142) FAIR VALUE OF PLAN ASSETS AT END OF YEAR $1,039 $975 $994 $893 $851 $870 FUNDED STATUS $(180) $(223) $(293) $(92) $(156) $(223) Unrecognized net loss/(gain) $(47) $(24) $28 $(85) $(42) $4 Unrecognized prior service costs (14) (31) (51) (7) (18) (32)
Schedule of Assumptions	The actuarial assumptions were as follows: 2017 2016 2015 Weighted-average assumptions used to determine benefit obligations at December 31: Discount rate 3.70 % 4.25 % 4.25 % Rate of compensation increase CECONY 4.25 % 4.25 % 4.25 % O&R 4.00 % 4.00 % 4.00 % Weighted-average assumptions used to determine net periodic benefit cost for the years ended December 31: Discount rate 4.25 % 4.25 % 3.90 % Expected return on plan assets 7.50 % 7.80 % 7.80 % Rate of compensation increase CECONY 4.25 % 4.25 % 4.25 % O&R 4.00 % 4.00 % 4.00 % The actuarial assumptions were as follows: 2017 2016 2015 Weighted-average assumptions used to determine benefit obligations at December 31: Discount Rate CECONY 3.55 % 4.00 % 4.05 % O&R 3.70 % 4.20 % 4.20 % Weighted-average assumptions used to determine net periodic benefit cost for the years ended December 31: Discount Rate CECONY 4.00 % 4.05 % 3.75 % O&R 4.20 % 4.20 % 3.85 % Expected Return on Plan Assets 7.50 % 7.00 % 7.75 %
Schedule of Expected Benefit Payments	Based on current assumptions, the Companies expect to make the following benefit payments over the next ten years : (Millions of Dollars) 2018 2019 2020 2021 2022 2023-2027 Con Edison $728 $738 $753 $765 $778 $4,083 CECONY 677 686 700 712 724 3,804 Based on current assumptions, the Companies expect to make the following benefit payments over the next ten years , net of receipt of governmental subsidies: (Millions of Dollars) 2018 2019 2020 2021 2022 2023-2027 Con Edison $83 $81 $78 $76 $75 $363 CECONY 73 70 67 65 64 303
Schedule of Plan Assets Allocations	The asset allocations for the pension plan at the end of 2017 , 2016 and 2015 , and the target allocation for 2018 are as follows: Target Allocation Range Plan Assets at December 31, Asset Category 2018 2017 2016 2015 Equity Securities 53% - 63% 58 % 58 % 57 % Debt Securities 28% - 38% 33 % 33 % 33 % Real Estate 7% -11% 9 % 9 % 10 % Total 100% 100 % 100 % 100 % The asset allocations for CECONY’s other postretirement benefit plans at the end of 2017 , 2016 and 2015 , and the target allocation for 2018 are as follows: Target Allocation Range Plan Assets at December 31, Asset Category 2018 2017 2016 2015 Equity Securities 50%-80% 60 % 60 % 59 % Debt Securities 20%-50% 40 % 40 % 41 % Total 100% 100 % 100 % 100 %
Schedule of Fair Value of Plan Assets	The fair values of the pension plan assets at December 31, 2017 by asset category are as follows: (Millions of Dollars) Level 1 Level 2 Total Investments within the fair value hierarchy U.S. Equity (a) $3,872 $28 $3,900 International Equity (b) 4,132 — 4,132 U.S. Government Issued Debt (c) — 1,786 1,786 Corporate Bonds Debt (d) — 2,450 2,450 Structured Assets Debt (e) — 3 3 Other Fixed Income Debt (f) — 125 125 Cash and Cash Equivalents (g) 124 352 476 Futures (h) 308 — 308 Total investments within the fair value hierarchy $8,436 $4,744 $13,180 Investments measured at NAV per share (n) Private Equity (i) 336 Real Estate (j) 1,214 Hedge Funds (k) 251 Total investments valued using NAV per share $1,801 Funds for retiree health benefits (l) (168) (94) (262) Funds for retiree health benefits measured at NAV per share (l)(n) (36) Total funds for retiree health benefits $(298) Investments (excluding funds for retiree health benefits) $8,268 $4,650 $14,683 Pending activities (m) (409) Total fair value of plan net assets $14,274 (a) U.S. Equity includes both actively- and passively-managed assets with investments in domestic equity index funds and actively-managed small-capitalization equities. (b) International Equity includes international equity index funds and actively-managed international equities. (c) U.S. Government Issued Debt includes agency and treasury securities. (d) Corporate Bonds Debt consists of debt issued by various corporations. (e) Structured Assets Debt includes commercial-mortgage-backed securities and collateralized mortgage obligations. (f) Other Fixed Income Debt includes municipal bonds, sovereign debt and regional governments. (g) Cash and Cash Equivalents include short term investments, money markets, foreign currency and cash collateral. (h) Futures consist of exchange-traded financial contracts encompassing U.S. Equity, International Equity and U.S. Government indices. (i) Private Equity consists of global equity funds that are not exchange-traded. (j) Real Estate investments include real estate funds based on appraised values that are broadly diversified by geography and property type. (k) Hedge Funds are within a commingled structure which invests in various hedge fund managers who can invest in all financial instruments. (l) The Companies set aside funds for retiree health benefits through a separate account within the pension trust, as permitted under Section 401(h) of the Internal Revenue Code of 1986, as amended. In accordance with the Code, the plan’s investments in the 401(h) account may not be used for, or diverted to, any purpose other than providing health benefits for retirees. The net assets held in the 401(h) account are calculated based on a pro-rata percentage allocation of the net assets in the pension plan. The related obligations for health benefits are not included in the pension plan’s obligations and are included in the Companies’ other postretirement benefit obligation. See Note F. (m) Pending activities include security purchases and sales that have not settled, interest and dividends that have not been received and reflects adjustments for available estimates at year end. (n) In accordance with ASU 2015-07, Fair Value Measurements (Topic 820): Disclosures for Investments in Certain Entities That Calculate Net Asset Value per Share (or its equivalent), certain investments that are measured at fair value using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. The fair values of the pension plan assets at December 31, 2016 by asset category are as follows: (Millions of Dollars) Level 1 Level 2 Total Investments within the fair value hierarchy U.S. Equity (a) $3,466 $— $3,466 International Equity (b) 3,187 371 3,558 U.S. Government Issued Debt (c) — 1,337 1,337 Corporate Bonds Debt (d) — 2,140 2,140 Structured Assets Debt (e) — 1 1 Other Fixed Income Debt (f) — 200 200 Cash and Cash Equivalents (g) 147 389 536 Futures (h) 296 68 364 Total investments within the fair value hierarchy $7,096 $4,506 $11,602 Investments measured at NAV per share (n) Private Equity (i) 247 Real Estate (j) 1,139 Hedge Funds (k) 229 Total investments valued using NAV per share $1,615 Funds for retiree health benefits (l) (165) (105) (270) Funds for retiree health benefits measured at NAV per share (l)(n) (37) Total funds for retiree health benefits $(307) Investments (excluding funds for retiree health benefits) $6,931 $4,401 $12,910 Pending activities (m) (438) Total fair value of plan net assets $12,472 (a) - (n) Reference is made to footnotes (a) through (n) in the above table of pension plan assets at December 31, 2017 by asset category. The fair values of the plan assets at December 31, 2017 by asset category as defined by the accounting rules for fair value measurements (see Note P) are as follows: (Millions of Dollars) Level 1 Level 2 Total Equity (a) $— $420 $420 Other Fixed Income Debt (b) — 286 286 Cash and Cash Equivalents (c) — 16 16 Total investments $— $722 $722 Funds for retiree health benefits (d) 168 94 262 Investments (including funds for retiree health benefits) $168 $816 $984 Funds for retiree health benefits measured at net asset value (d)(e) 36 Pending activities (f) 19 Total fair value of plan net assets $1,039 (a) Equity includes a passively managed commingled index fund benchmarked to the MSCI All Country World Index. (b) Other Fixed Income Debt includes a passively managed commingled index fund benchmarked to the Barclays Capital Aggregate Index. (c) Cash and Cash Equivalents include short term investments and money markets. (d) The Companies set aside funds for retiree health benefits through a separate account within the pension trust, as permitted under Section 401(h) of the Internal Revenue Code of 1986, as amended. In accordance with the Code, the plan’s investments in the 401(h) account may not be used for, or diverted to, any purpose other than providing health benefits for retirees. The net assets held in the 401(h) account are calculated based on a pro-rata percentage allocation of the net assets in the pension plan. The related obligations for health benefits are not included in the pension plan’s obligations and are included in the Companies’ other postretirement benefit obligation. See Note E. (e) In accordance with ASU 2015-07, Fair Value Measurements (Topic 820): Disclosures for Investments in Certain Entities That Calculate Net Asset Value per Share (or its equivalent), certain investments that are measured at fair value using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. (f) Pending activities include security purchases and sales that have not settled, interest and dividends that have not been received, and reflects adjustments for available estimates at year end. The fair values of the plan assets at December 31, 2016 by asset category (see Note P) are as follows: (Millions of Dollars) Level 1 Level 2 Total Equity (a) $— $391 $391 Other Fixed Income Debt (b) — 250 250 Cash and Cash Equivalents (c) — 13 13 Total investments $— $654 $654 Funds for retiree health benefits (d) 165 105 270 Investments (including funds for retiree health benefits) $165 $759 $924 Funds for retiree health benefits measured at net asset value (d)(e) 37 Pending activities (f) 14 Total fair value of plan net assets $975 (a) - (f) Reference is made to footnotes (a) through (f) in the above table of other postretirement benefit plan assets at December 31, 2017 by asset category.
Schedule of Employer Contribution to Defined Savings Plan	The Companies also offer a defined contribution savings plan that covers substantially all employees and made contributions to the plan as follows: For the Years Ended December 31, (Millions of Dollars) 2017 2016 2015 Con Edison $40 $36 $34 CECONY 35 32 29

Other Postretirement Benefits (

Other Postretirement Benefits (Tables)	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Net Periodic Benefit Costs	The components of the Companies’ total periodic benefit costs for 2017 , 2016 and 2015 were as follows: Con Edison CECONY (Millions of Dollars) 2017 2016 2015 2017 2016 2015 Service cost – including administrative expenses $263 $275 $297 $246 $258 $279 Interest cost on projected benefit obligation 591 596 575 554 559 538 Expected return on plan assets (968) (947) (886) (917) (898) (840) Recognition of net actuarial loss 595 596 775 563 565 734 Recognition of prior service costs (17) 4 4 (19) 2 2 NET PERIODIC BENEFIT COST $464 $524 $765 $427 $486 $713 Amortization of regulatory asset (a) — — 1 — — 1 TOTAL PERIODIC BENEFIT COST $464 $524 $766 $427 $486 $714 Cost capitalized (181) (214) (301) (169) (203) (285) Reconciliation to rate level (34) 54 (74) (41) 58 (74) Cost charged to operating expenses $249 $364 $391 $217 $341 $355 (a) Relates to an increase in CECONY’s pension obligation of $45 million from a 1999 special retirement program. The components of the Companies’ total periodic postretirement benefit costs for 2017 , 2016 and 2015 were as follows: Con Edison CECONY (Millions of Dollars) 2017 2016 2015 2017 2016 2015 Service cost $20 $18 $20 $13 $13 $15 Interest cost on accumulated other postretirement benefit obligation 46 48 51 38 40 43 Expected return on plan assets (69) (77) (78) (61) (67) (68) Recognition of net actuarial loss 2 5 31 (3) 3 28 Recognition of prior service cost (17) (20) (20) (11) (14) (14) TOTAL PERIODIC POSTRETIREMENT BENEFIT COST $(18) $(26) $4 $(24) $(25) $4 Cost capitalized 8 11 (2) 10 10 (2) Reconciliation to rate level (4) 22 14 (2) 22 6 Cost charged to operating expenses $(14) $7 $16 $(16) $7 $8
Schedule of Funded Status	The funded status at December 31, 2017 , 2016 and 2015 was as follows: Con Edison CECONY (Millions of Dollars) 2017 2016 2015 2017 2016 2015 CHANGE IN PROJECTED BENEFIT OBLIGATION Projected benefit obligation at beginning of year $14,095 $14,377 $15,081 $13,203 $13,482 $14,137 Service cost – excluding administrative expenses 259 271 293 241 254 274 Interest cost on projected benefit obligation 591 596 575 554 559 538 Net actuarial loss/(gain) 1,231 (302) (996) 1,171 (282) (931) Plan amendments 6 (256) — — (259) — Benefits paid (646) (591) (576) (602) (551) (536) PROJECTED BENEFIT OBLIGATION AT END OF YEAR $15,536 $14,095 $14,377 $14,567 $13,203 $13,482 CHANGE IN PLAN ASSETS Fair value of plan assets at beginning of year $12,472 $11,759 $11,495 $11,815 $11,141 $10,897 Actual return on plan assets 2,041 829 126 1,935 787 118 Employer contributions 450 508 750 412 469 697 Benefits paid (646) (591) (576) (602) (551) (536) Administrative expenses (43) (33) (36) (41) (31) (35) FAIR VALUE OF PLAN ASSETS AT END OF YEAR $14,274 $12,472 $11,759 $13,519 $11,815 $11,141 FUNDED STATUS $(1,262) $(1,623) $(2,618) $(1,048) $(1,388) $(2,341) Unrecognized net loss $2,760 $3,157 $3,909 $2,624 $2,995 $3,704 Unrecognized prior service costs (223) (244) 16 (242) (258) 3 Accumulated benefit obligation 13,897 12,655 12,909 12,972 11,806 12,055 The funded status of the programs at December 31, 2017 , 2016 and 2015 were as follows: Con Edison CECONY (Millions of Dollars) 2017 2016 2015 2017 2016 2015 CHANGE IN BENEFIT OBLIGATION Benefit obligation at beginning of year $1,198 $1,287 $1,411 $1,007 $1,093 $1,203 Service cost 20 18 20 13 13 15 Interest cost on accumulated postretirement benefit obligation 46 48 51 38 40 43 Amendments — — — — — — Net actuarial loss/(gain) 53 (57) (103) 16 (52) (85) Benefits paid and administrative expenses (134) (134) (127) (124) (122) (117) Participant contributions 36 36 35 35 35 34 BENEFIT OBLIGATION AT END OF YEAR $1,219 $1,198 $1,287 $985 $1,007 $1,093 CHANGE IN PLAN ASSETS Fair value of plan assets at beginning of year $975 $994 $1,084 $851 $870 $950 Actual return on plan assets 150 60 (6) 130 52 (4) Employer contributions 17 7 6 8 7 6 EGWP payments 34 35 28 30 33 26 Participant contributions 35 36 35 35 35 34 Benefits paid (172) (157) (153) (161) (146) (142) FAIR VALUE OF PLAN ASSETS AT END OF YEAR $1,039 $975 $994 $893 $851 $870 FUNDED STATUS $(180) $(223) $(293) $(92) $(156) $(223) Unrecognized net loss/(gain) $(47) $(24) $28 $(85) $(42) $4 Unrecognized prior service costs (14) (31) (51) (7) (18) (32)
Schedule of Actuarial Assumptions	The actuarial assumptions were as follows: 2017 2016 2015 Weighted-average assumptions used to determine benefit obligations at December 31: Discount rate 3.70 % 4.25 % 4.25 % Rate of compensation increase CECONY 4.25 % 4.25 % 4.25 % O&R 4.00 % 4.00 % 4.00 % Weighted-average assumptions used to determine net periodic benefit cost for the years ended December 31: Discount rate 4.25 % 4.25 % 3.90 % Expected return on plan assets 7.50 % 7.80 % 7.80 % Rate of compensation increase CECONY 4.25 % 4.25 % 4.25 % O&R 4.00 % 4.00 % 4.00 % The actuarial assumptions were as follows: 2017 2016 2015 Weighted-average assumptions used to determine benefit obligations at December 31: Discount Rate CECONY 3.55 % 4.00 % 4.05 % O&R 3.70 % 4.20 % 4.20 % Weighted-average assumptions used to determine net periodic benefit cost for the years ended December 31: Discount Rate CECONY 4.00 % 4.05 % 3.75 % O&R 4.20 % 4.20 % 3.85 % Expected Return on Plan Assets 7.50 % 7.00 % 7.75 %
Schedule of Change of Assumed Health Care Cost Trend Rate	A one-percentage point change in the assumed health care cost trend rate would have the following effects at December 31, 2017 : Con Edison CECONY 1-Percentage-Point (Millions of Dollars) Increase Decrease Increase Decrease Effect on accumulated other postretirement benefit obligation $13 $11 $(20) $35 Effect on service cost and interest cost components for 2017 2 — (1) 1
Schedule of Expected Benefit Payments	Based on current assumptions, the Companies expect to make the following benefit payments over the next ten years : (Millions of Dollars) 2018 2019 2020 2021 2022 2023-2027 Con Edison $728 $738 $753 $765 $778 $4,083 CECONY 677 686 700 712 724 3,804 Based on current assumptions, the Companies expect to make the following benefit payments over the next ten years , net of receipt of governmental subsidies: (Millions of Dollars) 2018 2019 2020 2021 2022 2023-2027 Con Edison $83 $81 $78 $76 $75 $363 CECONY 73 70 67 65 64 303
Schedule of Plan Assets Allocations	The asset allocations for the pension plan at the end of 2017 , 2016 and 2015 , and the target allocation for 2018 are as follows: Target Allocation Range Plan Assets at December 31, Asset Category 2018 2017 2016 2015 Equity Securities 53% - 63% 58 % 58 % 57 % Debt Securities 28% - 38% 33 % 33 % 33 % Real Estate 7% -11% 9 % 9 % 10 % Total 100% 100 % 100 % 100 % The asset allocations for CECONY’s other postretirement benefit plans at the end of 2017 , 2016 and 2015 , and the target allocation for 2018 are as follows: Target Allocation Range Plan Assets at December 31, Asset Category 2018 2017 2016 2015 Equity Securities 50%-80% 60 % 60 % 59 % Debt Securities 20%-50% 40 % 40 % 41 % Total 100% 100 % 100 % 100 %
Schedule of Fair Value of Plan Assets	The fair values of the pension plan assets at December 31, 2017 by asset category are as follows: (Millions of Dollars) Level 1 Level 2 Total Investments within the fair value hierarchy U.S. Equity (a) $3,872 $28 $3,900 International Equity (b) 4,132 — 4,132 U.S. Government Issued Debt (c) — 1,786 1,786 Corporate Bonds Debt (d) — 2,450 2,450 Structured Assets Debt (e) — 3 3 Other Fixed Income Debt (f) — 125 125 Cash and Cash Equivalents (g) 124 352 476 Futures (h) 308 — 308 Total investments within the fair value hierarchy $8,436 $4,744 $13,180 Investments measured at NAV per share (n) Private Equity (i) 336 Real Estate (j) 1,214 Hedge Funds (k) 251 Total investments valued using NAV per share $1,801 Funds for retiree health benefits (l) (168) (94) (262) Funds for retiree health benefits measured at NAV per share (l)(n) (36) Total funds for retiree health benefits $(298) Investments (excluding funds for retiree health benefits) $8,268 $4,650 $14,683 Pending activities (m) (409) Total fair value of plan net assets $14,274 (a) U.S. Equity includes both actively- and passively-managed assets with investments in domestic equity index funds and actively-managed small-capitalization equities. (b) International Equity includes international equity index funds and actively-managed international equities. (c) U.S. Government Issued Debt includes agency and treasury securities. (d) Corporate Bonds Debt consists of debt issued by various corporations. (e) Structured Assets Debt includes commercial-mortgage-backed securities and collateralized mortgage obligations. (f) Other Fixed Income Debt includes municipal bonds, sovereign debt and regional governments. (g) Cash and Cash Equivalents include short term investments, money markets, foreign currency and cash collateral. (h) Futures consist of exchange-traded financial contracts encompassing U.S. Equity, International Equity and U.S. Government indices. (i) Private Equity consists of global equity funds that are not exchange-traded. (j) Real Estate investments include real estate funds based on appraised values that are broadly diversified by geography and property type. (k) Hedge Funds are within a commingled structure which invests in various hedge fund managers who can invest in all financial instruments. (l) The Companies set aside funds for retiree health benefits through a separate account within the pension trust, as permitted under Section 401(h) of the Internal Revenue Code of 1986, as amended. In accordance with the Code, the plan’s investments in the 401(h) account may not be used for, or diverted to, any purpose other than providing health benefits for retirees. The net assets held in the 401(h) account are calculated based on a pro-rata percentage allocation of the net assets in the pension plan. The related obligations for health benefits are not included in the pension plan’s obligations and are included in the Companies’ other postretirement benefit obligation. See Note F. (m) Pending activities include security purchases and sales that have not settled, interest and dividends that have not been received and reflects adjustments for available estimates at year end. (n) In accordance with ASU 2015-07, Fair Value Measurements (Topic 820): Disclosures for Investments in Certain Entities That Calculate Net Asset Value per Share (or its equivalent), certain investments that are measured at fair value using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. The fair values of the pension plan assets at December 31, 2016 by asset category are as follows: (Millions of Dollars) Level 1 Level 2 Total Investments within the fair value hierarchy U.S. Equity (a) $3,466 $— $3,466 International Equity (b) 3,187 371 3,558 U.S. Government Issued Debt (c) — 1,337 1,337 Corporate Bonds Debt (d) — 2,140 2,140 Structured Assets Debt (e) — 1 1 Other Fixed Income Debt (f) — 200 200 Cash and Cash Equivalents (g) 147 389 536 Futures (h) 296 68 364 Total investments within the fair value hierarchy $7,096 $4,506 $11,602 Investments measured at NAV per share (n) Private Equity (i) 247 Real Estate (j) 1,139 Hedge Funds (k) 229 Total investments valued using NAV per share $1,615 Funds for retiree health benefits (l) (165) (105) (270) Funds for retiree health benefits measured at NAV per share (l)(n) (37) Total funds for retiree health benefits $(307) Investments (excluding funds for retiree health benefits) $6,931 $4,401 $12,910 Pending activities (m) (438) Total fair value of plan net assets $12,472 (a) - (n) Reference is made to footnotes (a) through (n) in the above table of pension plan assets at December 31, 2017 by asset category. The fair values of the plan assets at December 31, 2017 by asset category as defined by the accounting rules for fair value measurements (see Note P) are as follows: (Millions of Dollars) Level 1 Level 2 Total Equity (a) $— $420 $420 Other Fixed Income Debt (b) — 286 286 Cash and Cash Equivalents (c) — 16 16 Total investments $— $722 $722 Funds for retiree health benefits (d) 168 94 262 Investments (including funds for retiree health benefits) $168 $816 $984 Funds for retiree health benefits measured at net asset value (d)(e) 36 Pending activities (f) 19 Total fair value of plan net assets $1,039 (a) Equity includes a passively managed commingled index fund benchmarked to the MSCI All Country World Index. (b) Other Fixed Income Debt includes a passively managed commingled index fund benchmarked to the Barclays Capital Aggregate Index. (c) Cash and Cash Equivalents include short term investments and money markets. (d) The Companies set aside funds for retiree health benefits through a separate account within the pension trust, as permitted under Section 401(h) of the Internal Revenue Code of 1986, as amended. In accordance with the Code, the plan’s investments in the 401(h) account may not be used for, or diverted to, any purpose other than providing health benefits for retirees. The net assets held in the 401(h) account are calculated based on a pro-rata percentage allocation of the net assets in the pension plan. The related obligations for health benefits are not included in the pension plan’s obligations and are included in the Companies’ other postretirement benefit obligation. See Note E. (e) In accordance with ASU 2015-07, Fair Value Measurements (Topic 820): Disclosures for Investments in Certain Entities That Calculate Net Asset Value per Share (or its equivalent), certain investments that are measured at fair value using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. (f) Pending activities include security purchases and sales that have not settled, interest and dividends that have not been received, and reflects adjustments for available estimates at year end. The fair values of the plan assets at December 31, 2016 by asset category (see Note P) are as follows: (Millions of Dollars) Level 1 Level 2 Total Equity (a) $— $391 $391 Other Fixed Income Debt (b) — 250 250 Cash and Cash Equivalents (c) — 13 13 Total investments $— $654 $654 Funds for retiree health benefits (d) 165 105 270 Investments (including funds for retiree health benefits) $165 $759 $924 Funds for retiree health benefits measured at net asset value (d)(e) 37 Pending activities (f) 14 Total fair value of plan net assets $975 (a) - (f) Reference is made to footnotes (a) through (f) in the above table of other postretirement benefit plan assets at December 31, 2017 by asset category.

Environmental Matters (Tables)

Environmental Matters (Tables)	12 Months Ended
	Dec. 31, 2017
Environmental Remediation Obligations [Abstract]
Accrued Liabilities and Regulatory Assets	The accrued liabilities and regulatory assets related to Superfund Sites at December 31, 2017 and 2016 were as follows: Con Edison CECONY (Millions of Dollars) 2017 2016 2017 2016 Accrued Liabilities: Manufactured gas plant sites $651 $664 $551 $567 Other Superfund Sites 86 89 86 88 Total $737 $753 $637 $655 Regulatory assets $793 $823 $677 $711
Environmental Remediation Costs	Environmental remediation costs incurred related to Superfund Sites at December 31, 2017 and 2016 were as follows: Con Edison CECONY (Millions of Dollars) 2017 2016 2017 2016 Remediation costs incurred $24 $34 $19 $21
Accrued Liability for Asbestos Suits and Workers' Compensation Proceedings	The accrued liability for asbestos suits and workers’ compensation proceedings (including those related to asbestos exposure) and the amounts deferred as regulatory assets for the Companies at December 31, 2017 and 2016 were as follows: Con Edison CECONY (Millions of Dollars) 2017 2016 2017 2016 Accrued liability – asbestos suits $8 $8 $7 $7 Regulatory assets – asbestos suits $8 $8 $7 $7 Accrued liability – workers’ compensation $84 $88 $80 $83 Regulatory assets – workers’ compensation $10 $13 $10 $13

Other Material Contingencies (T

Other Material Contingencies (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Summary of Total Guarantees	A summary, by type and term, of Con Edison’s total guarantees at December 31, 2017 is as follows: Guarantee Type 0 – 3 years 4 – 10 years > 10 years Total (Millions of Dollars) Con Edison Transmission $643 $404 $— $1,047 Energy transactions 431 27 211 669 Renewable electric production projects 210 — 24 234 Other 123 — — 123 Total $1,407 $431 $235 $2,073

Electricity Purchase Agreemen42

Electricity Purchase Agreements (Tables)	12 Months Ended
	Dec. 31, 2017
Regulated Operations [Abstract]
Summary of Significant Terms of Electricity Purchase Agreements	At December 31, 2017 , the significant terms of the electricity purchase agreements with non-utility generators were as follows: Facility Equity Owner Plant Output (MW) Contracted Output (MW) Contract Start Date Contract Term (Years) Brooklyn Navy Yard Brooklyn Navy Yard Cogeneration Partners, LP 322 303 November 1996 40 Indian Point (a) Entergy Nuclear Power Marketing, LLC 2,150 500 August 2001 16 (a) A portion of this contract ended in 2017 and a portion ends in 2018.
Summary of Estimated Capacity and Other Fixed Payments	The future capacity and other fixed payments under the contracts are estimated to be as follows: (Millions of Dollars) 2018 2019 2020 2021 2022 All Years Thereafter Con Edison $257 $202 $114 $65 $54 $656 CECONY 255 198 111 64 54 656
Summary of Capacity, Energy and Other Fixed Payments	The company’s payments under the significant terms of the agreements for capacity, energy and other fixed payments in 2017 , 2016 and 2015 were as follows: For the Years Ended December 31, (Millions of Dollars) 2017 2016 2015 Linden Cogeneration (a) $114 $304 $323 Indian Point 211 203 226 Astoria Energy (b) — 50 178 Astoria Generating Company 92 16 — Brooklyn Navy Yard 117 119 113 Indeck Corinth (c) — — 25 Cogen Technologies 18 — — Total $552 $692 $865 (a) Contract term ended in 2017. (b) Contract term ended in 2016. (c) Contract term ended in 2015.

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2017
Leases [Abstract]
Schedule of Capital Leases	The following assets under capital leases are included in the Companies’ consolidated balance sheets at December 31, 2017 and 2016 : Con Edison CECONY (Millions of Dollars) 2017 2016 2017 2016 UTILITY PLANT Common $2 $3 $1 $2
Future Minimum Rental Payments for Operating Leases	The future minimum lease commitments under the Companies’ operating lease agreements that are not cancellable by the Companies are as follows: (Millions of Dollars) Con Edison CECONY 2018 $63 $55 2019 63 56 2020 63 55 2021 62 54 2022 59 53 All years thereafter 746 645 Total $1,056 $918

Income Tax (Tables)

Income Tax (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax	The components of income tax are as follows: Con Edison CECONY (Millions of Dollars) 2017 2016 2015 2017 2016 2015 State Current $(2) $(42) $38 $37 $(1) $48 Deferred 103 188 93 75 114 82 Federal Current (11) (43) (86) 73 59 77 Deferred 391 604 569 504 435 372 Amortization of investment tax credits (9) (9) (9) (4) (4) (5) Total income tax expense $472 $698 $605 $685 $603 $574
Schedule of Differences on Deferred Tax Assets and Liabilities	The tax effects of temporary differences, which gave rise to deferred tax assets and liabilities, are as follows: Con Edison CECONY (Millions of Dollars) 2017 2016 2017 2016 Deferred tax liabilities: Property basis differences $6,555 $9,446 $5,968 $8,620 Regulatory assets: Unrecognized pension and other postretirement costs 697 1,162 656 1,104 Future income tax — 986 — 940 Environmental remediation costs 219 333 187 287 Deferred storm costs 11 23 — 1 Other regulatory assets 269 371 241 321 Equity investments 263 363 — — Total deferred tax liabilities $8,014 $12,684 $7,052 $11,273 Deferred tax assets: Accrued pension and other postretirement costs $264 $581 $187 $467 Regulatory liabilities: Future income tax 698 — 660 — Other regulatory liabilities 593 822 524 728 Superfund and other environmental costs 203 304 176 265 Asset retirement obligations 86 99 79 92 Loss carryforwards 95 59 — — Tax credits carryforward 658 498 — — Valuation allowance (33) (16) — — Other 112 303 148 312 Total deferred tax assets 2,676 2,650 1,774 1,864 Net deferred tax liabilities $5,338 $10,034 $5,278 $9,409 Unamortized investment tax credits 157 171 28 41 Net deferred tax liabilities and unamortized investment tax credits $5,495 $10,205 $5,306 $9,450
Schedule of Income Tax Reconciliation	Reconciliation of the difference between income tax expense and the amount computed by applying the prevailing statutory income tax rate to income before income taxes is as follows: Con Edison CECONY (% of Pre-tax income) 2017 2016 2015 2017 2016 2015 STATUTORY TAX RATE Federal 35 % 35 % 35 % 35 % 35 % 35 % Changes in computed taxes resulting from: State income tax 4 4 5 4 4 5 Cost of removal 1 (1 ) (5 ) 1 (1 ) (5 ) Other plant-related items (1 ) — — (1 ) (1 ) — TCJA tax rate reduction (13 ) — — — — — Renewable energy credits (1 ) (1 ) (1 ) — — — Research and development credits — (1 ) — — (1 ) — Other (2 ) — — (1 ) — — Effective tax rate 23 % 36 % 34 % 38 % 36 % 35 %
Summary of Unrecognized Tax Benefits	A reconciliation of the beginning and ending amounts of unrecognized tax benefits for Con Edison and CECONY follows: Con Edison CECONY (Millions of Dollars) 2017 2016 2015 2017 2016 2015 Balance at January 1, $42 $34 $34 $21 $2 $2 Additions based on tax positions related to the current year 1 2 — 1 2 — Additions based on tax positions of prior years 1 19 1 1 19 — Reductions for tax positions of prior years (24) (13) — (18) (2) — Reductions from expiration of statute of limitations (2) — (1) — — — Settlements (6) — — — — — Balance at December 31, $12 $42 $34 $5 $21 $2

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of Stock-Based Compensation Expense	The following table summarizes stock-based compensation expense recognized by the Companies in the years ended December 31, 2017 , 2016 and 2015 : Con Edison CECONY (Millions of Dollars) 2017 2016 2015 2017 2016 2015 Performance-based restricted stock $53 $42 $27 $45 $36 $23 Time-based restricted stock 2 2 1 2 2 1 Non-employee director deferred stock compensation 2 2 2 2 2 2 Stock purchase plan 6 4 4 6 4 3 Total $63 $50 $34 $55 $44 $29 Income tax benefit $25 $20 $14 $22 $18 $12
Assumptions Used to Calculate Fair Value of Awards	The assumptions used to calculate the fair value of the awards were as follows: 2017 2016 2015 Risk-free interest rate (a) 1.76% - 1.89% 0.85% - 1.20% 0.64% - 3.28% Expected term (b) 3 years 3 years 3 years Expected share price volatility (c) 11.01% - 14.70% 17.72% - 18.22% 15.82% (a) The risk-free rate is based on the U.S. Treasury zero-coupon yield curve. (b) The expected term of the Performance RSUs equals the vesting period. The Companies do not expect significant forfeitures to occur. (c) Based on historical experience.
Summary of Changes in Status of Performance RSUs	A summary of changes in the status of the Performance RSUs’ TSR and non-TSR portions during the year ended December 31, 2017 is as follows: Con Edison CECONY Weighted Average Grant Date Fair Value (a) Weighted Average Grant Date Fair Value (a) Units TSR Portion (b) Non-TSR Portion (c) Units TSR Portion (b) Non-TSR Portion (c) Non-vested at December 31, 2016 1,087,137 $55.45 $63.03 848,342 $54.92 $63.00 Granted 368,150 73.13 74.54 277,318 72.78 74.72 Vested (375,684) 25.36 53.66 (293,842) 25.32 53.66 Forfeited (50,671) 76.29 72.23 (46,226) 76.41 72.31 Transferred (d) — — — (1,426) 53.01 72.52 Non-vested at December 31, 2017 1,028,932 $71.74 $70.11 784,166 $71.06 $70.08 (a) The TSR and non-TSR Portions each account for 50 percent of the awards’ value. (b) Fair value is determined using the Monte Carlo simulation described above. Weighted average grant date fair value does not reflect any accrual or payment of dividends prior to vesting. (c) Fair value is determined using the market price of one share of Con Edison common stock on the grant date. The market price has not been discounted to reflect that dividends do not accrue and are not payable on Performance RSUs until vesting. (d) Represents allocation to another Con Edison subsidiary of a portion of the Performance RSUs that had been awarded to a CECONY officer who transferred to the other subsidiary.
Summary of Changes in Status of Time-Based Awards	A summary of changes in the status of time-based awards during the year ended December 31, 2017 is as follows: Con Edison CECONY Units Weighted Average Grant Date Fair Value Units Weighted Average Grant Date Fair Value Non-vested at December 31, 2016 65,980 $64.04 62,580 $64.03 Granted 23,000 77.66 21,800 77.66 Vested (21,359) 53.77 (20,359) 53.77 Forfeited (2,751) 71.62 (2,601) 71.93 Non-vested at December 31, 2017 64,870 $71.93 61,420 $71.93

Financial Information by Busi46

Financial Information by Business Segment (Tables)	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Financial Data for Business Segments	The financial data for the business segments are as follows: As of and for the Year Ended December 31, 2017 (Millions of Dollars) Operating revenues Inter- segment revenues Depreciation and amortization Operating income Other Income (deductions) Interest charges Income taxes on operating income (a) Total assets Capital expenditures CECONY Electric $7,972 $16 $925 $1,862 $7 $472 $511 $29,661 $1,905 Gas 1,901 6 185 472 — 113 152 8,387 909 Steam 595 75 85 71 — 38 25 2,403 90 Consolidation adjustments — (97) — — — — — — — Total CECONY $10,468 $— $1,195 $2,405 $7 $623 $688 $40,451 $2,904 O&R Electric $642 $— $51 $100 $1 $24 $30 $1,949 $128 Gas 232 — 20 41 — 12 12 824 61 Other — — — — — — — — — Total O&R $874 $— $71 $141 $1 $36 $42 $2,773 $189 Clean Energy Businesses $694 $— $74 $69 $33 $43 $(273) $2,735 $447 Con Edison Transmission 2 — 1 (8) 80 16 (11) 1,222 66 Other (b) (5) — — 3 (5) 11 13 930 — Total Con Edison $12,033 $— $1,341 $2,610 $116 $729 $459 $48,111 $3,606 As of and for the Year Ended December 31, 2016 (Millions of Dollars) Operating revenues Inter- segment revenues Depreciation and amortization Operating income Other Income (deductions) Interest charges Income taxes on operating income (a) Total assets Capital expenditures CECONY Electric $8,106 $17 $865 $1,847 $2 $459 $495 $30,708 $1,819 Gas 1,508 6 159 357 (1) 105 92 7,553 811 Steam 551 88 82 58 (1) 39 30 2,595 126 Consolidation adjustments — (111) — — — — — — — Total CECONY $10,165 $— $1,106 $2,262 $— $603 $617 $40,856 $2,756 O&R Electric $637 $— $49 $95 $1 $24 $30 $1,949 $114 Gas 184 — 18 35 — 12 10 809 52 Other — — — — — — — — — Total O&R $821 $— $67 $130 $1 $36 $40 $2,758 $166 Clean Energy Businesses $1,091 $7 $42 $183 $21 $34 $53 $2,551 $1,235 Con Edison Transmission — — — (3) 43 6 — 1,150 1,078 Other (b) (2) (7) 1 3 (1) 17 4 940 — Total Con Edison $12,075 $— $1,216 $2,575 $64 $696 $714 $48,255 $5,235 As of and for the Year Ended December 31, 2015 (Millions of Dollars) Operating revenues Inter- segment revenues Depreciation and amortization Operating income Other Income (deductions) Interest charges Income taxes on operating income (a) Total assets Capital expenditures CECONY Electric $8,172 $18 $820 $1,798 $(2) $447 $447 $30,603 $1,658 Gas 1,527 6 142 356 (2) 96 100 6,974 671 Steam 629 86 78 93 (1) 41 41 2,653 106 Consolidation adjustments — (110) — — — — — — — Total CECONY $10,328 $— $1,040 $2,247 $(5) $584 $588 $40,230 $2,435 O&R Electric $663 $— $50 $103 $(2) $23 $31 $2,140 $114 Gas 182 — 18 18 (2) 12 2 579 46 Other — — — — — — — — — Total O&R $845 $— $68 $121 $(4) $35 $33 $2,719 $160 Clean Energy Businesses $1,383 $(2) $22 $58 $35 $11 $22 $1,680 $823 Con Edison Transmission — — — — — — — 3 — Other (b) (2) 2 — 1 (2) 23 1 1,010 — Total Con Edison $12,554 $— $1,130 $2,427 $24 $653 $644 $45,642 $3,418 (a) For Con Edison, the income tax expense/(benefit) on non-operating income was $13 million , $(16) million and $(40) million in 2017 , 2016 and 2015 , respectively. For CECONY, the income tax expense/(benefit) on non-operating income was $(3) million , $(14) million and $(14) million in 2017 , 2016 and 2015 , respectively. At December 31, 2017, Con Edison re-measured its deferred tax assets and liabilities based upon the 21 percent corporate income tax rate under the TCJA. As a result, Con Edison, decreased its federal income tax expense by $259 million ( $269 million , $11 million and $(21) million , respectively, for Clean Energy Businesses, Con Edison Transmission and the parent company). See “Other Regulatory Matters” in Note B and Note L to the financial statements in Item 8. (b) Parent company and consolidation adjustments. Other does not represent a business segment.

Derivative Instruments and He47

Derivative Instruments and Hedging Activities (Tables)	12 Months Ended
	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Offsetting of Assets	The fair values of the Companies’ commodity derivatives including the offsetting of assets and liabilities on the consolidated balance sheet at December 31, 2017 and 2016 were: (Millions of Dollars) 2017 2016 Balance Sheet Location Gross Amounts of Recognized Assets/ (Liabilities) Gross Amounts Offset Net Amounts of Assets/(Liabilities) (a) Gross Amounts of Recognized Assets/ (Liabilities) Gross Amounts Offset Net Amounts of Assets/(Liabilities) (a) Con Edison Fair value of derivative assets Current $83 $(51) $32 (b) $81 $(64) $17 (b) Noncurrent 10 (4) 6 49 (43) 6 Total fair value of derivative assets $93 $(55) $38 $130 $(107) $23 Fair value of derivative liabilities Current $(67) $50 $(17) $(138) $61 $(77) Noncurrent (43) 5 (38) (91) 52 (39) (c) Total fair value of derivative liabilities $(110) $55 $(55) $(229) $113 $(116) Net fair value derivative assets/(liabilities) $(17) $— $(17) (b) $(99) $6 $(93) (b)(c) CECONY Fair value of derivative assets Current $39 $(15) $24 (b) $52 $(45) $7 (b) Noncurrent 9 (4) 5 41 (35) 6 Total fair value of derivative assets $48 $(19) $29 $93 $(80) $13 Fair value of derivative liabilities Current $(26) $14 $(12) $(111) $45 $(66) Noncurrent (36) 4 (32) (77) 44 (33) Total fair value of derivative liabilities $(62) $18 $(44) $(188) $89 $(99) Net fair value derivative assets/(liabilities) $(14) $(1) $(15) (b) $(95) $9 $(86) (b) (a) Derivative instruments and collateral were offset on the consolidated balance sheet as applicable under the accounting rules. The Companies enter into master agreements for their commodity derivatives. These agreements typically provide offset in the event of contract termination. In such case, generally the non-defaulting party’s payable will be offset by the defaulting party’s payable. The non-defaulting party will customarily notify the defaulting party within a specific time period and come to an agreement on the early termination amount. (b) At December 31, 2017 and 2016 , margin deposits for Con Edison ( $12 million and $7 million , respectively) and CECONY ( $11 million and $7 million , respectively) were classified as derivative assets on the consolidated balance sheet, but not included in the table. Margin is collateral, typically cash, that the holder of a derivative instrument is required to deposit in order to transact on an exchange and to cover its potential losses with its broker or the exchange. (c) Does not include ($1) million for interest rate swap (see below).
Offsetting of Liabilities	The fair values of the Companies’ commodity derivatives including the offsetting of assets and liabilities on the consolidated balance sheet at December 31, 2017 and 2016 were: (Millions of Dollars) 2017 2016 Balance Sheet Location Gross Amounts of Recognized Assets/ (Liabilities) Gross Amounts Offset Net Amounts of Assets/(Liabilities) (a) Gross Amounts of Recognized Assets/ (Liabilities) Gross Amounts Offset Net Amounts of Assets/(Liabilities) (a) Con Edison Fair value of derivative assets Current $83 $(51) $32 (b) $81 $(64) $17 (b) Noncurrent 10 (4) 6 49 (43) 6 Total fair value of derivative assets $93 $(55) $38 $130 $(107) $23 Fair value of derivative liabilities Current $(67) $50 $(17) $(138) $61 $(77) Noncurrent (43) 5 (38) (91) 52 (39) (c) Total fair value of derivative liabilities $(110) $55 $(55) $(229) $113 $(116) Net fair value derivative assets/(liabilities) $(17) $— $(17) (b) $(99) $6 $(93) (b)(c) CECONY Fair value of derivative assets Current $39 $(15) $24 (b) $52 $(45) $7 (b) Noncurrent 9 (4) 5 41 (35) 6 Total fair value of derivative assets $48 $(19) $29 $93 $(80) $13 Fair value of derivative liabilities Current $(26) $14 $(12) $(111) $45 $(66) Noncurrent (36) 4 (32) (77) 44 (33) Total fair value of derivative liabilities $(62) $18 $(44) $(188) $89 $(99) Net fair value derivative assets/(liabilities) $(14) $(1) $(15) (b) $(95) $9 $(86) (b) (a) Derivative instruments and collateral were offset on the consolidated balance sheet as applicable under the accounting rules. The Companies enter into master agreements for their commodity derivatives. These agreements typically provide offset in the event of contract termination. In such case, generally the non-defaulting party’s payable will be offset by the defaulting party’s payable. The non-defaulting party will customarily notify the defaulting party within a specific time period and come to an agreement on the early termination amount. (b) At December 31, 2017 and 2016 , margin deposits for Con Edison ( $12 million and $7 million , respectively) and CECONY ( $11 million and $7 million , respectively) were classified as derivative assets on the consolidated balance sheet, but not included in the table. Margin is collateral, typically cash, that the holder of a derivative instrument is required to deposit in order to transact on an exchange and to cover its potential losses with its broker or the exchange. (c) Does not include ($1) million for interest rate swap (see below).
Realized and Unrealized Gains or Losses on Commodity Derivatives	The following table presents the realized and unrealized gains or losses on commodity derivatives that have been deferred or recognized in earnings for the years ended December 31, 2017 and 2016 : Con Edison CECONY (Millions of Dollars) Balance Sheet Location 2017 2016 2017 2016 Pre-tax gains/(losses) deferred in accordance with accounting rules for regulated operations: Current Deferred derivative gains $3 $23 $4 $18 Noncurrent Deferred derivative gains — 1 — 2 Total deferred gains/(losses) $3 $24 $4 $20 Current Deferred derivative losses $51 $22 $49 $18 Current Recoverable energy costs (154) (212) (144) (194) Noncurrent Deferred derivative losses 4 2 5 4 Total deferred gains/(losses) $(99) $(188) $(90) $(172) Net deferred gains/(losses) $(96) $(164) $(86) $(152) Income Statement Location Pre-tax gain/(loss) recognized in income Purchased power expense $— $(101) (b) $— $— Gas purchased for resale 3 (112) — — Non-utility revenue 5 (a) 9 (b) — — Other operations and maintenance expense — 1 (c) — 1 (c) Total pre-tax gain/(loss) recognized in income $8 $(203) $— $1 (a) For the year ended December 31, 2017 , Con Edison recorded an immaterial unrealized pre-tax gain in non-utility operating revenue. (b) For the year ended December 31, 2016 , Con Edison recorded unrealized pre-tax gains and losses in non-utility operating revenue ( $5 million loss) and purchased power expense ( $11 million gain). (c) For the year ended December 31, 2016 , Con Edison and CECONY recorded an unrealized gain in other operations and maintenance expense ( $1 million ).
Hedged Volume of Derivative Transactions	The following table presents the hedged volume of Con Edison’s and CECONY’s derivative transactions at December 31, 2017 : Electric Energy (MWh) (a)(b) Capacity (MW) (a) Natural Gas (Dt) (a)(b) Refined Fuels (gallons) Con Edison 31,741,652 10,275 177,433,144 3,780,000 CECONY 29,696,600 5,100 169,790,000 3,780,000 (a) Volumes are reported net of long and short positions, except natural gas collars where the volumes of long positions are reported. (b) Excludes electric congestion and gas basis swap contracts which are associated with electric and gas contracts and hedged volumes.
Aggregate Fair Value of Companies' Derivative Instruments with Credit-Risk-Related Contingent Features	The following table presents the aggregate fair value of the Companies’ derivative instruments with credit-risk-related contingent features that are in a net liability position, the collateral posted for such positions and the additional collateral that would have been required to be posted had the lowest applicable credit rating been reduced one level and to below investment grade at December 31, 2017 : (Millions of Dollars) Con Edison (a) CECONY (a) Aggregate fair value – net liabilities $39 $31 Collateral posted 68 63 Additional collateral (b) (downgrade one level from current ratings) — — Additional collateral (b)(c) (downgrade to below investment grade from current ratings) 29 22 (a) Non-derivative transactions for the purchase and sale of electricity and gas and qualifying derivative instruments, which have been designated as normal purchases or normal sales, are excluded from the table. These transactions primarily include purchases of electricity from independent system operators. In the event the Utilities and the Clean Energy Businesses were no longer extended unsecured credit for such purchases, the Companies would be required to post additional collateral of $8 million at December 31, 2017 . For certain other such non-derivative transactions, the Companies could be required to post collateral under certain circumstances, including in the event counterparties had reasonable grounds for insecurity. (b) The Companies measure the collateral requirements by taking into consideration the fair value amounts of derivative instruments that contain credit-risk-related contingent features that are in a net liabilities position plus amounts owed to counterparties for settled transactions and amounts required by counterparties for minimum financial security. The fair value amounts represent unrealized losses, net of any unrealized gains where the Companies have a legally enforceable right to offset. (c) Derivative instruments that are net assets have been excluded from the table. At December 31, 2017 , if Con Edison had been downgraded to below investment grade, it would have been required to post additional collateral for such derivative instruments of $18 million .

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Assets and Liabilities Measured at Fair Value on Recurring Basis	Assets and liabilities measured at fair value on a recurring basis for the years ended December 31, 2017 and 2016 are summarized below. 2017 2016 (Millions of Dollars) Level 1 Level 2 Level 3 Netting Adjustment (e) Total Level 1 Level 2 Level 3 Netting Adjustment (e) Total Con Edison Derivative assets: Commodity (a)(b)(c) $5 $77 $7 $(39) $50 $14 $33 $7 $(24) $30 Other (a)(b)(d) 283 120 — — 403 222 111 — — 333 Total assets $288 $197 $7 $(39) $453 $236 $144 $7 $(24) $363 Derivative liabilities: Commodity (a)(b)(c) $8 $93 $6 $(52) $55 $4 $144 $6 $(38) $116 Interest Rate Swap (a)(b)(c)(f) — — — — — — 1 — — 1 Total liabilities $8 $93 $6 $(52) $55 $4 $145 $6 $(38) $117 CECONY Derivative assets: Commodity (a)(b)(c) $3 $40 $4 $(7) $40 $10 $19 $1 $(10) $20 Other (a)(b)(d) 260 114 — — 374 200 106 — — 306 Total assets $263 $154 $4 $(7) $414 $210 $125 $1 $(10) $326 Derivative liabilities: Commodity (a)(b)(c) $5 $57 $— $(18) $44 $1 $124 $— $(26) $99 (a) The Companies’ policy is to review the fair value hierarchy and recognize transfers into and transfers out of the levels at the end of each reporting period. Con Edison and CECONY had $11 million and $10 million , respectively, of commodity derivative liabilities transferred from level 3 to level 2 during the year ended December 31, 2017 because of availability of observable market data due to the decrease in the terms of certain contracts from beyond three years as of September 30, 2017 to less than three years as of December 31, 2017 . There were no transfers between levels 1 , 2 and 3 for the year ended December 31, 2016 . (b) Level 2 assets and liabilities include investments held in the deferred compensation plan and/or non-qualified retirement plans, exchange-traded contracts where there is insufficient market liquidity to warrant inclusion in Level 1, certain over-the-counter derivative instruments for electricity, refined products and natural gas. Derivative instruments classified as Level 2 are valued using industry standard models that incorporate corroborated observable inputs; such as pricing services or prices from similar instruments that trade in liquid markets, time value and volatility factors. (c) The accounting rules for fair value measurements and disclosures require consideration of the impact of nonperformance risk (including credit risk) from a market participant perspective in the measurement of the fair value of assets and liabilities. At December 31, 2017 and 2016 , the Companies determined that nonperformance risk would have no material impact on their financial position or results of operations. (d) Other assets are comprised of assets such as life insurance contracts within the deferred compensation plan and non-qualified retirement plans. (e) Amounts represent the impact of legally-enforceable master netting agreements that allow the Companies to net gain and loss positions and cash collateral held or placed with the same counterparties. (f) See Note O.
Schedule of Commodity Derivatives	Fair Value of Level 3 at December 31, 2017 (Millions of Dollars) Valuation Techniques Unobservable Inputs Range Con Edison — Commodity Electricity $(1) Discounted Cash Flow Forward energy prices (a) $15.52-$115.00 per MWh Discounted Cash Flow Forward capacity prices (a) $1.50-$12.50 per kW-month Transmission Congestion Contracts $2 Discounted Cash Flow Inter-zonal forward price curves adjusted for historical zonal losses (b) $0.19-$3.57 per MWh Total Con Edison — Commodity $1 CECONY — Commodity Electricity $3 Discounted Cash Flow Forward capacity prices (a) $2.35-$12.50 per kW-month Transmission Congestion Contracts $1 Discounted Cash Flow Inter-zonal forward price curves adjusted for historical zonal losses (b) $0.51-$3.00 per MWh Total CECONY — Commodity $4 (a) Generally, increases/(decreases) in this input in isolation would result in a higher/(lower) fair value measurement. (b) Generally, increases/(decreases) in this input in isolation would result in a lower/(higher) fair value measurement.
Reconciliation of Beginning and Ending Net Balances for Assets and Liabilities Measured at Level 3 Fair Value	The table listed below provides a reconciliation of the beginning and ending net balances for assets and liabilities measured at fair value for the years ended December 31, 2017 and 2016 and classified as Level 3 in the fair value hierarchy: Con Edison CECONY (Millions of Dollars) 2017 2016 2017 2016 Beginning balance as of January 1, $1 $6 $1 $8 Included in earnings 8 (7) 2 (1) Included in regulatory assets and liabilities (13) (6) (7) (6) Purchases 2 4 1 2 Sales — 4 — — Settlements (8) — (3) (2) Transfer out of level 3 11 — 10 — Ending balance as of December 31, $1 $1 $4 $1

Variable Interest Entities (Tab

Variable Interest Entities (Tables)	12 Months Ended
	Dec. 31, 2017
Equity Method Investments and Joint Ventures [Abstract]
Schedule of Business Acquisitions, by Acquisition	(Millions of Dollars) 2017 2016 Restricted cash $5 $8 Non-utility property, less accumulated depreciation of $12 and $9, respectively 101 104 Other assets 8 43 Total assets (a) $114 $155 Long-term debt due within one year $2 $3 Other liabilities 28 38 Long-term debt 58 60 Total liabilities (b) $88 $101 (a) The assets of Texas Solar 4 represent assets of a consolidated VIE that can be used only to settle obligations of the consolidated VIE. (b) The liabilities of Texas Solar 4 represent liabilities of a consolidated VIE for which creditors do not have recourse to the general credit of the primary beneficiary.
Summary of VIEs	The following table summarizes the VIEs in which Con Edison Development has entered into as of December 31, 2017 : Project Name (a) Generating Capacity (b) (MW AC) Power Purchase Agreement Term in Years Year of Initial Investment Location Maximum Millions of Dollars ) (c) Copper Mountain Solar 3 128 20 2014 Nevada $175 Mesquite Solar 1 83 20 2013 Arizona 103 Copper Mountain Solar 2 75 25 2013 Nevada 82 California Solar 55 25 2012 California 63 Broken Bow II 38 25 2014 Nebraska 44 Texas Solar 4 32 25 2014 Texas 19 (a) With the exception of Texas Solar 4, Con Edison’s ownership interest is 50 percent and these projects are accounted for using the equity method of accounting. With the exception of Texas Solar 4, Con Edison is not the primary beneficiary since the power to direct the activities that most significantly impact the economics of the entities are shared equally between Con Edison Development and third parties. Con Edison’s ownership interest in Texas Solar 4 is 80 percent and is consolidated in the financial statements. Con Edison is the primary beneficiary since the power to direct the activities that most significantly impact the economics of Texas Solar 4 is held by Con Edison Development. (b) Represents Con Edison Development’s ownership interest in the project. (c) For investments accounted for under the equity method, maximum exposure is equal to the carrying value of the investment on the consolidated balance sheet. For consolidated investments, such as Texas Solar 4, maximum exposure is equal to the net assets of the project on the consolidated balance sheet less any applicable noncontrolling interest ( $7 million for Texas Solar 4). Con Edison did not provide any financial or other support during the year that was not previously contractually required.

Related Party Transactions (Tab

Related Party Transactions (Tables)	12 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Summary of Costs of Administrative and Other Services Provided and Received	The costs of administrative and other services provided by CECONY to, and received by it from, Con Edison and its other subsidiaries for the years ended December 31, 2017 , 2016 and 2015 were as follows: CECONY (Millions of Dollars) 2017 2016 2015 Cost of services provided $111 $108 $99 Cost of services received 64 64 60

General (Details)

General (Details)	12 Months Ended
	Dec. 31, 2017subsidiaryregistrant
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of registrants | registrant	2
Number of regulated subsidiaries | subsidiary	2

Summary of Significant Accoun52

Summary of Significant Accounting Policies - Plant and Depreciation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Public Utility, Property, Plant and Equipment [Line Items]
Annual aggregate depreciation allowance	$ 1,253
Non-Utility Plant | Minimum
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	3 years
Non-Utility Plant | Maximum
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	30 years
CECONY
Public Utility, Property, Plant and Equipment [Line Items]
AFUDC rates (percent)	5.50%	4.70%	4.40%
Average depreciation rates (percent)	3.10%	3.10%	3.10%
Annual aggregate depreciation allowance	$ 1,184
CECONY | Electric | Minimum
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	5 years
CECONY | Electric | Maximum
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	95 years
CECONY | Gas | Minimum
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	5 years
CECONY | Gas | Maximum
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	100 years
CECONY | Steam | Minimum
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	5 years
CECONY | Steam | Maximum
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	80 years
CECONY | General Plant | Minimum
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	5 years
CECONY | General Plant | Maximum
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	55 years
O&R
Public Utility, Property, Plant and Equipment [Line Items]
AFUDC rates (percent)	2.50%	3.50%	0.40%
Average depreciation rates (percent)	2.90%	2.90%	3.00%
O&R | Electric | Minimum
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	5 years
O&R | Electric | Maximum
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	75 years
O&R | Gas | Minimum
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	5 years
O&R | Gas | Maximum
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	75 years
O&R | General Plant | Minimum
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	5 years
O&R | General Plant | Maximum
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	50 years

Summary of Significant Accoun53

Summary of Significant Accounting Policies - Capitalized Cost of Utility Plant (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Public Utility, Property, Plant and Equipment [Line Items]
General	$ 3,008	$ 2,719
Held for future use	76	74
Construction work in progress	1,605	1,175
NET UTILITY PLANT	35,273	33,045
Electric Generation
Public Utility, Property, Plant and Equipment [Line Items]
Generation	544	479
Electric Transmission
Public Utility, Property, Plant and Equipment [Line Items]
Transmission	3,210	3,184
Electric Distribution
Public Utility, Property, Plant and Equipment [Line Items]
Distribution	18,959	18,150
Gas
Public Utility, Property, Plant and Equipment [Line Items]
Gas	6,976	6,285
Steam
Public Utility, Property, Plant and Equipment [Line Items]
Steam	1,798	1,882
General
Public Utility, Property, Plant and Equipment [Line Items]
General	2,105	1,816
CECONY
Public Utility, Property, Plant and Equipment [Line Items]
General	2,753	2,490
Held for future use	67	65
Construction work in progress	1,502	1,104
NET UTILITY PLANT	33,205	31,115
CECONY | Electric Generation
Public Utility, Property, Plant and Equipment [Line Items]
Generation	544	479
CECONY | Electric Transmission
Public Utility, Property, Plant and Equipment [Line Items]
Transmission	2,990	2,963
CECONY | Electric Distribution
Public Utility, Property, Plant and Equipment [Line Items]
Distribution	17,996	17,234
CECONY | Gas
Public Utility, Property, Plant and Equipment [Line Items]
Gas	6,403	5,749
CECONY | Steam
Public Utility, Property, Plant and Equipment [Line Items]
Steam	1,798	1,882
CECONY | General
Public Utility, Property, Plant and Equipment [Line Items]
General	$ 1,905	$ 1,639

Summary of Significant Accoun54

Summary of Significant Accounting Policies - Goodwill (Details)	12 Months Ended
	Dec. 31, 2017USD ($)
Accounting Policies [Abstract]
Goodwill, impairment charge	$ 0

Summary of Significant Accoun55

Summary of Significant Accounting Policies - Long-Lived and Intangible Assets (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment charges on long-lived assets	$ 0	$ 0
Impairment charges on definite lived intangible assets	$ 0	$ 0	$ 0
Discontinued Operations, Held-for-sale | Pike
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment charge on assets held for sale			$ 5,000,000

Summary of Significant Accoun56

Summary of Significant Accounting Policies - Revenues (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Revenue deferral period (months)	12 months
Unbilled contracts receivable	$ 58	$ 21
Billings in excess of earned revenue	$ 87	$ 2

Summary of Significant Accoun57

Summary of Significant Accounting Policies - Schedule of Total Excise Taxes Recorded in Operating Revenues (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Excise Taxes [Line Items]
Excise taxes	$ 302	$ 336	$ 354
CECONY
Schedule of Excise Taxes [Line Items]
Excise taxes	$ 292	$ 316	$ 331

Summary of Significant Accoun58

Summary of Significant Accounting Policies - Recoverable Energy Costs (Details)	12 Months Ended
	Dec. 31, 2017
Minimum
Public Utilities, General Disclosures [Line Items]
Recovery or refund of energy costs, deferral period	1 month
Maximum
Public Utilities, General Disclosures [Line Items]
Recovery or refund of energy costs, deferral period	2 months

Summary of Significant Accoun59

Summary of Significant Accounting Policies - Investments (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 467	$ 488
Supplemental retirement income plan assets	330	273
Deferred income plan assets	73	60
Other	9	9
Total investments	2,001	1,921
CET | Stagecoach Gas Services, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	971	992
CET | Mountain Valley Pipeline LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	98	48
CET | New York Transco, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	53	51
CECONY
Schedule of Equity Method Investments [Line Items]
Equity method investments	0	0
Supplemental retirement income plan assets	301	246
Deferred income plan assets	73	60
Other	9	9
Total investments	383	315
CECONY | CET | Stagecoach Gas Services, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	0	0
CECONY | CET | Mountain Valley Pipeline LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	0	0
CECONY | CET | New York Transco, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 0	$ 0

Summary of Significant Accoun60

Summary of Significant Accounting Policies - Pension and Other Postretirement Benefits (Details)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Investment gains and losses recognized, time period (years)	15 years
Other actuarial gains and losses recognized, time period (years)	10 years
Difference between fair value and expected market related value of plan assets (percent)	20.00%

Summary of Significant Accoun61

Summary of Significant Accounting Policies - Federal Income Tax (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)
Income Taxes Disclosure [Line Items]
Decrease in net deferred tax liabilities resulting from TCJA	$ 5,312
Change in net income resulting from TCJA	259
Future Income Tax
Income Taxes Disclosure [Line Items]
Increase in regulatory liability resulting from TCJA	3,713
Future Income Tax
Income Taxes Disclosure [Line Items]
Decrease in regulatory asset resulting from TCJA	1,250
Revenue Taxes
Income Taxes Disclosure [Line Items]
Decrease in regulatory asset resulting from TCJA	90
CECONY
Income Taxes Disclosure [Line Items]
Decrease in net deferred tax liabilities resulting from TCJA	4,781
CECONY | Future Income Tax
Income Taxes Disclosure [Line Items]
Increase in regulatory liability resulting from TCJA	3,513
CECONY | Future Income Tax
Income Taxes Disclosure [Line Items]
Decrease in regulatory asset resulting from TCJA	1,182
CECONY | Revenue Taxes
Income Taxes Disclosure [Line Items]
Decrease in regulatory asset resulting from TCJA	$ 86

Summary of Significant Accoun62

Summary of Significant Accounting Policies - Research and Development Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Research and Development Expenses [Line Items]
Research and development costs	$ 24	$ 24	$ 23
CECONY
Research and Development Expenses [Line Items]
Research and development costs	$ 23	$ 22	$ 22

Summary of Significant Accoun63

Summary of Significant Accounting Policies - Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Net income	$ 1,525	$ 1,245	$ 1,193
Weighted average common shares outstanding – basic	307.1	300.4	293
Add: Incremental shares attributable to effect of potentially dilutive securities	1.7	1.5	1.4
Adjusted weighted average common shares outstanding – diluted	308.8	301.9	294.4
Net income per common share — basic (dollars per share)	$ 4.97	$ 4.15	$ 4.07
Net income per common share — diluted (dollars per share)	$ 4.94	$ 4.12	$ 4.05

Summary of Significant Accoun64

Summary of Significant Accounting Policies - Changes in Accumulated Other Comprehensive Income/(Loss) by Component (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
AOCI Attributable to Parent, Net of Tax [Roll Forward]
BALANCE AS OF BEGINNING OF PERIOD	$ 14,306	$ 13,061	$ 12,585
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	1	7	11
BALANCE AS OF END OF PERIOD	15,425	14,306	13,061
Accumulated OCI
AOCI Attributable to Parent, Net of Tax [Roll Forward]
BALANCE AS OF BEGINNING OF PERIOD	(27)	(34)	(45)
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	1	7	11
BALANCE AS OF END OF PERIOD	(26)	(27)	(34)
Pension Plan Liabilities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
OCI before reclassifications, net of tax	(4)	2	5
Amounts reclassified from accumulated OCI related to pension plan liabilities, net of tax	5	5	6
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	1	7	11
OCI before reclassifications, tax	3	(1)	(3)
Amounts reclassified from accumulated OCI related to pension plan liabilities, tax	(3)	(3)	(4)
CECONY
AOCI Attributable to Parent, Net of Tax [Roll Forward]
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	1	2	2
CECONY | Accumulated OCI
AOCI Attributable to Parent, Net of Tax [Roll Forward]
BALANCE AS OF BEGINNING OF PERIOD	(7)	(9)	(11)
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	1	2	2
BALANCE AS OF END OF PERIOD	(6)	(7)	(9)
CECONY | Pension Plan Liabilities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
OCI before reclassifications, net of tax	0	1	1
Amounts reclassified from accumulated OCI related to pension plan liabilities, net of tax	1	1	1
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	1	2	2
OCI before reclassifications, tax	1	(1)
Amounts reclassified from accumulated OCI related to pension plan liabilities, tax	$ (1)	$ (1)	$ (1)

Regulatory Matters - Summary of

Regulatory Matters - Summary of Utilities Rate Plans (CECONY-Electric) (Details) - USD ($)	1 Months Ended	12 Months Ended				36 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2016
Maximum | NYSPSC
Public Utilities, General Disclosures [Line Items]
Percentage of total consolidated revenues		15.00%
Percentage of debt to total consolidated debt		20.00%
CECONY | Electric
Public Utilities, General Disclosures [Line Items]
Amortization to income of net regulatory (assets) and liabilities			$ 123,000,000
Retention of annual transmission congestion revenues								$ 90,000,000
Actual earnings adjustment mechanism incentives		$ 13,000,000
Deferred revenues	$ 101,000,000	45,000,000	101,000,000	$ 98,000,000	$ 146,000,000			101,000,000
Negative revenue adjustments		0	0	0	5,000,000
Cost reconciliations, deferred net regulatory liabilities	68,000,000	35,000,000	68,000,000	26,000,000	57,000,000			$ 68,000,000
Net utility plant reconciliations		400,000	9,000,000	(17,000,000)	(6,000,000)
Earnings sharing, threshold limit		$ 0	6,500,000	44,400,000	$ 0
Earnings sharing, positive adjustment			5,700,000
Common equity ratio (percent)								48.00%
Base rate change deferral regulatory liability impact	0		$ 0	$ 30,000,000				$ 0
Increase in gas base rate due to expiration of temporary credit under the prior rate plan	$ 48,000,000
Deferrals for property taxes limitation from rates (percent)								90.00%
Recovery deferral (percentage)	80.00%		80.00%					80.00%
Maximum deferral (percentage)	30.00%		30.00%					30.00%
CECONY | Electric | Deferred storm costs
Public Utilities, General Disclosures [Line Items]
Amortization of regulatory asset								$ 107,000,000
Decrease in recoverable property damage costs								4,000,000
CECONY | Electric | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Retention of annual transmission congestion revenues							$ 75,000,000
Other earnings incentives						$ 5,000,000
Authorized return on common equity (percent)							9.00%
Actual return on common equity (percent)							9.30%
Earnings sharing (percentage)							9.50%
Common equity ratio (percent)							48.00%
Recovery or refund of energy costs, deferral period							10 years
CECONY | Electric | Scenario, Forecast | NYSPSC
Public Utilities, General Disclosures [Line Items]
Base rate changes							$ 199,000,000
CECONY | Electric | Year 1
Public Utilities, General Disclosures [Line Items]
Base rate changes	$ (76,200,000)		$ (76,200,000)					(76,200,000)
Amortization to income of net regulatory (assets) and liabilities								(37,000,000)
Average rate base								$ 17,323,000,000
Weighted average cost of capital (after-tax) (percent)								7.05%
Authorized return on common equity (percent)								9.20%
Actual return on common equity (percent)								9.04%
Earnings sharing (percentage)	9.80%		9.80%					9.80%
Cost of long-term debt (percent)	5.17%		5.17%					5.17%
Deferral, annual maximum (not more than) (percent)								0.05%
CECONY | Electric | Year 1 | Transmission and distribution
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations								$ 16,869,000,000
CECONY | Electric | Year 1 | Storm hardening
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations								89,000,000
CECONY | Electric | Year 1 | Other
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations								2,034,000,000
CECONY | Electric | Year 1 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)								400,000,000
CECONY | Electric | Year 1 | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Base rate changes							195,000,000
Amortization to income of net regulatory (assets) and liabilities							84,000,000
Potential earnings adjustment mechanism incentives							28,000,000
Potential penalties (annually)							376,000,000
Average rate base							$ 18,902,000,000
Weighted average cost of capital (after-tax) (percent)							6.82%
Cost of long-term debt (percent)							4.93%
Recovery of energy efficiency and savings program costs							$ 20,500,000
CECONY | Electric | Year 1 | Scenario, Forecast | Electric average excluding AMI
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations							21,689,000,000
CECONY | Electric | Year 1 | Scenario, Forecast | Advanced metering infrastructure (AMI)
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations							126,000,000
CECONY | Electric | Year 2
Public Utilities, General Disclosures [Line Items]
Base rate changes	$ 124,000,000		$ 124,000,000					124,000,000
Amortization to income of net regulatory (assets) and liabilities								(37,000,000)
Retention of annual transmission congestion revenues
Average rate base								$ 18,113,000,000
Weighted average cost of capital (after-tax) (percent)								7.08%
Authorized return on common equity (percent)								9.20%
Actual return on common equity (percent)								10.16%
Earnings sharing (percentage)	9.80%		9.80%					9.80%
Cost of long-term debt (percent)	5.23%		5.23%					5.23%
Deferral, annual maximum (not more than) (percent)								0.075%
CECONY | Electric | Year 2 | Transmission and distribution
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations								$ 17,401,000,000
CECONY | Electric | Year 2 | Storm hardening
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations								177,000,000
CECONY | Electric | Year 2 | Other
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations								2,102,000,000
CECONY | Electric | Year 2 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)								400,000,000
CECONY | Electric | Year 2 | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Base rate changes							155,000,000
Amortization to income of net regulatory (assets) and liabilities							83,000,000
Retention of annual transmission congestion revenues
Potential earnings adjustment mechanism incentives							47,000,000
Potential penalties (annually)							341,000,000
Average rate base							$ 19,530,000,000
Weighted average cost of capital (after-tax) (percent)							6.80%
Cost of long-term debt (percent)							4.88%
Recovery of energy efficiency and savings program costs							$ 49,000,000
CECONY | Electric | Year 2 | Scenario, Forecast | Electric average excluding AMI
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations							22,338,000,000
CECONY | Electric | Year 2 | Scenario, Forecast | Advanced metering infrastructure (AMI)
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations							257,000,000
CECONY | Electric | Year 3
Public Utilities, General Disclosures [Line Items]
Base rate changes	$ 0		$ 0					0
Amortization to income of net regulatory (assets) and liabilities								123,000,000
Retention of annual transmission congestion revenues
Average rate base								$ 18,282,000,000
Weighted average cost of capital (after-tax) (percent)								6.91%
Authorized return on common equity (percent)								9.00%
Actual return on common equity (percent)								9.66%
Earnings sharing (percentage)	9.60%		9.60%					9.60%
Cost of long-term debt (percent)	5.09%		5.09%					5.09%
Deferral, annual maximum (not more than) (percent)								0.10%
CECONY | Electric | Year 3 | Transmission and distribution
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations								$ 17,929,000,000
CECONY | Electric | Year 3 | Storm hardening
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations								268,000,000
CECONY | Electric | Year 3 | Other
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations								2,069,000,000
CECONY | Electric | Year 3 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)								$ 400,000,000
CECONY | Electric | Year 3 | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Base rate changes							155,000,000
Amortization to income of net regulatory (assets) and liabilities							69,000,000
Retention of annual transmission congestion revenues
Potential earnings adjustment mechanism incentives							64,000,000
Potential penalties (annually)							352,000,000
Average rate base							$ 20,277,000,000
Weighted average cost of capital (after-tax) (percent)							6.73%
Cost of long-term debt (percent)							4.74%
Recovery of energy efficiency and savings program costs							$ 107,500,000
CECONY | Electric | Year 3 | Scenario, Forecast | Electric average excluding AMI
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations							23,002,000,000
CECONY | Electric | Year 3 | Scenario, Forecast | Advanced metering infrastructure (AMI)
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations							$ 415,000,000

Regulatory Matters - Summary 66

Regulatory Matters - Summary of Utilities Rate Plans (CECONY-Gas) (Details) - CECONY - Gas - USD ($)	1 Months Ended	12 Months Ended				36 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2016
Public Utilities, General Disclosures [Line Items]
Amortization to income of net regulatory (assets) and liabilities								$ 4,000,000
Regulatory liabilities, amortization period								3 years
Amount of revenues retained	$ 65,000,000		$ 65,000,000	$ 66,000,000	$ 70,000,000			$ 65,000,000
Percentage of revenue reserve								15.00%
Deferred revenues	71,000,000	$ 3,000,000	71,000,000	54,000,000	28,000,000			$ 71,000,000
Negative revenue adjustments		5,000,000	0	0	0
Cost reconciliations, deferred net regulatory liabilities	$ 32,000,000	2,000,000	32,000,000	11,000,000	38,000,000			$ 32,000,000
Net utility plant reconciliations		$ 2,200,000	$ 0	1,000,000	0
Earnings sharing (percentage)	9.90%		9.90%					9.90%
Earnings sharing, threshold limit			$ 0	0	0
Common equity ratio (percent)								48.00%
Base rate change deferral regulatory liability impact	$ 32,000,000		32,000,000					$ 32,000,000
Increase in gas base rate due to expiration of temporary credit under the prior rate plan	41,000,000
Difference in property taxes (percent)								90.00%
Maximum
Public Utilities, General Disclosures [Line Items]
Amount of revenues retained	$ 65,000,000		65,000,000					$ 65,000,000
Potential penalties (annually)			$ 56,000,000	$ 44,000,000	$ 33,000,000
Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Percentage of revenue reserve							15.00%
Other earnings incentives						$ 7,000,000
Earnings sharing (percentage)							9.50%
Common equity ratio (percent)							48.00%
Deferral, annual maximum (not more than) (percent)							0.10%
Scenario, Forecast | Maximum
Public Utilities, General Disclosures [Line Items]
Amount of revenues retained							$ 65,000,000
Year 1
Public Utilities, General Disclosures [Line Items]
Base rate changes								(54,600,000)
Average rate base								$ 3,521,000,000
Weighted average cost of capital (after-tax) (percent)								7.10%
Authorized return on common equity (percent)								9.30%
Actual return on common equity (percent)								8.02%
Cost of long-term debt (percent)	5.17%		5.17%					5.17%
Year 1 | Gas delivery
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations								$ 3,899,000,000
Year 1 | Storm hardening
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations								3,000,000
Year 1 | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Base rate changes							(5,000,000)
Amortization to income of net regulatory (assets) and liabilities							39,000,000
Potential incentives if performance targets are met							7,000,000
Potential penalties (annually)							68,000,000
Average rate base							$ 4,841,000,000
Weighted average cost of capital (after-tax) (percent)							6.82%
Authorized return on common equity (percent)							9.00%
Actual return on common equity (percent)							9.22%
Cost of long-term debt (percent)							4.93%
Year 1 | Scenario, Forecast | Gas average excluding AMI
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations							$ 5,844,000,000
Year 1 | Scenario, Forecast | Advanced metering infrastructure (AMI)
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations							27,000,000
Year 2
Public Utilities, General Disclosures [Line Items]
Base rate changes								38,600,000
Average rate base								$ 3,863,000,000
Weighted average cost of capital (after-tax) (percent)								7.13%
Actual return on common equity (percent)								8.13%
Cost of long-term debt (percent)	5.23%		5.23%					5.23%
Year 2 | Gas delivery
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations								$ 4,258,000,000
Year 2 | Storm hardening
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations								8,000,000
Year 2 | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Base rate changes							92,000,000
Amortization to income of net regulatory (assets) and liabilities							37,000,000
Potential incentives if performance targets are met							8,000,000
Potential penalties (annually)							63,000,000
Average rate base							$ 5,395,000,000
Weighted average cost of capital (after-tax) (percent)							6.80%
Cost of long-term debt (percent)							4.88%
Year 2 | Scenario, Forecast | Gas average excluding AMI
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations							$ 6,512,000,000
Year 2 | Scenario, Forecast | Advanced metering infrastructure (AMI)
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations							57,000,000
Year 3
Public Utilities, General Disclosures [Line Items]
Base rate changes								56,800,000
Average rate base								$ 4,236,000,000
Weighted average cost of capital (after-tax) (percent)								7.21%
Actual return on common equity (percent)								7.83%
Cost of long-term debt (percent)	5.39%		5.39%					5.39%
Year 3 | Gas delivery
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations								$ 4,698,000,000
Year 3 | Storm hardening
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations								$ 30,000,000
Year 3 | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Base rate changes							90,000,000
Amortization to income of net regulatory (assets) and liabilities							36,000,000
Potential incentives if performance targets are met							8,000,000
Potential penalties (annually)							70,000,000
Average rate base							$ 6,005,000,000
Weighted average cost of capital (after-tax) (percent)							6.73%
Cost of long-term debt (percent)							4.74%
Year 3 | Scenario, Forecast | Gas average excluding AMI
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations							$ 7,177,000,000
Year 3 | Scenario, Forecast | Advanced metering infrastructure (AMI)
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations							$ 100,000,000

Regulatory Matters - Summary 67

Regulatory Matters - Summary of Utilities Rate Plans (CECONY-Steam) (Details) - CECONY - Steam - USD ($)	12 Months Ended				36 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2016
Public Utilities, General Disclosures [Line Items]
Amortization to income of net regulatory (assets) and liabilities					$ 37,000,000
Regulatory liabilities, amortization period					3 years
Negative revenue adjustments	$ 0	$ 0	$ 0	$ 0
Cost reconciliation, deferred net regulatory liabilities	14,000,000	8,000,000		42,000,000	$ 8,000,000
Cost reconciliations			17,000,000
Net utility plant reconciliations	0	$ 0	0	$ 100,000
Authorized return on common equity (percent)					9.30%
Earnings sharing (percentage)		9.90%			9.90%
Earnings sharing, threshold limit	$ 8,500,000	$ 7,800,000	$ 11,500,000
Earnings sharing, positive adjustment		4,000,000
Common equity ratio (percent)					48.00%
Other regulatory liabilities		$ 8,000,000			$ 8,000,000
Difference in property taxes (percent)					90.00%
Deferral, annual maximum (not more than) (percent)					0.10%
Year 1
Public Utilities, General Disclosures [Line Items]
Base rate changes					$ (22,400,000)
Average rate base					$ 1,511,000,000
Weighted average cost of capital (after-tax) (percent)					7.10%
Actual return on common equity (percent)					9.82%
Cost of long-term debt (percent)		5.17%			5.17%
Year 1 | Production
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations					$ 1,752,000,000
Year 1 | Distribution
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations					6,000,000
Year 1 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)					1,000,000
Year 2
Public Utilities, General Disclosures [Line Items]
Base rate changes					19,800,000
Average rate base					$ 1,547,000,000
Weighted average cost of capital (after-tax) (percent)					7.13%
Actual return on common equity (percent)					10.88%
Cost of long-term debt (percent)		5.23%			5.23%
Year 2 | Production
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations					$ 1,732,000,000
Year 2 | Distribution
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations					11,000,000
Year 2 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)					1,000,000
Year 3
Public Utilities, General Disclosures [Line Items]
Base rate changes					20,300,000
Average rate base					$ 1,604,000,000
Weighted average cost of capital (after-tax) (percent)					7.21%
Actual return on common equity (percent)					10.54%
Cost of long-term debt (percent)		5.39%			5.39%
Year 3 | Production
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations					$ 1,720,000,000
Year 3 | Distribution
Public Utilities, General Disclosures [Line Items]
Net utility plant reconciliations					25,000,000
Year 3 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)					1,000,000
Year 4
Public Utilities, General Disclosures [Line Items]
Base rate changes					$ 0
Actual return on common equity (percent)					9.51%

Regulatory Matters - Summary 68

Regulatory Matters - Summary of Utilities Rate Plans (O&R New York-Electric) (Details) - O&R - Electric - USD ($)	12 Months Ended						24 Months Ended	40 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Oct. 31, 2017	Oct. 31, 2015
Public Utilities, General Disclosures [Line Items]
Deferred revenues	$ 11,200,000	$ 6,300,000	$ 0	$ (3,400,000)	$ 3,200,000	$ 2,600,000
Negative revenue adjustments	0	0	1,250,000	0	0	0
Deferral of net increase (decrease) to regulatory assets	3,200,000	7,400,000	300,000	(200,000)	4,100,000	7,800,000
Net utility plant reconciliations	(1,900,000)	(1,900,000)	$ 2,200,000	(2,300,000)	$ (1,100,000)	$ 4,200,000
Authorized return on common equity (percent)							9.00%
Earnings sharing (percentage)							9.60%
Earnings sharing, threshold limit	$ 300,000	$ 6,100,000		$ 1,000,000
Common equity ratio (percent)							48.00%	48.00%
Deferred storm and property reserve deficiency, noncurrent							$ 59,300,000
Deferred storm and property reserve deficiency, recovery period							5 years
Deferred storm and property reserve deficiency not recovered							$ 1,000,000
Property Tax and Interest Rate Reconciliations
Public Utilities, General Disclosures [Line Items]
Regulatory assets not recoverable							4,000,000
Year 1
Public Utilities, General Disclosures [Line Items]
Base rate changes							9,300,000	$ 19,400,000
Amortization to income of net regulatory assets							(8,500,000)	(32,200,000)
Net utility plant reconciliations							928,000,000	678,000,000
Average rate base							$ 763,000,000	$ 671,000,000
Weighted average cost of capital (after-tax) (percent)							7.10%	7.61%
Authorized return on common equity (percent)								9.40%
Actual return on common equity (percent)							10.80%	12.90%
Cost of long-term debt (percent)							5.42%	6.07%
Deferred storm and property reserve deficiency, noncurrent							$ 11,850,000
Rate exclusion amount with balance below regulatory threshold							1,000,000
Year 1 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)							4,000,000	$ 3,000,000
Year 2
Public Utilities, General Disclosures [Line Items]
Base rate changes							8,800,000	$ 8,800,000
Amortization to income of net regulatory assets							(9,400,000)
Regulatory assets, amortization period								3 years
Net utility plant reconciliations							970,000,000	$ 704,000,000
Average rate base							$ 805,000,000	$ 708,000,000
Weighted average cost of capital (after-tax) (percent)							7.06%	7.65%
Authorized return on common equity (percent)								9.50%
Actual return on common equity (percent)							9.70%	8.70%
Cost of long-term debt (percent)							5.35%	6.07%
Deferred storm and property reserve deficiency, noncurrent							$ 11,850,000
Rate exclusion amount with balance below regulatory threshold							9,000,000
Year 2 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)							4,000,000	$ 3,000,000
Year 3
Public Utilities, General Disclosures [Line Items]
Base rate changes								15,200,000
Net utility plant reconciliations								753,000,000
Average rate base								$ 759,000,000
Weighted average cost of capital (after-tax) (percent)								7.48%
Authorized return on common equity (percent)								9.60%
Actual return on common equity (percent)								9.40%
Cost of long-term debt (percent)								5.64%
Year 3 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)							$ 4,000,000	$ 3,000,000

Regulatory Matters - Summary 69

Regulatory Matters - Summary of Utilities Rate Plans (O&R New York-Gas) (Details) - O&R - Gas - USD ($)	12 Months Ended						36 Months Ended	72 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Oct. 31, 2018	Oct. 31, 2015
Public Utilities, General Disclosures [Line Items]
Amortization to income of net regulatory assets								$ (2,000,000)
Regulatory assets, amortization period								3 years
Deferred revenues	$ 1,700,000	$ 6,200,000	$ (800,000)	$ (100,000)	$ 700,000	$ 4,700,000
Negative revenue adjustments	0	0	0	0	0	0
Cost reconciliations	(3,500,000)	6,600,000	(4,500,000)	8,300,000	8,300,000	700,000
Net utility plant reconciliations	0	0	0	0	0	700,000
Weighted average cost of capital (after-tax) (percent)								8.49%
Authorized return on common equity (percent)								10.40%
Earnings sharing, threshold limit	$ 200,000	$ 4,000,000	$ 0	$ 0	$ 0	$ 0
Cost of long-term debt (percent)								6.81%
Common equity ratio (percent)								48.00%
Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Authorized return on common equity (percent)							9.00%
Earnings sharing (percentage)							9.60%
Common equity ratio (percent)							48.00%
Scenario, Forecast | Property Tax and Interest Rate Reconciliations
Public Utilities, General Disclosures [Line Items]
Regulatory assets not recoverable							$ 14,000,000
Year 1
Public Utilities, General Disclosures [Line Items]
Base rate changes								$ 9,000,000
Average rate base								$ 280,000,000
Actual return on common equity (percent)								10.20%
Earnings sharing (percentage)				11.40%
Year 1 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)								$ 1,400,000
Year 1 | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Base rate changes							16,400,000
Amortization to income of net regulatory assets							(1,700,000)
Net utility plant reconciliations							492,000,000
Average rate base							$ 366,000,000
Weighted average cost of capital (after-tax) (percent)							7.10%
Actual return on common equity (percent)							11.20%
Cost of long-term debt (percent)							5.42%
Rate exclusion amount with balance below regulatory threshold							$ 500,000
Year 1 | Scenario, Forecast | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)							3,700,000
Year 2
Public Utilities, General Disclosures [Line Items]
Base rate changes								9,000,000
Average rate base								$ 296,000,000
Actual return on common equity (percent)								9.60%
Year 2 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)								$ 1,400,000
Year 2 | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Base rate changes							16,400,000
Amortization to income of net regulatory assets							(2,100,000)
Net utility plant reconciliations							518,000,000
Average rate base							$ 391,000,000
Weighted average cost of capital (after-tax) (percent)							7.06%
Actual return on common equity (percent)							9.70%
Cost of long-term debt (percent)							5.35%
Rate exclusion amount with balance below regulatory threshold							$ 4,200,000
Year 2 | Scenario, Forecast | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)							4,700,000
Year 3
Public Utilities, General Disclosures [Line Items]
Base rate changes								4,600,000
Base rate change through surcharge								4,300,000
Average rate base								$ 309,000,000
Actual return on common equity (percent)								12.60%
Year 3 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)								$ 1,400,000
Year 3 | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Base rate changes							5,800,000
Amortization to income of net regulatory assets							(2,500,000)
Net utility plant reconciliations							546,000,000
Average rate base							$ 417,000,000
Weighted average cost of capital (after-tax) (percent)							7.06%
Cost of long-term debt (percent)							5.35%
Rate exclusion amount with balance below regulatory threshold							$ 7,200,000
Year 3 | Scenario, Forecast | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)							4,900,000
Year 4
Public Utilities, General Disclosures [Line Items]
Base rate changes								$ 0
Actual return on common equity (percent)								10.20%
Year 4 | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Base rate change through surcharge							$ 10,600,000
Year 5
Public Utilities, General Disclosures [Line Items]
Base rate changes								$ 0
Actual return on common equity (percent)								6.10%

Regulatory Matters - Summary 70

Regulatory Matters - Summary of Utilities Rate Plans (RECO) (Details) - RECO - USD ($) $ in Millions	1 Months Ended	12 Months Ended	31 Months Ended
	Mar. 31, 2017	Dec. 31, 2017	Feb. 28, 2017
Public Utilities, General Disclosures [Line Items]
Amortization to income of net regulatory (assets) and liabilities	$ 0.2		$ 0.4
Regulatory liabilities, amortization period	3 years		3 years
Amortization to income of net regulatory assets	$ (25.6)		$ (25.6)
Regulatory assets, amortization period	4 years		4 years
Average rate base	$ 178.7		$ 172.2
Weighted average cost of capital (after-tax) (percent)	7.47%		7.83%
Authorized return on common equity (percent)	9.60%		9.75%
Cost of long-term debt (percent)	5.37%		5.89%
Common equity ratio (percent)	49.70%		50.00%
Electric
Public Utilities, General Disclosures [Line Items]
Plan electric system storm hardening amount		$ 15.7
Plan period (years)		3 years
Year 1
Public Utilities, General Disclosures [Line Items]
Base rate changes	$ 1.7		$ 13
Actual return on common equity (percent)			9.20%
Year 2
Public Utilities, General Disclosures [Line Items]
Actual return on common equity (percent)			8.70%

Regulatory Matters - Additional

Regulatory Matters - Additional Information (Details) - USD ($) $ in Millions	1 Months Ended			3 Months Ended	9 Months Ended	12 Months Ended
	Jan. 31, 2019	Jan. 31, 2018	Apr. 30, 2017	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2016
Public Utilities, General Disclosures [Line Items]
Regulatory assets					$ 4,333	$ 4,333		$ 7,124
Decrease in net deferred tax liabilities resulting from TCJA						5,312
Regulatory liabilities					4,577	4,577		1,905
Future Income Tax
Public Utilities, General Disclosures [Line Items]
Increase in regulatory liability resulting from TCJA						3,713
Regulatory liabilities					2,545	2,545		0
Net Unbilled Revenue Deferrals
Public Utilities, General Disclosures [Line Items]
Regulatory liabilities					$ 183	183		145
Future Income Tax
Public Utilities, General Disclosures [Line Items]
Decrease in regulatory asset resulting from TCJA						1,250
Revenue Taxes
Public Utilities, General Disclosures [Line Items]
Decrease in regulatory asset resulting from TCJA						90
O&R
Public Utilities, General Disclosures [Line Items]
Decrease in net deferred tax liabilities resulting from TCJA						216
O&R | Future Income Tax
Public Utilities, General Disclosures [Line Items]
Increase in regulatory liability resulting from TCJA						161
O&R | Future Income Tax
Public Utilities, General Disclosures [Line Items]
Decrease in regulatory asset resulting from TCJA						51
O&R | Revenue Taxes
Public Utilities, General Disclosures [Line Items]
Decrease in regulatory asset resulting from TCJA						4
O&R | NYSPSC | Subsequent Event
Public Utilities, General Disclosures [Line Items]
Requested rate increase, amount		$ 4.5
Requested return on equity (percent)		9.75%
Requested equity capital structure (percent)		48.00%
O&R | NYSPSC | Electric | Subsequent Event
Public Utilities, General Disclosures [Line Items]
Requested rate increase, amount	$ 20.3
Requested return on equity (percent)	9.75%
Requested equity capital structure (percent)	48.00%
RECO
Public Utilities, General Disclosures [Line Items]
Decrease in net deferred tax liabilities resulting from TCJA						45
RECO | Future Income Tax
Public Utilities, General Disclosures [Line Items]
Increase in regulatory liability resulting from TCJA						28
RECO | Future Income Tax
Public Utilities, General Disclosures [Line Items]
Decrease in regulatory asset resulting from TCJA						17
RECO | Revenue Taxes
Public Utilities, General Disclosures [Line Items]
Decrease in regulatory asset resulting from TCJA						0
RECO | FERC
Public Utilities, General Disclosures [Line Items]
Requested rate increase, amount			$ 17.7	$ 11.8
Requested return on equity (percent)					10.00%
CECONY
Public Utilities, General Disclosures [Line Items]
Regulatory assets					$ 3,925	3,925		6,563
Decrease in net deferred tax liabilities resulting from TCJA						4,781
Regulatory liabilities					4,219	4,219		1,712
CECONY | Future Income Tax
Public Utilities, General Disclosures [Line Items]
Increase in regulatory liability resulting from TCJA						3,513
Regulatory liabilities					2,390	2,390		0
CECONY | Net Unbilled Revenue Deferrals
Public Utilities, General Disclosures [Line Items]
Regulatory liabilities					183	183		$ 145
CECONY | Future Income Tax
Public Utilities, General Disclosures [Line Items]
Decrease in regulatory asset resulting from TCJA						1,182
CECONY | Revenue Taxes
Public Utilities, General Disclosures [Line Items]
Decrease in regulatory asset resulting from TCJA						86
CECONY | NYSPSC | Issued by NYSPSC on MTA Subway Power Outage
Public Utilities, General Disclosures [Line Items]
Regulatory costs					65	65
Regulatory assets					50	50
CECONY | NYSPSC | Scenario, Forecast | Issued by NYSPSC on MTA Subway Power Outage
Public Utilities, General Disclosures [Line Items]
Regulatory costs							$ 137
Regulatory assets							127
CECONY | NYSPSC | Electric | Issued by NYSPSC on MTA Subway Power Outage
Public Utilities, General Disclosures [Line Items]
Regulatory costs					$ 15	$ 15
CECONY | NYSPSC | Electric | Scenario, Forecast | Issued by NYSPSC on MTA Subway Power Outage
Public Utilities, General Disclosures [Line Items]
Regulatory costs							$ 10

Regulatory Matters - Regulatory

Regulatory Matters - Regulatory Assets (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	$ 4,266	$ 7,024
Regulatory assets – current	67	100
Total Regulatory Assets	4,333	7,124
Unrecognized pension and other postretirement costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	2,526	2,874
Future income tax
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	0	2,439
Environmental remediation costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	793	823
Revenue taxes
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	260	295
Pension and other postretirement benefits deferrals
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	79	38
Recoverable energy costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	60	42
Regulatory assets – current	27	9
Municipal infrastructure support costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	56	44
Property tax reconciliation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	51	37
MTA power reliability deferral
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	50	0
Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	44	48
Deferred storm costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	38	56
Brooklyn Queens demand management program
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	37	29
Unamortized loss on reacquired debt
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	37	43
Indian Point Energy Center program costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	29	50
Preferred stock redemption
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	24	25
Workers’ compensation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	10	13
Net electric deferrals
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	9	24
O&R transition bond charges
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	9	15
Surcharge for New York State assessment
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	2	28
Other
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	152	101
Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – current	40	91
CECONY
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	3,863	6,473
Regulatory assets – current	62	90
Total Regulatory Assets	3,925	6,563
CECONY | Unrecognized pension and other postretirement costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	2,376	2,730
CECONY | Future income tax
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	0	2,325
CECONY | Environmental remediation costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	677	711
CECONY | Revenue taxes
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	248	280
CECONY | Pension and other postretirement benefits deferrals
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	58	7
CECONY | Recoverable energy costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	52	38
Regulatory assets – current	25	4
CECONY | Municipal infrastructure support costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	56	44
CECONY | Property tax reconciliation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	25	0
CECONY | MTA power reliability deferral
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	50	0
CECONY | Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	37	42
CECONY | Deferred storm costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	0	3
CECONY | Brooklyn Queens demand management program
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	37	29
CECONY | Unamortized loss on reacquired debt
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	35	41
CECONY | Indian Point Energy Center program costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	29	50
CECONY | Preferred stock redemption
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	24	25
CECONY | Workers’ compensation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	10	13
CECONY | Net electric deferrals
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	9	24
CECONY | O&R transition bond charges
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	0	0
CECONY | Surcharge for New York State assessment
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	2	26
CECONY | Other
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	138	85
CECONY | Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – current	$ 37	$ 86

Regulatory Matters - Regulato73

Regulatory Matters - Regulatory Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	$ 4,577	$ 1,905
Regulatory liabilities—current	101	128
Total Regulatory Liabilities	4,678	2,033
Future income tax
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	2,545	0
Allowance for cost of removal less salvage
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	846	755
Pension and other postretirement benefit deferrals
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	207	193
Net unbilled revenue deferrals
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	183	145
Energy efficiency portfolio standard unencumbered funds
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	127	0
Property tax reconciliation
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	107	178
Unrecognized other postretirement costs
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	92	60
Settlement of prudence proceeding
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	66	95
Property tax refunds
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	44	1
Carrying charges on repair allowance and bonus depreciation
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	43	68
New York State income tax rate change
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	36	61
Variable-rate tax-exempt debt - cost rate reconciliation
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	30	55
Earnings sharing - electric, gas and steam
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	29	39
Settlement of gas proceedings
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	27	27
Base rate change deferrals
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	21	40
Net utility plant reconciliations
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	12	16
Other
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	162	172
Refundable energy costs
Regulatory Liabilities [Line Items]
Regulatory liabilities—current	41	29
Deferred derivative gains
Regulatory Liabilities [Line Items]
Regulatory liabilities—current	31	28
Revenue decoupling mechanism
Regulatory Liabilities [Line Items]
Regulatory liabilities—current	29	71
CECONY
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	4,219	1,712
Regulatory liabilities—current	65	90
Total Regulatory Liabilities	4,284	1,802
CECONY | Future income tax
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	2,390	0
CECONY | Allowance for cost of removal less salvage
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	719	641
CECONY | Pension and other postretirement benefit deferrals
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	181	162
CECONY | Net unbilled revenue deferrals
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	183	145
CECONY | Energy efficiency portfolio standard unencumbered funds
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	122	0
CECONY | Property tax reconciliation
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	107	178
CECONY | Unrecognized other postretirement costs
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	92	60
CECONY | Settlement of prudence proceeding
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	66	95
CECONY | Property tax refunds
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	44	1
CECONY | Carrying charges on repair allowance and bonus depreciation
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	42	67
CECONY | New York State income tax rate change
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	35	60
CECONY | Variable-rate tax-exempt debt - cost rate reconciliation
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	26	48
CECONY | Earnings sharing - electric, gas and steam
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	19	28
CECONY | Settlement of gas proceedings
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	27	27
CECONY | Base rate change deferrals
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	21	40
CECONY | Net utility plant reconciliations
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	8	15
CECONY | Other
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	137	145
CECONY | Refundable energy costs
Regulatory Liabilities [Line Items]
Regulatory liabilities—current	16	5
CECONY | Deferred derivative gains
Regulatory Liabilities [Line Items]
Regulatory liabilities—current	28	24
CECONY | Revenue decoupling mechanism
Regulatory Liabilities [Line Items]
Regulatory liabilities—current	$ 21	$ 61

Capitalization - Additional Inf

Capitalization - Additional Information (Details)	12 Months Ended
	Dec. 31, 2017USD ($)shares	Dec. 31, 2016USD ($)
Schedule of Capitalization [Line Items]
Percentage limitation for income available for dividends (not more than)	100.00%
Rolling average calculation of income available for dividends (years)	2 years
Long-term debt	$ 16,029,000,000	$ 14,774,000,000
Non-recourse debt	$ 915,000,000	845,000,000
Ratio of consolidated debt to consolidated total capital	0.51
Maximum
Schedule of Capitalization [Line Items]
Ratio of consolidated debt to consolidated total capital	0.65
Transition Bonds, Issued in 2004
Schedule of Capitalization [Line Items]
Long-term debt	$ 7,000,000	11,000,000
Level 2
Schedule of Capitalization [Line Items]
Long-term debt, fair value	17,511,000,000
Level 3
Schedule of Capitalization [Line Items]
Long-term debt, fair value	636,000,000
Notes
Schedule of Capitalization [Line Items]
Covenant principal balance amount limit	$ 100,000,000
Notes | Maximum
Schedule of Capitalization [Line Items]
Ratio of consolidated debt to consolidated total capital	0.675
CECONY
Schedule of Capitalization [Line Items]
Common stock shares, outstanding | shares	21,976,200
Long-term debt	$ 13,265,000,000	12,073,000,000
Ratio of consolidated debt to consolidated total capital	0.52
CECONY | Maximum
Schedule of Capitalization [Line Items]
Ratio of consolidated debt to consolidated total capital	0.65
Covenant principal balance amount limit	$ 100,000,000
CECONY | Minimum
Schedule of Capitalization [Line Items]
Covenant principal balance amount limit	150,000,000
CECONY | Level 2
Schedule of Capitalization [Line Items]
Long-term debt, fair value	14,527,000,000
CECONY | Level 3
Schedule of Capitalization [Line Items]
Long-term debt, fair value	636,000,000
CECONY | Tax-Exempt Debt
Schedule of Capitalization [Line Items]
Tax-exempt debt issued, value	450,000,000
Long-term debt	1,086,000,000	$ 1,086,000,000
CECONY | Tax-Exempt Debt | Level 3
Schedule of Capitalization [Line Items]
Long-term debt	$ 636,000,000

Capitalization - Schedule of Lo

Capitalization - Schedule of Long-Term Debt Maturities (Details) $ in Millions	Dec. 31, 2017USD ($)
Debt Instrument [Line Items]
2,018	$ 1,298
2,019	578
2,020	791
2,021	544
2,022	335
CECONY
Debt Instrument [Line Items]
2,018	1,200
2,019	475
2,020	350
2,021	0
2,022	$ 0

Capitalization - Carrying Amoun

Capitalization - Carrying Amounts and Fair Values of Long-Term Debt (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Unamortized debt expense	$ 142	$ 134
Carrying Amount
Debt Instrument [Line Items]
Long-Term Debt (including current portion)	16,029	14,774
Fair Value
Debt Instrument [Line Items]
Long-Term Debt (including current portion)	18,147	16,093
CECONY
Debt Instrument [Line Items]
Unamortized debt discount	121	113
CECONY | Carrying Amount
Debt Instrument [Line Items]
Long-Term Debt (including current portion)	13,265	12,073
CECONY | Fair Value
Debt Instrument [Line Items]
Long-Term Debt (including current portion)	$ 15,163	$ 13,268

Short-Term Borrowing (Details)

Short-Term Borrowing (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Short-term Debt [Line Items]
Commercial paper, outstanding	$ 577,000,000	$ 1,054,000,000
Weighted average interest rate	1.80%	1.00%
Loans outstanding under credit agreement	$ 0	$ 0
Letters of credit outstanding under the Credit Agreement	$ 0	2,000,000
Ratio of consolidated debt to consolidated total capital	0.51
Minimum percentage of liens on assets	5.00%
Maximum
Short-term Debt [Line Items]
Ratio of consolidated debt to consolidated total capital	0.65
Revolving Credit
Short-term Debt [Line Items]
Maximum borrowing capacity	$ 1,500,000,000
Current amount available	1,000,000,000
Letters of Credit
Short-term Debt [Line Items]
Maximum borrowing capacity	1,200,000,000
CECONY
Short-term Debt [Line Items]
Commercial paper, outstanding	$ 150,000,000	$ 600,000,000
Weighted average interest rate	1.80%	1.00%
Letters of credit outstanding under the Credit Agreement		$ 2,000,000
Ratio of consolidated debt to consolidated total capital	0.52
CECONY | Maximum
Short-term Debt [Line Items]
Ratio of consolidated debt to consolidated total capital	0.65
CECONY | Revolving Credit
Short-term Debt [Line Items]
Maximum borrowing capacity	$ 2,250,000,000

Pension Benefits - Total Period

Pension Benefits - Total Periodic Benefit Costs (Details) - Pension Benefits - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Service cost – including administrative expenses	$ 263	$ 275	$ 297
Interest cost on projected benefit obligation	591	596	575
Expected return on plan assets	(968)	(947)	(886)
Recognition of net actuarial loss	595	596	775
Recognition of prior service costs	(17)	4	4
NET PERIODIC BENEFIT COST	464	524	765
Amortization of regulatory asset	0	0	1
TOTAL PERIODIC BENEFIT COST	464	524	766
Cost capitalized	(181)	(214)	(301)
Reconciliation to rate level	(34)	54	(74)
Cost charged to operating expenses	249	364	391
CECONY
Defined Benefit Plan Disclosure [Line Items]
Service cost – including administrative expenses	246	258	279
Interest cost on projected benefit obligation	554	559	538
Expected return on plan assets	(917)	(898)	(840)
Recognition of net actuarial loss	563	565	734
Recognition of prior service costs	(19)	2	2
NET PERIODIC BENEFIT COST	427	486	713
Amortization of regulatory asset	0	0	1
TOTAL PERIODIC BENEFIT COST	427	486	714
Cost capitalized	(169)	(203)	(285)
Reconciliation to rate level	(41)	58	(74)
Cost charged to operating expenses	$ 217	$ 341	355
Increase in CECONY's pension obligation			$ 45

Pension Benefits - Schedule of

Pension Benefits - Schedule of Funded Status (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
CHANGE IN PLAN ASSETS
Fair value of plan assets at beginning of year	$ 273
FAIR VALUE OF PLAN ASSETS AT END OF YEAR	330	$ 273
Pension Benefits
CHANGE IN PROJECTED BENEFIT OBLIGATION
Projected benefit obligation at beginning of year	14,095	14,377	$ 15,081
Service cost – excluding administrative expenses	259	271	293
Interest cost on projected benefit obligation	591	596	575
Net actuarial loss/(gain)	1,231	(302)	(996)
Plan amendments	6	(256)	0
Benefits paid	(646)	(591)	(576)
PROJECTED BENEFIT OBLIGATION AT END OF YEAR	15,536	14,095	14,377
CHANGE IN PLAN ASSETS
Fair value of plan assets at beginning of year	12,472	11,759	11,495
Actual return on plan assets	2,041	829	126
Employer contributions	450	508	750
Benefits paid	(646)	(591)	(576)
Administrative expenses	(43)	(33)	(36)
FAIR VALUE OF PLAN ASSETS AT END OF YEAR	14,274	12,472	11,759
FUNDED STATUS	(1,262)	(1,623)	(2,618)
Unrecognized net loss	2,760	3,157	3,909
Unrecognized prior service costs	(223)	(244)	16
Accumulated benefit obligation	13,897	12,655	12,909
CECONY
CHANGE IN PLAN ASSETS
Fair value of plan assets at beginning of year	246
FAIR VALUE OF PLAN ASSETS AT END OF YEAR	301	246
CECONY | Pension Benefits
CHANGE IN PROJECTED BENEFIT OBLIGATION
Projected benefit obligation at beginning of year	13,203	13,482	14,137
Service cost – excluding administrative expenses	241	254	274
Interest cost on projected benefit obligation	554	559	538
Net actuarial loss/(gain)	1,171	(282)	(931)
Plan amendments	0	(259)	0
Benefits paid	(602)	(551)	(536)
PROJECTED BENEFIT OBLIGATION AT END OF YEAR	14,567	13,203	13,482
CHANGE IN PLAN ASSETS
Fair value of plan assets at beginning of year	11,815	11,141	10,897
Actual return on plan assets	1,935	787	118
Employer contributions	412	469	697
Benefits paid	(602)	(551)	(536)
Administrative expenses	(41)	(31)	(35)
FAIR VALUE OF PLAN ASSETS AT END OF YEAR	13,519	11,815	11,141
FUNDED STATUS	(1,048)	(1,388)	(2,341)
Unrecognized net loss	2,624	2,995	3,704
Unrecognized prior service costs	(242)	(258)	3
Accumulated benefit obligation	$ 12,972	$ 11,806	$ 12,055

Pension Benefits - Additional I

Pension Benefits - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Pension liability	$ 361,000,000
Investments value	330,000,000	$ 273,000,000
CECONY
Defined Benefit Plan Disclosure [Line Items]
Pension liability	340,000,000
Investments value	301,000,000	246,000,000
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Regulatory assets and liabilities for future income taxes, net	368,000,000
Charge to OCI	4,000,000
Net loss estimated to be amortized	689,000,000
Prior service cost estimated to be amortized	(17,000,000)
Investments value	14,274,000,000	12,472,000,000	$ 11,759,000,000	$ 11,495,000,000
Accumulated benefit obligation	13,897,000,000	12,655,000,000	12,909,000,000
Defined benefit plan, bond amount (excess of)	50,000,000
Estimated future employer contributions	473,000,000
Pension Benefits | CECONY
Defined Benefit Plan Disclosure [Line Items]
Regulatory assets and liabilities for future income taxes, net	353,000,000
Charge to OCI	1,000,000
Net loss estimated to be amortized	654,000,000
Prior service cost estimated to be amortized	(19,000,000)
Investments value	13,519,000,000	11,815,000,000	11,141,000,000	$ 10,897,000,000
Accumulated benefit obligation	12,972,000,000	11,806,000,000	$ 12,055,000,000
Estimated future employer contributions	435,000,000
Other Nonqualified Supplemental Defined Benefit Pension
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	331,000,000	303,000,000
Other Nonqualified Supplemental Defined Benefit Pension | CECONY
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	$ 297,000,000	$ 268,000,000

Pension Benefits - Schedule o81

Pension Benefits - Schedule of Assumptions (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
CECONY
Defined Benefit Plan Disclosure [Line Items]
Rate of compensation increase	4.25%	4.25%	4.25%
Rate of compensation increase	4.25%	4.25%	4.25%
O&R
Defined Benefit Plan Disclosure [Line Items]
Rate of compensation increase	4.00%	4.00%	4.00%
Rate of compensation increase	4.00%	4.00%	4.00%
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Discount rate, benefit obligations	3.70%	4.25%	4.25%
Discount rate, net periodic benefit cost	4.25%	4.25%	3.90%
Expected return on plan assets	7.50%	7.80%	7.80%

Pension Benefits - Schedule o82

Pension Benefits - Schedule of Expected Benefit Payments (Details) - Pension Benefits $ in Millions	Dec. 31, 2017USD ($)
Defined Benefit Plan Disclosure [Line Items]
2,018	$ 728
2,019	738
2,020	753
2,021	765
2,022	778
2023-2027	4,083
CECONY
Defined Benefit Plan Disclosure [Line Items]
2,018	677
2,019	686
2,020	700
2,021	712
2,022	724
2023-2027	$ 3,804

Pension Benefits - Schedule o83

Pension Benefits - Schedule of Plan Assets Allocations (Details) - Pension Benefits	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Target Allocation Range	100.00%
Plan Assets Percentage	100.00%	100.00%	100.00%
Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Plan Assets Percentage	58.00%	58.00%	57.00%
Equity Securities | Minimum
Defined Benefit Plan Disclosure [Line Items]
Target Allocation Range	53.00%
Equity Securities | Maximum
Defined Benefit Plan Disclosure [Line Items]
Target Allocation Range	63.00%
Debt Securities
Defined Benefit Plan Disclosure [Line Items]
Plan Assets Percentage	33.00%	33.00%	33.00%
Debt Securities | Minimum
Defined Benefit Plan Disclosure [Line Items]
Target Allocation Range	0.28%
Debt Securities | Maximum
Defined Benefit Plan Disclosure [Line Items]
Target Allocation Range	0.38%
Real Estate
Defined Benefit Plan Disclosure [Line Items]
Plan Assets Percentage	9.00%	9.00%	10.00%
Real Estate | Minimum
Defined Benefit Plan Disclosure [Line Items]
Target Allocation Range	7.00%
Real Estate | Maximum
Defined Benefit Plan Disclosure [Line Items]
Target Allocation Range	11.00%

Pension Benefits - Schedule o84

Pension Benefits - Schedule of Fair Value of Plan Assets (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	$ 330	$ 273
Private Equity
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets		247
Real Estate
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets		1,139
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Funds for retiree health benefits	(262)	(270)
Funds for retiree health benefits measured at NAV per share (l)(n)	(36)	(37)
Total funds for retiree health benefits	(298)	307
Investments (excluding funds for retiree health benefits)	14,683	12,910
Pending activities	(409)	(438)
Total fair value of plan net assets	14,274	12,472	$ 11,759	$ 11,495
Pension Benefits | U.S. Equity
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	3,900	3,466
Pension Benefits | International Equity
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	4,132	3,558
Pension Benefits | U.S. Government Issued Debt
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	1,786	1,337
Pension Benefits | Corporate Bonds Debt
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	2,450	2,140
Pension Benefits | Structured Assets Debt
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	3	1
Pension Benefits | Other Fixed Income Debt
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	125	200
Pension Benefits | Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	476	536
Pension Benefits | Futures
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	308	364
Pension Benefits | Total investments
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	13,180	11,602
Pension Benefits | Private Equity
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	336
Pension Benefits | Real Estate
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	1,214
Pension Benefits | Hedge Funds
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	251	229
Pension Benefits | Investments Valued Using NAV Per Share
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	1,801	1,615
Pension Benefits | Level 1
Defined Benefit Plan Disclosure [Line Items]
Funds for retiree health benefits	(168)	(165)
Investments (excluding funds for retiree health benefits)	8,268	6,931
Pension Benefits | Level 1 | U.S. Equity
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	3,872	3,466
Pension Benefits | Level 1 | International Equity
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	4,132	3,187
Pension Benefits | Level 1 | U.S. Government Issued Debt
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	0	0
Pension Benefits | Level 1 | Corporate Bonds Debt
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	0	0
Pension Benefits | Level 1 | Structured Assets Debt
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	0	0
Pension Benefits | Level 1 | Other Fixed Income Debt
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	0	0
Pension Benefits | Level 1 | Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	124	147
Pension Benefits | Level 1 | Futures
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	308	296
Pension Benefits | Level 1 | Total investments
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	8,436	7,096
Pension Benefits | Level 2
Defined Benefit Plan Disclosure [Line Items]
Funds for retiree health benefits	(94)	(105)
Investments (excluding funds for retiree health benefits)	4,650	4,401
Pension Benefits | Level 2 | U.S. Equity
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	28
Pension Benefits | Level 2 | International Equity
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets		371
Pension Benefits | Level 2 | U.S. Government Issued Debt
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	1,786	1,337
Pension Benefits | Level 2 | Corporate Bonds Debt
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	2,450	2,140
Pension Benefits | Level 2 | Structured Assets Debt
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	3	1
Pension Benefits | Level 2 | Other Fixed Income Debt
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	125	200
Pension Benefits | Level 2 | Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	352	389
Pension Benefits | Level 2 | Futures
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets		68
Pension Benefits | Level 2 | Total investments
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	$ 4,744	$ 4,506

Pension Benefits - Schedule o85

Pension Benefits - Schedule of Employer Contribution to Defined Savings Plan (Details) - Defined Contribution Savings Plan - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Employer contribution to the defined savings plan	$ 40	$ 36	$ 34
CECONY
Defined Benefit Plan Disclosure [Line Items]
Employer contribution to the defined savings plan	$ 35	$ 32	$ 29

Other Postretirement Benefits -

Other Postretirement Benefits - Net Periodic Postretirement Benefit Costs (Details) - Other Postretirement Benefits - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 20	$ 18	$ 20
Interest cost on accumulated other postretirement benefit obligation	46	48	51
Expected return on plan assets	(69)	(77)	(78)
Recognition of net actuarial loss	2	5	31
Recognition of prior service cost	(17)	(20)	(20)
NET PERIODIC BENEFIT COST	(18)	(26)	4
Cost capitalized	8	11	(2)
Reconciliation to rate level	(4)	22	14
Cost charged to operating expenses	(14)	7	16
CECONY
Defined Benefit Plan Disclosure [Line Items]
Service cost	13	13	15
Interest cost on accumulated other postretirement benefit obligation	38	40	43
Expected return on plan assets	(61)	(67)	(68)
Recognition of net actuarial loss	(3)	3	28
Recognition of prior service cost	(11)	(14)	(14)
NET PERIODIC BENEFIT COST	(24)	(25)	4
Cost capitalized	10	10	(2)
Reconciliation to rate level	(2)	22	6
Cost charged to operating expenses	$ (16)	$ 7	$ 8

Other Postretirement Benefits87

Other Postretirement Benefits - Schedule of Funded Status (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
CHANGE IN PLAN ASSETS
Fair value of plan assets at beginning of year	$ 273
FAIR VALUE OF PLAN ASSETS AT END OF YEAR	330	$ 273
CECONY
CHANGE IN PLAN ASSETS
Fair value of plan assets at beginning of year	246
FAIR VALUE OF PLAN ASSETS AT END OF YEAR	301	246
Other Postretirement Benefits
CHANGE IN BENEFIT OBLIGATION
Projected benefit obligation at beginning of year	1,198	1,287	$ 1,411
Service cost	20	18	20
Interest cost on accumulated other postretirement benefit obligation	46	48	51
Amendments	0	0	0
Net actuarial loss/(gain)	53	(57)	(103)
Benefits paid and administrative expenses	(134)	(134)	(127)
Participant contributions	36	36	35
PROJECTED BENEFIT OBLIGATION AT END OF YEAR	1,219	1,198	1,287
CHANGE IN PLAN ASSETS
Fair value of plan assets at beginning of year	975	994	1,084
Actual return on plan assets	150	60	(6)
Employer contributions	17	7	6
EGWP payments	34	35	28
Participant contributions	35	36	35
Benefits paid	(172)	(157)	(153)
FAIR VALUE OF PLAN ASSETS AT END OF YEAR	1,039	975	994
FUNDED STATUS	(180)	(223)	(293)
Unrecognized net loss/(gain)	(47)	(24)	28
Unrecognized prior service costs	(14)	(31)	(51)
Other Postretirement Benefits | CECONY
CHANGE IN BENEFIT OBLIGATION
Projected benefit obligation at beginning of year	1,007	1,093	1,203
Service cost	13	13	15
Interest cost on accumulated other postretirement benefit obligation	38	40	43
Amendments	0	0	0
Net actuarial loss/(gain)	16	(52)	(85)
Benefits paid and administrative expenses	(124)	(122)	(117)
Participant contributions	35	35	34
PROJECTED BENEFIT OBLIGATION AT END OF YEAR	985	1,007	1,093
CHANGE IN PLAN ASSETS
Fair value of plan assets at beginning of year	851	870	950
Actual return on plan assets	130	52	(4)
Employer contributions	8	7	6
EGWP payments	30	33	26
Participant contributions	35	35	34
Benefits paid	(161)	(146)	(142)
FAIR VALUE OF PLAN ASSETS AT END OF YEAR	893	851	870
FUNDED STATUS	(92)	(156)	(223)
Unrecognized net loss/(gain)	(85)	(42)	4
Unrecognized prior service costs	$ (7)	$ (18)	$ (32)

Other Postretirement Benefits88

Other Postretirement Benefits - Additional Information (Details) - Other Postretirement Benefits $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)
Defined Benefit Plan Disclosure [Line Items]
Decrease in liability for other postretirement benefits	$ 43
Increase in regulatory liabilities	11
Net losses unrecognized to be amortized	8
Prior service cost estimated to be amortized	$ (6)
Health care cost trend rate for net periodic benefit cost, current	5.80%
Health care cost trend rate for net periodic benefit cost	4.50%
Health care cost trend rate for benefit obligations, current	5.60%
Health care cost trend rate for benefit obligations	4.50%
Expected contributions	$ 7
Clean Energy Businesses, Con Edison Transmission and RECO
Defined Benefit Plan Disclosure [Line Items]
Debit to OCI (net of taxes) for unrecognized net losses	3
Change to OCI (net of taxes) for unrecognized prior service costs	0
CECONY
Defined Benefit Plan Disclosure [Line Items]
Decrease in liability for other postretirement benefits	64
Increase in regulatory liabilities	32
Net losses unrecognized to be amortized	1
Prior service cost estimated to be amortized	$ (2)

Other Postretirement Benefits89

Other Postretirement Benefits - Schedule of Actuarial Assumptions (Details) - Other Postretirement Benefits	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Expected Return on Plan Assets	7.50%	7.00%	7.75%
CECONY
Defined Benefit Plan Disclosure [Line Items]
Discount Rate, Benefit Obligations	3.55%	4.00%	4.05%
Discount rate, net periodic benefit cost	4.00%	4.05%	3.75%
O&R
Defined Benefit Plan Disclosure [Line Items]
Discount Rate, Benefit Obligations	3.70%	4.20%	4.20%
Discount rate, net periodic benefit cost	4.20%	4.20%	3.85%

Other Postretirement Benefits90

Other Postretirement Benefits - Schedule of Change of Assumed Health Care Cost Trend Rate (Details) - Other Postretirement Benefits $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)
Increase
Effect on accumulated other postretirement benefit obligation	$ 13
Effect on service cost and interest cost components for 2017	2
Decrease
Effect on accumulated other postretirement benefit obligation	11
Effect on service cost and interest cost components for 2017	0
CECONY
Increase
Effect on accumulated other postretirement benefit obligation	(20)
Effect on service cost and interest cost components for 2017	(1)
Decrease
Effect on accumulated other postretirement benefit obligation	35
Effect on service cost and interest cost components for 2017	$ 1

Other Postretirement Benefits91

Other Postretirement Benefits - Schedule of Expected Benefit Payments (Details) - Other Postretirement Benefits $ in Millions	Dec. 31, 2017USD ($)
Defined Benefit Plan Disclosure [Line Items]
2,018	$ 83
2,019	81
2,020	78
2,021	76
2,022	75
2023-2027	363
CECONY
Defined Benefit Plan Disclosure [Line Items]
2,018	73
2,019	70
2,020	67
2,021	65
2,022	64
2023-2027	$ 303

Other Postretirement Benefits92

Other Postretirement Benefits - Schedule of Plan Assets Allocations (Details) - Other Postretirement Benefits - CECONY	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Target Allocation Range	100.00%
Plan Assets Percentage	100.00%	100.00%	100.00%
Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Plan Assets Percentage	60.00%	60.00%	59.00%
Equity Securities | Minimum
Defined Benefit Plan Disclosure [Line Items]
Target Allocation Range	50.00%
Equity Securities | Maximum
Defined Benefit Plan Disclosure [Line Items]
Target Allocation Range	80.00%
Debt Securities
Defined Benefit Plan Disclosure [Line Items]
Plan Assets Percentage	40.00%	40.00%	41.00%
Debt Securities | Minimum
Defined Benefit Plan Disclosure [Line Items]
Target Allocation Range	20.00%
Debt Securities | Maximum
Defined Benefit Plan Disclosure [Line Items]
Target Allocation Range	50.00%

Other Postretirement Benefits93

Other Postretirement Benefits - Schedule of Fair Values of Plan Assets (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	$ 330	$ 273
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Funds for retiree health benefits	262	270
Investments (including funds for retiree health benefits)	984	924
Funds for retiree health benefits measured at NAV per share (l)(n)	36	37
Pending activities	19	14
Total fair value of plan net assets	1,039	975	$ 994	$ 1,084
Other Postretirement Benefits | Equity
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	420	391
Other Postretirement Benefits | Other Fixed Income Debt
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	286	250
Other Postretirement Benefits | Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	16	13
Other Postretirement Benefits | Total investments
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	722	654
Other Postretirement Benefits | Level 1
Defined Benefit Plan Disclosure [Line Items]
Funds for retiree health benefits	168	165
Investments (including funds for retiree health benefits)	168	165
Other Postretirement Benefits | Level 1 | Equity
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	0	0
Other Postretirement Benefits | Level 1 | Other Fixed Income Debt
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	0	0
Other Postretirement Benefits | Level 1 | Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	0	0
Other Postretirement Benefits | Level 1 | Total investments
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	0	0
Other Postretirement Benefits | Level 2
Defined Benefit Plan Disclosure [Line Items]
Funds for retiree health benefits	94	105
Investments (including funds for retiree health benefits)	816	759
Other Postretirement Benefits | Level 2 | Equity
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	420	391
Other Postretirement Benefits | Level 2 | Other Fixed Income Debt
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	286	250
Other Postretirement Benefits | Level 2 | Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	16	13
Other Postretirement Benefits | Level 2 | Total investments
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	$ 722	$ 654

Environmental Matters - Accrued

Environmental Matters - Accrued Liabilities and Regulatory Assets (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Site Contingency [Line Items]
Accrued Liabilities	$ 737	$ 753
Regulatory assets	4,333	7,124
Manufactured gas plant sites
Site Contingency [Line Items]
Accrued Liabilities	651	664
Other Superfund Sites
Site Contingency [Line Items]
Accrued Liabilities	86	89
Superfund Sites
Site Contingency [Line Items]
Accrued Liabilities	737	753
Regulatory assets	793	823
CECONY
Site Contingency [Line Items]
Accrued Liabilities	637	655
Regulatory assets	3,925	6,563
CECONY | Manufactured gas plant sites
Site Contingency [Line Items]
Accrued Liabilities	551	567
CECONY | Other Superfund Sites
Site Contingency [Line Items]
Accrued Liabilities	86	88
CECONY | Superfund Sites
Site Contingency [Line Items]
Accrued Liabilities	637	655
Regulatory assets	$ 677	$ 711

Environmental Matters - Environ

Environmental Matters - Environmental Remediation Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Environmental Exit Cost [Line Items]
Remediation costs incurred	$ 24	$ 34
CECONY
Environmental Exit Cost [Line Items]
Remediation costs incurred	$ 19	$ 21

Environmental Matters - Additio

Environmental Matters - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Site Contingency [Line Items]
Insurance recoveries received	$ 0	$ 1
Asbestos Proceedings
Site Contingency [Line Items]
Estimated undiscounted asbestos liability (years)	15 years
Superfund Sites
Site Contingency [Line Items]
Remediation cost estimate	$ 47
Superfund Sites | Manufactured Gas Plant Sites | Maximum
Site Contingency [Line Items]
Estimated aggregate undiscounted potential liability related environmental contaminants (up to)	2,700
CECONY
Site Contingency [Line Items]
Insurance recoveries received	$ 0	$ 1
CECONY | Asbestos Proceedings
Site Contingency [Line Items]
Estimated undiscounted asbestos liability (years)	15 years
CECONY | Superfund Sites
Site Contingency [Line Items]
Remediation cost estimate	$ 34
CECONY | Superfund Sites | Manufactured Gas Plant Sites | Maximum
Site Contingency [Line Items]
Estimated aggregate undiscounted potential liability related environmental contaminants (up to)	$ 2,500

Environmental Matters - Accru97

Environmental Matters - Accrued Liability for Asbestos Suits and Workers' Compensation Proceedings (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Site Contingency [Line Items]
Regulatory assets	$ 4,333	$ 7,124
Asbestos Suits
Site Contingency [Line Items]
Accrued liability	8	8
Regulatory assets	8	8
Workers' Compensation
Site Contingency [Line Items]
Accrued liability	84	88
Regulatory assets	10	13
CECONY
Site Contingency [Line Items]
Regulatory assets	3,925	6,563
CECONY | Asbestos Suits
Site Contingency [Line Items]
Accrued liability	7	7
Regulatory assets	7	7
CECONY | Workers' Compensation
Site Contingency [Line Items]
Accrued liability	80	83
Regulatory assets	$ 10	$ 13

Other Material Contingencies -

Other Material Contingencies - Manhattan Explosion and Fire (Details) $ in Millions	Mar. 12, 2014buildingpeople	Feb. 28, 2017USD ($)	Dec. 31, 2017USD ($)lawsuit	Dec. 31, 2016USD ($)
Loss Contingencies [Line Items]
Accrued regulatory liability			$ 4,577	$ 1,905
Settlement of gas proceedings
Loss Contingencies [Line Items]
Accrued regulatory liability			$ 27	$ 27
Manhattan Explosion and Fire
Loss Contingencies [Line Items]
Number of buildings destroyed by fire | building	2
Number of people died in explosion and fire incident | people	8
Number of people injured in explosion and fire incident (more than) | people	50
Amount of costs that will not recover from customers		$ 126
Number of pending lawsuits | lawsuit			80
Manhattan Explosion and Fire | Settlement of gas proceedings
Loss Contingencies [Line Items]
Accrued regulatory liability		$ 27

Other Material Contingencies 99

Other Material Contingencies - Guarantees (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Guarantee obligations maximum exposure	$ 2,073	$ 2,370

Other Material Contingencies100

Other Material Contingencies - Total Guarantees (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Guarantor Obligations [Line Items]
Total guarantees, by type and term	$ 2,073	$ 2,370
Con Edison Transmission
Guarantor Obligations [Line Items]
Total guarantees, by type and term	1,047
Energy transactions
Guarantor Obligations [Line Items]
Total guarantees, by type and term	669
Renewable electric production projects
Guarantor Obligations [Line Items]
Total guarantees, by type and term	234
Other
Guarantor Obligations [Line Items]
Total guarantees, by type and term	123
0 – 3 years
Guarantor Obligations [Line Items]
Total guarantees, by type and term	1,407
0 – 3 years | Con Edison Transmission
Guarantor Obligations [Line Items]
Total guarantees, by type and term	643
0 – 3 years | Energy transactions
Guarantor Obligations [Line Items]
Total guarantees, by type and term	431
0 – 3 years | Renewable electric production projects
Guarantor Obligations [Line Items]
Total guarantees, by type and term	210
0 – 3 years | Other
Guarantor Obligations [Line Items]
Total guarantees, by type and term	123
4 – 10 years
Guarantor Obligations [Line Items]
Total guarantees, by type and term	431
4 – 10 years | Con Edison Transmission
Guarantor Obligations [Line Items]
Total guarantees, by type and term	404
4 – 10 years | Energy transactions
Guarantor Obligations [Line Items]
Total guarantees, by type and term	27
4 – 10 years | Renewable electric production projects
Guarantor Obligations [Line Items]
Total guarantees, by type and term	0
4 – 10 years | Other
Guarantor Obligations [Line Items]
Total guarantees, by type and term	0
Greater than 10 years
Guarantor Obligations [Line Items]
Total guarantees, by type and term	235
Greater than 10 years | Con Edison Transmission
Guarantor Obligations [Line Items]
Total guarantees, by type and term	0
Greater than 10 years | Energy transactions
Guarantor Obligations [Line Items]
Total guarantees, by type and term	211
Greater than 10 years | Renewable electric production projects
Guarantor Obligations [Line Items]
Total guarantees, by type and term	24
Greater than 10 years | Other
Guarantor Obligations [Line Items]
Total guarantees, by type and term	$ 0

Other Material Contingencies101

Other Material Contingencies - Con Edison Transmission (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2014
Guarantor Obligations [Line Items]
Guarantee obligations maximum exposure	$ 2,073	$ 2,370
Payment Guarantee by CET Electric of Contributions to New York Transco LLC
Guarantor Obligations [Line Items]
Ownership interest, percentage			45.70%
Estimated project cost percentage	175.00%
Financial Guarantee in Behalf of CET Gas for Proposed Gas Transmission Project
Guarantor Obligations [Line Items]
Guarantee obligations maximum exposure	$ 25

Other Material Contingencies102

Other Material Contingencies - Other (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Guarantor Obligations [Line Items]
Guarantee obligations maximum exposure	$ 2,073	$ 2,370
Financial Guarantee for Indemnity Agreements for Surety Bonds in Connection with Operation of Solar Energy Facilities and Energy Service Projects
Guarantor Obligations [Line Items]
Guarantee obligations maximum exposure	70
Certain Obligations Under Agreement to Sell the Retail Electric Supply Business
Guarantor Obligations [Line Items]
Guarantee obligations maximum exposure	$ 53

Electricity Purchase Agreeme103

Electricity Purchase Agreements - Summary of Significant Terms of Electricity Purchase Agreements (Details)	12 Months Ended
	Dec. 31, 2017MW
Brooklyn Navy Yard
Long-term Contract for Purchase of Electric Power [Line Items]
Plant Output (MW)	322
Contracted Output (MW)	303
Contract Term (Years)	40 years
Indian Point
Long-term Contract for Purchase of Electric Power [Line Items]
Plant Output (MW)	2,150
Contracted Output (MW)	500
Contract Term (Years)	16 years

Electricity Purchase Agreeme104

Electricity Purchase Agreements - Summary of Estimated Capacity and Other Fixed Payments (Details) $ in Millions	Dec. 31, 2017USD ($)
Long-term Contract for Purchase of Electric Power [Line Items]
2,018	$ 257
2,019	202
2,020	114
2,021	65
2,022	54
All Years Thereafter	656
CECONY
Long-term Contract for Purchase of Electric Power [Line Items]
2,018	255
2,019	198
2,020	111
2,021	64
2,022	54
All Years Thereafter	$ 656

Electricity Purchase Agreeme105

Electricity Purchase Agreements - Summary of Capacity, Energy and Other Fixed Payments (Details) - CECONY - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Long-term Contract for Purchase of Electric Power [Line Items]
Capacity, energy and other fixed payments	$ 552	$ 692	$ 865
Linden Cogeneration
Long-term Contract for Purchase of Electric Power [Line Items]
Capacity, energy and other fixed payments	114	304	323
Indian Point
Long-term Contract for Purchase of Electric Power [Line Items]
Capacity, energy and other fixed payments	211	203	226
Astoria Energy
Long-term Contract for Purchase of Electric Power [Line Items]
Capacity, energy and other fixed payments	0	50	178
Astoria Generating Company
Long-term Contract for Purchase of Electric Power [Line Items]
Capacity, energy and other fixed payments	92	16	0
Brooklyn Navy Yard
Long-term Contract for Purchase of Electric Power [Line Items]
Capacity, energy and other fixed payments	117	119	113
Indeck Corinth
Long-term Contract for Purchase of Electric Power [Line Items]
Capacity, energy and other fixed payments	0	0	25
Cogen Technologies
Long-term Contract for Purchase of Electric Power [Line Items]
Capacity, energy and other fixed payments	$ 18	$ 0	$ 0

Leases - Schedule of Capital Le

Leases - Schedule of Capital Leases (Details) - Common - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Property Subject to or Available for Operating Lease [Line Items]
Utility Plant	$ 2	$ 3
CECONY
Property Subject to or Available for Operating Lease [Line Items]
Utility Plant	$ 1	$ 2

Leases - Additional Information

Leases - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Operating Leased Assets [Line Items]
Accumulated amortization	$ 3	$ 3
CECONY
Operating Leased Assets [Line Items]
Accumulated amortization	$ 2	$ 1
Increase in annual payments, percentage	2.18%
Decrease in transformer installations, percentage	0.50%

Leases - Future Minimum Rental

Leases - Future Minimum Rental Payments for Operating Leases (Details) $ in Millions	Dec. 31, 2017USD ($)
Operating Leased Assets [Line Items]
2,018	$ 63
2,019	63
2,020	63
2,021	62
2,022	59
All years thereafter	746
Total	1,056
CECONY
Operating Leased Assets [Line Items]
2,018	55
2,019	56
2,020	55
2,021	54
2,022	53
All years thereafter	645
Total	$ 918

Goodwill and Other Intangibl109

Goodwill and Other Intangible Assets (Details)	12 Months Ended
	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)business_acquisition	Dec. 31, 2015USD ($)
Goodwill [Line Items]
Goodwill	$ 428,000,000	$ 428,000,000
Impairment charge	0
Finite lived intangible assets, accumulated amortization	15,000,000	6,000,000
Amortization expense	9,000,000	2,000,000	$ 0
Intangibles Future Amortization:
Year 1	9,000,000
Year 2	9,000,000
Year 3	9,000,000
Year 4	9,000,000
Year 5	9,000,000
Other Intangible Assets
Goodwill [Line Items]
Finite lived intangible assets, net	0	5,000,000
Finite lived intangible assets, accumulated amortization	6,000,000	5,000,000
CECONY
Goodwill [Line Items]
Goodwill	245,000,000	245,000,000
CECONY | Other Intangible Assets
Goodwill [Line Items]
Finite lived intangible assets, net	0	0
O&R
Goodwill [Line Items]
Goodwill	161,000,000	161,000,000
O&R Merger
Goodwill [Line Items]
Goodwill	406,000,000	406,000,000
Gas Storage Company | CET Gas
Goodwill [Line Items]
Goodwill	8,000,000	8,000,000
Energy Services Company | Clean Energy Businesses
Goodwill [Line Items]
Goodwill		$ 15,000,000
Number of businesses acquired included in goodwill impairment test | business_acquisition		2
Impairment charge		$ 15,000,000
Impairment charge, net of tax		12,000,000
Residential Solar Company | Clean Energy Businesses
Goodwill [Line Items]
Goodwill		14,000,000
Power Purchase
Goodwill [Line Items]
Finite lived intangible assets, net	131,000,000	119,000,000
Finite lived intangible assets, accumulated amortization	$ 9,000,000	$ 1,000,000

Income Tax - Schedule of Compon

Income Tax - Schedule of Components of Income Tax (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
State
Current	$ (2)	$ (42)	$ 38
Deferred	103	188	93
Federal
Current	(11)	(43)	(86)
Deferred	391	604	569
Amortization of investment tax credits	(9)	(9)	(9)
Total income tax expense	472	698	605
CECONY
State
Current	37	(1)	48
Deferred	75	114	82
Federal
Current	73	59	77
Deferred	504	435	372
Amortization of investment tax credits	(4)	(4)	(5)
Total income tax expense	$ 685	$ 603	$ 574

Income Tax - Schedule of Differ

Income Tax - Schedule of Differences on Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Deferred tax liabilities:
Property basis differences	$ 6,555	$ 9,446
Regulatory assets:
Unrecognized pension and other postretirement costs	697	1,162
Future income tax	0	986
Environmental remediation costs	219	333
Deferred storm costs	11	23
Other regulatory assets	269	371
Equity investments	263	363
Total deferred tax liabilities	8,014	12,684
Deferred tax assets:
Accrued pension and other postretirement costs	264	581
Future income tax	698	0
Other regulatory liabilities	593	822
Superfund and other environmental costs	203	304
Asset retirement obligations	86	99
Loss carryforwards	95	59
Tax credits carryforward	658	498
Valuation allowance	(33)	(16)
Other	112	303
Total deferred tax assets	2,676	2,650
Net deferred tax liabilities	5,338	10,034
Unamortized investment tax credits	157	171
Net deferred tax liabilities and unamortized investment tax credits	5,495	10,205
CECONY
Deferred tax liabilities:
Property basis differences	5,968	8,620
Regulatory assets:
Unrecognized pension and other postretirement costs	656	1,104
Future income tax	0	940
Environmental remediation costs	187	287
Deferred storm costs	0	1
Other regulatory assets	241	321
Equity investments	0	0
Total deferred tax liabilities	7,052	11,273
Deferred tax assets:
Accrued pension and other postretirement costs	187	467
Future income tax	660	0
Other regulatory liabilities	524	728
Superfund and other environmental costs	176	265
Asset retirement obligations	79	92
Loss carryforwards	0	0
Tax credits carryforward	0	0
Valuation allowance	0	0
Other	148	312
Total deferred tax assets	1,774	1,864
Net deferred tax liabilities	5,278	9,409
Unamortized investment tax credits	28	41
Net deferred tax liabilities and unamortized investment tax credits	$ 5,306	$ 9,450

Income Tax - Schedule of Income

Income Tax - Schedule of Income Tax Reconciliation (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
STATUTORY TAX RATE
Federal	35.00%	35.00%	35.00%
Changes in computed taxes resulting from:
State income tax	4.00%	4.00%	5.00%
Cost of removal	1.00%	(1.00%)	(5.00%)
Other plant-related items	(1.00%)	0.00%	0.00%
TCJA tax rate reduction	(13.00%)	0.00%	0.00%
Renewable energy credits	(1.00%)	(1.00%)	(1.00%)
Research and development credits	(0.00%)	(1.00%)	(0.00%)
Other	(2.00%)	0.00%	0.00%
Effective tax rate	23.00%	36.00%	34.00%
CECONY
STATUTORY TAX RATE
Federal	35.00%	35.00%	35.00%
Changes in computed taxes resulting from:
State income tax	4.00%	4.00%	5.00%
Cost of removal	1.00%	(1.00%)	(5.00%)
Other plant-related items	(1.00%)	(1.00%)	0.00%
TCJA tax rate reduction	0.00%	0.00%	0.00%
Renewable energy credits	(0.00%)	(0.00%)	(0.00%)
Research and development credits	(0.00%)	(1.00%)	(0.00%)
Other	(1.00%)	0.00%	0.00%
Effective tax rate	38.00%	36.00%	35.00%

Income Tax - Additional Informa

Income Tax - Additional Information (Details) - USD ($)	1 Months Ended	12 Months Ended
	Feb. 29, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Loss Carryforwards [Line Items]
Decrease in net deferred tax liabilities resulting from TCJA		$ 5,312,000,000
Change in net income resulting from TCJA		259,000,000
Operating loss carryforwards, accelerated bonus depreciation		19,000,000
Deferred tax asset, valuation allowance		33,000,000	$ 16,000,000
Deferred tax assets, charitable contribution carryforwards		4,000,000	5,000,000	$ 5,000,000
Income tax refund	$ 160,000,000
Decrease in uncertain tax positions resulting from settlement of claims filed in previous years		6,000,000	0	0
Effective income tax rate reconciliation, uncertainty of taxes		8,000,000
Effective income tax rate reconciliation, uncertainty net of federal taxes		7,000,000
Penalties for uncertain tax positions		0	0	0
Amount of interest and penalties in their consolidated balance sheets		0	0
Unrecognized tax benefits that would have an impact on effective tax rate		12,000,000
Unrecognized tax benefits that would have an impact on effective tax rate, net of taxes		11,000,000
Charitable Contribution
Operating Loss Carryforwards [Line Items]
Deferred tax asset, valuation allowance				3,000,000
New York State
Operating Loss Carryforwards [Line Items]
Decrease in effective tax rate resulting from tax settlement		6,000,000
General Business Tax Credit
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards		176,000,000
Renewable Energy Tax Credits
Operating Loss Carryforwards [Line Items]
Valuation allowance		658,000,000
Tax credit carryforward, valuation allowance		0
Charitable Contribution
Operating Loss Carryforwards [Line Items]
Tax credit carryforward, valuation allowance		0	0	0
Federal
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards		121,000,000
Federal | Carryback to 2007 and 2014
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards		53,000,000
Federal | Year 2036
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards		68,000,000
State
Operating Loss Carryforwards [Line Items]
Deferred tax asset, valuation allowance		12,000,000
State | New York State
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards		137,000,000
Decrease in uncertain tax positions resulting from settlement of claims filed in previous years		30,000,000
Decrease in effective tax rate resulting from tax settlement, net of taxes		4,000,000
New York City
Operating Loss Carryforwards [Line Items]
Deferred tax asset, valuation allowance		21,000,000
Parent Company
Operating Loss Carryforwards [Line Items]
Change in net income resulting from TCJA		(21,000,000)
Clean Energy Businesses
Operating Loss Carryforwards [Line Items]
Change in net income resulting from TCJA		269,000,000
Con Edison Transmission
Operating Loss Carryforwards [Line Items]
Change in net income resulting from TCJA		11,000,000
Future Income Tax
Operating Loss Carryforwards [Line Items]
Increase in regulatory liability resulting from TCJA		3,713,000,000
Accelerated Tax Depreciation Benefits
Operating Loss Carryforwards [Line Items]
Increase in regulatory liability resulting from TCJA		2,684,000,000
Future Income Tax
Operating Loss Carryforwards [Line Items]
Decrease in regulatory asset resulting from TCJA		1,250,000,000
Revenue Taxes
Operating Loss Carryforwards [Line Items]
Decrease in regulatory asset resulting from TCJA		90,000,000
CECONY
Operating Loss Carryforwards [Line Items]
Decrease in net deferred tax liabilities resulting from TCJA		4,781,000,000
Deferred tax asset, valuation allowance		0	0
Income tax refund	$ 143,000,000
Decrease in uncertain tax positions resulting from settlement of claims filed in previous years		0	$ 0	$ 0
Effective income tax rate reconciliation, uncertainty of taxes		4,000,000
Unrecognized tax benefits that would have an impact on effective tax rate		5,000,000
CECONY | New York State
Operating Loss Carryforwards [Line Items]
Decrease in effective tax rate resulting from tax settlement		18,000,000
CECONY | State | New York State
Operating Loss Carryforwards [Line Items]
Decrease in effective tax rate resulting from tax settlement, net of taxes		12,000,000
CECONY | Future Income Tax
Operating Loss Carryforwards [Line Items]
Increase in regulatory liability resulting from TCJA		3,513,000,000
CECONY | Accelerated Tax Depreciation Benefits
Operating Loss Carryforwards [Line Items]
Increase in regulatory liability resulting from TCJA		2,542,000,000
CECONY | Future Income Tax
Operating Loss Carryforwards [Line Items]
Decrease in regulatory asset resulting from TCJA		1,182,000,000
CECONY | Revenue Taxes
Operating Loss Carryforwards [Line Items]
Decrease in regulatory asset resulting from TCJA		$ 86,000,000

Income Tax - Summary of Unrecog

Income Tax - Summary of Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of period	$ 42	$ 34	$ 34
Additions based on tax positions related to the current year	1	2	0
Additions based on tax positions of prior years	1	19	1
Reductions for tax positions of prior years	(24)	(13)	0
Reductions from expiration of statute of limitations	(2)	0	(1)
Settlements	(6)	0	0
Balance at end of period	12	42	34
CECONY
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of period	21	2	2
Additions based on tax positions related to the current year	1	2	0
Additions based on tax positions of prior years	1	19	0
Reductions for tax positions of prior years	(18)	(2)	0
Reductions from expiration of statute of limitations	0	0	0
Settlements	0	0	0
Balance at end of period	$ 5	$ 21	$ 2

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options exercised	$ 0	$ 2,000,000
Cash received by Con Edison for payment of exercise price		3,000,000
Income tax benefit realized from stock options exercised	25,000,000	20,000,000	$ 14,000,000
Maximum employer contribution match (up to)	1
Amount employee contribution for employer match	9
Maximum employee investment per year (up to)	$ 25,000
Maximum percentage allowed to invest (not more than)	20.00%
CECONY
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options exercised		2,000,000
Cash received by Con Edison for payment of exercise price		3,000,000
Income tax benefit realized from stock options exercised	$ 22,000,000	18,000,000	12,000,000
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (years)	3 years
Income tax benefit realized from stock options exercised		$ 1,000,000	$ 1,000,000
Stock Options | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award expiration period (years)	10 years
Performance RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock received upon vesting (shares)	1
Compensation expense to be recognized	$ 38,000,000
Nonvested awards, compensation cost not yet recognized, period for recognition (years)	1 year
Performance RSUs | CECONY
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense to be recognized	$ 31,000,000
Nonvested awards, compensation cost not yet recognized, period for recognition (years)	1 year
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (years)	3 years
Time-based Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense to be recognized	$ 2,000,000
Nonvested awards, compensation cost not yet recognized, period for recognition (years)	1 year
Weighted average grant date price per share (in dollars per share)	$ 77.66
Time-based Awards | CECONY
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense to be recognized	$ 2,000,000
Nonvested awards, compensation cost not yet recognized, period for recognition (years)	1 year
Weighted average grant date price per share (in dollars per share)	$ 77.66
2013 LTIP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares of common stock that can be awarded under the plan	5,000,000
TSR Portion | Performance RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Adjustment percentage used for Performance awards	50.00%
Factor used for adjustment of Performance awards, low end (percent)	0.00%
Factor used for adjustment of Performance awards, high end (percent)	200.00%
Weighted average grant date price per share (in dollars per share)	$ 73.13
TSR Portion | Performance RSUs | CECONY
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant date price per share (in dollars per share)	$ 72.78
Non-TSR Portion | Performance RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Adjustment percentage used for Performance awards	50.00%
Factor used for adjustment of Performance awards, low end (percent)	0.00%
Factor used for adjustment of Performance awards, high end (percent)	200.00%
Weighted average grant date price per share (in dollars per share)	$ 74.54
Non-TSR Portion | Performance RSUs | CECONY
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant date price per share (in dollars per share)	$ 74.72
LTIP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of units issued (in shares)	28,100
Weighted average grant date price per share (in dollars per share)	$ 81.15
Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares purchased on the open market	719,125	720,268	761,784
Weighted average share price per share, on shares purchased on open market (in dollars per share)	$ 79.57	$ 72.67	$ 62.75

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock-Based Compensation Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 63	$ 50	$ 34
Income tax benefit	25	20	14
Performance-based restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	53	42	27
Time-based restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	2	2	1
Non-employee director deferred stock compensation
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	2	2	2
Stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	6	4	4
CECONY
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	55	44	29
Income tax benefit	22	18	12
CECONY | Performance-based restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	45	36	23
CECONY | Time-based restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	2	2	1
CECONY | Non-employee director deferred stock compensation
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	2	2	2
CECONY | Stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 6	$ 4	$ 3

Stock-Based Compensation - Assu

Stock-Based Compensation - Assumptions Used to Calculate Fair Value (Details) - Performance RSUs	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate, minimum	1.76%	0.85%	0.64%
Risk-free interest rate, maximum	1.89%	1.20%	3.28%
Expected term (years)	3 years	3 years	3 years
Expected share price volatility, minimum (percent)	11.01%	17.72%
Expected share price volatility, maximum (percent)	14.70%	18.22%
Expected share price volatility (percent)			15.82%

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Changes in Status of Performance RSUs' (Details) - Performance RSUs	12 Months Ended
	Dec. 31, 2017$ / sharesshares
Units
Non-vested at beginning of period (in shares) | shares	1,087,137
Granted (in shares) | shares	368,150
Vested (in shares) | shares	(375,684)
Forfeited (in shares) | shares	(50,671)
Transferred (in shares) | shares	0
Non-vested at end of period (in shares) | shares	1,028,932
CECONY
Units
Non-vested at beginning of period (in shares) | shares	848,342
Granted (in shares) | shares	277,318
Vested (in shares) | shares	(293,842)
Forfeited (in shares) | shares	(46,226)
Transferred (in shares) | shares	(1,426)
Non-vested at end of period (in shares) | shares	784,166
TSR Portion
Weighted Average Grant Date Fair Value
Non-vested at beginning of period (in dollars per share)	$ 55.45
Granted (in dollars per share)	73.13
Vested (in dollars per share)	25.36
Forfeited (in dollars per share)	76.29
Transferred (in dollars per share)	0
Non-vested at end of period (in dollars per share)	$ 71.74
Adjustment percentage used for Performance awards	50.00%
TSR Portion | CECONY
Weighted Average Grant Date Fair Value
Non-vested at beginning of period (in dollars per share)	$ 54.92
Granted (in dollars per share)	72.78
Vested (in dollars per share)	25.32
Forfeited (in dollars per share)	76.41
Transferred (in dollars per share)	53.01
Non-vested at end of period (in dollars per share)	71.06
Non-TSR Portion
Weighted Average Grant Date Fair Value
Non-vested at beginning of period (in dollars per share)	63.03
Granted (in dollars per share)	74.54
Vested (in dollars per share)	53.66
Forfeited (in dollars per share)	72.23
Transferred (in dollars per share)	0
Non-vested at end of period (in dollars per share)	$ 70.11
Adjustment percentage used for Performance awards	50.00%
Non-TSR Portion | CECONY
Weighted Average Grant Date Fair Value
Non-vested at beginning of period (in dollars per share)	$ 63
Granted (in dollars per share)	74.72
Vested (in dollars per share)	53.66
Forfeited (in dollars per share)	72.31
Transferred (in dollars per share)	72.52
Non-vested at end of period (in dollars per share)	$ 70.08

Stock-Based Compensation - S119

Stock-Based Compensation - Summary of Changes in Status of Time-Based Awards (Details) - Time-based Awards	12 Months Ended
	Dec. 31, 2017$ / sharesshares
Units
Non-vested at beginning of period (in shares) | shares	65,980
Granted (in shares) | shares	23,000
Vested (in shares) | shares	(21,359)
Forfeited (in shares) | shares	(2,751)
Non-vested at end of period (in shares) | shares	64,870
Weighted Average Grant Date Fair Value
Non-vested at beginning of period (in dollars per share) | $ / shares	$ 64.04
Granted (in dollars per share) | $ / shares	77.66
Vested (in dollars per share) | $ / shares	53.77
Forfeited (in dollars per share) | $ / shares	71.62
Non-vested at end of period (in dollars per share) | $ / shares	$ 71.93
CECONY
Units
Non-vested at beginning of period (in shares) | shares	62,580
Granted (in shares) | shares	21,800
Vested (in shares) | shares	(20,359)
Forfeited (in shares) | shares	(2,601)
Non-vested at end of period (in shares) | shares	61,420
Weighted Average Grant Date Fair Value
Non-vested at beginning of period (in dollars per share) | $ / shares	$ 64.03
Granted (in dollars per share) | $ / shares	77.66
Vested (in dollars per share) | $ / shares	53.77
Forfeited (in dollars per share) | $ / shares	71.93
Non-vested at end of period (in dollars per share) | $ / shares	$ 71.93

Financial Information by Bus120

Financial Information by Business Segment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Revenues	$ 12,033	$ 12,075	$ 12,554
Depreciation and amortization	1,341	1,216	1,130
Operating income	2,610	2,575	2,427
Other Income (deductions)	116	64	24
Interest charges	729	696	653
Income taxes on operating income	459	714	644
Total assets	48,111	48,255	45,642
Capital expenditures	3,606	5,235	3,418
Income taxes on non-operating income	$ 13	$ (16)	$ (40)
Corporate income tax rate	35.00%	35.00%	35.00%
Federal income tax expense	$ 259
Parent Company
Segment Reporting Information [Line Items]
Interest charges	50	$ 41	$ 29
Total assets	17,231	16,192
Federal income tax expense	(21)
Clean Energy Businesses
Segment Reporting Information [Line Items]
Federal income tax expense	269
Con Edison Transmission
Segment Reporting Information [Line Items]
Federal income tax expense	11
CECONY
Segment Reporting Information [Line Items]
Revenues	10,468	10,165	10,328
Depreciation and amortization	1,195	1,106	1,040
Operating income	2,405	2,262	2,247
Other Income (deductions)	7	0	(5)
Interest charges	623	603	584
Total assets	40,451	40,856
Income taxes on non-operating income	$ (3)	$ (14)	$ (14)
Corporate income tax rate	35.00%	35.00%	35.00%
Operating segment | Clean Energy Businesses
Segment Reporting Information [Line Items]
Revenues	$ 694	$ 1,091	$ 1,383
Depreciation and amortization	74	42	22
Operating income	69	183	58
Other Income (deductions)	33	21	35
Interest charges	43	34	11
Income taxes on operating income	(273)	53	22
Total assets	2,735	2,551	1,680
Capital expenditures	447	1,235	823
Operating segment | Con Edison Transmission
Segment Reporting Information [Line Items]
Revenues	2	0	0
Depreciation and amortization	1	0	0
Operating income	(8)	(3)	0
Other Income (deductions)	80	43	0
Interest charges	16	6	0
Income taxes on operating income	(11)	0	0
Total assets	1,222	1,150	3
Capital expenditures	66	1,078	0
Operating segment | CECONY
Segment Reporting Information [Line Items]
Revenues	10,468	10,165	10,328
Depreciation and amortization	1,195	1,106	1,040
Operating income	2,405	2,262	2,247
Other Income (deductions)	7	0	(5)
Interest charges	623	603	584
Income taxes on operating income	688	617	588
Total assets	40,451	40,856	40,230
Capital expenditures	2,904	2,756	2,435
Operating segment | CECONY | Electric
Segment Reporting Information [Line Items]
Revenues	7,972	8,106	8,172
Depreciation and amortization	925	865	820
Operating income	1,862	1,847	1,798
Other Income (deductions)	7	2	(2)
Interest charges	472	459	447
Income taxes on operating income	511	495	447
Total assets	29,661	30,708	30,603
Capital expenditures	1,905	1,819	1,658
Operating segment | CECONY | Gas
Segment Reporting Information [Line Items]
Revenues	1,901	1,508	1,527
Depreciation and amortization	185	159	142
Operating income	472	357	356
Other Income (deductions)	0	(1)	(2)
Interest charges	113	105	96
Income taxes on operating income	152	92	100
Total assets	8,387	7,553	6,974
Capital expenditures	909	811	671
Operating segment | CECONY | Steam
Segment Reporting Information [Line Items]
Revenues	595	551	629
Depreciation and amortization	85	82	78
Operating income	71	58	93
Other Income (deductions)	0	(1)	(1)
Interest charges	38	39	41
Income taxes on operating income	25	30	41
Total assets	2,403	2,595	2,653
Capital expenditures	90	126	106
Operating segment | O&R
Segment Reporting Information [Line Items]
Revenues	874	821	845
Depreciation and amortization	71	67	68
Operating income	141	130	121
Other Income (deductions)	1	1	(4)
Interest charges	36	36	35
Income taxes on operating income	42	40	33
Total assets	2,773	2,758	2,719
Capital expenditures	189	166	160
Operating segment | O&R | Electric
Segment Reporting Information [Line Items]
Revenues	642	637	663
Depreciation and amortization	51	49	50
Operating income	100	95	103
Other Income (deductions)	1	1	(2)
Interest charges	24	24	23
Income taxes on operating income	30	30	31
Total assets	1,949	1,949	2,140
Capital expenditures	128	114	114
Operating segment | O&R | Gas
Segment Reporting Information [Line Items]
Revenues	232	184	182
Depreciation and amortization	20	18	18
Operating income	41	35	18
Other Income (deductions)	0	0	(2)
Interest charges	12	12	12
Income taxes on operating income	12	10	2
Total assets	824	809	579
Capital expenditures	61	52	46
Other
Segment Reporting Information [Line Items]
Revenues	(5)	(2)	(2)
Depreciation and amortization	0	1	0
Operating income	3	3	1
Other Income (deductions)	(5)	(1)	(2)
Interest charges	11	17	23
Income taxes on operating income	13	4	1
Total assets	930	940	1,010
Capital expenditures	0	0	0
Other | O&R
Segment Reporting Information [Line Items]
Revenues	0	0	0
Depreciation and amortization	0	0	0
Operating income	0	0	0
Other Income (deductions)	0	0	0
Interest charges	0	0	0
Income taxes on operating income	0	0	0
Total assets	0	0	0
Capital expenditures	0	0	0
Inter-segment
Segment Reporting Information [Line Items]
Revenues	0	(7)	2
Inter-segment | Clean Energy Businesses
Segment Reporting Information [Line Items]
Revenues	0	7	(2)
Inter-segment | CECONY
Segment Reporting Information [Line Items]
Revenues	(97)	(111)	(110)
Inter-segment | CECONY | Electric
Segment Reporting Information [Line Items]
Revenues	16	17	18
Inter-segment | CECONY | Gas
Segment Reporting Information [Line Items]
Revenues	6	6	6
Inter-segment | CECONY | Steam
Segment Reporting Information [Line Items]
Revenues	$ 75	$ 88	$ 86

Derivative Instruments and H121

Derivative Instruments and Hedging Activities - Fair Values of Commodity Derivatives Including Offsetting of Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Fair value of derivative assets
Net Amounts of Assets/ (Liabilities)	$ 453	$ 363
Fair value of derivative liabilities
Net Amounts of Assets/ (Liabilities)	(55)	(117)
Net fair value derivative assets/(liabilities)
Gross Amounts of Recognized Assets/ (Liabilities)	(17)	(99)
Gross Amounts Offset	0	6
Net Amounts of Assets/ (Liabilities)	(17)	(93)
Margin deposits	12	7
Interest Rate Swap
Fair value of derivative liabilities
Net Amounts of Assets/ (Liabilities)	(1)	(1)
CECONY
Fair value of derivative assets
Net Amounts of Assets/ (Liabilities)	414	326
Net fair value derivative assets/(liabilities)
Gross Amounts of Recognized Assets/ (Liabilities)	(14)	(95)
Gross Amounts Offset	(1)	9
Net Amounts of Assets/ (Liabilities)	(15)	(86)
Margin deposits	11	7
Fair Value of Derivative Liabilities, Current
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/ (Liabilities)	(67)	(138)
Gross Amounts Offset	50	61
Net Amounts of Assets/ (Liabilities)	(17)	(77)
Fair Value of Derivative Liabilities, Current | CECONY
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/ (Liabilities)	(26)	(111)
Gross Amounts Offset	14	45
Net Amounts of Assets/ (Liabilities)	(12)	(66)
Fair Value of Derivative Liabilities, Non-current
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/ (Liabilities)	(43)	(91)
Gross Amounts Offset	5	52
Net Amounts of Assets/ (Liabilities)	(38)	(39)
Fair Value of Derivative Liabilities, Non-current | CECONY
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/ (Liabilities)	(36)	(77)
Gross Amounts Offset	4	44
Net Amounts of Assets/ (Liabilities)	(32)	(33)
Fair Value of Derivative Liabilities
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/ (Liabilities)	(110)	(229)
Gross Amounts Offset	55	113
Net Amounts of Assets/ (Liabilities)	(55)	(116)
Fair Value of Derivative Liabilities | CECONY
Fair value of derivative liabilities
Gross Amounts of Recognized Assets/ (Liabilities)	(62)	(188)
Gross Amounts Offset	18	89
Net Amounts of Assets/ (Liabilities)	(44)	(99)
Fair Value of Derivative Assets, Current
Fair value of derivative assets
Gross Amounts of Recognized Assets/ (Liabilities)	83	81
Gross Amounts Offset	(51)	(64)
Net Amounts of Assets/ (Liabilities)	32	17
Fair Value of Derivative Assets, Current | CECONY
Fair value of derivative assets
Gross Amounts of Recognized Assets/ (Liabilities)	39	52
Gross Amounts Offset	(15)	(45)
Net Amounts of Assets/ (Liabilities)	24	7
Fair Value of Derivative Assets, Non-current
Fair value of derivative assets
Gross Amounts of Recognized Assets/ (Liabilities)	10	49
Gross Amounts Offset	(4)	(43)
Net Amounts of Assets/ (Liabilities)	6	6
Fair Value of Derivative Assets, Non-current | CECONY
Fair value of derivative assets
Gross Amounts of Recognized Assets/ (Liabilities)	9	41
Gross Amounts Offset	(4)	(35)
Net Amounts of Assets/ (Liabilities)	5	6
Fair Value of Derivative Assets
Fair value of derivative assets
Gross Amounts of Recognized Assets/ (Liabilities)	93	130
Gross Amounts Offset	(55)	(107)
Net Amounts of Assets/ (Liabilities)	38	23
Fair Value of Derivative Assets | CECONY
Fair value of derivative assets
Gross Amounts of Recognized Assets/ (Liabilities)	48	93
Gross Amounts Offset	(19)	(80)
Net Amounts of Assets/ (Liabilities)	$ 29	$ 13

Derivative Instruments and H122

Derivative Instruments and Hedging Activities - Realized and Unrealized Gains or Losses on Commodity Derivatives (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Pre-tax gains/(losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains/(losses)	$ 3	$ 24
Total deferred gains/(losses)	(99)	(188)
Net deferred gains/(losses)	(96)	(164)
Pre-tax gain/(loss) recognized in income
Total pre-tax gain/(loss) recognized in income	8	(203)
Purchased power expense
Pre-tax gain/(loss) recognized in income
Total pre-tax gain/(loss) recognized in income	0	(101)
Unrealized gain/(loss) on derivatives		11
Gas purchased for resale
Pre-tax gain/(loss) recognized in income
Total pre-tax gain/(loss) recognized in income	3	(112)
Non-utility revenue
Pre-tax gain/(loss) recognized in income
Total pre-tax gain/(loss) recognized in income	5	9
Other operations and maintenance expense
Pre-tax gain/(loss) recognized in income
Total pre-tax gain/(loss) recognized in income	0	1
Unrealized gain/(loss) on derivatives		1
Non-utility operating revenue
Pre-tax gain/(loss) recognized in income
Unrealized gain/(loss) on derivatives		(5)
Deferred Derivative Gains,Current
Pre-tax gains/(losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains/(losses)	3	23
Deferred Derivative Gains, Noncurrent
Pre-tax gains/(losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains/(losses)	0	1
Deferred Derivative Losses, Current
Pre-tax gains/(losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains/(losses)	51	22
Recoverable Energy Costs, Current
Pre-tax gains/(losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains/(losses)	(154)	(212)
Deferred Derivative Losses, Noncurrent
Pre-tax gains/(losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains/(losses)	4	2
CECONY
Pre-tax gains/(losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains/(losses)	4	20
Total deferred gains/(losses)	(90)	(172)
Net deferred gains/(losses)	(86)	(152)
Pre-tax gain/(loss) recognized in income
Total pre-tax gain/(loss) recognized in income	0	1
CECONY | Purchased power expense
Pre-tax gain/(loss) recognized in income
Total pre-tax gain/(loss) recognized in income	0	0
CECONY | Gas purchased for resale
Pre-tax gain/(loss) recognized in income
Total pre-tax gain/(loss) recognized in income	0	0
CECONY | Non-utility revenue
Pre-tax gain/(loss) recognized in income
Total pre-tax gain/(loss) recognized in income	0	0
CECONY | Other operations and maintenance expense
Pre-tax gain/(loss) recognized in income
Total pre-tax gain/(loss) recognized in income	0	1
Unrealized gain/(loss) on derivatives		1
CECONY | Deferred Derivative Gains,Current
Pre-tax gains/(losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains/(losses)	4	18
CECONY | Deferred Derivative Gains, Noncurrent
Pre-tax gains/(losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains/(losses)	0	2
CECONY | Deferred Derivative Losses, Current
Pre-tax gains/(losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains/(losses)	49	18
CECONY | Recoverable Energy Costs, Current
Pre-tax gains/(losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains/(losses)	(144)	(194)
CECONY | Deferred Derivative Losses, Noncurrent
Pre-tax gains/(losses) deferred in accordance with accounting rules for regulated operations:
Total deferred gains/(losses)	$ 5	$ 4

Derivative Instruments and H123

Derivative Instruments and Hedging Activities - Hedged Volume of Derivative Transactions (Details) gal in Thousands	Dec. 31, 2017MWMMBTUgalMWh
Electric Energy
Derivatives, Fair Value [Line Items]
Notional amount | MWh	31,741,652
Capacity
Derivatives, Fair Value [Line Items]
Notional amount | MW	10,275
Natural Gas
Derivatives, Fair Value [Line Items]
Notional amount | MMBTU	177,433,144
Refined Fuels
Derivatives, Fair Value [Line Items]
Notional amount | gal	3,780
CECONY | Electric Energy
Derivatives, Fair Value [Line Items]
Notional amount | MWh	29,696,600
CECONY | Capacity
Derivatives, Fair Value [Line Items]
Notional amount | MW	5,100
CECONY | Natural Gas
Derivatives, Fair Value [Line Items]
Notional amount | MMBTU	169,790,000
CECONY | Refined Fuels
Derivatives, Fair Value [Line Items]
Notional amount | gal	3,780

Derivative Instruments and H124

Derivative Instruments and Hedging Activities - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Investment Holdings [Line Items]
Energy supply and hedging activities credit exposure total	$ 103
Makeup of net credit exposure with investment-grade counterparties	39
Makeup of net credit exposure independent system operators	29
Makeup of net credit exposure with commodity exchange brokers	22
Makeup of net credit exposure non-investment grade/non-rated counterparties	13
Derivative liabilities	55	$ 117
Interest Rate Swap
Investment Holdings [Line Items]
Derivative liabilities	1	$ 1
CECONY
Investment Holdings [Line Items]
Energy supply and hedging activities credit exposure total	28
Makeup of net credit exposure with investment-grade counterparties	17
Makeup of net credit exposure with commodity exchange brokers	11
Clean Energy Businesses | Coram | Interest Rate Swap
Investment Holdings [Line Items]
Derivative, fixed interest rate		2.0855%
Derivative liabilities	$ 0	$ 1

Derivative Instruments and H125

Derivative Instruments and Hedging Activities - Aggregate Fair Value of Companies' Derivative Instruments with Credit-Risk-Related Contingent Features (Details) $ in Millions	Dec. 31, 2017USD ($)
Derivatives, Fair Value [Line Items]
Aggregate fair value – net liabilities	$ 39
Collateral posted	68
Downgrade One Level from Current Ratings
Derivatives, Fair Value [Line Items]
Additional collateral	0
Downgrade to Below Investment Grade from Current Ratings
Derivatives, Fair Value [Line Items]
Additional collateral	29
Derivatives in net asset position additional collateral	18
Additional Collateral Required Due To Loss Of Unsecured Credit
Derivatives, Fair Value [Line Items]
Collateral posted	8
CECONY
Derivatives, Fair Value [Line Items]
Aggregate fair value – net liabilities	31
Collateral posted	63
CECONY | Downgrade One Level from Current Ratings
Derivatives, Fair Value [Line Items]
Additional collateral	0
CECONY | Downgrade to Below Investment Grade from Current Ratings
Derivatives, Fair Value [Line Items]
Additional collateral	$ 22

Fair Value Measurements - Asset

Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	$ 453	$ 363
Derivative liabilities	55	117
CECONY
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	414	326
Netting Adjustment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	(39)	(24)
Derivative liabilities	(52)	(38)
Netting Adjustment | CECONY
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	(7)	(10)
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	288	236
Derivative liabilities	8	4
Level 1 | CECONY
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	263	210
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	197	144
Derivative liabilities	93	145
Level 2 | CECONY
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	154	125
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	7	7
Derivative liabilities	6	6
Level 3 | CECONY
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	4	1
Commodity
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	50	30
Derivative liabilities	55	116
Derivative liabilities transferred from Level 3 to Level 2	11
Commodity | CECONY
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	40	20
Derivative liabilities	44	99
Derivative liabilities transferred from Level 3 to Level 2	10
Commodity | Netting Adjustment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	(39)	(24)
Derivative liabilities	(52)	(38)
Commodity | Netting Adjustment | CECONY
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	(7)	(10)
Derivative liabilities	(18)	(26)
Commodity | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	5	14
Derivative liabilities	8	4
Commodity | Level 1 | CECONY
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	3	10
Derivative liabilities	5	1
Commodity | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	77	33
Derivative liabilities	93	144
Commodity | Level 2 | CECONY
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	40	19
Derivative liabilities	57	124
Commodity | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	7	7
Derivative liabilities	6	6
Commodity | Level 3 | CECONY
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	4	1
Derivative liabilities	0	0
Interest Rate Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	1	1
Interest Rate Swap | Netting Adjustment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0	0
Interest Rate Swap | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0	0
Interest Rate Swap | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities		1
Interest Rate Swap | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0	0
Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	403	333
Other | CECONY
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	374	306
Other | Netting Adjustment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0	0
Other | Netting Adjustment | CECONY
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0	0
Other | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	283	222
Other | Level 1 | CECONY
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	260	200
Other | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	120	111
Other | Level 2 | CECONY
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	114	106
Other | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0	0
Other | Level 3 | CECONY
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	$ 0	$ 0

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Commodity Derivatives (Details) - Level 3 $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)$ / MWh$ / kWh$ / kW-month	Sep. 30, 2017USD ($)
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Fair Value of commodity derivatives | $	$ 1
CECONY
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Fair Value of commodity derivatives | $		$ 4
Electricity
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Fair Value of commodity derivatives | $	$ (1)
Electricity | CECONY
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Fair Value of commodity derivatives | $		3
Electricity | Forward Energy Prices | Minimum
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Unobservable Inputs Range (dollar per MWh/Dt) | $ / MWh	15.52
Electricity | Forward Energy Prices | Maximum
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Unobservable Inputs Range (dollar per MWh/Dt) | $ / MWh	115
Electricity | Forward Capacity Prices | Minimum
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Unobservable Inputs Range (dollar per kW-month) | $ / kW-month	1.50
Electricity | Forward Capacity Prices | Minimum | CECONY
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Unobservable Inputs Range (dollar per kW-month) | $ / kWh	2.35
Electricity | Forward Capacity Prices | Maximum
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Unobservable Inputs Range (dollar per kW-month) | $ / kW-month	12.50
Electricity | Forward Capacity Prices | Maximum | CECONY
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Unobservable Inputs Range (dollar per kW-month) | $ / kWh	12.50
Transmission Congestion Contracts
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Fair Value of commodity derivatives | $		$ 2
Transmission Congestion Contracts | CECONY
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Fair Value of commodity derivatives | $	$ 1
Transmission Congestion Contracts | Inter Zonal Forward Price Curves Adjusted for Historical Zonal Losses | Minimum
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Unobservable Inputs Range (dollar per MWh/Dt) | $ / MWh	0.19
Transmission Congestion Contracts | Inter Zonal Forward Price Curves Adjusted for Historical Zonal Losses | Minimum | CECONY
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Unobservable Inputs Range (dollar per MWh/Dt) | $ / MWh	0.51
Transmission Congestion Contracts | Inter Zonal Forward Price Curves Adjusted for Historical Zonal Losses | Maximum
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Unobservable Inputs Range (dollar per MWh/Dt) | $ / MWh	3.57
Transmission Congestion Contracts | Inter Zonal Forward Price Curves Adjusted for Historical Zonal Losses | Maximum | CECONY
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Unobservable Inputs Range (dollar per MWh/Dt) | $ / MWh	3

Fair Value Measurements - Recon

Fair Value Measurements - Reconciliation of Beginning and Ending Net Balances for Assets and Liabilities Measured at Level 3 Fair Value (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	$ 1	$ 6
Included in earnings	8	(7)
Included in regulatory assets and liabilities	(13)	(6)
Purchases	2	4
Sales	0	4
Settlements	(8)	0
Transfer out of level 3	11	0
Ending Balance	1	1
CECONY
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	1	8
Included in earnings	2	(1)
Included in regulatory assets and liabilities	(7)	(6)
Purchases	1	2
Sales	0	0
Settlements	(3)	(2)
Transfer out of level 3	10	0
Ending Balance	$ 4	$ 1

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Non-utility revenue
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, assets and liabilities measured on recurring basis, change in unrealized gain (loss)	$ 2	$ 0
Purchased power expense
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, assets and liabilities measured on recurring basis, change in unrealized gain (loss)	0	(1)
Clean Energy Businesses | Non-utility revenue
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Gain (loss) on Level 3 energy derivative assets and liabilities	2	0
Clean Energy Businesses | Purchased power expense
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Gain (loss) on Level 3 energy derivative assets and liabilities	$ 0	$ (6)

Variable Interest Entities - Ad

Variable Interest Entities - Additional Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)MW	Dec. 31, 2016USD ($)
Variable Interest Entity [Line Items]
Noncontrolling interest	$ 7	$ 8
Noncontrolling Interest
Variable Interest Entity [Line Items]
Noncontrolling interest	$ 7	7
Variable Interest Entity, Primary Beneficiary | Texas Solar 4
Variable Interest Entity [Line Items]
Percentage of variable interests	80.00%
Generating capacity (MW AC) | MW	40
VIE consolidated, carrying amount, assets and liabilities, net	$ 26	$ 54
Con Edison Development | Variable Interest Entity, Primary Beneficiary | Texas Solar 4
Variable Interest Entity [Line Items]
Percentage of variable interests	80.00%

Variable Interest Entities - Ne

Variable Interest Entities - Net Assets of Texas Solar 4 (Details) - Texas Solar 4 - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Restricted cash	$ 5	$ 8
Non-utility property, less accumulated depreciation of $12 and $9, respectively	101	104
Other assets	8	43
Total assets	114	155
Long-term debt due within one year	2	3
Other liabilities	28	38
Long-term debt	58	60
Total liabilities	88	101
Accumulated depreciation	$ 12	$ 9

Variable Interest Entities - Su

Variable Interest Entities - Summary of VIEs (Details)	12 Months Ended
	Dec. 31, 2017USD ($)MW
Variable Interest Entity, Not Primary Beneficiary | Copper Mountain Solar 3
Variable Interest Entity [Line Items]
Generating Capacity Owned (MW AC) | MW	128
Power Purchase Agreement Term in Years	20 years
Maximum Exposure to Loss	$ 175,000,000
Variable Interest Entity, Not Primary Beneficiary | Mesquite Solar 1
Variable Interest Entity [Line Items]
Generating Capacity Owned (MW AC) | MW	83
Power Purchase Agreement Term in Years	20 years
Maximum Exposure to Loss	$ 103,000,000
Variable Interest Entity, Not Primary Beneficiary | Copper Mountain Solar 2
Variable Interest Entity [Line Items]
Generating Capacity Owned (MW AC) | MW	75
Power Purchase Agreement Term in Years	25 years
Maximum Exposure to Loss	$ 82,000,000
Variable Interest Entity, Not Primary Beneficiary | California Solar
Variable Interest Entity [Line Items]
Generating Capacity Owned (MW AC) | MW	55
Power Purchase Agreement Term in Years	25 years
Maximum Exposure to Loss	$ 63,000,000
Variable Interest Entity, Not Primary Beneficiary | Broken Bow II
Variable Interest Entity [Line Items]
Generating Capacity Owned (MW AC) | MW	38
Power Purchase Agreement Term in Years	25 years
Maximum Exposure to Loss	$ 44,000,000
Variable Interest Entity, Primary Beneficiary | Texas Solar 4
Variable Interest Entity [Line Items]
Generating Capacity Owned (MW AC) | MW	32
Power Purchase Agreement Term in Years	25 years
Maximum Exposure to Loss	$ 19,000,000
Percentage of variable interests	80.00%
Maximum exposure for consolidated investments	$ 7,000,000
Variable Interest Entity, Not Primary Beneficiary, Aggregated Disclosure
Variable Interest Entity [Line Items]
Percentage of variable interests	50.00%

Asset Retirement Obligations (D

Asset Retirement Obligations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Regulatory Liabilities [Line Items]
Accrued liability - asset retirement obligations	$ 314	$ 246
Increase in liabilities for asset retirement obligations due to changes in estimated cash flows	98
Asset retirement obligations, accretion expense	10
Asset retirement obligations, liabilities settled	40
Asset retirement obligations, reductions	36	37
CECONY
Regulatory Liabilities [Line Items]
Accrued liability - asset retirement obligations	287	227
Increase in liabilities for asset retirement obligations due to changes in estimated cash flows	91
Asset retirement obligations, accretion expense	9
Asset retirement obligations, liabilities settled	40
Asset retirement obligations, reductions	$ 36	$ 37

Related Party Transactions - Su

Related Party Transactions - Summary of Costs of Administrative and Other Services Provided and Received (Details) - CECONY - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Cost of services provided	$ 111	$ 108	$ 99
Cost of services received	$ 64	$ 64	$ 60

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details)	7 Months Ended	12 Months Ended
	Dec. 31, 2016USD ($)	Dec. 31, 2017USD ($)MMBTUagreement	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Nov. 30, 2016	Jan. 31, 2016
Related Party Transaction [Line Items]
Gas purchased for resale		$ 808,000,000	$ 477,000,000	$ 495,000,000
CECONY
Related Party Transaction [Line Items]
Sale of natural gas		66,000,000	47,000,000	54,000,000
Gas purchased for resale		510,000,000	319,000,000	$ 337,000,000
Funding limit of CECONY to O&R (not to exceed)		$ 250,000,000
CECONY | Related Party, Lending of Funds
Related Party Transaction [Line Items]
Lending period (not more than) (months)		12 months
CECONY | Equity Method Investee | Mountain Valley Pipeline
Related Party Transaction [Line Items]
Transportation contract term		20 years
Generating capacity per day (in dekatherms) | MMBTU		250,000
Amount of transaction		$ 0
CECONY | Equity Method Investee | Stagecoach | Purchased Power Costs
Related Party Transaction [Line Items]
Gas purchased for resale	$ 49,000,000
CECONY | Equity Method Investee | Stagecoach | Purchased Power Costs | Clean Energy Businesses
Related Party Transaction [Line Items]
Number of electricity sales agreements entered into | agreement		2
CECONY | Affiliated Entity | Financial Electric Capacity Contract | Con Edison Energy
Related Party Transaction [Line Items]
Amount of transaction		$ 3,000,000	0
CET Electric
Related Party Transaction [Line Items]
Ownership interest, percentage		45.70%
CET Gas | Stagecoach
Related Party Transaction [Line Items]
Percentage of equity interest owned					50.00%
CET Gas | Mountain Valley Pipeline
Related Party Transaction [Line Items]
Percentage of equity interest owned		12.50%				12.50%
O&R
Related Party Transaction [Line Items]
Outstanding loans to O&R		$ 0	$ 0

Acquisitions, Investments an136

Acquisitions, Investments and Dispositions - Texas Solar 7 (Details) - Texas Solar 7 $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2016USD ($)MW	Dec. 31, 2016USD ($)	Dec. 31, 2017USD ($)
Business Acquisition [Line Items]
Generating capacity (MW AC) | MW	106
Con Edison Development
Business Acquisition [Line Items]
Percentage of voting interest acquired	100.00%
Payments to acquire business	$ 227
Non-utility construction work in progress	218
Receivable from parent company	$ 9
Net assets		$ 127	$ 137
Intangible assets		$ 41

Acquisitions, Investments an137

Acquisitions, Investments and Dispositions - Mountain Valley Pipeline (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Equity method investment			$ 467	$ 488
Mountain Valley Pipeline | Scenario, Forecast | Minimum
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity interest		$ 3,000
Mountain Valley Pipeline | Scenario, Forecast | Maximum
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity interest		$ 3,500
CET Gas | Mountain Valley Pipeline
Schedule of Equity Method Investments [Line Items]
Percentage of equity interest acquired	12.50%		12.50%
Payments to acquire equity interest	$ 18
Equity method investment			$ 98	$ 48

Acquisitions, Investments an138

Acquisitions, Investments and Dispositions - NY Transco (Details) - USD ($) $ in Millions	1 Months Ended
	May 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Equity method investment		$ 467	$ 488
CET Electric
Schedule of Equity Method Investments [Line Items]
Ownership interest, percentage		45.70%
CET Electric | NY Transco
Schedule of Equity Method Investments [Line Items]
Ownership interest, percentage	45.70%
Equity method investment		$ 53	51
CECONY
Schedule of Equity Method Investments [Line Items]
Equity method investment		$ 0	$ 0
CECONY | NY Transco | Equity Method Investee | Purchase Price of TOTS Project Transfer
Schedule of Equity Method Investments [Line Items]
Amount of transaction	$ 122
CECONY | NY Transco | Equity Method Investee | TOTS Project, Lease Payments
Schedule of Equity Method Investments [Line Items]
Payment for easement rights	$ 8

Acquisitions, Investments an139

Acquisitions, Investments and Dispositions - Stagecoach Gas Services (Details) - USD ($) $ in Millions	8 Months Ended
	Nov. 30, 2016	Dec. 31, 2017	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Equity method investment		$ 467	$ 488
CET Gas | Stagecoach Gas Services
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity interest	$ 974
Percentage of equity interest acquired	50.00%
Equity method investment		$ 971	$ 992

Acquisitions, Investments an140

Acquisitions, Investments and Dispositions - Pilesgrove (Details) $ in Millions	1 Months Ended
	Aug. 31, 2016USD ($)	Jun. 30, 2016USD ($)MW	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Pilesgrove
Business Acquisition [Line Items]
Generating capacity (MW AC) | MW		18
Net assets			$ 45	$ 45
Con Edison Development | Pilesgrove
Business Acquisition [Line Items]
Percentage of voting interest acquired	50.00%
Purchase price	$ 16
Bargain purchase gain	8
Bargain purchase gain, net of taxes	5
Non-utility property	45
Other current assets	$ 3
Con Edison Development | Pilesgrove
Business Acquisition [Line Items]
Equity method investment, impairment charge		$ 8
Equity method investment, impairment charge, net of taxes		$ 5
Percentage of equity interest owned		50.00%

Acquisitions, Investments an141

Acquisitions, Investments and Dispositions - Panoche Valley (Details) $ in Millions	1 Months Ended
	Oct. 31, 2016USD ($)MW	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Panoche Valley
Business Acquisition [Line Items]
Generating capacity (MW AC) | MW	240
Net assets		$ 435	$ 388
Con Edison Development | Panoche Valley
Business Acquisition [Line Items]
Percentage of voting interest acquired	50.00%
Cash consideration	$ 28
Outstanding note payable relieved at acquisition	242
Non-utility construction work in progress	290
Other assets	22
Current liabilities	$ 14
Con Edison Development | Panoche Valley
Business Acquisition [Line Items]
Percentage of equity interest owned	50.00%

Acquisitions, Investments an142

Acquisitions, Investments and Dispositions - Coram Wind (Details) - Coram Wind $ in Millions	1 Months Ended
	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)MW
Business Acquisition [Line Items]
Generating capacity (MW AC) | MW		102
Net assets	$ 87	$ 96
Con Edison Development
Business Acquisition [Line Items]
Percentage of voting interest acquired	100.00%
Purchase price		97
Non-utility property		191
Intangible assets		78
Restricted cash, current		8
Long-term debt		$ 180
Increase in intangible asset	$ 22
Decrease in non-utility property	$ 22

Acquisitions, Investments an143

Acquisitions, Investments and Dispositions - Pike County Light & Power Company (Details) - Pike - USD ($) $ in Millions	Sep. 30, 2015	Aug. 31, 2016	Dec. 31, 2015
Discontinued Operations, Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Impairment charge on assets held for sale			$ 5
O&R | Discontinued Operations, Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from divestiture of business		$ 15
Period for transition services (up to)		18 months
Agreement to purchase and sell, term		3 years
Agreement to purchase and sell, term of extension option		3 years
O&R | Discontinued Operations, Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Impairment charge on assets held for sale	$ 5
Impairment of long-lived assets to be disposed of, net of tax	$ 3

Acquisitions, Investments an144

Acquisitions, Investments and Dispositions - Con Edison Solutions' Retail Electric Supply Business (Details) - Con Edison Solutions - Retail Electric Supply Business - Discontinued Operations, Disposed of by Sale $ in Millions	1 Months Ended
	Sep. 30, 2016USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from divestiture of business	$ 235
Gain on sale of business	104
Gain on sale of business, after tax	56
Gain on sale of derivatives	65
Gain on sale of derivatives, after tax	42
Tax effect of sale, state tax related to change in apportionment of state income taxes	16
Tax effect of sale, state tax related to change in apportionment of state income taxes, net of federal tax	$ 10

Acquisitions, Investments an145

Acquisitions, Investments and Dispositions - Upton 2 (Details) - Con Edison Development $ in Millions	1 Months Ended	12 Months Ended
	May 31, 2017USD ($)	Dec. 31, 2018MW
Upton 2 | Scenario, Forecast
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Generating capacity (MW AC) | MW		180
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Upton 2
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Consideration the project is sold	$ 11
Gain on sale of project	1
Gain on sale of project, net of tax	$ 0.7

Schedule I - Condensed Finan146

Schedule I - Condensed Financial Information - Condensed Statement of Income and Comprehensive Income (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Income Statements,Captions [Line Items]
Interest expense	$ (729)	$ (696)	$ (653)
NET INCOME	1,525	1,245	1,193
Comprehensive Income	$ 1,526	$ 1,252	$ 1,204
Net Income Per Share – Basic (dollars per share)	$ 4.97	$ 4.15	$ 4.07
Net Income Per Share – Diluted (dollars per share)	4.94	4.12	4.05
Dividends Declared Per Share (dollars per share)	$ 2.76	$ 2.68	$ 2.60
Average Number Of Shares Outstanding—Basic (In Millions)	307.1	300.4	293
Average Number Of Shares Outstanding—Diluted (In Millions)	308.8	301.9	294.4
Parent Company
Condensed Income Statements,Captions [Line Items]
Equity in earnings of subsidiaries	$ 1,544	$ 1,254	$ 1,195
Other income (deductions), net of taxes	31	32	27
Interest expense	(50)	(41)	(29)
NET INCOME	1,525	1,245	1,193
Comprehensive Income	$ 1,526	$ 1,252	$ 1,204
Average Number Of Shares Outstanding—Basic (In Millions)	307.1	300.4	293
Average Number Of Shares Outstanding—Diluted (In Millions)	308.8	301.9	294.4

Schedule I - Condensed Finan147

Schedule I - Condensed Financial Information - Condensed Statement of Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Cash Flow Statements, Captions [Line Items]
Net Income	$ 1,525	$ 1,245	$ 1,193
Change in Assets:
Taxes receivable	15	87	58
Other – net	(44)	54	(27)
NET CASH FLOWS FROM OPERATING ACTIVITIES	3,367	3,459	3,277
INVESTING ACTIVITIES
NET CASH FLOWS USED IN INVESTING ACTIVITIES	(3,703)	(4,976)	(3,657)
FINANCING ACTIVITIES
Net proceeds of short-term debt	(477)	(475)	729
Issuance of long-term debt	1,697	2,590	1,147
Retirement of long-term debt	(434)	(735)	(500)
Debt issuance costs	(19)	(24)	(15)
Issuance of common shares for stock plans, net of repurchases	51	51	1
Issuance of common shares - public offering	343	702	0
Common stock dividends	(803)	(763)	(733)
NET CASH FLOWS FROM FINANCING ACTIVITIES	357	1,345	629
NET CHANGE FOR THE PERIOD	21	(172)	249
BALANCE AT BEGINNING OF PERIOD	776	944	699
BALANCE AT END OF PERIOD EXCLUDING HELD FOR SALE	797	776	944
CECONY
Condensed Cash Flow Statements, Captions [Line Items]
Net Income	1,104	1,056	1,084
Change in Assets:
Other – net	8	(11)	38
NET CASH FLOWS FROM OPERATING ACTIVITIES	2,866	3,038	2,819
INVESTING ACTIVITIES
NET CASH FLOWS USED IN INVESTING ACTIVITIES	(3,078)	(2,739)	(2,638)
FINANCING ACTIVITIES
Net proceeds of short-term debt	(450)	(433)	583
Issuance of long-term debt	1,200	1,300	650
Retirement of long-term debt	0	(650)	(350)
Debt issuance costs	(15)	(13)	(7)
NET CASH FLOWS FROM FINANCING ACTIVITIES	240	(440)	17
NET CHANGE FOR THE PERIOD	28	(141)	198
BALANCE AT BEGINNING OF PERIOD	702	843	645
BALANCE AT END OF PERIOD EXCLUDING HELD FOR SALE	730	702	843
Parent Company
Condensed Cash Flow Statements, Captions [Line Items]
Net Income	1,525	1,245	1,193
Equity in earnings of subsidiaries	(1,544)	(1,254)	(1,195)
Change in Assets:
Special deposits	0	0	0
Taxes receivable	34	87	58
Other – net	21	(152)	(382)
NET CASH FLOWS FROM OPERATING ACTIVITIES	896	723	635
INVESTING ACTIVITIES
Contributions to subsidiaries	(434)	(691)	(15)
Long term debt receivable from affiliated companies	0	(900)	0
NET CASH FLOWS USED IN INVESTING ACTIVITIES	(434)	(1,591)	(15)
FINANCING ACTIVITIES
Net proceeds of short-term debt	(53)	(53)	162
Issuance of long-term debt	400	900	0
Retirement of long-term debt	(402)	(2)	(2)
Debt issuance costs	(2)	(5)	0
Issuance of common shares for stock plans, net of repurchases	51	51	1
Issuance of common shares - public offering	343	702	0
Common stock dividends	(803)	(763)	(733)
NET CASH FLOWS FROM FINANCING ACTIVITIES	(466)	830	(572)
NET CHANGE FOR THE PERIOD	(4)	(38)	48
BALANCE AT BEGINNING OF PERIOD	13	51	3
BALANCE AT END OF PERIOD EXCLUDING HELD FOR SALE	9	13	51
Parent Company | CECONY
Condensed Cash Flow Statements, Captions [Line Items]
Dividends received	796	744	872
Parent Company | O&R
Condensed Cash Flow Statements, Captions [Line Items]
Dividends received	44	43	81
Parent Company | Clean Energy Businesses
Condensed Cash Flow Statements, Captions [Line Items]
Dividends received	12	10	8
Parent Company | Con Edison Transmission
Condensed Cash Flow Statements, Captions [Line Items]
Dividends received	$ 8	$ 0	$ 0

Schedule I - Condensed Finan148

Schedule I - Condensed Financial Information - Condensed Balance Sheet (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current Assets
Cash and temporary cash investments	$ 797	$ 776	$ 944	$ 699
Taxes receivable	64	79
Prepayments	178	159
Other current assets	189	151
TOTAL CURRENT ASSETS	3,537	3,406
Investments in subsidiaries	2,001	1,921
Goodwill	428	428
Other noncurrent assets	4,973	7,712
TOTAL ASSETS	48,111	48,255	45,642
Current Liabilities
Long-term debt due within one year	1,298	39
Notes payable	577	1,054
Other current liabilities	386	297
TOTAL CURRENT LIABILITIES	4,902	3,843
Long-term debt	14,731	14,735
Shareholders’ Equity
Equity	15,418	14,298
TOTAL LIABILITIES AND EQUITY	48,111	48,255
Parent Company
Current Assets
Cash and temporary cash investments	9	13	$ 51	$ 3
Taxes receivable	45	79
Accounts receivable from affiliated companies	687	702
Prepayments	36	24
Other current assets	18	19
TOTAL CURRENT ASSETS	795	837
Investments in subsidiaries	15,110	13,991
Goodwill	406	406
Deferred income tax	18	42
Long term debt receivable from affiliated companies	900	900
Other noncurrent assets	2	16
TOTAL ASSETS	17,231	16,192
Current Liabilities
Long-term debt due within one year	2	2
Notes payable	331	384
Accounts payable to affiliated companies	274	288
Other current liabilities	10	22
TOTAL CURRENT LIABILITIES	617	696
Total Liabilities	617	696
Long-term debt	1,195	1,198
Shareholders’ Equity
Common stock, including additional paid-in capital	6,331	5,887
Retained earnings	9,088	8,411
Equity	15,419	14,298
TOTAL LIABILITIES AND EQUITY	$ 17,231	$ 16,192

Schedule II - Valuation and 149

Schedule II - Valuation and Qualifying Accounts (Details) - Allowance For Uncollectible Accounts - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 83	$ 96	$ 106
Charged To Costs And Expenses	64	63	77
Charged To Other Accounts	0	0	0
Deductions	77	76	87
Balance At End of Period	70	83	96
CECONY
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	78	91	98
Charged To Costs And Expenses	60	57	69
Charged To Other Accounts	0	0	0
Deductions	73	70	76
Balance At End of Period	$ 65	$ 78	$ 91