UIL (UIL) 10-Q 4 Nov 13 2013 Q3 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
	Sep. 30, 2013	Oct. 30, 2013
Document and Entity Information [Abstract]	'	'
Entity Registrant Name	'UIL HOLDINGS CORP	'
Entity Central Index Key	'0001082510	'
Current Fiscal Year End Date	'--12-31	'
Entity Well-known Seasoned Issuer	'Yes	'
Entity Voluntary Filers	'No	'
Entity Current Reporting Status	'Yes	'
Entity Filer Category	'Large Accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	56,462,507
Document Fiscal Year Focus	'2013	'
Document Fiscal Period Focus	'Q3	'
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	30-Sep-13	'

CONSOLIDATED_STATEMENT_OF_INCO

CONSOLIDATED STATEMENT OF INCOME (Unaudited) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
CONSOLIDATED STATEMENT OF INCOME (UNAUDITED) [Abstract]	'	'	'	'
Operating Revenues	$316,478	$322,888	$1,183,591	$1,063,547
Operating Expenses	'	'	'	'
Purchased power	37,314	43,565	105,996	118,581
Natural gas purchased	37,343	51,570	315,520	242,328
Operation and maintenance	89,810	87,281	273,539	260,887
Transmission wholesale	28,659	26,565	65,994	59,847
Depreciation and amortization (Note F)	50,761	46,279	146,537	135,886
Taxes - other than income taxes (Note F)	32,389	28,502	96,335	82,924
Regulatory disallowances (Note C)	17,543	0	17,543	0
Total Operating Expenses	293,819	283,762	1,021,464	900,453
Operating Income	22,659	39,126	162,127	163,094
Other Income and (Deductions), net (Note F)	5,153	7,416	15,718	21,205
Interest Charges, net	'	'	'	'
Interest on long-term debt	21,896	21,578	65,272	64,505
Other interest, net	-106	1,165	2,442	4,012
Interest charges, gross	21,790	22,743	67,714	68,517
Amortization of debt expense and redemption premiums	609	610	1,819	1,818
Total Interest Charges, net	22,399	23,353	69,533	70,335
Income from Equity Investments	3,930	3,421	11,590	11,823
Income Before Income Taxes	9,343	26,610	119,902	125,787
Income Taxes (Note E)	4,186	10,835	45,004	50,924
Net Income	5,157	15,775	74,898	74,863
Less: Preferred Stock Dividends of Subsidiary, Noncontrolling Interests	13	26	39	65
Net Income attributable to UIL Holdings	$5,144	$15,749	$74,859	$74,798
Average Number of Common Shares Outstanding - Basic (in shares)	50,989	50,799	50,956	50,760
Average Number of Common Shares Outstanding - Diluted (in shares)	51,231	51,032	51,237	51,004
Earnings Per Share of Common Stock - Basic (Note A): (in dollars per share)	$0.10	$0.31	$1.47	$1.47
Earnings Per Share of Common Stock - Diluted (Note A): (in dollars per share)	$0.10	$0.31	$1.46	$1.46
Cash Dividends Declared per share of Common Stock (in dollars per share)	$0.43	$0.43	$1.30	$1.30

CONSOLIDATED_STATEMENT_OF_COMP

CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME (Unaudited) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME (Unaudited) [Abstract]	'	'	'	'
Net Income	$5,157	$15,775	$74,898	$74,863
Other Comprehensive Income (Loss), net of deferred income taxes	250	350	456	551
Comprehensive Income	5,407	16,125	75,354	75,414
Less:	'	'	'	'
Preferred Stock Dividends of Subsidiary, Noncontrolling Interests	13	26	39	65
Comprehensive Income attributable to UIL Holdings	$5,394	$16,099	$75,315	$75,349

CONSOLIDATED_BALANCE_SHEET_Una

CONSOLIDATED BALANCE SHEET (Unaudited) (USD $)	Sep. 30, 2013		Dec. 31, 2012
In Thousands, unless otherwise specified
Current Assets	'		'
Unrestricted cash and temporary cash investments	$18,696		$17,857
Restricted cash	1,887		2,805
Accounts receivable less allowance of $13,609 and $11,867, respectively	200,314		238,986
Unbilled revenues	49,554		83,956
Current regulatory assets (Note A)	98,323		120,935
Natural gas in storage, at average cost	88,791		84,768
Deferred income taxes	28,591		41,605
Refundable taxes	0		1,686
Current portion of derivative assets (Note A)	9,063		12,671
Prepayments	25,521		11,907
Other	12,886		11,507
Total Current Assets	533,626		628,683
Other investments	'		'
Equity investment in GenConn (Note A)	126,609		124,799
Other	25,210		23,931
Total Other investments	151,819		148,730
Net Property, Plant and Equipment	2,930,507		2,787,354
Regulatory Assets (future amounts due from customers through the ratemaking process) (Note A)	909,864		1,014,515
Deferred Charges and Other Assets	'		'
Unamortized debt issuance expenses	15,356		16,625
Other long-term receivable	1,497		1,501
Derivative assets (Note A)	45,759		67,167
Goodwill	266,205		266,205
Other	11,145		28,587
Total Deferred Charges and Other Assets	339,962		380,085
Total Assets	4,865,778	[1]	4,959,367	[1]
Current Liabilities	'		'
Line of credit borrowings	227,000		187,000
Current portion of long-term debt	32,028		48,296
Accounts payable	109,667		189,991
Dividends payable	21,908		21,887
Accrued liabilities	75,623		85,132
Current regulatory liabilities (Note A)	7,135		21,284
Taxes accrued	40,797		18,235
Interest accrued	24,389		22,427
Current portion of derivative liabilities (Note A)	26,915		30,804
Total Current Liabilities	565,462		625,056
Deferred Income Taxes (future tax liabilities owed to taxing authorities)	481,264		462,940
Regulatory Liabilities (future amounts owed to customers through the ratemaking process) (Note A)	487,170		445,156
Other Noncurrent Liabilities	'		'
Pension accrued	286,798		325,547
Connecticut Yankee contract obligation (Note J)	0		11,129
Other post-retirement benefits accrued	97,614		98,147
Derivative liabilities (Note A)	175,662		224,639
Other	50,302		49,506
Total Other Noncurrent Liabilities	610,376		708,968
Commitments and Contingencies (Note J)	'		'
Capitalization (Note B)	'		'
Long-term debt, net of unamortized discount and premium	1,591,517		1,600,354
Preferred Stock of Subsidiary	'		'
Preferred stock, not subject to mandatory redemption	340		340
Common Stock Equity	'		'
Common stock	939,177		936,702
Paid-in capital	21,422		20,400
Retained earnings	169,043		159,900
Accumulated other comprehensive income (loss)	7		-449
Net Common Stock Equity	1,129,649		1,116,553
Total Capitalization	2,721,506		2,717,247
Total Liabilities and Capitalization	$4,865,778		$4,959,367
[1]	Information for segmenting total assets between Distribution and Transmission is not available.  Total Electric Distribution and Transmission assets are disclosed in the Total Electric Distribution and Transmission column.  Net plant in service is segregated by segment and, as of September 30, 2013, was $1,099.1 million and $644.7 million for Distribution and Transmission, respectively.  As of December 31, 2012, net plant in service was $1,058.6 million and $607.8 million for Distribution and  Transmission, respectively.

CONSOLIDATED_BALANCE_SHEET_Una1

CONSOLIDATED BALANCE SHEET (Unaudited) (Parenthetical) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Current Assets	'	'
Allowance for doubtful accounts receivable	$13,609	$11,867

CONSOLIDATED_STATEMENT_OF_CASH

CONSOLIDATED STATEMENT OF CASH FLOWS (Unaudited) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012
Cash Flows From Operating Activities	'		'
Net income	$74,898		$74,863
Adjustments to reconcile net income to net cash provided by operating activities:	'		'
Depreciation and amortization	148,356		137,704
Deferred income taxes	17,501		46,504
Allowance for funds used during construction (AFUDC) - equity	-8,085		-5,473
Stock-based compensation expense (Note A)	4,104		3,914
Pension expense	36,756		29,949
Undistributed (earnings) losses in equity investments	-11,622		-11,990
Deferred purchased gas	24,337		18,672
Deferred Transmission (income) expense	10,635		-19,822
Regulatory disallowances (Note C)	17,543		0
Other non-cash items, net	2,360		20,812
Changes in:	'		'
Accounts receivable, net	36,930		-30,047
Unbilled revenues	34,474		19,372
Natural gas in storage	-4,023		19,099
Prepayments	-13,615		-6,942
Accounts payable	-54,889		-41,532
Cash distributions from GenConn	7,704		16,304
Interest accrued	1,962		3,735
Taxes accrued/refundable, net	24,248		34,441
Accrued liabilities	-5,065		-1,685
Accrued pension	-69,963		-57,680
Other assets	-512		3,583
Other liabilities	-6,128		-5,848
Total Adjustments	193,008		173,070
Net Cash provided by Operating Activities	267,906		247,933
Cash Flows from Investing Activities	'		'
Plant expenditures including AFUDC debt	-224,172	[1]	-214,240	[1]
Cash distributions from GenConn	2,063		1,300
Changes in restricted cash	918		3,377
Deposits in New England East West Solution (NEEWS) (Note C)	-982		-5,885
Other	350		810
Net Cash (used in) Investing Activities	-221,823		-214,638
Cash Flows from Financing Activities	'		'
Issuance of common stock	72		1,943
Issuances of long-term debt	0		203,500
Payments on long-term debt	-20,000		-108,500
Line of credit borrowings (repayments), net	40,000		-80,000
Payment of common stock dividend	-65,695		-65,602
Other	379		-434
Net Cash (used in) Financing Activities	-45,244		-49,093
Unrestricted Cash and Temporary Cash Investments:	'		'
Net change for the period	839		-15,798
Balance at beginning of period	17,857		30,999
Balance at end of period	18,696		15,201
Non-cash investing activity:	'		'
Plant expenditures included in ending accounts payable	21,149		26,944
Plant expenditures funded by deposits in NEEWS	-18,469		-6,346
Deposits in New England East West Solution (NEEWS)	$18,469		$6,346
[1]	Information for segmenting total capital expenditures between Distribution and Transmission is not available.  Total Electric Distribution and Transmission capital expenditures are disclosed in the Total Electric Distribution and Transmission column.

BUSINESS_ORGANIZATION_AND_STAT

BUSINESS ORGANIZATION AND STATEMENT OF ACCOUNTING POLICIES	9 Months Ended
	Sep. 30, 2013
BUSINESS ORGANIZATION AND STATEMENT OF ACCOUNTING POLICIES [Abstract]	'
BUSINESS ORGANIZATION AND STATEMENT OF ACCOUNTING POLICIES	'
	(A)	BUSINESS ORGANIZATION AND STATEMENT OF ACCOUNTING POLICIES
	UIL Holdings is headquartered in New Haven, Connecticut, where its senior management maintains offices and is responsible for overall planning, operating and financial functions.  The primary business of UIL Holdings is ownership of its operating regulated utility businesses.  The utility businesses consist of the electric distribution and transmission operations of The United Illuminating Company (UI) and the natural gas transportation, distribution and sales operations of The Southern Connecticut Gas Company (SCG), Connecticut Natural Gas Corporation (CNG), and The Berkshire Gas Company (Berkshire, and together with SCG and CNG,  the Gas Companies).
	UI is also a party to a joint venture with certain affiliates of NRG Energy, Inc. (NRG affiliates) pursuant to which UI holds 50% of the membership interests in GCE Holding LLC, whose wholly owned subsidiary, GenConn Energy LLC (collectively with GCE Holding LLC, GenConn) operates peaking generation plants in Devon, Connecticut (GenConn Devon) and Middletown, Connecticut (GenConn Middletown).
	Basis of Presentation
	The financial statements of UIL Holdings are prepared on a consolidated basis and therefore include the accounts of UIL Holdings’ majority-owned subsidiaries noted above.  The year‑end balance sheet data was derived from audited financial statements, but does not include all disclosures required by accounting principles generally accepted in the United States of America (GAAP).  Certain information and footnote disclosures, which are normally included in financial statements prepared in accordance with GAAP, have been condensed or omitted in accordance with Securities and Exchange Commission (SEC) rules and regulations.  UIL Holdings believes that the disclosures made are adequate to make the information presented not misleading.  The information presented in the Consolidated Financial Statements reflects all adjustments which, in the opinion of UIL Holdings, are necessary for a fair statement of the financial position and results of operations for the interim periods described herein.  All such adjustments are of a normal and recurring nature.  The results for the nine-month period ended September 30, 2013 are not necessarily indicative of the results for the entire fiscal year ending December 31, 2013.
	The Income from Equity Investments line item on UIL Holdings Consolidated Statement of Income, which was previously presented below the Income Taxes line item, is now being presented above the Income Taxes line item.
	The Company has revised its previously issued annual financial statements for a correction in the 2012 Consolidated Balance Sheet.  The effect of this revision on the balance sheet is a $13.1 million adjustment increasing accounts payable and decreasing accrued liabilities in the Consolidated Balance Sheet as of December 31, 2012.  This adjustment is not considered to be material to previously issued financial statements.  Additionally, certain immaterial amounts that were reported in the Consolidated Balance Sheet and Consolidated Statement of Income in previous periods have been reclassified to conform to the current presentation.
	Derivatives
	UIL Holdings’ regulated subsidiaries are parties to contracts, and involved in transactions, that are derivatives.  The fair values of the gross derivative assets and liabilities as of September 30, 2013 and December 31, 2012 were as follows:
			September 30,			December 31,
			2013			2012
			(In Thousands)
	Gross derivative assets:
	Current Assets		$	9,063		$	12,671
	Deferred Charges and Other Assets		$	45,759		$	67,167
	Gross derivative liabilties:
	Current Liabilities		$	26,915		$	30,804
	Noncurrent Liabilities		$	175,662		$	224,639
	Contracts for Differences (CfDs)
	Pursuant to Connecticut’s 2005 Energy Independence Act, the Connecticut Public Utilities Regulatory Authority (PURA) solicited bids to create new or incremental capacity resources in order to reduce federally mandated congestion charges, and selected four new capacity resources.  To facilitate the transactions between the selected capacity resources and Connecticut electric customers, and provide the commitment necessary for owners of these resources to obtain necessary financing, PURA required that UI and The Connecticut Light and Power Company (CL&P) execute long-term contracts with the selected resources.  In August 2007, PURA approved four CfDs, each of which specifies a capacity quantity and a monthly settlement that reflects the difference between a forward market price and the contract price.  UI executed two of the contracts and CL&P executed the other two contracts.  The costs or benefits of each contract will be paid by or allocated to customers and will be subject to a cost-sharing agreement whereby approximately 20% of the cost or benefit is borne by or allocated to UI customers and approximately 80% is borne by or allocated to CL&P customers.
	PURA has determined that costs associated with these CfDs will be recoverable by UI and CL&P, and in accordance with ASC 980 “Regulated Operations,” UI has deferred recognition of costs (a regulatory asset) or obligations (a regulatory liability).  The CfDs are marked-to-market in accordance with ASC 815 “Derivatives and Hedging.”  For those CfDs signed by CL&P, UI records its approximate 20% portion pursuant to the cost-sharing agreement noted above.  As of September 30, 2013, UI has recorded a gross derivative asset of $54.8 million, a regulatory asset of $147.8 million, and a gross derivative liability of $202.6 million ($134.0 million of which is related to UI’s portion of CL&P’s derivative liabilities).  See Note (K) “Fair Value of Financial Instruments” for additional CfD information.
	The unrealized gains and losses from fair value adjustments to these derivatives recorded in regulatory assets or regulatory liabilities for the three- and nine-month periods ended September 30, 2013 and 2012 were as follows:
			Three Months Ended						Nine Months Ended
			September 30,						September 30,
			2013			2012			2013			2012
			(In Thousands)						(In Thousands)
	Regulatory Assets - Derivative liabilities		$	(5,585	)	$	(1,832	)	$	(28,849	)	$	(7,613	)
	Regulatory Liabilities - Derivative assets		$	-		$	(27	)	$	-		$	(15	)
	The increased unrealized losses in the three- and nine-month periods ended September 30, 2013 compared to September 30, 2012 is primarily due to increases in forward pricing.
	Weather Insurance Contracts
	On an annual basis, the Gas Companies each assess the need for weather insurance contracts for the upcoming heating season in order to provide financial protection from significant weather fluctuations.  According to the terms of such contracts, if temperatures are warmer than normal at a prescribed level for the contract period, a payment is received by the gas company; in addition, under certain of the contracts, if temperatures are colder than normal at a prescribed level for the contract period, the gas company is required to make a payment.  The premiums paid are amortized over the terms of the contracts.  The intrinsic value of the contracts is carried on the balance sheet with changes in value recorded in the income statement as Other Income and (Deductions).
	In October of 2013, CNG entered into a weather insurance contract for the period of November 1, 2013 through December 31, 2013.  If temperatures are warmer than normal, CNG will receive a payment, up to a maximum of $1.5 million; however, if temperatures are colder than normal, CNG will make a payment of up to a maximum of $1 million.  As a result of the request in CNG’s current rate proceeding for a decoupling mechanism which is anticipated to go into effect in January 2014, the contract does not extend into the 2014 portion of the heating season.
	In October 2013, Berkshire entered into a weather insurance contract for the winter period of November 1, 2013 through April 30, 2014.  If temperatures are warmer than normal, Berkshire will receive a payment, up to a maximum of $1 million; however, if temperatures are colder than normal, Berkshire will make a payment of up to a maximum of $0.2 million.
	In September 2013, SCG entered into a weather insurance contract for the winter period of November 1, 2013 through April 30, 2014.  If temperatures are warmer than normal, SCG will receive a payment, up to a maximum of $3 million; however, if temperatures are colder than normal, SCG will make a payment of up to a maximum of $2 million.
	In October 2012, SCG and CNG each entered into weather insurance contracts for the winter period of November 1, 2012 through April 30, 2013.  If temperatures were warmer than normal, SCG and CNG each would have received a payment, up to a maximum of $3 million; however, if temperatures were colder than normal, SCG and CNG each would have made a payment of up to a maximum of $2 million.  Upon the expiration of their respective contracts, SCG and CNG neither received nor made a payment since the variation from normal weather during the contract period did not reach the prescribed level stated in the contracts.
	In November 2011, Berkshire entered into a weather insurance contract for calendar year 2012 in order to provide financial protection from significant weather fluctuations.  According to the terms of the contract, because temperatures were warmer than normal for the contract period, Berkshire received a payment of $1 million on January 8, 2013.  The premiums paid were amortized over the term of the contract.  The intrinsic value of the contract is carried on the balance sheet, which totaled $1 million at December 31, 2012, with changes in value recorded in the income statement as Other Income and (Deductions).
	Earnings per Share
	The following table presents a reconciliation of the basic and diluted earnings per share calculations for the three- and nine‑month periods ended September 30, 2013 and 2012:
			Three Months Ended September 30,						Nine Months Ended September 30,
			2013			2012			2013			2012
			(In Thousands, except per share amounts)
	Numerator:
	Net income		$	5,144		$	15,749		$	74,859		$	74,798
	Less:  Net income allocated to unvested units			5			23			83			126
	Net income attributable to common shareholders		$	5,139		$	15,726		$	74,776		$	74,672
	Denominator:
	Basic average number of shares outstanding			50,989			50,799			50,956			50,760
	Effect of dilutive securities			242			233			281			244
	Diluted average number of shares outstanding			51,231			51,032			51,237			51,004
	Earnings per share:
	Basic		$	0.1		$	0.31		$	1.47		$	1.47
	Diluted		$	0.1		$	0.31		$	1.46		$	1.46
	All outstanding options to purchase shares of common stock during the nine-month periods ending September 30, 2013 and 2012 and the three-month period ending September 30, 2012 were included in the computation of diluted earnings per share because the options’ exercise prices were lower than the average market price of UIL Holdings’ common shares during such period.  There were no outstanding options to purchase shares of common stock during the three-month period ending September 30, 2013.
	Equity Investments
	UI is party to a 50-50 joint venture with NRG affiliates in GenConn, which operates two peaking generation plants in Connecticut.  UI’s investment in GenConn is being accounted for as an equity investment, the carrying value of which was $126.6 million and $124.8 million as of September 30, 2013 and December 31, 2012, respectively.  As of September 30, 2013, there were approximately $4.0 million of undistributed earnings from UI’s equity investment in GenConn.
	UI’s pre-tax income from its equity investment in GenConn was $11.6 million and $11.8 million for the nine-month periods ended September 30, 2013 and 2012, respectively.  The decline in 2013 earnings compared to 2012 is primarily due to the absence in the first quarter 2013 of non-recurring adjustments recorded in the first quarter of 2012 largely relating to 2011.  UI’s pre-tax income from its equity investment in GenConn was $3.9 million and $3.4 million for the three‑month periods ended September 30, 2013 and 2012, respectively.
	Cash distributions from GenConn are reflected as either distributions of earnings or as returns of capital in the operating and investing sections of the Consolidated Statement of Cash Flows, respectively.  UI received cash distributions from GenConn of $9.8 million and $17.6 million during the nine-month periods ended September 30, 2013 and 2012, respectively.  Due to timing, UI did not receive any cash distributions from GenConn during the three‑month period ended September 30, 2013 but received distributions of $8.2 million in October of 2013.  UI received cash distributions from GenConn of $4.7 million during the three-month period ended September 30, 2012.
	Regulatory Accounting
	Unless otherwise stated below, all of UIL Holdings’ regulatory assets earn a return.  UIL Holdings’ regulatory assets and liabilities as of September 30, 2013 and December 31, 2012 included the following:
	Remaining Period			September 30,			December 31,
				2013			2012
				(In Thousands)
	Regulatory Assets:
Nuclear plant investments – above market	(a)		$	238,868		$	252,498
Connecticut Yankee	Not applicable			-			11,129
Unamortized redemption costs	8 to 20 years			11,502			12,103
Pension and other post-retirement benefit plans	(b)			444,038			458,019
Environmental remediation costs	4 to 5 years			16,754			14,772
Hardship programs	(c)			23,833			29,852
Debt premium	1 to 24 years			35,671			41,016
Deferred purchased gas	(d)			-			12,444
Unfunded future income taxes	(e)			27,201			17,319
Contracts for differences	(f)			147,726			176,597
Excess generation service charge	(g)			8,228			8,864
Deferred transmission income/expense	(h)			10,744			21,379
Storm costs	(i)			15,797			52,009
Other	(j)			27,825			27,449
Total regulatory assets				1,008,187			1,135,450
Less current portion of regulatory assets				98,323			120,935
Regulatory Assets, Net			$	909,864		$	1,014,515
Regulatory Liabilities:
Accumulated deferred investment tax credits	30 years		$	4,502		$	4,612
Income taxes due principally to book-tax differences	(j)			57,828			41,928
Deferred gain on sale of property	(a)			37,933			37,933
Middletown/Norwalk local transmission network service collections	36 years			21,545			21,975
Pension and other post-retirement benefit plans	1 to 7 years			11,985			15,016
Deferred income taxes	(e)			44,522			41,816
Asset retirement obligation	(k)			4,254			4,995
Deferred purchased gas	(d)			11,893			-
Low income programs	(l)			23,509			17,651
Asset removal costs	(j)			254,131			243,854
Other	(j)			22,203			36,660
Total regulatory liabilities				494,305			466,440
Less current portion of regulatory liabilities				7,135			21,284
Regulatory Liabilities, Net			$	487,170		$	445,156
(a) Asset/Liability relates to the Competitive Transition Assessment (CTA).  Total CTA costs recovery and stranded cost amortization were substantially completed in the third quarter of 2013.  The remaining balances are fully offset by amounts primarily included in income taxes, due principally to book-tax differences.  As a result of the outcome of UI’s 2013 distribution rate request, PURA approved UI’s proposed rate treatment to leave CTA rates unchanged until January 1, 2014 at which point the charge will end and the remaining balances will be extinguished.
(b) Asset life is dependent upon timing of final pension plan distribution; balance, which is fully offset by a corresponding liability, is recalculated each year in accordance with ASC 715 "Compensation-Retirement Benefits." See Note (G) “Pension and Other Benefits” for additional information.
(c) Hardship customer accounts deferred for future recovery to the extent they exceed the amount in rates.
(d) Deferred purchase gas costs balances at the end of the rate year are normally recorded/returned in the next year.
(e) The balance will be extinguished when the asset, which is fully offset by a corresponding liability, or liability has been realized or settled, respectively.
(f) Asset life is equal to delivery term of related contracts (which vary from approximately 7 - 14 years); balance fluctuates based upon quarterly market analysis performed on the related derivatives (Note K); amount, which does not earn a return, is fully offset by corresponding derivative asset/liability.  See “-Contracts for Differences” discussion above for additional information.
(g) Working capital allowance for generation service charge; this amount fluctuates based upon cash inflows and outflows in a given period.
(h) Regulatory asset or liability which defers transmission income or expense and fluctuates based upon actual revenues and revenue requirements.
(i) Storm costs include accumulated costs for major storms occurring from January 2009 forward. See Note (C) “Regulatory Proceedings – Electric Distribution and Transmission – Rates” for a discussion of the recovery of these costs.
(j) Amortization period and/or balance vary depending on the nature, cost of removal and/or remaining life of the underlying assets/liabilities; asset amount includes decoupling ($12.4 million) and certain other amounts that are not currently earning a return. See Note (C) “Regulatory Proceedings – Electric Distribution and Transmission – Rates” for a discussion of the decoupling recovery period.
(k) The liability will be extinguished simultaneous with the retirement of the assets and settlement of the corresponding asset retirement obligation.
(l) Various hardship and payment plan programs approved for recovery.
Stock-Based Compensation
Pursuant to the UIL Holdings 2008 Stock and Incentive Compensation Plan (2008 Stock Plan), target amounts of 101,150 and 5,860 performance shares were granted to certain members of management in March and May of 2013, respectively; the averages of the high and low market prices on the grant dates, which approximates fair value, were $38.73 and $41.34 per share, respectively.
Also in March 2013, UIL Holdings granted a total of 2,033 shares of restricted stock to its President and Chief Executive Officer under the 2008 Stock Plan and in accordance with his employment agreement; the average of the high and low market price on the date of grant, which approximates fair value, was $38.73 per share.  Such shares vest in equal annual installments over a five-year period.
In May 2013, UIL Holdings granted a total of 21,558 shares of restricted stock to non-employee directors under the 2008 Stock Plan; the average of the high and low market price on the date of grant, which approximates fair value, was $40.69 per share.  Such shares vest in May 2014.
Also in May 2013, UIL Holdings granted a total of 2,177 shares of restricted stock to its Vice President – Information Technology and Chief Information Officer under the Amended and Restated UIL Holdings 2008 Stock and Incentive Compensation Plan; the average of the high and low market price on the date of grant, which approximates fair value, was $41.34 per share.  Such shares vest in May 2016.
Total stock-based compensation expense for the nine-month periods ended September 30, 2013 and 2012 was $4.1 million and $3.9 million, respectively.  Total stock-based compensation expense for the three-month periods ended September 30, 2013 and 2012 was $1.1 million and $0.2 million, respectively.
Variable Interest Entities
UIL Holdings has identified GenConn as a variable interest entity (VIE), which is accounted for under the equity method.  UIL Holdings is not the primary beneficiary of GenConn, as defined in ASC 810 “Consolidation,” because it shares control of all significant activities of GenConn with its joint venturer, NRG affiliates.  As such, GenConn is not subject to consolidation.  GenConn recovers its costs through CfDs, which are cost of service-based and have been approved by PURA.  As a result, with the achievement of commercial operation by GenConn Devon and GenConn Middletown, UIL Holdings’ exposure to loss is primarily related to the potential for unrecovered GenConn operating or capital costs in a regulatory proceeding, the effect of which would be reflected in the carrying value of UIL Holdings’ 50% ownership position in GenConn and through “Income from Equity Investments” in UIL Holdings’ Consolidated Financial Statements.  Such exposure to loss cannot be determined at this time.  For further discussion of GenConn, see “–Equity Investments” as well as Note (C) “Regulatory Proceedings – Electric Distribution and Transmission – Equity Investment in Peaking Generation.”
UIL Holdings has identified the selected capacity resources with which UI has CfDs as VIEs and has concluded that UI is not the primary beneficiary as UI does not have the power to direct any of the significant activities of these capacity resources.   As such, UIL Holdings has not consolidated the selected capacity resources.  UI’s maximum exposure to loss through these agreements is limited to the settlement amount under the CfDs as described in “–Derivatives – Contracts for Differences (CfDs)” above.  UI has no requirement to absorb additional losses nor has UI provided any financial or other support during the periods presented that were not previously contractually required.
UIL Holdings has identified the entities for which UI is required to enter into long-term contracts to purchase Renewable Energy Credits (RECs) as VIEs.  In assessing these contracts for VIE identification and reporting purposes, UIL Holdings has aggregated the contracts based on similar risk characteristics and significance to UI.  UI is not the primary beneficiary as UI does not have the power to direct any of the significant activities of these entities.  UI’s exposure to loss is primarily related to the purchase and resale of the RECs, but, any losses incurred are recoverable through electric rates.  For further discussion of RECs, see Note (C) “Regulatory Proceedings – Electric Distribution and Transmission – New Renewable Source Generation.”
New Accounting Pronouncements
In July 2013, the FASB issued updated guidance to ASC 740 “Income Taxes” which prescribes the presentation of an unrecognized tax benefit when a net operating loss carryforward, a similar tax loss, or a tax credit carryforward exists.    This guidance is effective during interim and annual periods beginning after December 15, 2013 and is to be applied on a prospective basis.  The implementation of this guidance is not expected to have a material impact on UIL Holdings’ consolidated financial statements.

CAPITALIZATION

CAPITALIZATION	9 Months Ended
	Sep. 30, 2013
CAPITALIZATION [Abstract]	'
CAPITALIZATION	'
	(B)  CAPITALIZATION
	Common Stock
	UIL Holdings had 50,712,507 shares of its common stock, no par value, outstanding at September 30, 2013.
	On October 2, 2013, UIL Holdings issued 5,750,000   shares of its common stock at $37.25 per share in an underwritten public offering.  This issuance included 750,000 shares issued upon the exercise by the underwriters of their over-allotment option.  Net proceeds of the offering, including the over-allotment option, were approximately $206.4 million, after expenses and underwriting discounts, and were accounted for as an addition to common stock on UIL Holdings’ Consolidated Balance Sheet.  The Company plans to use the net proceeds from this issuance to repay short-term debt and for general corporate purposes.
	Long‑Term Debt
	On October 25, 2013, UI entered into a note purchase agreement with a group of institutional accredited investors providing for the sale to such investors on October 25, 2013 of senior unsecured 3.95% notes in the principal amount of $75 million, due on October 25, 2023.  UI used the net proceeds from this long-term debt issuance to repay short-term debt.
	On October 25, 2013, CNG entered into a note purchase agreement with a group of qualified institutional buyers providing for the sale to such buyers on October 25, 2013 of senior unsecured 4.30% notes in the principal amount of $25 million, due on October 25, 2028 and 5.23% notes in the principal amount of $20 million, due on October 25, 2043.  CNG used $20 million of the net proceeds of this long-term debt issuance to replenish cash that had been used to repay $20 million of debt that matured in September 2013 and expects to use $20 million of the proceeds to repay $20 million of 6.50% Medium Term Notes, Series D, due December 15, 2013.  CNG expects to use the remainder of the proceeds for capital expenditures and general corporate purposes.
	On October 25, 2013, Berkshire entered into a note purchase agreement with a group of institutional accredited investors providing for the sale to such investors on December 10, 2013 of senior unsecured 5.33% notes in the principal amount of $15 million, due on December 10, 2043.  Berkshire expects to use the net proceeds of this long‑term debt issuance for capital expenditures, repayment of short-term debt, general working capital, environmental expenditures and issuance fees and expenses.

REGULATORY_PROCEEDINGS

REGULATORY PROCEEDINGS	9 Months Ended
	Sep. 30, 2013
REGULATORY PROCEEDINGS [Abstract]	'
REGULATORY PROCEEDINGS	'
	(C)  REGULATORY PROCEEDINGS
	In November 2012, pursuant to PA 12-148, PURA opened a docket to investigate UI’s and the Gas Companies’ performance in restoring service following Superstorm Sandy, which passed through Connecticut in October 2012. A final decision was issued on August 21, 2013, in which PURA found that the electric distribution companies and the gas local distribution companies performed their storm-related activities in a timely and effective manner and made recommendations for certain improvements.
	Electric Distribution and Transmission
	Superstorm Sandy caused extensive damage to the electric system in UI's service territory and resulted in approximately 284,000 customer outages.  In accordance with PURA regulatory decisions and past storm cost guidance, UI has established a regulatory asset for its storm-related expense.  UI’s cost of repairing the damage resulting from the storm and restoring service to customers was approximately $35.8 million, of which approximately $13.9 million was capitalized as property plant and equipment and the remainder as a regulatory asset.  As a result of PURA’s final decision in UI’s 2013 distribution rate case, a portion of this regulatory asset was disallowed.  See   “‑Rates” below for additional information regarding the recovery and disallowance of storm costs, including costs of Superstorm Sandy.
	Rates
	On February 15, 2013, UI filed an application to amend its existing distribution rate schedules for two rate years.  Included in this request is the initiation of the recovery of UI’s storm regulatory asset of approximately $53 million for previously incurred storm costs not included in rates.  UI’s application proposed a six-year recovery period for these costs along with the establishment of a storm reserve of $2 million per year to help address future storm costs, and the ability to defer additional storm costs above the reserve amount as a regulatory asset for recovery in a future proceeding.  UI does not currently have a storm reserve funded in rates.  In addition, UI proposed to use revenue from other sources, such as the 2010 and 2012 earnings sharing amounts owed to customers along with anticipated excess CTA revenue collections, to recover increased distribution revenue requirements through the end of 2013, which would allow the implementation of the proposed distribution rate increase to be deferred until January 1, 2014 coincident with the expiration of the CTA.
	On August 14, 2013, PURA issued a final decision which became effective on that date and which, among other things, increased the UI distribution and CTA allowed return on equity (ROE) from 8.75% to 9.15%, continued UI’s existing earnings sharing mechanism by which UI and customers share on a 50/50 basis all distribution earnings above the allowed ROE in a calendar year,  continued the existing decoupling mechanism, and approved the establishment of the requested storm reserve.  Additionally, the final decision disallowed approximately $22 million related to deferred storm costs and capital costs related to UI’s recently constructed administrative and operations buildings.  As a result of these disallowances and other adjustments related to the rate proceeding, UIL Holdings recorded a one-time pretax write off of $17.5 million related to UI in the third quarter of 2013.
	On August 26, 2013, UI filed with PURA a Motion for Reconsideration of the Decision, seeking the correction of certain errors in the determination of UI’s revenue requirements, along with the reconsideration of certain elements of the disallowed items discussed above.  On September 18, 2013, PURA issued a decision to review UI’s petition for reconsideration.  The reconsideration to be undertaken by PURA could impact rates and the total amount written off in this quarter.
	On September 30, 2013, PURA approved UI’s revised distribution decoupling filings for the 2011 and 2012 rate years which included decoupling adjustments of $4.0 million and $6.4 million, respectively.  UI began recovering these amounts from customers on October 1, 2013.  The recovery period for the decoupling adjustments will run through September 30, 2014.  On October 11, 2013, UI filed its distribution decoupling filing for the 2013 rate year under its previous rate case that ended on August 13, 2013 which included a decoupling adjustment of $0.9 million.  UI proposes to begin recovery of this amount from customers on January 1, 2014.  The recovery period for the decoupling adjustment is proposed to run through September 30, 2014.
	Approval for the Issuance of Debt
	Long-term debt issuances require regulatory authorization which is typically obtained for a specified amount of debt to be issued during a specified period of time.
	UI has PURA approval for the issuance of up to $379 million principal amount of debt securities from 2010 through 2013 (the Proposed Notes).  UI was authorized to use the proceeds from the sale of the Proposed Notes for the following purposes:  (1) to finance capital expenditures; (2) the repayment of an equity bridge loan, the proceeds of which were used to finance UI’s equity contribution in GenConn for the development and construction of  GenConn Devon and GenConn Middletown; (3) to fund UI’s pension plan; (4) to partially repay short‑term borrowings that are incurred to temporarily fund the preceding needs; (5) to pay issuance costs related to the Proposed Notes; (6) to repay $103.5 million principal amount outstanding of pollution control revenue bonds, and (7) for general corporate purposes.  UI has issued $378.5 million principal amount of senior unsecured notes pursuant to such PURA approval, $100 million of which were issued in July 2010, $103.5 million of which were issued in January 2012,  $100 million of which were issued in April 2012, and $75 million of which were issued in October 2013.
	Power Supply Arrangements
	UI has wholesale power supply agreements in place for the supply of all of its standard service customers for all of 2013, and 30% for the first half of 2014.  Supplier of last resort service is procured on a quarterly basis.  UI determined that its contracts for standard service and supplier of last resort service are derivatives under ASC 815 “Derivatives and Hedging” and elected the “normal purchase, normal sale” exception under ASC 815 “Derivatives and Hedging.”  UI regularly assesses the accounting treatment for its power supply contracts.  These wholesale power supply agreements contain default provisions that include required performance assurance, including certain collateral obligations, in the event that UI’s credit rating on senior debt were to fall below investment grade.  If UI’s credit rating were to decline one rating and UI were to be placed on negative credit watch, monthly amounts due and payable to the power suppliers would be accelerated to semi-monthly payments.  UI’s credit rating would have to decline two ratings to fall below investment grade at either rating service.  If this were to occur, UI would have to deliver collateral security in an amount equal to the receivables due to the sellers for the thirty-day period immediately preceding the default notice.  If such an event had occurred as of September 30, 2013, UI would have had to post an aggregate of approximately $7.7 million in collateral.
	New Renewable Source Generation
	Under a 2011 Connecticut law (PA 11-80), UI and CL&P are required to enter into long-term contracts to purchase renewable energy credits (RECs) from small renewable generators located on customer premises.  Under this program, UI is required to enter into contracts totaling approximately $200 million in commitments over an approximate 21-year period.  The obligations will phase in over a six-year solicitation period, and are expected to peak at an annual commitment level of about $13.6 million per year after six years.  Upon purchase, the RECs will be accounted for as inventory.  UI expects to partially mitigate the cost of the contracts through the resale of the RECs.  PA 11-80 provides that the remaining costs of the contracts, including any gain or loss resulting from the resale of the RECs, are recoverable through electric rates.  In December 2011, UI and CL&P submitted a joint petition to PURA outlining a plan to address these requirements and in April 2012, PURA approved the program.  As of September 30, 2013, UI has entered into contracts totaling up to $2.9 million annually in payments for 15-year delivery terms commencing in 2013 and 2014.
	Under PA 11-80 Connecticut electric utilities are authorized to submit a proposal to the Connecticut Department of Energy and Environmental Protection (DEEP) to build, own or operate one or more generation facilities up to 10 MW using Class I renewable energy.  In December 2011, DEEP announced that it had selected two 5 MW solar projects in CL&P service territory and CL&P executed contracts with the developers to purchase energy and associated products from both projects.  These contracts and the associated cost recovery have been approved by DEEP and PURA, respectively.  UI and CL&P executed a sharing arrangement, pursuant to which UI will pay 20% of the costs, and receive 20% of the benefits, associated with the projects.  Pursuant to PURA’s approval of the cost recovery, the payments made to projects are recoverable through electric rates.
	Additionally, in January 2012, UI filed a proposal with PURA outlining a framework for approval of UI’s renewable connections program under which UI would develop up to 10 MW of renewable generation for recovery on a cost of service basis.  PURA issued a final decision in July 2012 approving the construction of one solar facility and two fuel cell facilities.  The decision approved an ROE equal to UI’s then currently allowed distribution ROE, which was 8.75%, over the life of the facility.  UI had requested an ROE of 9.5%.  In September 2012, PURA reopened the proceeding on its own motion and issued interrogatories, responses to which were filed by UI.  On August 28, 2013, UI and the Prosecutorial Division of PURA entered into a settlement agreement addressing the issues of disagreement, including balancing the risks of the projects with the ROE.  On October 23, 2013, PURA approved the settlement.  The settlement establishes a base ROE to be calculated as the greater of:  (A) current UI distribution ROE plus 25 basis points; and (B) current authorized distribution ROE for CL&P less (-) target equivalent market revenues (reflected as 25 basis points).  In addition, UI will retain a percentage of the market revenues from the project which percentage is expected to equate to approximately 25 basis points of the after-tax ROE.  Under the settlement, UI agreed to submit to PURA the budget for the approximately 7.8 MW in projects identified in its January 2012 filing with PURA within three months and to submit project details and budgets for the remaining 2.2 MW within twelve months.  If PURA fails to approve, or rejects or modifies the budget in any way, UI has the right to cancel the development of such project with no further liability.  The Settlement also provides that construction of any of these projects will be subject to the receipt of all required permits and approvals acceptable in form and substance to UI.
	Under Section 6 of Public Act 13-303 (PA 13-303), DEEP may direct Connecticut’s electric distribution companies, including UI, to enter into contracts for energy and/or RECs from Class I renewable resources in a quantity up to 4% of UI’s distribution load.  On July 8, 2013, DEEP issued a request for proposals (RFP),and directed UI to enter into power purchase agreements with the winning bidders.  On September 19, 2013 UI entered into contracts that are pending approval by PURA.  The contracts are for 48.1 MW produced by a 250 MW wind farm in Maine, and 3.8 MW produced by a 20 MW solar project in Connecticut.  The quantity of energy and RECs to be purchased under these contracts total approximately 3.5% of UI’s distribution load.  PA 13-303 provides that costs of any such agreement are recoverable from customers.
	Under Section 8 of Public Act 13-303 (PA 13-303), DEEP may direct Connecticut’s electric distribution companies, including UI, to enter into contracts for energy and/or RECs from biomass, landfill gas and small hydro projects that qualify as Connecticut Class I renewable resources in a quantity up to 4% of UI’s distribution load.  On October 21, 2013, DEEP issued an RFP and contracts are expected to be executed in December of 2013.  PA 13-303 provides that costs of any such agreements are recoverable from customers.
	New England East-West Solution
	Pursuant to an agreement with CL&P (the Agreement), UI has the right to invest in, and own transmission assets associated with, the Connecticut portion of CL&P’s New England East West Solution (NEEWS) projects to improve regional energy reliability.  NEEWS consists of four inter-related transmission projects being developed by subsidiaries of Northeast Utilities (NU), the parent company of CL&P, in collaboration with National Grid USA.  Three of the projects have portions located in Connecticut:  (1) the Greater Springfield Reliability Project, which is substantially complete, (2) the Interstate Reliability Project, which has Connecticut Siting Council approval and (3) the Central Connecticut Reliability Project being studied now as part of the "Greater Hartford Central Connecticut Study" (GHCC) due to the expanded scope of ISO-NE’s reassessment.  GHCC transmission solutions are being considered and a set of preferred solutions are expected to be identified by ISO-NE in late 2013 or early 2014.
	Under the terms of the Agreement, UI has the option to make quarterly deposits to CL&P in exchange for ownership of specific NEEWS transmission assets as they are placed in service.  UI has the right to invest up to the greater of $60 million or an amount equal to 8.4% of CL&P’s costs for the Connecticut portions of the NEEWS projects.  Based upon the current projected costs, this amount is approximately $60 million.  As assets are placed in service, CL&P will transfer title to certain NEEWS transmission assets to UI in proportion to its investments, but CL&P will continue to maintain these portions of the transmission system pursuant to an operating and maintenance agreement (O&M Agreement) with UI.  Also, under the terms of the Agreement, there are certain circumstances under which CL&P can terminate the Agreement.  Such termination would have no effect on the assets previously transferred to UI.
	Deposits associated with NEEWS are recorded as assets at the time the deposit is made and they are reported in the ‘Other’ line item within the Deferred Charges and Other Assets section of the consolidated balance sheet.   When title to the assets is transferred to UI, the amount of the corresponding deposit is reclassified from other assets to plant-in-service on the balance sheet and shown as a non-cash investing activity in the consolidated statement of cash flows.
	As of September 30, 2013, UI has made aggregate deposits of $34.5 million under the Agreement since inception.  In September 2012, CL&P transferred approximately $6.2 million of transmission assets associated with the Greater Springfield Reliability Project to UI, at which time the O&M Agreement became effective.  In February 2013, CL&P transferred approximately $18.4 million of transmission assets, representing the remaining portion of the Greater Springfield Reliability Project, to UI.  UI earned pre-tax income on deposits, net of transferred assets, of approximately $0.3 million and $0.4 million in the three-month periods ended September 30, 2013 and 2012, respectively.  UI earned pre-tax income on deposits, net of transferred assets, of approximately $1.2 million and $1.1million in the nine-month periods ended September 30, 2013 and 2012, respectively.
	Equity Investment in Peaking Generation
	UI is party to a 50-50 joint venture with NRG affiliates in GenConn, which operates two peaking generation plants in Connecticut.  The two peaking generation plants, GenConn Devon and GenConn Middletown, are both participating in the ISO-New England markets.  PURA has approved revenue requirements for the period from January 1, 2013 through December 31, 2013 of $33.1 million and $40.2 million for GenConn Devon and GenConn Middletown, respectively.  In addition, PURA has ruled that GenConn project costs incurred that were in excess of the proposed costs originally submitted in 2008 were prudently incurred and are recoverable.  Such costs are included in the determination of the 2013 approved revenue requirements.
	GenConn filed a rate case request with PURA on June 28, 2013, seeking approval of 2014 revenue requirements for the annual period commencing January 1, 2014 for both the GenConn Devon and GenConn Middletown facilities.  A final decision on this request is expected by the end of 2013.
	Transmission Return on Equity (ROE)
	PURA decisions do not affect the revenue requirements determination for transmission, including the applicable ROE, which are within the jurisdiction of the FERC.  For 2013, UI is estimating an overall allowed weighted-average ROE for its transmission business in the range of 12.2% to 12.4%, excluding the potential impacts of the final outcome of the complaints discussed below.
	In September 2011, several New England governmental entities, including PURA, the Connecticut Attorney General and the Connecticut Office of Consumer Counsel, filed a joint complaint with the FERC against ISO-NE and several New England transmission owners, including UI, claiming that the current approved base ROE used in calculating formula rates for transmission service under the ISO-NE Open Access Transmission Tariff by the New England transmission owners  of 11.14% is not just and reasonable and seeking a proposed reduction of the base ROE to 9.20% to be effective for the period of October 1, 2011 through December 31, 2012.  A 25 basis point change in the weighted-average ROE for UI’s transmission business would change net income by approximately $0.6 million annually, for example.
	On August 6, 2013, the presiding Administrative Law Judge issued an initial decision finding that the existing base ROE was unjust and unreasonable, and that the just and reasonable base ROE is 10.6% for the refund period of October 1, 2011 through December 31, 2012, and for the period after a final opinion is issued by FERC, 9.7%, prior to any adjustments that may be applied by the FERC in a final order based on the change in 10-year U.S. Treasury Bond rates from the date hearings closed to the date of the FERC's order. We expect the FERC to issue its final opinion in 2014. UI recorded a reserve for the refund period of $2.6 million during the third quarter based upon its assessment of the ultimate outcome of the proceeding.
	In December 2012, various additional parties filed a complaint with the FERC against several New England transmission owners, including UI, seeking a proposed reduction of the base ROE to 8.70%, effective January 1, 2013.  The transmission owners filed an answer and request for dismissal in January 2013, including opposition to the establishment of a second 15 month refund period because the complaint seeks substantially the same relief against the same respondents but for a different 15 month period as the pending complaint of governmental entities.  The complainants filed their answer to the transmission owners’ answer in February 2013.  UI is unable to predict the outcome of this proceeding at this time.
	Gas Distribution
	Rates
	The allowed ROEs established by PURA are 9.41% and 9.36% for CNG and SCG, respectively.  Berkshire’s rates are established by the Massachusetts Department of Public Utilities (DPU).  Berkshire’s 10-year rate plan, which was approved by the DPU and included an approved ROE of 10.5%, expired on January 31, 2012.  Berkshire continues to charge the rates that were in effect at the end of the rate plan.
	On July 8, 2013, CNG filed an application to amend its existing base delivery rate.   With a proposed 10.25% ROE, the change is designed to produce additional annual base delivery rate revenues of approximately $20.1 million, as amended, which is 6.4% above the projected revenues produced by CNG's existing rate schedules, and which will support capital investments as well as the expansion of the availability of gas service in response to Connecticut’s Comprehensive Energy Strategy.  In addition, the application includes a proposed revenue-per-customer based decoupling mechanism as well as a tracking mechanism for timely recovery of costs associated with an accelerated infrastructure replacement program.  PURA is expected to issue a final decision in the first quarter of 2014.
	Approval for the Issuance of Debt
	Long-term debt issuances require regulatory authorization which is typically obtained for a specified amount of debt to be issued during a specified period of time.
	CNG has PURA approval for the issuance of up to $110 million principal amount of debt securities through October 2013 as part of an unsecured medium-term notes program.  CNG is authorized to use the proceeds from the sale of the debt securities for the refinancing of maturing debt securities, and for funding various capital expenditures and working capital associated with gas supply costs.  Any debt issuances under the approved program are subject to further PURA approval of the terms and conditions at the time of issuance.  CNG issued $20 million of medium term notes in December 2008 and $45 million of medium term notes in October 2013 pursuant to such PURA approval.
	SCG has PURA approval for the issuance of up to $200 million principal amount of debt securities through October 2013 as part of a secured medium-term notes program.  SCG is authorized to use the proceeds from the sale of the debt securities for the following purposes:  (1) to refinance maturing debt securities; (2) to finance a potential put option on an outstanding debt security; and (3) to fund various capital expenditures and working capital associated with gas costs.  Any debt issuance under the approved program is subject to further PURA approval of the terms and conditions at the time of issuance.  SCG issued $50 million of medium-term notes in December 2008 and $50 million of medium-term notes in September 2011 pursuant to such PURA approval.
	Berkshire has DPU approval to issue, from time to time, long-term debt in an aggregate principal amount not to exceed $20 million through December 14, 2014.  Berkshire is authorized to use the proceeds from any such debt issuances for the following purposes: (1) to finance capital expenditures; (2) to refinance short-term debt; (3) to pay anticipated environmental expenditures; (4) to provide general working capital; and (5) any other purposes as the DPU may authorize.

SHORTTERM_CREDIT_ARRANGEMENTS

SHORT-TERM CREDIT ARRANGEMENTS	9 Months Ended
	Sep. 30, 2013
SHORT TERM CREDIT ARRANGEMENTS [Abstract]	'
SHORT-TERM CREDIT ARRANGEMENTS	'
	(D)  SHORT‑TERM CREDIT ARRANGEMENTS
	As of September 30, 2013, UIL Holdings had $127 million outstanding under a revolving credit agreement with a group of banks that will expire on November 30, 2016 (the UIL Holdings Credit Facility).  Under the UIL Holdings Credit Facility, UIL Holdings has outstanding standby letters of credit in the aggregate amount of $4.4 million, which expire on January 31, 2014 and June 16, 2014.  Available credit under the UIL Holdings Credit Facility at September 30, 2013 totaled $268.6 million for UIL Holdings and its subsidiaries in the aggregate.  UIL Holdings records borrowings under the UIL Holdings Credit Facility as short‑term debt, but the UIL Holdings Credit Facility provides for longer term commitments from banks allowing UIL Holdings to borrow and reborrow funds, at its option, until the facility’s expiration, thus affording UIL Holdings flexibility in managing its working capital requirements.
	Additionally, as of September 30, 2013, UIL Holdings had $100 million outstanding under a credit agreement that expired on October 31, 2013.  The outstanding balance was repaid upon expiration.

INCOME_TAXES

INCOME TAXES	9 Months Ended
	Sep. 30, 2013
INCOME TAXES [Abstract]	'
INCOME TAXES	'
	(E) INCOME TAXES
	The significant combined statutory federal and state income tax rate for UIL Holdings for the three- and nine-month periods ended September 30, 2013 and 2012 was 40.9%.
	Differences in the treatment of certain transactions for book and tax purposes occur which cause the rate of UIL Holdings’ reported income tax expense to differ from the statutory tax rate described above.  The effective book income tax rates for each of the three- and nine-month periods ended September 30, 2013 were 44.8% and 37.5%, respectively, as compared to 40.7% and 40.5% for each of the three- and nine-month periods ended September 30, 2012.  The increase in the effective book income tax rate for the third quarter of 2013 compared to the third quarter of 2012 is due primarily to the impact of provision to return adjustments recorded in the third quarter of 2013 as compared to the third quarter of 2012.  The decrease in the effective book income tax rate for the 2013 year-to-date period is due primarily to lower CTA amortizations and higher equity allowance for funds used during construction.

SUPPLEMENTARY_INFORMATION

SUPPLEMENTARY INFORMATION	9 Months Ended
	Sep. 30, 2013
SUPPLEMENTARY INFORMATION [Abstract]	'
SUPPLEMENTARY INFORMATION	'
	(F)  SUPPLEMENTARY INFORMATION
		Three Months Ended				Nine Months Ended
		September 30,				September 30,
		2013		2012		2013		2012
		(In Thousands)
	Depreciation and Amortization
	Property, plant and equipment depreciation	$	30,870	$	28,648	$	89,788	$	83,143
	Amortization of nuclear plant regulatory assets		16,782		14,272		39,935		35,433
	Amortization of other regulatory assets		3,105		3,346		16,785		17,272
	Other amortization		4		13		29		38
	Total Amortization		19,891		17,631		56,749		52,743
	Total Depreciation and Amortization	$	50,761	$	46,279	$	146,537	$	135,886
	Taxes - Other than Income Taxes
	Connecticut gross earnings	$	17,780	$	16,438	$	54,873	$	48,290
	Local real estate and personal property		12,417		10,866		34,416		29,630
	Payroll taxes		2,069		1,117		6,584		4,747
	Other		123		81		462		257
	Total Taxes - Other than Income Taxes	$	32,389	$	28,502	$	96,335	$	82,924
	Other Income and (Deductions), net
	Interest income	$	243	$	645	$	1,449	$	1,720
	Allowance for funds used during construction - equity		2,751		1,589		8,085		5,473
	Allowance for funds used during construction - debt		1,533		1,427		5,869		5,231
	Weather insurance		-		-		-		3,488
	TSO Incentives		-		2,745		-		2,745
	Miscellaneous other income and (deductions) - net		626		1,010		315		2,548
	Total Other Income and (Deductions), net	$	5,153	$	7,416	$	15,718	$	21,205

PENSION_AND_OTHER_BENEFITS

PENSION AND OTHER BENEFITS	9 Months Ended
	Sep. 30, 2013
PENSION AND OTHER BENEFITS [Abstract]	'
PENSION AND OTHER BENEFITS	'
	(G)  PENSION AND OTHER BENEFITS
	During the nine-months ended September 30, 2013, UIL Holdings made pension contributions of approximately $55 million.  No further contributions are expected during the remainder of 2013.
	The following tables represent the components of net periodic benefit cost for pension and other postretirement benefits as well as the actuarial weighted-average assumptionsused in calculating net periodic benefit cost for the three- and nine‑month periods ended September 30, 2013 and 2012:
		Three Months Ended September 30,
		Pension Benefits						Other Postretirement Benefits
		2013			2012			2013			2012
		(In Thousands)
	Components of net periodic benefit cost:
	Service cost	$	3,696		$	3,008		$	481		$	401
	Interest cost		9,988			10,368			1,384			1,562
	Expected return on plan assets		(12,863	)		(11,219	)		(648	)		(626	)
	Amortization of:
	Prior service costs		151			162			(13	)		(17	)
	Transition obligation		-			-			-			98
	Actuarial loss		5,208			3,294			444			241
	Settlements (1)		632			-			-			-
	Net periodic benefit cost	$	6,812		$	5,613		$	1,648		$	1,659
		Nine Months Ended September 30,
		Pension Benefits						Other Postretirement Benefits
		2013			2012			2013			2012
		(In Thousands)
	Components of net periodic benefit cost:
	Service cost	$	11,088		$	9,024		$	1,443		$	1,203
	Interest cost		29,964			31,104			4,152			4,686
	Expected return on plan assets		(38,589	)		(33,657	)		(1,944	)		(1,878	)
	Amortization of:
	Prior service costs		453			486			(39	)		(51	)
	Transition obligation		-			-			-			294
	Actuarial loss		15,624			9,882			1,332			723
	Settlements (1)		632			-			-			-
	Net periodic benefit cost	$	19,172		$	16,839		$	4,944		$	4,977
		Three and Nine Months Ended September 30,
		Pension Benefits						Other Postretirement Benefits
		2013			2012			2013			2012
	Discount rate		4.00% - 4.25	%		5.05% - 5.30	%		4.00% - 4.25	%		5.05% - 5.30	%
	Average wage increase		3.50% - 3.80	%		3.50% - 3.80	%		N/	A		N/	A
	Return on plan assets		7.75% - 8.00	%		7.75% - 8.00	%		5.56% - 8.00	%		5.56% - 8.00	%
	Composite health care trend rate (current year)		N/	A		N/	A		7.5	%		8	%
	Composite health care trend rate (2018 forward)		N/	A		N/	A		5	%		5	%
	(1) Reflects settlement charges resulting from a distribution to a former employee upon retirement
	N/A – not applicable

RELATED_PARTY_TRANSACTIONS

RELATED PARTY TRANSACTIONS	9 Months Ended
	Sep. 30, 2013
RELATED PARTY TRANSACTIONS [Abstract]	'
RELATED PARTY TRANSACTIONS	'
	(H)  RELATED PARTY TRANSACTIONS
	A Director of UIL Holdings holds a beneficial interest in the building located at 157 Church Street, New Haven, Connecticut, where UIL Holdings leases office space.  UIL Holdings’ lease payments for this office space for each of the three-month periods ended September 30, 2013 and 2012 totaled $0.4 million.  UIL Holdings’ lease payments for this office space for each of the nine-month periods ended September 30, 2013 and 2012 totaled $1.1 million and $4.4 million, respectively.  The decrease in lease payments in 2013 is due to a reduction in office space utilized by UIL Holdings.

COMMITMENTS_AND_CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	9 Months Ended
	Sep. 30, 2013
COMMITMENTS AND CONTINGENCIES [Abstract]	'
COMMITMENTS AND CONTINGENCIES	'
	(J)  COMMITMENTS AND CONTINGENCIES
	In the ordinary course of business, UIL Holdings and its subsidiaries are involved in various proceedings, including legal, tax, regulatory and environmental matters, which require management’s assessment to determine the probability of whether a loss will occur and, if probable, an estimate of probable loss.  When assessments indicate that it is probable that a liability has been incurred and an amount can be reasonably estimated, UIL Holdings accrues a reserve and discloses the reserve and related matter.  UIL Holdings discloses matters when losses are probable but for which an estimate cannot be reasonably estimated or when losses are not probable but are reasonably possible.  Subsequent analysis is performed on a periodic basis to assess the impact of any changes in events or circumstances and any resulting need to adjust existing reserves or record additional reserves.
	Connecticut Yankee Atomic Power Company
	UI has a 9.5% stock ownership share in the Connecticut Yankee Atomic Power Company (Connecticut Yankee), the carrying value of which was $0.1 million as of September 30, 2013.  In 1996, the Board of Directors of Connecticut Yankee voted unanimously to retire the Connecticut Yankee nuclear plant (the Connecticut Yankee Unit) from commercial operation.  Connecticut Yankee updates the cost of its remaining decommissioning activity, which consists primarily of groundwater monitoring and nuclear fuel storage, at least annually, and provides UI with a projected schedule depicting annual costs expected to be billed to UI.
	On May 1, 2013, Connecticut Yankee filed an application with FERC to, among other things, reduce its rates and eliminate future decommissioning funding requirements for its owners.  On June 27, 2013, FERC issued a final decision which approved both the proposed rate reduction and the elimination of future decommissioning funding requirements.  As a result, UI’s obligation and corresponding regulatory asset were eliminated at that time.  The final decision also allows Connecticut Yankee to distribute the United States Department of Energy (DOE) damage award, discussed below, to its owners and it incorporates Connecticut Yankee’s proposed periodic review mechanism related to the continued adequacy of the Nuclear Decommissioning Trust to meet its financial obligations.
	DOE Spent Fuel Litigation
	The Nuclear Waste Policy Act of 1982 (the Act) requires the DOE to dispose of spent nuclear fuel and other high-level waste (Nuclear Waste) from nuclear generating plants.  In 1983, Connecticut Yankee and the DOE entered into a standard disposal contract mandated by the Act which required the DOE to begin disposing of Connecticut Yankee’s Nuclear Waste by the end of January 1998.
	In 1998, Connecticut Yankee filed claims in the United States Court of Federal Claims seeking damages resulting from the breach of the 1983 contracts by the DOE.  In September 2010, the court issued its decision and awarded Connecticut Yankee damages of $39.7 million for its spent fuel-related costs through 2001.  In May 2012, the United States Court of Appeals affirmed the September 2010 United States Court of Federal Claims award.  Connecticut Yankee has received payment of the damage award and, in light of its ownership share, in July 2013 UI received approximately $3.8 million of such award which will be refunded to customers.
	In December 2007, Connecticut Yankee filed a second set of complaints with the United States Court of Federal Claims against the DOE seeking unspecified damages incurred since January 1, 2002 for the DOE’s failure to remove Connecticut Yankee’s spent fuel.  In July 2009, Connecticut Yankee provided the DOE with a second set of damage claims totaling approximately $135 million for damages incurred from January 1, 2002 through December 31, 2008.  In light of its ownership share, UI would receive approximately $12.8 million of such award which would be refunded to customers.    In August 2013, Connecticut Yankee filed a third set of complaints with the United States Court of Federal Claims against the DOE seeking unspecified damages incurred since January 1, 2009.  As an interim measure until the DOE complies with its contractual obligation to dispose of Connecticut Yankee’s spent fuel, Connecticut Yankee constructed an independent spent fuel storage installation (ISFSI), utilizing dry-cask storage, on the site of the Connecticut Yankee Unit and completed the transfer of its Nuclear Waste to the ISFSI in 2005.
	Environmental Matters
	In complying with existing environmental statutes and regulations and further developments in areas of environmental concern, including legislation and studies in the fields of water quality, hazardous waste handling and disposal, toxic substances, climate change and electric and magnetic fields, UIL Holdings and its wholly-owned direct and indirect subsidiaries may incur substantial capital expenditures for equipment modifications and additions, monitoring equipment and recording devices, as well as additional operating expenses.  The total amount of these expenditures is not now determinable.  Environmental damage claims may also arise from the operations of UIL Holdings’ subsidiaries.  Significant environmental issues known to UIL Holdings at this time are described below.
	Site Decontamination, Demolition and Remediation Costs
	In June 2006, UI executed an agreement with the City of Bridgeport and its Redevelopment Authority (the City) to transfer title of UI’s Steel Point property to the City.  Pursuant to a Memorandum of Understanding (MOU) among UI, the City, and the City’s selected developer for the property, the City and the developer released UI from any further liability with respect to the Steel Point property after title transferred, and the City and/or the developer has indemnified UI for environmental matters related to the Steel Point property.  The Steel Point property includes the land up to the bulkhead.  The MOU provides that there is no indemnity for liability related to contaminated harbor sediments, and UI is not aware of any such claims.  UI would seek to recover any uninsured costs related to such sediments that are UI’s responsibility, to the extent incurred, through the CTA, in accordance with the ratemaking treatment approved in PURA’s July 2006 decision.
	A former generation site on the Mill River in New Haven owned by UI (English Station) was conveyed in 2000 by UI to an unaffiliated entity, Quinnipiac Energy LLC (QE), reserving to UI permanent easements for the operation of its transmission facilities on the site.  At the time of the sale, a fund of approximately $1.9 million, an amount equal to the then-current estimate for remediation, was placed in escrow for purposes of bringing soil and groundwater on the English Station site into compliance with applicable environmental laws.  As of June 30, 2013, approximately $0.1 million of the escrow fund remained.  In 2006, QE sold the property to Evergreen Power, LLC (Evergreen Power) and Asnat Realty LLC (Asnat).  In January 2012, Evergreen Power and Asnat filed a lawsuit in federal district court in Connecticut against UI seeking, among other things: (i) an order directing UI to reimburse the plaintiffs for costs they have incurred and will incur for the testing, investigating and remediation of hazardous substances at the English Station site and (ii) an order directing UI to investigate and remediate the site.  In May 2012, UI filed an answer and counterclaims, and the plaintiffs filed an answer to UI’s counterclaims.  In July 2012, Evergreen Power and Asnat filed a motion for partial summary judgment with respect to UI’s liability under the federal Comprehensive Environmental Response, Compensation, and Liability Act.  On October 12, 2012, the motion for summary judgment was denied without prejudice.  UI’s knowledge of the current conditions at the English Station site is insufficient to make a reliable update of the original $1.9 million remediation estimate.  Management cannot presently assess the potential financial impact, if any, of the suit, and thus has not recorded a liability related to it.
	On April 8, 2013, DEEP issued an administrative order addressed to UI, QE, Evergreen Power, Asnat and others, ordering the parties to take certain actions related to investigating and remediating the English Station site.  Mediation is scheduled to take place in the fourth quarter of 2013.  At this time, management cannot predict the financial impact on UI of the DEEP order or other matters relating to this site.
	In April 1999, UI completed the sale of its Bridgeport Harbor Station and New Haven Harbor Station generating plants in compliance with Connecticut’s electric utility industry restructuring legislation.  With respect to the portion of the New Haven Harbor Station site that UI retained, UI has performed an additional environmental analysis, indicating that approximately $3.2 million in remediation expenses will be incurred.  Actual remediation costs may be higher or lower than what is currently estimated.  The required remediation is virtually all on transmission‑related property and UI has accrued these estimated expenses, which were recovered in transmission rates.
	From 1961 to 1976, UI owned a parcel of property in Derby, Connecticut, on which it operated an oil‑fired electric generating unit.  For several years, DEEP has been monitoring and remediating a migration of fuel oil contamination from a neighboring parcel of property into the adjacent Housatonic River.  Based on its own investigation to date, UI believes it has no responsibility for this contamination.  If regulatory agencies determine that UI is responsible for the cost of these remediation activities, UI may incur substantial costs, no estimate of which is currently available.
	The Gas Companies own or have previously owned properties where Manufactured Gas Plants (MGPs) had historically operated.  MGP operations have led to contamination of soil and groundwater with petroleum hydrocarbons, benzene and metals, among other things, at these properties, the regulation and cleanup of which is regulated by the federal Resource Conservation and Recovery Act as well as other federal and state statutes and regulations.  Each of the Gas Companies has or had an ownership interest in one of such properties contaminated as a result of MGP-related activities.  Under the existing regulations, the cleanup of such sites requires state and at times, federal, regulators’ involvement and approval before cleanup can commence.  In certain cases, such contamination has been evaluated, characterized and remediated.  In other cases, the sites have been evaluated and characterized, but not yet remediated.  Finally, at some of these sites, the scope of the contamination has not yet been fully characterized; no liability was recorded in respect of these sites as of September 30, 2013.  In the past, the Gas Companies have received approval for the recovery of MGP-related remediation expenses from customers through rates and will seek recovery in rates for ongoing MGP-related remediation expenses for all of their MGP sites.
	SCG owns properties on Housatonic Avenue in Bridgeport, and on Chapel Street in New Haven, and CNG owns a property located on Columbus Boulevard in Hartford, all of which are former MGP sites.  Costs associated with the remediation of the sites could be significant and will be subject to a review by PURA as to whether these costs are recoverable in rates.  UIL Holdings cannot presently estimate the costs of remediation or the likelihood of recoverability.  As a result, as of September 30, 2013, no liabilities related to these properties have been recorded.
	Berkshire owns property on Mill Street in Greenfield, Massachusetts, a former MGP site.  UIL Holdings estimates that expenses associated with the remaining remedial activities, as well as the required ongoing monitoring and reporting to the Massachusetts Department of Environmental Protection will most likely amount to $4.3 million and has recorded a liability and offsetting regulatory asset for such expenses as of September 30, 2013.  Historically, Berkshire has received approval from the DPU for recovery of environmental expenses in its customer rates.  While management cannot predict the exact costs of the ongoing and future remediation and monitoring expenses, Berkshire will seek regulatory rate recovery of these expenses.
	Berkshire formerly owned a site on East Street (the East Street Site) in Pittsfield, Massachusetts, a former MGP site.  The East Street Site is part of a larger site known as the GE–Pittsfield/Housatonic River Site.  Berkshire sold the East Street Site to the General Electric Company (GE) in the 1970s and was named a potentially responsible party by the EPA in 1990.  In December 2002, Berkshire reached a settlement with GE (the Settlement Agreement) which provides, among other things, a framework for Berkshire and GE to allocate various monitoring and remediation costs at the East Street Site.  As of September 30, 2013, UIL Holdings has accrued approximately $2.0 million and established a regulatory asset for these and future costs incurred by GE in responding to releases of hazardous substances at the East Street Site.  Historically, Berkshire has received approval from the DPU for recovery of remediation expenses in its customer rates.  While management cannot predict the exact costs of the ongoing and future remediation and monitoring expenses, Berkshire will seek regulatory rate recovery of these expenses.
	Middletown/Norwalk Transmission Project
	The general contractor and two subcontractors responsible for civil construction work in connection with the installation of UI’s portion of the Middletown/Norwalk Transmission Project’s underground electric cable system filed lawsuits in Connecticut state court on September 22, 2009, March 23, 2009 and January 25, 2010, respectively.  The claims, as revised by the general contractor in October 2011, sought payment for change order requests of approximately $33.3 million, a 10% general contractor mark-up on any approved subcontractor change order claims (approximately $2.3 million), interest, costs, and attorneys' fees.  In December 2011, UI settled claims brought by the two subcontractors and their respective lawsuits were dismissed with prejudice, reducing UI’s estimate of the general contractor’s claims to approximately $7.7 million, exclusive of the contractor’s claims for interest, costs, and attorneys’ fees.    UI also is pursuing an indemnification claim against the general contractor for the payments made in settlement to the two subcontractors.
	On September 3, 2013, a Memorandum of Decision was issued by the court finding for UI on all claims but one related to certain change orders, and ordering UI to pay the Contractor approximately $1.3 million, which has been accrued.  The decision also found against UI on the indemnification claims.  On October 22, 2013, the general contractor filed an appeal of the Court’s ruling.  UI expects to recover any amounts paid to resolve the contractor and subcontractor claims through UI’s transmission revenue requirements.
	On April 30, 2013, an affiliate of the general contractor for the Middletown/Norwalk Transmission Project, purporting to act as a shareholder on behalf of UIL Holdings, filed a complaint against the UIL Holdings Board of Directors alleging that the directors breached a fiduciary duty by failing to undertake an independent investigation in response to a letter from the affiliate asking for an investigation regarding alleged improper practices by UI in connection with the Middletown/Norwalk Transmission Project.  The complaint seeks an order for such an investigation, and seeks recovery by the complainant of its expenses and costs in the action.  The defendants have filed a motion to dismiss which included an affidavit stating that an investigation had commenced shortly after receiving the letter from the affiliate.  UIL Holdings believes the claims are without merit and cannot presently estimate the potential liability, if any, as a result of this complaint.

FAIR_VALUE_MEASUREMENTS

FAIR VALUE MEASUREMENTS	9 Months Ended
	Sep. 30, 2013
FAIR VALUE MEASUREMENTS [Abstract]	'
FAIR VALUE MEASUREMENTS	'
	(K) FAIR VALUE MEASUREMENTS
	As required by ASC 820 “Fair Value Measurements and Disclosures,” financial assets and liabilities are classified in their entirety, based on the lowest level of input that is significant to the fair value measurement.  UIL Holdings’ assessment of the significance of a particular input to the fair value measurement requires judgment, and may affect the valuation of the fair value of assets and liabilities and their placement within the fair value hierarchy levels.
	The following tables set forth the fair value of UIL Holdings’ financial assets and liabilities, other than pension benefits and other postretirement benefits, as of September 30, 2013 and December 31, 2012.
			Fair Value Measurements Using
			Quoted Prices in
			Active Markets				Significant Other			Significant
			for Identical				Observable Inputs			Unobservable
			Assets (Level 1)				(Level 2)			Inputs (Level 3)			Total
	30-Sep-13		(In Thousands)
	Assets:
	Derivative assets		$	-			$	-		$	54,822		$	54,822
	Noncurrent investments available for sale			10,725				-			-			10,725
	Deferred Compensation Plan			3,604				-			-			3,604
	Supplemental retirement benefit trust life insurance policies			-				7,317			-			7,317
			$	14,329			$	7,317		$	54,822		$	76,468
	Liabilities:
	Derivative liabilities		$	-			$	-		$	202,577		$	202,577
	Long-term debt			-				1,757,983			-			1,757,983
			$	-			$	1,757,983		$	202,577		$	1,960,560
	Net fair value assets/(liabilities), September 30, 2013		$	14,329			$	(1,750,666	)	$	(147,755	)	$	(1,884,092	)
	31-Dec-12
	Assets:
	Derivative assets		$	-			$	-		$	79,838		$	79,838
	Noncurrent investments available for sale			9,902				-			-			9,902
	Deferred Compensation Plan			3,745				-			-			3,745
	Supplemental retirement benefit trust life insurance policies			-				6,438			-			6,438
			$	13,647			$	6,438		$	79,838		$	99,923
	Liabilities:
	Derivative liabilities		$	-			$	-		$	255,443		$	255,443
	Long-term debt			-				1,886,440			-			1,886,440
			$	-			$	1,886,440		$	255,443		$	2,141,883
	Net fair value assets/(liabilities), December 31, 2012		$	13,647			$	(1,880,002	)	$	(175,605	)	$	(2,041,960	)
	Fair value measurements categorized in Level 3 of the fair value hierarchy are prepared by individuals with expertise in valuation techniques, pricing of energy and energy-related products, and accounting requirements.  The derivative assets and liabilities consist primarily of CfDs and weather insurance contracts.    The determination of fair value of the CfDs was based on a probability-based expected cash flow analysis that was discounted at the September 30, 2013 or December 31, 2012 risk-free interest rates, as applicable, and an adjustment for non-performance risk using credit default swap rates.  Certain management assumptions were required, including development of pricing that extended over the term of the contracts.  UIL Holdings believes this methodology provides the most reasonable estimates of the amount of future discounted cash flows associated with the CfDs.  Additionally, on a quarterly basis, analytics are performed to ensure that the fair value of the derivatives is consistent with changes, if any, in the various fair value model inputs.  For information regarding the determination of the fair value of the weather insurance contracts, see Note (A) “Business Organization and Statement of Accounting Policies – Derivatives.”  Additional quantitative information about Level 3 fair value measurements is as follows:
		Unobservable Input		Range
	Contracts for differences	Risk of non-performance			0.33% - 0.92	%
		Discount rate			2.02% - 2.83	%
		Forward pricing ($ per MW)		$	1.40 - $9.83
	Significant isolated changes in the risk of non-performance, the discount rate or the contract term pricing would result in an inverse change in the fair value of the CfDs.
	In addition, UIL performed an assessment of risks related to obtaining regulatory, legal and siting approvals, as well as obtaining financing resources and ultimately attaining commercial operation.   PURA has determined that changes in fair value associated with the CfDs are fully recoverable.  As a result, such changes have no impact on UIL Holdings’ net income.
	The determination of the fair value of the supplemental retirement benefit trust life insurance policies was based on quoted prices as of September 30, 2013 and December 31, 2012 in the active markets for the various funds within which the assets are held.
	Long-term debt is carried at cost on the consolidated balance sheet.  The fair value of long-term debt as displayed in the table above is based on evaluated prices that reflect significant observable market information such as reported trades, actual trade information of similar securities, benchmark yields, broker/dealer quotes of new issue prices and relevant credit information.
	The following tables set forth a reconciliation of changes in the fair value of the assets and liabilities above that are classified as Level 3 in the fair value hierarchy for the nine-month period ended September 30, 2013.
			Nine Months Ended
			30-Sep-13
			(In Thousands)
	Net fair value assets/(liabilities), December 31, 2012		$	(175,605	)
	Unrealized gains and (losses), net
	Included in regulatory assets/(liabilities)			28,850
	Settlements			(1,000	)
	Net fair value assets/(liabilities), September 30, 2013		$	(147,755	)
	Change in unrealized gains (losses), net relating to net fair value
	assets/(liabilities), still held as of September 30, 2013		$	28,850
	The following table sets forth a reconciliation of changes in the net regulatory asset/(liability) balances that were established to recover any unrealized gains/(losses) associated with the CfDs for the nine-month period ended September 30, 2013. The amounts offset the net CfDs liabilities included in the derivative liabilities detailed above.
			Nine Months Ended
			September 30, 2013
			(In Thousands)
	Net regulatory assets/(liabilities), December 31, 2012		$	176,605
	Unrealized (gains) and losses, net			(28,850	)
	Net regulatory assets/(liabilities), September 30, 2013		$	147,755

SEGMENT_INFORMATION

SEGMENT INFORMATION	9 Months Ended
	Sep. 30, 2013
SEGMENT INFORMATION [Abstract]	'
SEGMENT INFORMATION	'
	(M)  SEGMENT INFORMATION
	UIL Holdings is organized between Electric Distribution, Electric Transmission and Gas Distribution reporting segments based on several factors including, but not limited to, the nature of each segment’s products and services, the sources of operating revenues and expenses and the regulatory environment in which each segment operates.     The following measures of segment profit and loss are utilized by management to make decisions about allocating resources to the segments and assessing performance.  The following table reconciles certain segment information with that provided in UIL Holdings’ Consolidated Financial Statements.  In the table, distribution includes all electric utility revenue and expenses except for transmission, which is provided in a separate column.  “Other” includes the information for the remainder of UIL Holdings’ non‑utility activities and unallocated corporate costs, including minority interest investments and administrative costs.  Revenues from inter‑segment transactions are not material.  All of UIL Holdings’ revenues are derived in the United States.
			Three months ended September 30, 2013
			Electric Distribution and Transmission
			Distribution		Transmission		Total		Gas Distribution			Other			Total
			(In Thousands)
	Operating Revenues		$	151,369	$	67,830	$	219,199	$	97,244		$	35		$	316,478
	Purchased power and gas			37,314		-		37,314		37,343			-			74,657
	Operation and maintenance			43,387		11,532		54,919		36,271			(1,380	)		89,810
	Transmission wholesale			-		28,659		28,659		-			-			28,659
	Depreciation and amortization			28,397		4,152		32,549		17,202			1,010			50,761
	Taxes - other than income taxes			13,390		10,466		23,856		8,410			123			32,389
	Regulatory disallowances			17,543		-		17,543		-			-			17,543
	Operating Income			11,338		13,021		24,359		(1,982	)		282			22,659
	Other Income and (Deductions), net			3,534		746		4,280		234			639			5,153
	Interest Charges, net			6,088		2,763		8,851		7,507			6,041			22,399
	Income from Equity Investments			3,930		-		3,930		-			-			3,930
	Income (Loss) Before Income Taxes			12,714		11,004		23,718		(9,255	)		(5,120	)		9,343
	Income taxes			5,607		3,890		9,497		(2,970	)		(2,341	)		4,186
	Net Income (Loss)			7,107		7,114		14,221		(6,285	)		(2,779	)		5,157
	Less:
	Preferred Stock Dividends of Subsidiary, Noncontrolling Interests			-		-		-		13			-			13
	Net Income (Loss) attributable to UIL Holdings		$	7,107	$	7,114	$	14,221	$	(6,298	)	$	(2,779	)	$	5,144
	Total Capital Expenditures (1)		$	-	$	-	$	41,310	$	25,968		$	12,910		$	80,188
			Three months ended September 30, 2012
			Electric Distribution and Transmission
			Distribution		Transmission		Total		Gas Distribution			Other			Total
			(In Thousands)
	Operating Revenues		$	154,165	$	62,932	$	217,097	$	105,755		$	36		$	322,888
	Purchased power and gas			43,565		-		43,565		51,570			-			95,135
	Operation and maintenance			42,599		9,840		52,439		35,788			(946	)		87,281
	Transmission wholesale			-		26,565		26,565		-			-			26,565
	Depreciation and amortization			25,286		3,787		29,073		16,410			796			46,279
	Taxes - other than income taxes			12,202		8,256		20,458		8,011			33			28,502
	Regulatory disallowances			-		-		-		-			-			-
	Operating Income (Loss)			30,513		14,484		44,997		(6,024	)		153			39,126
	Other Income and (Deductions), net			6,071		863		6,934		372			110			7,416
	Interest Charges, net			7,242		3,148		10,390		7,070			5,893			23,353
	Income from Equity Investments			3,421		-		3,421		-			-			3,421
	Income (Loss) Before Income Taxes			32,763		12,199		44,962		(12,722	)		(5,630	)		26,610
	Income taxes			14,597		3,955		18,552		(5,423	)		(2,294	)		10,835
	Net Income (Loss)			18,166		8,244		26,410		(7,299	)		(3,336	)		15,775
	Less:
	Preferred Stock Dividends of Subsidiary, Noncontrolling Interests			-		-		-		26			-			26
	Net Income (Loss) attributable to UIL Holdings		$	18,166	$	8,244	$	26,410	$	(7,325	)	$	(3,336	)	$	15,749
	Total Capital Expenditures (1)		$	-	$	-	$	39,584	$	22,968		$	6,489		$	69,041
			Nine months ended September 30, 2013
			Electric Distribution and Transmission
			Distribution		Transmission		Total		Gas Distribution			Other			Total
			(In Thousands)
	Operating Revenues		$	421,959	$	180,412	$	602,371	$	581,115		$	105		$	1,183,591
	Purchased power and gas			105,996		-		105,996		315,520			-			421,516
	Operation and maintenance			132,919		33,212		166,131		111,496			(4,088	)		273,539
	Transmission wholesale			-		65,994		65,994		-			-			65,994
	Depreciation and amortization			72,924		12,123		85,047		58,515			2,975			146,537
	Taxes - other than income taxes			36,860		25,260		62,120		33,769			446			96,335
	Regulatory disallowances			17,543		-		17,543		-			-			17,543
	Operating Income (Loss)			55,717		43,823		99,540		61,815			772			162,127
	Other Income and (Deductions), net			10,687		3,465		14,152		(298	)		1,864			15,718
	Interest Charges, net			19,834		9,104		28,938		22,415			18,180			69,533
	Income from Equity Investments			11,590		-		11,590		-			-			11,590
	Income (Loss) Before Income Taxes			58,160		38,184		96,344		39,102			(15,544	)		119,902
	Income taxes			24,464		13,474		37,938		14,770			(7,704	)		45,004
Net Income (Loss)			33,696		24,710		58,406		24,332			(7,840	)		74,898
Less:
Preferred Stock Dividends of Subsidiary, Noncontrolling Interests			-		-		-		39			-			39
Net Income (Loss) attributable to UIL Holdings		$	33,696	$	24,710	$	58,406	$	24,293		$	(7,840	)	$	74,859
Total Capital Expenditures (1)		$	-	$	-	$	124,437	$	63,771		$	35,964		$	224,172
		Nine months ended September 30, 2012
		Electric Distribution and Transmission
		Distribution		Transmission		Total		Gas Distribution			Other			Total
		(In Thousands)
Operating Revenues		$	424,060	$	162,729	$	586,789	$	476,644		$	114		$	1,063,547
Purchased power and gas			118,581		-		118,581		242,328			-			360,909
Operation and maintenance			130,071		30,791		160,862		101,944			(1,919	)		260,887
Transmission wholesale			-		59,847		59,847		-			-			59,847
Depreciation and amortization			66,763		10,942		77,705		56,499			1,682			135,886
Taxes - other than income taxes			32,828		19,858		52,686		30,111			127			82,924
Regulatory disallowances			-		-		-		-			-			-
Operating Income (Loss)			75,817		41,291		117,108		45,762			224			163,094
Other Income and (Deductions), net			13,556		2,889		16,445		4,286			474			21,205
Interest Charges, net			21,732		10,042		31,774		21,281			17,280			70,335
Income from Equity Investments			11,823		-		11,823		-			-			11,823
Income (Loss) Before Income Taxes			79,464		34,138		113,602		28,767			(16,582	)		125,787
Income taxes			36,163		10,709		46,872		10,807			(6,755	)		50,924
Net Income (Loss)			43,301		23,429		66,730		17,960			(9,827	)		74,863
Less:
Preferred Stock Dividends of Subsidiary, Noncontrolling Interests			-		-		-		65			-			65
Net Income (Loss) attributable to UIL Holdings		$	43,301	$	23,429	$	66,730	$	17,895		$	(9,827	)	$	74,798
Total Capital Expenditures (1)		$	-	$	-	$	134,769	$	55,840		$	23,631		$	214,240
		Electric Distribution and Transmission (2)
		Distribution		Transmission		Total		Gas Distribution			Other			Total
Total Assets at September 30, 2013		$	-	$	-	$	2,847,227	$	1,934,249		$	84,302		$	4,865,778
Total Assets at December 31, 2012		$	-	$	-	$	2,875,765	$	1,993,560		$	90,042		$	4,959,367
-1	Information for segmenting total capital expenditures between Distribution and Transmission is not available. Total Electric Distribution and Transmission capital expenditures are disclosed in the Total Electric Distribution and Transmission column.
-2	Information for segmenting total assets between Distribution and Transmission is not available.  Total Electric Distribution and Transmission assets are disclosed in the Total Electric Distribution and Transmission column.  Net plant in service is segregated by segment and, as of September 30, 2013, was $1,099.1 million and $644.7 million for Distribution and Transmission, respectively.  As of December 31, 2012, net plant in service was $1,058.6 million and $607.8 million for Distribution and  Transmission, respectively.

BUSINESS_ORGANIZATION_AND_STAT1

BUSINESS ORGANIZATION AND STATEMENT OF ACCOUNTING POLICIES (Policies)	9 Months Ended
	Sep. 30, 2013
BUSINESS ORGANIZATION AND STATEMENT OF ACCOUNTING POLICIES [Abstract]	'
Basis of Presentation	'
	Basis of Presentation
	The financial statements of UIL Holdings are prepared on a consolidated basis and therefore include the accounts of UIL Holdings’ majority-owned subsidiaries noted above.  The year‑end balance sheet data was derived from audited financial statements, but does not include all disclosures required by accounting principles generally accepted in the United States of America (GAAP).  Certain information and footnote disclosures, which are normally included in financial statements prepared in accordance with GAAP, have been condensed or omitted in accordance with Securities and Exchange Commission (SEC) rules and regulations.  UIL Holdings believes that the disclosures made are adequate to make the information presented not misleading.  The information presented in the Consolidated Financial Statements reflects all adjustments which, in the opinion of UIL Holdings, are necessary for a fair statement of the financial position and results of operations for the interim periods described herein.  All such adjustments are of a normal and recurring nature.  The results for the nine-month period ended September 30, 2013 are not necessarily indicative of the results for the entire fiscal year ending December 31, 2013.
	The Income from Equity Investments line item on UIL Holdings Consolidated Statement of Income, which was previously presented below the Income Taxes line item, is now being presented above the Income Taxes line item.
	The Company has revised its previously issued annual financial statements for a correction in the 2012 Consolidated Balance Sheet.  The effect of this revision on the balance sheet is a $13.1 million adjustment increasing accounts payable and decreasing accrued liabilities in the Consolidated Balance Sheet as of December 31, 2012.  This adjustment is not considered to be material to previously issued financial statements.  Additionally, certain immaterial amounts that were reported in the Consolidated Balance Sheet and Consolidated Statement of Income in previous periods have been reclassified to conform to the current presentation.
Derivatives	'
	Derivatives
	UIL Holdings’ regulated subsidiaries are parties to contracts, and involved in transactions, that are derivatives.  The fair values of the gross derivative assets and liabilities as of September 30, 2013 and December 31, 2012 were as follows:
			September 30,			December 31,
			2013			2012
			(In Thousands)
	Gross derivative assets:
	Current Assets		$	9,063		$	12,671
	Deferred Charges and Other Assets		$	45,759		$	67,167
	Gross derivative liabilties:
	Current Liabilities		$	26,915		$	30,804
	Noncurrent Liabilities		$	175,662		$	224,639
	Contracts for Differences (CfDs)
	Pursuant to Connecticut’s 2005 Energy Independence Act, the Connecticut Public Utilities Regulatory Authority (PURA) solicited bids to create new or incremental capacity resources in order to reduce federally mandated congestion charges, and selected four new capacity resources.  To facilitate the transactions between the selected capacity resources and Connecticut electric customers, and provide the commitment necessary for owners of these resources to obtain necessary financing, PURA required that UI and The Connecticut Light and Power Company (CL&P) execute long-term contracts with the selected resources.  In August 2007, PURA approved four CfDs, each of which specifies a capacity quantity and a monthly settlement that reflects the difference between a forward market price and the contract price.  UI executed two of the contracts and CL&P executed the other two contracts.  The costs or benefits of each contract will be paid by or allocated to customers and will be subject to a cost-sharing agreement whereby approximately 20% of the cost or benefit is borne by or allocated to UI customers and approximately 80% is borne by or allocated to CL&P customers.
	PURA has determined that costs associated with these CfDs will be recoverable by UI and CL&P, and in accordance with ASC 980 “Regulated Operations,” UI has deferred recognition of costs (a regulatory asset) or obligations (a regulatory liability).  The CfDs are marked-to-market in accordance with ASC 815 “Derivatives and Hedging.”  For those CfDs signed by CL&P, UI records its approximate 20% portion pursuant to the cost-sharing agreement noted above.  As of September 30, 2013, UI has recorded a gross derivative asset of $54.8 million, a regulatory asset of $147.8 million, and a gross derivative liability of $202.6 million ($134.0 million of which is related to UI’s portion of CL&P’s derivative liabilities).  See Note (K) “Fair Value of Financial Instruments” for additional CfD information.
	The unrealized gains and losses from fair value adjustments to these derivatives recorded in regulatory assets or regulatory liabilities for the three- and nine-month periods ended September 30, 2013 and 2012 were as follows:
			Three Months Ended						Nine Months Ended
			September 30,						September 30,
			2013			2012			2013			2012
			(In Thousands)						(In Thousands)
	Regulatory Assets - Derivative liabilities		$	(5,585	)	$	(1,832	)	$	(28,849	)	$	(7,613	)
	Regulatory Liabilities - Derivative assets		$	-		$	(27	)	$	-		$	(15	)
	The increased unrealized losses in the three- and nine-month periods ended September 30, 2013 compared to September 30, 2012 is primarily due to increases in forward pricing.
Weather Insurance Contracts	'
	Weather Insurance Contracts
	On an annual basis, the Gas Companies each assess the need for weather insurance contracts for the upcoming heating season in order to provide financial protection from significant weather fluctuations.  According to the terms of such contracts, if temperatures are warmer than normal at a prescribed level for the contract period, a payment is received by the gas company; in addition, under certain of the contracts, if temperatures are colder than normal at a prescribed level for the contract period, the gas company is required to make a payment.  The premiums paid are amortized over the terms of the contracts.  The intrinsic value of the contracts is carried on the balance sheet with changes in value recorded in the income statement as Other Income and (Deductions).
	In October of 2013, CNG entered into a weather insurance contract for the period of November 1, 2013 through December 31, 2013.  If temperatures are warmer than normal, CNG will receive a payment, up to a maximum of $1.5 million; however, if temperatures are colder than normal, CNG will make a payment of up to a maximum of $1 million.  As a result of the request in CNG’s current rate proceeding for a decoupling mechanism which is anticipated to go into effect in January 2014, the contract does not extend into the 2014 portion of the heating season.
	In October 2013, Berkshire entered into a weather insurance contract for the winter period of November 1, 2013 through April 30, 2014.  If temperatures are warmer than normal, Berkshire will receive a payment, up to a maximum of $1 million; however, if temperatures are colder than normal, Berkshire will make a payment of up to a maximum of $0.2 million.
	In September 2013, SCG entered into a weather insurance contract for the winter period of November 1, 2013 through April 30, 2014.  If temperatures are warmer than normal, SCG will receive a payment, up to a maximum of $3 million; however, if temperatures are colder than normal, SCG will make a payment of up to a maximum of $2 million.
	In October 2012, SCG and CNG each entered into weather insurance contracts for the winter period of November 1, 2012 through April 30, 2013.  If temperatures were warmer than normal, SCG and CNG each would have received a payment, up to a maximum of $3 million; however, if temperatures were colder than normal, SCG and CNG each would have made a payment of up to a maximum of $2 million.  Upon the expiration of their respective contracts, SCG and CNG neither received nor made a payment since the variation from normal weather during the contract period did not reach the prescribed level stated in the contracts.
	In November 2011, Berkshire entered into a weather insurance contract for calendar year 2012 in order to provide financial protection from significant weather fluctuations.  According to the terms of the contract, because temperatures were warmer than normal for the contract period, Berkshire received a payment of $1 million on January 8, 2013.  The premiums paid were amortized over the term of the contract.  The intrinsic value of the contract is carried on the balance sheet, which totaled $1 million at December 31, 2012, with changes in value recorded in the income statement as Other Income and (Deductions).
Earnings per Share	'
	Earnings per Share
	The following table presents a reconciliation of the basic and diluted earnings per share calculations for the three- and nine‑month periods ended September 30, 2013 and 2012:
			Three Months Ended September 30,						Nine Months Ended September 30,
			2013			2012			2013			2012
			(In Thousands, except per share amounts)
	Numerator:
	Net income		$	5,144		$	15,749		$	74,859		$	74,798
	Less:  Net income allocated to unvested units			5			23			83			126
	Net income attributable to common shareholders		$	5,139		$	15,726		$	74,776		$	74,672
	Denominator:
	Basic average number of shares outstanding			50,989			50,799			50,956			50,760
	Effect of dilutive securities			242			233			281			244
	Diluted average number of shares outstanding			51,231			51,032			51,237			51,004
	Earnings per share:
	Basic		$	0.1		$	0.31		$	1.47		$	1.47
	Diluted		$	0.1		$	0.31		$	1.46		$	1.46
	All outstanding options to purchase shares of common stock during the nine-month periods ending September 30, 2013 and 2012 and the three-month period ending September 30, 2012 were included in the computation of diluted earnings per share because the options’ exercise prices were lower than the average market price of UIL Holdings’ common shares during such period.  There were no outstanding options to purchase shares of common stock during the three-month period ending September 30, 2013.
Equity Investments	'
	Equity Investments
	UI is party to a 50-50 joint venture with NRG affiliates in GenConn, which operates two peaking generation plants in Connecticut.  UI’s investment in GenConn is being accounted for as an equity investment, the carrying value of which was $126.6 million and $124.8 million as of September 30, 2013 and December 31, 2012, respectively.  As of September 30, 2013, there were approximately $4.0 million of undistributed earnings from UI’s equity investment in GenConn.
	UI’s pre-tax income from its equity investment in GenConn was $11.6 million and $11.8 million for the nine-month periods ended September 30, 2013 and 2012, respectively.  The decline in 2013 earnings compared to 2012 is primarily due to the absence in the first quarter 2013 of non-recurring adjustments recorded in the first quarter of 2012 largely relating to 2011.  UI’s pre-tax income from its equity investment in GenConn was $3.9 million and $3.4 million for the three‑month periods ended September 30, 2013 and 2012, respectively.
	Cash distributions from GenConn are reflected as either distributions of earnings or as returns of capital in the operating and investing sections of the Consolidated Statement of Cash Flows, respectively.  UI received cash distributions from GenConn of $9.8 million and $17.6 million during the nine-month periods ended September 30, 2013 and 2012, respectively.  Due to timing, UI did not receive any cash distributions from GenConn during the three‑month period ended September 30, 2013 but received distributions of $8.2 million in October of 2013.  UI received cash distributions from GenConn of $4.7 million during the three-month period ended September 30, 2012.
Regulatory Accounting	'
	Regulatory Accounting
	Unless otherwise stated below, all of UIL Holdings’ regulatory assets earn a return.  UIL Holdings’ regulatory assets and liabilities as of September 30, 2013 and December 31, 2012 included the following:
	Remaining Period			September 30,			December 31,
				2013			2012
				(In Thousands)
	Regulatory Assets:
	Nuclear plant investments – above market	(a)		$	238,868		$	252,498
	Connecticut Yankee	Not applicable			-			11,129
	Unamortized redemption costs	8 to 20 years			11,502			12,103
	Pension and other post-retirement benefit plans	(b)			444,038			458,019
	Environmental remediation costs	4 to 5 years			16,754			14,772
	Hardship programs	(c)			23,833			29,852
	Debt premium	1 to 24 years			35,671			41,016
	Deferred purchased gas	(d)			-			12,444
	Unfunded future income taxes	(e)			27,201			17,319
	Contracts for differences	(f)			147,726			176,597
	Excess generation service charge	(g)			8,228			8,864
	Deferred transmission income/expense	(h)			10,744			21,379
	Storm costs	(i)			15,797			52,009
	Other	(j)			27,825			27,449
	Total regulatory assets				1,008,187			1,135,450
	Less current portion of regulatory assets				98,323			120,935
	Regulatory Assets, Net			$	909,864		$	1,014,515
	Regulatory Liabilities:
	Accumulated deferred investment tax credits	30 years		$	4,502		$	4,612
	Income taxes due principally to book-tax differences	(j)			57,828			41,928
	Deferred gain on sale of property	(a)			37,933			37,933
	Middletown/Norwalk local transmission network service collections	36 years			21,545			21,975
	Pension and other post-retirement benefit plans	1 to 7 years			11,985			15,016
	Deferred income taxes	(e)			44,522			41,816
	Asset retirement obligation	(k)			4,254			4,995
	Deferred purchased gas	(d)			11,893			-
	Low income programs	(l)			23,509			17,651
	Asset removal costs	(j)			254,131			243,854
	Other	(j)			22,203			36,660
	Total regulatory liabilities				494,305			466,440
	Less current portion of regulatory liabilities				7,135			21,284
	Regulatory Liabilities, Net			$	487,170		$	445,156
	(a) Asset/Liability relates to the Competitive Transition Assessment (CTA).  Total CTA costs recovery and stranded cost amortization were substantially completed in the third quarter of 2013.  The remaining balances are fully offset by amounts primarily included in income taxes, due principally to book-tax differences.  As a result of the outcome of UI’s 2013 distribution rate request, PURA approved UI’s proposed rate treatment to leave CTA rates unchanged until January 1, 2014 at which point the charge will end and the remaining balances will be extinguished.
	(b) Asset life is dependent upon timing of final pension plan distribution; balance, which is fully offset by a corresponding liability, is recalculated each year in accordance with ASC 715 "Compensation-Retirement Benefits." See Note (G) “Pension and Other Benefits” for additional information.
	(c) Hardship customer accounts deferred for future recovery to the extent they exceed the amount in rates.
	(d) Deferred purchase gas costs balances at the end of the rate year are normally recorded/returned in the next year.
	(e) The balance will be extinguished when the asset, which is fully offset by a corresponding liability, or liability has been realized or settled, respectively.
	(f) Asset life is equal to delivery term of related contracts (which vary from approximately 7 - 14 years); balance fluctuates based upon quarterly market analysis performed on the related derivatives (Note K); amount, which does not earn a return, is fully offset by corresponding derivative asset/liability.  See “-Contracts for Differences” discussion above for additional information.
	(g) Working capital allowance for generation service charge; this amount fluctuates based upon cash inflows and outflows in a given period.
	(h) Regulatory asset or liability which defers transmission income or expense and fluctuates based upon actual revenues and revenue requirements.
	(i) Storm costs include accumulated costs for major storms occurring from January 2009 forward. See Note (C) “Regulatory Proceedings – Electric Distribution and Transmission – Rates” for a discussion of the recovery of these costs.
	(j) Amortization period and/or balance vary depending on the nature, cost of removal and/or remaining life of the underlying assets/liabilities; asset amount includes decoupling ($12.4 million) and certain other amounts that are not currently earning a return. See Note (C) “Regulatory Proceedings – Electric Distribution and Transmission – Rates” for a discussion of the decoupling recovery period.
	(k) The liability will be extinguished simultaneous with the retirement of the assets and settlement of the corresponding asset retirement obligation.
	(l) Various hardship and payment plan programs approved for recovery.
Stock-Based Compensation	'
	Stock-Based Compensation
	Pursuant to the UIL Holdings 2008 Stock and Incentive Compensation Plan (2008 Stock Plan), target amounts of 101,150 and 5,860 performance shares were granted to certain members of management in March and May of 2013, respectively; the averages of the high and low market prices on the grant dates, which approximates fair value, were $38.73 and $41.34 per share, respectively.
	Also in March 2013, UIL Holdings granted a total of 2,033 shares of restricted stock to its President and Chief Executive Officer under the 2008 Stock Plan and in accordance with his employment agreement; the average of the high and low market price on the date of grant, which approximates fair value, was $38.73 per share.  Such shares vest in equal annual installments over a five-year period.
	In May 2013, UIL Holdings granted a total of 21,558 shares of restricted stock to non-employee directors under the 2008 Stock Plan; the average of the high and low market price on the date of grant, which approximates fair value, was $40.69 per share.  Such shares vest in May 2014.
	Also in May 2013, UIL Holdings granted a total of 2,177 shares of restricted stock to its Vice President – Information Technology and Chief Information Officer under the Amended and Restated UIL Holdings 2008 Stock and Incentive Compensation Plan; the average of the high and low market price on the date of grant, which approximates fair value, was $41.34 per share.  Such shares vest in May 2016.
	Total stock-based compensation expense for the nine-month periods ended September 30, 2013 and 2012 was $4.1 million and $3.9 million, respectively.  Total stock-based compensation expense for the three-month periods ended September 30, 2013 and 2012 was $1.1 million and $0.2 million, respectively.
Variable Interest Entities	'
	Variable Interest Entities
	UIL Holdings has identified GenConn as a variable interest entity (VIE), which is accounted for under the equity method.  UIL Holdings is not the primary beneficiary of GenConn, as defined in ASC 810 “Consolidation,” because it shares control of all significant activities of GenConn with its joint venturer, NRG affiliates.  As such, GenConn is not subject to consolidation.  GenConn recovers its costs through CfDs, which are cost of service-based and have been approved by PURA.  As a result, with the achievement of commercial operation by GenConn Devon and GenConn Middletown, UIL Holdings’ exposure to loss is primarily related to the potential for unrecovered GenConn operating or capital costs in a regulatory proceeding, the effect of which would be reflected in the carrying value of UIL Holdings’ 50% ownership position in GenConn and through “Income from Equity Investments” in UIL Holdings’ Consolidated Financial Statements.  Such exposure to loss cannot be determined at this time.  For further discussion of GenConn, see “–Equity Investments” as well as Note (C) “Regulatory Proceedings – Electric Distribution and Transmission – Equity Investment in Peaking Generation.”
	UIL Holdings has identified the selected capacity resources with which UI has CfDs as VIEs and has concluded that UI is not the primary beneficiary as UI does not have the power to direct any of the significant activities of these capacity resources.   As such, UIL Holdings has not consolidated the selected capacity resources.  UI’s maximum exposure to loss through these agreements is limited to the settlement amount under the CfDs as described in “–Derivatives – Contracts for Differences (CfDs)” above.  UI has no requirement to absorb additional losses nor has UI provided any financial or other support during the periods presented that were not previously contractually required.
	UIL Holdings has identified the entities for which UI is required to enter into long-term contracts to purchase Renewable Energy Credits (RECs) as VIEs.  In assessing these contracts for VIE identification and reporting purposes, UIL Holdings has aggregated the contracts based on similar risk characteristics and significance to UI.  UI is not the primary beneficiary as UI does not have the power to direct any of the significant activities of these entities.  UI’s exposure to loss is primarily related to the purchase and resale of the RECs, but, any losses incurred are recoverable through electric rates.  For further discussion of RECs, see Note (C) “Regulatory Proceedings – Electric Distribution and Transmission – New Renewable Source Generation.”
New Accounting Pronouncements	'
	New Accounting Pronouncements
	In July 2013, the FASB issued updated guidance to ASC 740 “Income Taxes” which prescribes the presentation of an unrecognized tax benefit when a net operating loss carryforward, a similar tax loss, or a tax credit carryforward exists.    This guidance is effective during interim and annual periods beginning after December 15, 2013 and is to be applied on a prospective basis.  The implementation of this guidance is not expected to have a material impact on UIL Holdings’ consolidated financial statements.

BUSINESS_ORGANIZATION_AND_STAT2

BUSINESS ORGANIZATION AND STATEMENT OF ACCOUNTING POLICIES (Tables)	9 Months Ended
	Sep. 30, 2013
BUSINESS ORGANIZATION AND STATEMENT OF ACCOUNTING POLICIES [Abstract]	'
Fair Value of Gross Derivative Assets and Liabilities	'
	UIL Holdings’ regulated subsidiaries are parties to contracts, and involved in transactions, that are derivatives.  The fair values of the gross derivative assets and liabilities as of September 30, 2013 and December 31, 2012 were as follows:
			September 30,			December 31,
			2013			2012
			(In Thousands)
	Gross derivative assets:
	Current Assets		$	9,063		$	12,671
	Deferred Charges and Other Assets		$	45,759		$	67,167
	Gross derivative liabilties:
	Current Liabilities		$	26,915		$	30,804
	Noncurrent Liabilities		$	175,662		$	224,639
Unrealized Gains and Losses From Mark-To-Market Adjustments	'
	The unrealized gains and losses from fair value adjustments to these derivatives recorded in regulatory assets or regulatory liabilities for the three- and nine-month periods ended September 30, 2013 and 2012 were as follows:
			Three Months Ended						Nine Months Ended
			September 30,						September 30,
			2013			2012			2013			2012
			(In Thousands)						(In Thousands)
	Regulatory Assets - Derivative liabilities		$	(5,585	)	$	(1,832	)	$	(28,849	)	$	(7,613	)
	Regulatory Liabilities - Derivative assets		$	-		$	(27	)	$	-		$	(15	)
Reconciliation of Basic and Diluted Earnings Per Share	'
	The following table presents a reconciliation of the basic and diluted earnings per share calculations for the three- and nine‑month periods ended September 30, 2013 and 2012:
			Three Months Ended September 30,						Nine Months Ended September 30,
			2013			2012			2013			2012
			(In Thousands, except per share amounts)
	Numerator:
	Net income		$	5,144		$	15,749		$	74,859		$	74,798
	Less:  Net income allocated to unvested units			5			23			83			126
	Net income attributable to common shareholders		$	5,139		$	15,726		$	74,776		$	74,672
	Denominator:
	Basic average number of shares outstanding			50,989			50,799			50,956			50,760
	Effect of dilutive securities			242			233			281			244
	Diluted average number of shares outstanding			51,231			51,032			51,237			51,004
	Earnings per share:
	Basic		$	0.1		$	0.31		$	1.47		$	1.47
	Diluted		$	0.1		$	0.31		$	1.46		$	1.46
Regulatory Assets and Liabilities	'
	Unless otherwise stated below, all of UIL Holdings’ regulatory assets earn a return.  UIL Holdings’ regulatory assets and liabilities as of September 30, 2013 and December 31, 2012 included the following:
	Remaining Period			September 30,			December 31,
				2013			2012
				(In Thousands)
	Regulatory Assets:
	Nuclear plant investments – above market	(a)		$	238,868		$	252,498
	Connecticut Yankee	Not applicable			-			11,129
	Unamortized redemption costs	8 to 20 years			11,502			12,103
	Pension and other post-retirement benefit plans	(b)			444,038			458,019
	Environmental remediation costs	4 to 5 years			16,754			14,772
	Hardship programs	(c)			23,833			29,852
	Debt premium	1 to 24 years			35,671			41,016
	Deferred purchased gas	(d)			-			12,444
	Unfunded future income taxes	(e)			27,201			17,319
	Contracts for differences	(f)			147,726			176,597
	Excess generation service charge	(g)			8,228			8,864
	Deferred transmission income/expense	(h)			10,744			21,379
	Storm costs	(i)			15,797			52,009
	Other	(j)			27,825			27,449
	Total regulatory assets				1,008,187			1,135,450
	Less current portion of regulatory assets				98,323			120,935
	Regulatory Assets, Net			$	909,864		$	1,014,515
	Regulatory Liabilities:
	Accumulated deferred investment tax credits	30 years		$	4,502		$	4,612
	Income taxes due principally to book-tax differences	(j)			57,828			41,928
	Deferred gain on sale of property	(a)			37,933			37,933
	Middletown/Norwalk local transmission network service collections	36 years			21,545			21,975
	Pension and other post-retirement benefit plans	1 to 7 years			11,985			15,016
	Deferred income taxes	(e)			44,522			41,816
	Asset retirement obligation	(k)			4,254			4,995
	Deferred purchased gas	(d)			11,893			-
	Low income programs	(l)			23,509			17,651
	Asset removal costs	(j)			254,131			243,854
	Other	(j)			22,203			36,660
	Total regulatory liabilities				494,305			466,440
	Less current portion of regulatory liabilities				7,135			21,284
	Regulatory Liabilities, Net			$	487,170		$	445,156
	(a) Asset/Liability relates to the Competitive Transition Assessment (CTA).  Total CTA costs recovery and stranded cost amortization were substantially completed in the third quarter of 2013.  The remaining balances are fully offset by amounts primarily included in income taxes, due principally to book-tax differences.  As a result of the outcome of UI’s 2013 distribution rate request, PURA approved UI’s proposed rate treatment to leave CTA rates unchanged until January 1, 2014 at which point the charge will end and the remaining balances will be extinguished.
	(b) Asset life is dependent upon timing of final pension plan distribution; balance, which is fully offset by a corresponding liability, is recalculated each year in accordance with ASC 715 "Compensation-Retirement Benefits." See Note (G) “Pension and Other Benefits” for additional information.
	(c) Hardship customer accounts deferred for future recovery to the extent they exceed the amount in rates.
	(d) Deferred purchase gas costs balances at the end of the rate year are normally recorded/returned in the next year.
	(e) The balance will be extinguished when the asset, which is fully offset by a corresponding liability, or liability has been realized or settled, respectively.
	(f) Asset life is equal to delivery term of related contracts (which vary from approximately 7 - 14 years); balance fluctuates based upon quarterly market analysis performed on the related derivatives (Note K); amount, which does not earn a return, is fully offset by corresponding derivative asset/liability.  See “-Contracts for Differences” discussion above for additional information.
	(g) Working capital allowance for generation service charge; this amount fluctuates based upon cash inflows and outflows in a given period.
	(h) Regulatory asset or liability which defers transmission income or expense and fluctuates based upon actual revenues and revenue requirements.
	(i) Storm costs include accumulated costs for major storms occurring from January 2009 forward. See Note (C) “Regulatory Proceedings – Electric Distribution and Transmission – Rates” for a discussion of the recovery of these costs.
	(j) Amortization period and/or balance vary depending on the nature, cost of removal and/or remaining life of the underlying assets/liabilities; asset amount includes decoupling ($12.4 million) and certain other amounts that are not currently earning a return. See Note (C) “Regulatory Proceedings – Electric Distribution and Transmission – Rates” for a discussion of the decoupling recovery period.
	(k) The liability will be extinguished simultaneous with the retirement of the assets and settlement of the corresponding asset retirement obligation.
	(l) Various hardship and payment plan programs approved for recovery.

SUPPLEMENTARY_INFORMATION_Tabl

SUPPLEMENTARY INFORMATION (Tables)	9 Months Ended
	Sep. 30, 2013
SUPPLEMENTARY INFORMATION [Abstract]	'
Supplementary Information	'
		Three Months Ended				Nine Months Ended
		September 30,				September 30,
		2013		2012		2013		2012
		(In Thousands)
	Depreciation and Amortization
	Property, plant and equipment depreciation	$	30,870	$	28,648	$	89,788	$	83,143
	Amortization of nuclear plant regulatory assets		16,782		14,272		39,935		35,433
	Amortization of other regulatory assets		3,105		3,346		16,785		17,272
	Other amortization		4		13		29		38
	Total Amortization		19,891		17,631		56,749		52,743
	Total Depreciation and Amortization	$	50,761	$	46,279	$	146,537	$	135,886
	Taxes - Other than Income Taxes
	Connecticut gross earnings	$	17,780	$	16,438	$	54,873	$	48,290
	Local real estate and personal property		12,417		10,866		34,416		29,630
	Payroll taxes		2,069		1,117		6,584		4,747
	Other		123		81		462		257
	Total Taxes - Other than Income Taxes	$	32,389	$	28,502	$	96,335	$	82,924
	Other Income and (Deductions), net
	Interest income	$	243	$	645	$	1,449	$	1,720
	Allowance for funds used during construction - equity		2,751		1,589		8,085		5,473
	Allowance for funds used during construction - debt		1,533		1,427		5,869		5,231
	Weather insurance		-		-		-		3,488
	TSO Incentives		-		2,745		-		2,745
	Miscellaneous other income and (deductions) - net		626		1,010		315		2,548
	Total Other Income and (Deductions), net	$	5,153	$	7,416	$	15,718	$	21,205

PENSION_AND_OTHER_BENEFITS_Tab

PENSION AND OTHER BENEFITS (Tables)	9 Months Ended
	Sep. 30, 2013
PENSION AND OTHER BENEFITS [Abstract]	'
Components of Net Periodic Benefit Cost for Pension and Other Postretirement Benefits	'
	The following tables represent the components of net periodic benefit cost for pension and other postretirement benefits as well as the actuarial weighted-average assumptionsused in calculating net periodic benefit cost for the three- and nine‑month periods ended September 30, 2013 and 2012:
		Three Months Ended September 30,
		Pension Benefits						Other Postretirement Benefits
		2013			2012			2013			2012
		(In Thousands)
	Components of net periodic benefit cost:
	Service cost	$	3,696		$	3,008		$	481		$	401
	Interest cost		9,988			10,368			1,384			1,562
	Expected return on plan assets		(12,863	)		(11,219	)		(648	)		(626	)
	Amortization of:
	Prior service costs		151			162			(13	)		(17	)
	Transition obligation		-			-			-			98
	Actuarial loss		5,208			3,294			444			241
	Settlements (1)		632			-			-			-
	Net periodic benefit cost	$	6,812		$	5,613		$	1,648		$	1,659
		Nine Months Ended September 30,
		Pension Benefits						Other Postretirement Benefits
		2013			2012			2013			2012
		(In Thousands)
	Components of net periodic benefit cost:
	Service cost	$	11,088		$	9,024		$	1,443		$	1,203
	Interest cost		29,964			31,104			4,152			4,686
	Expected return on plan assets		(38,589	)		(33,657	)		(1,944	)		(1,878	)
	Amortization of:
	Prior service costs		453			486			(39	)		(51	)
	Transition obligation		-			-			-			294
	Actuarial loss		15,624			9,882			1,332			723
	Settlements (1)		632			-			-			-
	Net periodic benefit cost	$	19,172		$	16,839		$	4,944		$	4,977
		Three and Nine Months Ended September 30,
		Pension Benefits						Other Postretirement Benefits
		2013			2012			2013			2012
	Discount rate		4.00% - 4.25	%		5.05% - 5.30	%		4.00% - 4.25	%		5.05% - 5.30	%
	Average wage increase		3.50% - 3.80	%		3.50% - 3.80	%		N/	A		N/	A
	Return on plan assets		7.75% - 8.00	%		7.75% - 8.00	%		5.56% - 8.00	%		5.56% - 8.00	%
	Composite health care trend rate (current year)		N/	A		N/	A		7.5	%		8	%
	Composite health care trend rate (2018 forward)		N/	A		N/	A		5	%		5	%
	(1) Reflects settlement charges resulting from a distribution to a former employee upon retirement
	N/A – not applicable

FAIR_VALUE_MEASUREMENTS_Tables

FAIR VALUE MEASUREMENTS (Tables)	9 Months Ended
	Sep. 30, 2013
FAIR VALUE MEASUREMENTS [Abstract]	'
Fair Value of Financial Assets and Liabilities	'
	The following tables set forth the fair value of UIL Holdings’ financial assets and liabilities, other than pension benefits and other postretirement benefits, as of September 30, 2013 and December 31, 2012.
			Fair Value Measurements Using
			Quoted Prices in
			Active Markets				Significant Other			Significant
			for Identical				Observable Inputs			Unobservable
			Assets (Level 1)				(Level 2)			Inputs (Level 3)			Total
	30-Sep-13		(In Thousands)
	Assets:
	Derivative assets		$	-			$	-		$	54,822		$	54,822
	Noncurrent investments available for sale			10,725				-			-			10,725
	Deferred Compensation Plan			3,604				-			-			3,604
	Supplemental retirement benefit trust life insurance policies			-				7,317			-			7,317
			$	14,329			$	7,317		$	54,822		$	76,468
	Liabilities:
	Derivative liabilities		$	-			$	-		$	202,577		$	202,577
	Long-term debt			-				1,757,983			-			1,757,983
			$	-			$	1,757,983		$	202,577		$	1,960,560
	Net fair value assets/(liabilities), September 30, 2013		$	14,329			$	(1,750,666	)	$	(147,755	)	$	(1,884,092	)
	31-Dec-12
	Assets:
	Derivative assets		$	-			$	-		$	79,838		$	79,838
	Noncurrent investments available for sale			9,902				-			-			9,902
	Deferred Compensation Plan			3,745				-			-			3,745
	Supplemental retirement benefit trust life insurance policies			-				6,438			-			6,438
			$	13,647			$	6,438		$	79,838		$	99,923
	Liabilities:
	Derivative liabilities		$	-			$	-		$	255,443		$	255,443
	Long-term debt			-				1,886,440			-			1,886,440
			$	-			$	1,886,440		$	255,443		$	2,141,883
	Net fair value assets/(liabilities), December 31, 2012		$	13,647			$	(1,880,002	)	$	(175,605	)	$	(2,041,960	)
Additional Quantitative Information about Level 3 Fair Value Measurements	'
	Fair value measurements categorized in Level 3 of the fair value hierarchy are prepared by individuals with expertise in valuation techniques, pricing of energy and energy-related products, and accounting requirements.  The derivative assets and liabilities consist primarily of CfDs and weather insurance contracts.    The determination of fair value of the CfDs was based on a probability-based expected cash flow analysis that was discounted at the September 30, 2013 or December 31, 2012 risk-free interest rates, as applicable, and an adjustment for non-performance risk using credit default swap rates.  Certain management assumptions were required, including development of pricing that extended over the term of the contracts.  UIL Holdings believes this methodology provides the most reasonable estimates of the amount of future discounted cash flows associated with the CfDs.  Additionally, on a quarterly basis, analytics are performed to ensure that the fair value of the derivatives is consistent with changes, if any, in the various fair value model inputs.  For information regarding the determination of the fair value of the weather insurance contracts, see Note (A) “Business Organization and Statement of Accounting Policies – Derivatives.”  Additional quantitative information about Level 3 fair value measurements is as follows:
		Unobservable Input		Range
	Contracts for differences	Risk of non-performance			0.33% - 0.92	%
		Discount rate			2.02% - 2.83	%
		Forward pricing ($ per MW)		$	1.40 - $9.83
Changes in Fair Value of Assets and Liabilities Classified as level 3	'
	The following tables set forth a reconciliation of changes in the fair value of the assets and liabilities above that are classified as Level 3 in the fair value hierarchy for the nine-month period ended September 30, 2013.
			Nine Months Ended
			30-Sep-13
			(In Thousands)
	Net fair value assets/(liabilities), December 31, 2012		$	(175,605	)
	Unrealized gains and (losses), net
	Included in regulatory assets/(liabilities)			28,850
	Settlements			(1,000	)
	Net fair value assets/(liabilities), September 30, 2013		$	(147,755	)
	Change in unrealized gains (losses), net relating to net fair value
	assets/(liabilities), still held as of September 30, 2013		$	28,850
Change in Regulatory Asset/(Liability) Balance	'
	The following table sets forth a reconciliation of changes in the net regulatory asset/(liability) balances that were established to recover any unrealized gains/(losses) associated with the CfDs for the nine-month period ended September 30, 2013. The amounts offset the net CfDs liabilities included in the derivative liabilities detailed above.
			Nine Months Ended
			September 30, 2013
			(In Thousands)
	Net regulatory assets/(liabilities), December 31, 2012		$	176,605
	Unrealized (gains) and losses, net			(28,850	)
	Net regulatory assets/(liabilities), September 30, 2013		$	147,755

SEGMENT_INFORMATION_Tables

SEGMENT INFORMATION (Tables)	9 Months Ended
	Sep. 30, 2013
SEGMENT INFORMATION [Abstract]	'
Reconciliation of Operating Profit (Loss) from Segments to Consolidated Financial Statements	'
	UIL Holdings is organized between Electric Distribution, Electric Transmission and Gas Distribution reporting segments based on several factors including, but not limited to, the nature of each segment’s products and services, the sources of operating revenues and expenses and the regulatory environment in which each segment operates.     The following measures of segment profit and loss are utilized by management to make decisions about allocating resources to the segments and assessing performance.  The following table reconciles certain segment information with that provided in UIL Holdings’ Consolidated Financial Statements.  In the table, distribution includes all electric utility revenue and expenses except for transmission, which is provided in a separate column.  “Other” includes the information for the remainder of UIL Holdings’ non‑utility activities and unallocated corporate costs, including minority interest investments and administrative costs.  Revenues from inter‑segment transactions are not material.  All of UIL Holdings’ revenues are derived in the United States.
			Three months ended September 30, 2013
			Electric Distribution and Transmission
			Distribution		Transmission		Total		Gas Distribution			Other			Total
			(In Thousands)
	Operating Revenues		$	151,369	$	67,830	$	219,199	$	97,244		$	35		$	316,478
	Purchased power and gas			37,314		-		37,314		37,343			-			74,657
	Operation and maintenance			43,387		11,532		54,919		36,271			(1,380	)		89,810
	Transmission wholesale			-		28,659		28,659		-			-			28,659
	Depreciation and amortization			28,397		4,152		32,549		17,202			1,010			50,761
	Taxes - other than income taxes			13,390		10,466		23,856		8,410			123			32,389
	Regulatory disallowances			17,543		-		17,543		-			-			17,543
	Operating Income			11,338		13,021		24,359		(1,982	)		282			22,659
	Other Income and (Deductions), net			3,534		746		4,280		234			639			5,153
	Interest Charges, net			6,088		2,763		8,851		7,507			6,041			22,399
	Income from Equity Investments			3,930		-		3,930		-			-			3,930
	Income (Loss) Before Income Taxes			12,714		11,004		23,718		(9,255	)		(5,120	)		9,343
	Income taxes			5,607		3,890		9,497		(2,970	)		(2,341	)		4,186
	Net Income (Loss)			7,107		7,114		14,221		(6,285	)		(2,779	)		5,157
	Less:
	Preferred Stock Dividends of Subsidiary, Noncontrolling Interests			-		-		-		13			-			13
	Net Income (Loss) attributable to UIL Holdings		$	7,107	$	7,114	$	14,221	$	(6,298	)	$	(2,779	)	$	5,144
	Total Capital Expenditures (1)		$	-	$	-	$	41,310	$	25,968		$	12,910		$	80,188
			Three months ended September 30, 2012
			Electric Distribution and Transmission
			Distribution		Transmission		Total		Gas Distribution			Other			Total
			(In Thousands)
	Operating Revenues		$	154,165	$	62,932	$	217,097	$	105,755		$	36		$	322,888
	Purchased power and gas			43,565		-		43,565		51,570			-			95,135
	Operation and maintenance			42,599		9,840		52,439		35,788			(946	)		87,281
	Transmission wholesale			-		26,565		26,565		-			-			26,565
	Depreciation and amortization			25,286		3,787		29,073		16,410			796			46,279
	Taxes - other than income taxes			12,202		8,256		20,458		8,011			33			28,502
	Regulatory disallowances			-		-		-		-			-			-
	Operating Income (Loss)			30,513		14,484		44,997		(6,024	)		153			39,126
	Other Income and (Deductions), net			6,071		863		6,934		372			110			7,416
	Interest Charges, net			7,242		3,148		10,390		7,070			5,893			23,353
	Income from Equity Investments			3,421		-		3,421		-			-			3,421
	Income (Loss) Before Income Taxes			32,763		12,199		44,962		(12,722	)		(5,630	)		26,610
	Income taxes			14,597		3,955		18,552		(5,423	)		(2,294	)		10,835
	Net Income (Loss)			18,166		8,244		26,410		(7,299	)		(3,336	)		15,775
	Less:
	Preferred Stock Dividends of Subsidiary, Noncontrolling Interests			-		-		-		26			-			26
	Net Income (Loss) attributable to UIL Holdings		$	18,166	$	8,244	$	26,410	$	(7,325	)	$	(3,336	)	$	15,749
	Total Capital Expenditures (1)		$	-	$	-	$	39,584	$	22,968		$	6,489		$	69,041
			Nine months ended September 30, 2013
			Electric Distribution and Transmission
			Distribution		Transmission		Total		Gas Distribution			Other			Total
			(In Thousands)
	Operating Revenues		$	421,959	$	180,412	$	602,371	$	581,115		$	105		$	1,183,591
	Purchased power and gas			105,996		-		105,996		315,520			-			421,516
	Operation and maintenance			132,919		33,212		166,131		111,496			(4,088	)		273,539
	Transmission wholesale			-		65,994		65,994		-			-			65,994
	Depreciation and amortization			72,924		12,123		85,047		58,515			2,975			146,537
	Taxes - other than income taxes			36,860		25,260		62,120		33,769			446			96,335
	Regulatory disallowances			17,543		-		17,543		-			-			17,543
	Operating Income (Loss)			55,717		43,823		99,540		61,815			772			162,127
	Other Income and (Deductions), net			10,687		3,465		14,152		(298	)		1,864			15,718
	Interest Charges, net			19,834		9,104		28,938		22,415			18,180			69,533
	Income from Equity Investments			11,590		-		11,590		-			-			11,590
	Income (Loss) Before Income Taxes			58,160		38,184		96,344		39,102			(15,544	)		119,902
	Income taxes			24,464		13,474		37,938		14,770			(7,704	)		45,004
	Net Income (Loss)			33,696		24,710		58,406		24,332			(7,840	)		74,898
Less:
Preferred Stock Dividends of Subsidiary, Noncontrolling Interests			-		-		-		39			-			39
Net Income (Loss) attributable to UIL Holdings		$	33,696	$	24,710	$	58,406	$	24,293		$	(7,840	)	$	74,859
Total Capital Expenditures (1)		$	-	$	-	$	124,437	$	63,771		$	35,964		$	224,172
		Nine months ended September 30, 2012
		Electric Distribution and Transmission
		Distribution		Transmission		Total		Gas Distribution			Other			Total
		(In Thousands)
Operating Revenues		$	424,060	$	162,729	$	586,789	$	476,644		$	114		$	1,063,547
Purchased power and gas			118,581		-		118,581		242,328			-			360,909
Operation and maintenance			130,071		30,791		160,862		101,944			(1,919	)		260,887
Transmission wholesale			-		59,847		59,847		-			-			59,847
Depreciation and amortization			66,763		10,942		77,705		56,499			1,682			135,886
Taxes - other than income taxes			32,828		19,858		52,686		30,111			127			82,924
Regulatory disallowances			-		-		-		-			-			-
Operating Income (Loss)			75,817		41,291		117,108		45,762			224			163,094
Other Income and (Deductions), net			13,556		2,889		16,445		4,286			474			21,205
Interest Charges, net			21,732		10,042		31,774		21,281			17,280			70,335
Income from Equity Investments			11,823		-		11,823		-			-			11,823
Income (Loss) Before Income Taxes			79,464		34,138		113,602		28,767			(16,582	)		125,787
Income taxes			36,163		10,709		46,872		10,807			(6,755	)		50,924
Net Income (Loss)			43,301		23,429		66,730		17,960			(9,827	)		74,863
Less:
Preferred Stock Dividends of Subsidiary, Noncontrolling Interests			-		-		-		65			-			65
Net Income (Loss) attributable to UIL Holdings		$	43,301	$	23,429	$	66,730	$	17,895		$	(9,827	)	$	74,798
Total Capital Expenditures (1)		$	-	$	-	$	134,769	$	55,840		$	23,631		$	214,240
		Electric Distribution and Transmission (2)
		Distribution		Transmission		Total		Gas Distribution			Other			Total
Total Assets at September 30, 2013		$	-	$	-	$	2,847,227	$	1,934,249		$	84,302		$	4,865,778
Total Assets at December 31, 2012		$	-	$	-	$	2,875,765	$	1,993,560		$	90,042		$	4,959,367
-1	Information for segmenting total capital expenditures between Distribution and Transmission is not available. Total Electric Distribution and Transmission capital expenditures are disclosed in the Total Electric Distribution and Transmission column.
-2	Information for segmenting total assets between Distribution and Transmission is not available.  Total Electric Distribution and Transmission assets are disclosed in the Total Electric Distribution and Transmission column.  Net plant in service is segregated by segment and, as of September 30, 2013, was $1,099.1 million and $644.7 million for Distribution and Transmission, respectively.  As of December 31, 2012, net plant in service was $1,058.6 million and $607.8 million for Distribution and  Transmission, respectively.

BUSINESS_ORGANIZATION_AND_STAT3

BUSINESS ORGANIZATION AND STATEMENT OF ACCOUNTING POLICIES (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Ownership percentage in GenConn [Abstract]	'	'
Ownership percentage in joint venture (in hundredths)	50.00%	'
Error Corrections and Prior Period Adjustments Restatement [Line Items]	'	'
Accounts payable	$109,667	$189,991
Accrued liabilities	-75,623	-85,132
Restatement Adjustment [Member]	'	'
Error Corrections and Prior Period Adjustments Restatement [Line Items]	'	'
Accounts payable	13,100	'
Accrued liabilities	($13,100)	'

BUSINESS_ORGANIZATION_AND_STAT4

BUSINESS ORGANIZATION AND STATEMENT OF ACCOUNTING POLICIES, DERIVATIVES, EARNINGS PER SHARE (Details) (USD $)

3 Months Ended

9 Months Ended

12 Months Ended

Share data in Thousands, except Per Share data, unless otherwise specified

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Dec. 31, 2012

Nov. 01, 2012

Nov. 01, 2012

Nov. 01, 2013

Nov. 01, 2013

Nov. 01, 2013

CapacityResources

CapacityResources

Current Assets [Member]

Current Assets [Member]

Deferred Charges and Other Assets [Member]

Deferred Charges and Other Assets [Member]

Current Liabilities [Member]

Current Liabilities [Member]

Noncurrent Liabilities [Member]

Noncurrent Liabilities [Member]

Weather Insurance Contracts, January 2012 - December 2012 [Member]

Weather Insurance Contracts, November 2012 - April 2013 [Member]

Weather Insurance Contracts, November 2012 - April 2013 [Member]

Weather Insurance Contracts, November 2013 - April 2014 [Member]

Weather Insurance Contracts, November 2013 - December 2013 [Member]

Weather Insurance Contracts, November 2013 - December 2013 [Member]

ContractforDifferences

ContractforDifferences

Berkshire [Member]

Southern Connecticut Gas Company (SCG) [Member]

Connecticut Natural Gas Corporation (CNG) [Member]

Southern Connecticut Gas Company (SCG) [Member]

Connecticut Natural Gas Corporation (CNG) [Member]

Berkshire [Member]

Subsequent Event [Member]

Subsequent Event [Member]

Subsequent Event [Member]

Derivative [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Regulatory asset

$147,800,000

'

$147,800,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Gross derivative liability, UIL's portion of entity

134,000,000

'

134,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Payment received under weather insurance contract

'

'

'

'

'

'

'

'

'

'

'

'

1,000,000

'

'

'

'

'

Maximum receivable amount allowed under weather insurance contract

'

'

'

'

'

'

'

'

'

'

'

'

'

3,000,000

3,000,000

3,000,000

1,500,000

1,000,000

Maximum payable amount allowed under weather insurance contract

'

'

'

'

'

'

'

'

'

'

'

'

'

2,000,000

2,000,000

2,000,000

1,000,000

200,000

Weather insurance contracts

'

'

'

'

'

'

'

'

'

'

'

'

1,000,000

'

'

'

'

'

Derivative fair value, net [Abstract]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Gross derivative asset

54,800,000

'

54,800,000

'

9,063,000

12,671,000

45,759,000

67,167,000

'

'

'

'

'

'

'

'

'

'

Gross derivative liability

202,600,000

'

202,600,000

'

'

'

'

'

26,915,000

30,804,000

175,662,000

224,639,000

'

'

'

'

'

'

Derivatives [Abstract]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of new capacity resources selected

4

'

4

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of Contracts for Differences (CfDs) approved by Public Utility Regulatory Authority (PURA)

4

'

4

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of Contracts for Differences (CfDs) executed by UI

2

'

2

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of Contracts for Differences (CfDs) executed by CL&P

2

'

2

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Percentage of cost borne by UI customers for CFDs (in hundredths)

'

'

20.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Percentage of cost borne by CL&P customers (in hundredths)

'

'

80.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Unrealized gain and losses from mark-to-market adjustments [Abstract]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Regulatory Assets - Derivative liability

-5,585,000

-1,832,000

-28,849,000

-7,613,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Regulatory Liabilities - Derivative assets

0

-27,000

0

-15,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Numerator [Abstract]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Net income

5,144,000

15,749,000

74,859,000

74,798,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Less: Net income allocated to unvested units

5,000

23,000

83,000

126,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Net income attributable to common shareholders

$5,139,000

$15,726,000

$74,776,000

$74,672,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Denominator [Abstract]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Basic average number of shares outstanding (in shares)

50,989

50,799

50,956

50,760

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Effect of dilutive securities (in shares)

242

233

281

244

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Diluted average number of shares outstanding (in shares)

51,231

51,032

51,237

51,004

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Earnings per share [Abstract]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Basic (in dollars per share)

$0.10

$0.31

$1.47

$1.47

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Diluted (in dollars per share)

$0.10

$0.31

$1.46

$1.46

'

'

'

'

'

'

'

'

'

'

'

'

'

'

BUSINESS_ORGANIZATION_AND_STAT5

BUSINESS ORGANIZATION AND STATEMENT OF ACCOUNTING POLICIES, EQUITY INVESTMENTS (Details) (GenConn [Member], USD $)	3 Months Ended		9 Months Ended			1 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Oct. 31, 2013
						Subsequent Event [Member]
Equity Investments [Abstract]	'	'	'	'	'	'
Carrying value of joint venture	$126.60	'	$126.60	'	$124.80	'
Income (loss) from equity investment in GenConn	3.9	3.4	11.6	11.8	'	'
Distributions received from joint venture	0	4.7	9.8	17.6	'	8.2
Undistributed earnings in equity method investment	$4	'	$4	'	'	'

BUSINESS_ORGANIZATION_AND_STAT6

BUSINESS ORGANIZATION AND STATEMENT OF ACCOUNTING POLICIES, REGULATORY ASSETS (Details) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012
Regulatory Assets [Line Items]	'		'
Total Regulatory Assets	$1,008,187		$1,135,450
Less current portion of regulatory assets	98,323		120,935
Regulatory Assets, Net	909,864		1,014,515
Remaining period	'n/a		'
Nuclear Plant Investments - Above Market [Member]	'		'
Regulatory Assets [Line Items]	'		'
Total Regulatory Assets	238,868	[1]	252,498	[1]
Connecticut Yankee [Member]	'		'
Regulatory Assets [Line Items]	'		'
Total Regulatory Assets	0		11,129
Unamortized Redemption Costs [Member]	'		'
Regulatory Assets [Line Items]	'		'
Total Regulatory Assets	11,502		12,103
Remaining period, minimum	'8 years		'
Remaining period, maximum	'20 years		'
Pension and Other Post-Retirement Benefit Plans [Member]	'		'
Regulatory Assets [Line Items]	'		'
Total Regulatory Assets	444,038	[2]	458,019	[2]
Environmental Remediation Costs [Member]	'		'
Regulatory Assets [Line Items]	'		'
Total Regulatory Assets	16,754		14,772
Remaining period, minimum	'4 years		'
Remaining period, maximum	'5 years		'
Hardship Programs [Member]	'		'
Regulatory Assets [Line Items]	'		'
Total Regulatory Assets	23,833	[3]	29,852	[3]
Debt Premium [Member]	'		'
Regulatory Assets [Line Items]	'		'
Total Regulatory Assets	35,671		41,016
Remaining period, minimum	'1 year		'
Remaining period, maximum	'24 years		'
Deferred Purchased Gas [Member]	'		'
Regulatory Assets [Line Items]	'		'
Total Regulatory Assets	0	[4]	12,444	[4]
Unfunded Future Income Taxes [Member]	'		'
Regulatory Assets [Line Items]	'		'
Total Regulatory Assets	27,201	[5]	17,319	[5]
Contracts For Differences [Member]	'		'
Regulatory Assets [Line Items]	'		'
Total Regulatory Assets	147,726	[6]	176,597	[6]
Term of contract minimum	'7 years		'
Term of contact maximum	'14 years		'
Excess Generation Service Charge [Member]	'		'
Regulatory Assets [Line Items]	'		'
Total Regulatory Assets	8,228	[7]	8,864	[7]
Deferred Transmission Income/Expense [Member]	'		'
Regulatory Assets [Line Items]	'		'
Total Regulatory Assets	10,744	[8]	21,379	[8]
Storm Costs [Member]	'		'
Regulatory Assets [Line Items]	'		'
Total Regulatory Assets	15,797	[9]	52,009	[9]
Other [Member]	'		'
Regulatory Assets [Line Items]	'		'
Total Regulatory Assets	$27,825	[10]	$27,449	[10]
[1]	Asset/Liability relates to the Competitive Transition Assessment (CTA). Total CTA costs recovery and stranded cost amortization were substantially completed in the third quarter of 2013. The remaining balances are fully offset by amounts primarily included in income taxes, due principally to book-tax differences. As a result of the outcome of UI’s 2013 distribution rate request, PURA approved UI’s proposed rate treatment to leave CTA rates unchanged until January 1, 2014 at which point the charge will end and the remaining balances will be extinguished.
[2]	Asset life is dependent upon timing of final pension plan distribution; balance, which is fully offset by a corresponding liability, is recalculated each year in accordance with ASC 715 "Compensation-Retirement Benefits." See Note (G) “Pension and Other Benefits” for additional information.
[3]	Hardship customer accounts deferred for future recovery to the extent they exceed the amount in rates.
[4]	Deferred purchase gas costs balances at the end of the rate year are normally recorded/returned in the next year.
[5]	The balance will be extinguished when the asset, which is fully offset by a corresponding liability, or liability has been realized or settled, respectively.
[6]	Asset life is equal to delivery term of related contracts (which vary from approximately 7 - 14 years); balance fluctuates based upon quarterly market analysis performed on the related derivatives (Note K); amount, which does not earn a return, is fully offset by corresponding derivative asset/liability. See “-Contracts for Differences” discussion above for additional information.
[7]	Working capital allowance for generation service charge; this amount fluctuates based upon cash inflows and outflows in a given period.
[8]	Regulatory asset or liability which defers transmission income or expense and fluctuates based upon actual revenues and revenue requirements.
[9]	Storm costs include accumulated costs for major storms occurring from January 2009 forward. See Note (C) “Regulatory Proceedings – Electric Distribution and Transmission – Rates” for a discussion of the recovery of these costs.
[10]	Amortization period and/or balance vary depending on the nature, cost of removal and/or remaining life of the underlying assets/liabilities; asset amount includes decoupling ($12.4 million) and certain other amounts that are not currently earning a return. See Note (C) “Regulatory Proceedings – Electric Distribution and Transmission – Rates” for a discussion of the decoupling recovery period.

BUSINESS_ORGANIZATION_AND_STAT7

BUSINESS ORGANIZATION AND STATEMENT OF ACCOUNTING POLICIES, REGULATORY LIABILITIES (Details) (USD $)	9 Months Ended
	Sep. 30, 2013		Dec. 31, 2012
Regulatory Liabilities [Line Items]	'		'
Total regulatory liabilities	$494,305,000		$466,440,000
Less current portion of regulatory liabilities	7,135,000		21,284,000
Regulatory Liabilities, Net	487,170,000		445,156,000
Decoupling of Asset	12,400,000		'
Accumulated Deferred Investment Tax Credits [Member]	'		'
Regulatory Liabilities [Line Items]	'		'
Total regulatory liabilities	4,502,000		4,612,000
Remaining period	'30 years		'
Income Taxes Due Principally To Book Tax Differences [Member]	'		'
Regulatory Liabilities [Line Items]	'		'
Total regulatory liabilities	57,828,000	[1]	41,928,000	[1]
Deferred Gain on Sale of Property [Member]	'		'
Regulatory Liabilities [Line Items]	'		'
Total regulatory liabilities	37,933,000	[2]	37,933,000	[2]
Middletown/Norwalk Local Transmission Network Service Collections [Member]	'		'
Regulatory Liabilities [Line Items]	'		'
Total regulatory liabilities	21,545,000		21,975,000
Remaining period	'36 years		'
Pension And Other Post-Retirement Benefit Plans [Member]	'		'
Regulatory Liabilities [Line Items]	'		'
Total regulatory liabilities	11,985,000		15,016,000
Remaining period, minimum	'1 year		'
Remaining period, maximum	'7 years		'
Deferred Income Taxes [Member]	'		'
Regulatory Liabilities [Line Items]	'		'
Total regulatory liabilities	44,522,000	[3]	41,816,000	[3]
Asset Retirement Obligation [Member]	'		'
Regulatory Liabilities [Line Items]	'		'
Total regulatory liabilities	4,254,000	[4]	4,995,000	[4]
Deferred Purchased Gas [Member]	'		'
Regulatory Liabilities [Line Items]	'		'
Total regulatory liabilities	11,893,000	[5]	0	[5]
Low Income Program [Member]	'		'
Regulatory Liabilities [Line Items]	'		'
Total regulatory liabilities	23,509,000	[6]	17,651,000	[6]
Asset Removal Costs [Member]	'		'
Regulatory Liabilities [Line Items]	'		'
Total regulatory liabilities	254,131,000	[1]	243,854,000	[1]
Other [Member]	'		'
Regulatory Liabilities [Line Items]	'		'
Total regulatory liabilities	$22,203,000	[1]	$36,660,000	[1]
[1]	Amortization period and/or balance vary depending on the nature, cost of removal and/or remaining life of the underlying assets/liabilities; asset amount includes decoupling ($12.4 million) and certain other amounts that are not currently earning a return. See Note (C) “Regulatory Proceedings – Electric Distribution and Transmission – Rates” for a discussion of the decoupling recovery period.
[2]	Asset/Liability relates to the Competitive Transition Assessment (CTA). Total CTA costs recovery and stranded cost amortization were substantially completed in the third quarter of 2013. The remaining balances are fully offset by amounts primarily included in income taxes, due principally to book-tax differences. As a result of the outcome of UI’s 2013 distribution rate request, PURA approved UI’s proposed rate treatment to leave CTA rates unchanged until January 1, 2014 at which point the charge will end and the remaining balances will be extinguished.
[3]	The balance will be extinguished when the asset, which is fully offset by a corresponding liability, or liability has been realized or settled, respectively.
[4]	The liability will be extinguished simultaneous with the retirement of the assets and settlement of the corresponding asset retirement obligation.
[5]	Deferred purchase gas costs balances at the end of the rate year are normally recorded/returned in the next year.
[6]	Various hardship and payment plan programs approved for recovery.

BUSINESS_ORGANIZATION_AND_STAT8

BUSINESS ORGANIZATION AND STATEMENT OF ACCOUNTING POLICIES, STOCK BASED COMPENSATION (Details) (USD $)	3 Months Ended		9 Months Ended		3 Months Ended
In Millions, except Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Jun. 30, 2013	Mar. 31, 2013	Mar. 31, 2013	Jun. 30, 2013	Jun. 30, 2013
					Management [Member]	Management [Member]	President and Chief Executive Officer [Member]	Vice President Information Technology and Chief Information Officer [Member]	Non-employee director [Member]
					Performance Shares [Member]	Performance Shares [Member]	Restricted Stock [Member]	Restricted Stock [Member]	Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'	'	'	'	'	'
Number of shares granted (in shares)	'	'	'	'	5,860	101,150	2,033	2,177	21,558
Weighted average grant date fair value (in dollars per share)	'	'	'	'	$41.34	$38.73	$38.73	$41.34	$40.69
Vesting period	'	'	'	'	'	'	'5 years	'	'
Vesting rights	'	'	'	'	'	'	'equal annual installments over a five year period	'	'
Total stock-based compensation expense	$1.10	$0.20	$4.10	$3.90	'	'	'	'	'

CAPITALIZATION_Details

CAPITALIZATION (Details) (USD $)	1 Months Ended					1 Months Ended
In Millions, except Share data, unless otherwise specified	Oct. 31, 2013	Oct. 25, 2013	Oct. 25, 2013	Oct. 25, 2013	Oct. 25, 2013	Oct. 25, 2013	Sep. 30, 2013
	Subsequent Event [Member]	Subsequent Event [Member]	Subsequent Event [Member]	Subsequent Event [Member]	Subsequent Event [Member]	Subsequent Event [Member]	Common Stock [Member]
		United Illuminating Company (UI) [Member]	Connecticut Natural Gas Corporation (CNG) [Member]	Connecticut Natural Gas Corporation (CNG) [Member]	Connecticut Natural Gas Corporation (CNG) [Member]	Berkshire [Member]
		Senior Unsecured Notes Due 2023 [Member]	Senior Unsecured Notes Due 2028 [Member]	Senior Unsecured Notes Due 2043 [Member]	Series D Medium Term Notes Due 2013 [Member]	Senior Unsecured Notes Due 2043 [Member]
Temporary Equity [Line Items]	'	'	'	'	'	'	'
Common stock outstanding (in shares)	'	'	'	'	'	'	50,712,507
Common stock par value (in dollars per share)	'	'	'	'	'	'	$0
Common stock issued in underwritten public offering (in shares)	5,750,000	'	'	'	'	'	'
Common stock issued (in dollars per share)	$37.25	'	'	'	'	'	'
Shares issued upon exercise of underwriters over-allotment option (in shares)	750,000	'	'	'	'	'	'
Net proceeds of the offering	$206.40	'	'	'	'	'	'
Long-term debt [Abstract]	'	'	'	'	'	'	'
Interest rate (in hundredths)	'	3.95%	4.30%	5.23%	6.50%	5.33%	'
Long-term debt payable	'	75	25	20	20	15	'
Debt instrument, maturity date	'	25-Oct-23	25-Oct-28	25-Oct-43	'	10-Dec-43	'
Proceeds from Long-term debt issuance used to replenish cash	'	'	20	'	'	'	'
Proceeds from long-term debt issuance to be used for future debt repayment	'	'	'	$20	'	'	'

REGULATORY_PROCEEDINGS_Details

REGULATORY PROCEEDINGS (Details) (Superstorm Sandy [Member], USD $)	Sep. 30, 2013
In Millions, unless otherwise specified	Customer
Superstorm Sandy [Member]	'
Catastrophic Event [Line Items]	'
Approximate number of customer outages	284,000
Estimate of costs to repair damages	$35.80
Estimate of costs to repair damages, amount capitalized	$13.90

REGULATORY_PROCEEDINGS_PART_TW

REGULATORY PROCEEDINGS, PART TWO (Details) (USD $)

1 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

12 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

Feb. 15, 2013

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Dec. 31, 2011

Oct. 31, 2013

Aug. 14, 2013

Aug. 13, 2013

Feb. 28, 2013

Dec. 31, 2012

Apr. 30, 2012

Jan. 31, 2012

Jul. 10, 2010

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

United Illuminating Company (UI) [Member]

United Illuminating Company (UI) [Member]

United Illuminating Company (UI) [Member]

United Illuminating Company (UI) [Member]

United Illuminating Company (UI) [Member]

United Illuminating Company (UI) [Member]

United Illuminating Company (UI) [Member]

United Illuminating Company (UI) [Member]

United Illuminating Company (UI) [Member]

United Illuminating Company (UI) [Member]

United Illuminating Company (UI) [Member]

United Illuminating Company (UI) [Member]

United Illuminating Company (UI) [Member]

United Illuminating Company (UI) [Member]

United Illuminating Company (UI) [Member]

Connecticut Natural Gas Corporation (CNG) [Member]

Connecticut Natural Gas Corporation (CNG) [Member]

Connecticut Natural Gas Corporation (CNG) [Member]

The Southern Connecticut Gas Company (SCG) [Member]

The Southern Connecticut Gas Company (SCG) [Member]

The Southern Connecticut Gas Company (SCG) [Member]

The Berkshire Gas Company [Member]

GenConn Devon [Member]

GenConn Middletown [Member]

Megawatt

Megawatt

Megawatt

Maximum Transmission [Member]

Minimum Transmission [Member]

December 2008 [Member]

October 2013 [Member]

December 2008 [Member]

September 2011 [Member]

Rates [Abstract]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Length of time for proposed rate amendment

'2 years

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Revenues for past incurred storm costs included in proposed additional revenues

$53,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Proposed additional revenues for past incurred storm costs, recovery period

'6 years

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Proposed additional revenues to establish storm reserve per year

2,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Schedule of Regulatory Proceedings [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Allowed distribution return on equity (in hundredths)

'

'

'

'

'

'

'

'

'

'

'

'

8.75%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Allowed distribution return on equity per 2013 final decision (in hundredths)

'

'

'

'

'

'

'

'

'

'

'

9.15%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Percentage of earnings retained by company (in hundredths)

'

'

'

'

'

50.00%

'

50.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Disallowance of deferred storm costs and capital costs per PURA final decision rate case

'

'

'

'

'

'

'

'

'

'

'

22,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Regulatory disallowances

'

17,543,000

0

17,543,000

0

17,543,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Decoupling charge approved by PURA

'

'

'

'

'

'

'

'

'

4,000,000

'

'

'

'

6,400,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Decoupling charge to be approved by PURA

'

'

'

'

'

'

'

'

'

'

'

'

900,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Approval for issuance of Debt [Abstract]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Principal amount of debt securities PURA approved for issuance

'

'

'

'

'

379,000,000

'

379,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Principal amount of pollution control revenue bonds

'

'

'

'

'

103,500,000

'

103,500,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Principal amount of senior unsecured notes issued

'

'

'

'

'

378,500,000

'

378,500,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Debt included in principal amount of senior unsecured notes issued

'

'

'

'

'

'

'

'

'

'

75,000,000

'

'

'

'

100,000,000

103,500,000

100,000,000

'

'

'

'

'

'

'

'

'

'

'

Power Supply Arrangements [Abstract]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Percentage of standard service customers with wholesale power supply agreements in place for 2013 (in hundredths)

'

'

'

'

'

'

'

100.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Percentage of standard service customers with wholesale power supply agreements in place for 2014 (in hundredths)

'

'

'

'

'

'

'

30.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Collateral required to be posted if the entity's credit rating declined two ratings to fall below investment grade

'

'

'

'

'

7,700,000

'

7,700,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

New Renewable Source Generation [Abstract]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Approximate amount of required commitment to purchase Renewable Energy Credits (RECs) from new facilities behind distribution customer meters

'

'

'

'

'

200,000,000

'

200,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Period of commitment to purchase Renewable Energy Credits (RECs)

'

'

'

'

'

'

'

'21 years

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Solicitation period obligations will phase-in

'

'

'

'

'

'

'

'6 years

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Maximum annual commitment level obligation after year six

'

'

'

'

'

13,600,000

'

13,600,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Total amount of annual payments related to REC purchase contracts entered into by UI

'

'

'

'

'

2,900,000

'

2,900,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Delivery terms of REC purchase contracts

'

'

'

'15 years

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of mega watts of grid connected renewable energy allowed to be developed by each company (in MW)

'

'

'

'

'

'

'

10

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Mega watts of solar projects selected by DEEP (in MW)

'

'

'

'

'

'

'

'

'

5

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Percentage of cost from contract executed with CL&P (in hundredths)

'

'

'

'

'

'

'

20.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Percentage of benefit from contract executed with CL&P (in hundredths)

'

'

'

'

'

'

'

20.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Renewable generation capacity for recovery (in MW)

'

'

'

'

'

10

'

10

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Requested ROE, by UI (in hundredths)

'

'

'

'

'

'

'

9.50%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Basis point added to return on equity (in hundredths)

'

'

'

'

'

'

'

0.25%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Megawatts of projects for which budget must be submitted within three months (in MW)

'

'

'

'

'

'

'

7.8

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Megawatts of projects for which budget must be submitted within twelve months (in MW)

'

'

'

'

'

'

'

2.2

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Percentage of UIs distribution load for which UI may be directed to enter to contracts for energy and/or RECs (in hundredths)

'

'

'

'

'

4.00%

'

4.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Total Megawatts of power purchase agreements pending PURA approval (in MW)

'

'

'

'

'

'

'

48.1

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Energy under power purchase agreements by solar project (in MW)

'

'

'

'

'

'

'

3.8

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Capacity of energy by wind farm (in MW)

'

'

'

'

'

'

'

250

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Capacity of energy by solar project (in MW)

'

'

'

'

'

'

'

20

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Percentage of UI's distribution load represented by quantity of energy and RECs to be purchased, pending PURA approval

'

'

'

'

'

'

'

3.50%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

New England East-West Solution [Abstract]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Minimum amount of entity's investment for ownership of specific transmission assets

'

'

'

'

'

60,000,000

'

60,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Threshold percentage of CL&P's costs for the Connecticut portions of projects (in hundredths)

'

'

'

'

'

8.40%

'

8.40%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Expected amount of investment

'

'

'

'

'

60,000,000

'

60,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Cumulative amount of deposits

'

'

'

'

'

34,500,000

'

34,500,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Amount of transmission assets

'

'

'

'

'

'

6,200,000

'

6,200,000

'

'

'

'

18,400,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Pre-tax income earned on each deposit in NEEWS project.

'

'

'

'

'

300,000

400,000

1,200,000

1,100,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Equity Investment in Peaking Generation [Abstract]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Ratio of equity investment in peaking generation for joint venture

'

'

'

'

'

'50-50

'

'50-50

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Revenue requirements for equity investment in peaking generation

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

33,100,000

40,200,000

Transmission Return of Equity (ROE) [Abstract]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Weighted average return on equity (in hundredths)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

12.40%

12.20%

'

'

'

'

'

'

'

'

'

Current approved base return on equity (in hundredths)

'

'

'

'

'

11.14%

'

11.14%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Return on equity sought by complainants (in hundredths)

'

'

'

'

'

9.20%

'

9.20%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Change in weighted average return on equity in basis points (in hundredths)

'

'

'

'

'

'

'

0.25%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Change in annual net income

'

'

'

'

'

600,000

'

600,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Return on equity per initial decision for refund period of October 1, 2011 through December 31, 2012 (in hundredths)

'

'

'

'

'

'

'

10.60%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Return on equity, per initial decision, for the period after final opinion issued by FERC (in hundredths)

'

'

'

'

'

'

'

9.70%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Reserve for refund period

'

'

'

'

'

2,600,000

'

2,600,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Refund period

'

'

'

'

'

'

'

'15 months

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Requested ROE by additional parties (in hundredths)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

8.70%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Rates [Abstract]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Duration of approved rate plan

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'10 years

'

'

Approved return on equity (in hundredths)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

9.41%

'

'

9.36%

'

'

10.50%

'

'

Proposed ROE (in hundredths)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

10.25%

'

'

Additional annual base delivery rate revenues

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

20,100,000

'

'

'

'

'

0

'

'

Incremental revenues above existing rate schedule (in hundredths)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

6.40%

'

'

'

'

'

0.00%

'

'

Approval for the Issuance of Debt [Abstract]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Principal amount of debt securities

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

110,000,000

'

'

200,000,000

'

'

20,000,000

'

'

Medium term notes

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$20,000,000

$45,000,000

'

$50,000,000

$50,000,000

'

'

'

SHORTTERM_CREDIT_ARRANGEMENTS_

SHORT-TERM CREDIT ARRANGEMENTS (Details) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013
Disclosure of short-term credit arrangements [Abstract]	'
Standby letter of credit outstanding	4.4
Standby Letter of Credit Expiring January 2014 [Member] | UIL [Member]	'
Disclosure of short-term credit arrangements [Abstract]	'
Expiration date	31-Jan-14
Standby Letter of Credit Expiring June 2014 [Member] | UIL [Member]	'
Disclosure of short-term credit arrangements [Abstract]	'
Expiration date	16-Jun-14
Revolving Credit Facility [Member] | UIL [Member]	'
Disclosure of short-term credit arrangements [Abstract]	'
Amounts outstanding under the Credit Agreement	127
Expiration date	30-Nov-16
Available credit under the Credit Facility	268.6
Credit Agreement [Member] | UIL [Member]	'
Disclosure of short-term credit arrangements [Abstract]	'
Amounts outstanding under the Credit Agreement	100
Expiration date	31-Oct-13

INCOME_TAXES_Details

INCOME TAXES (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
INCOME TAXES [Abstract]	'	'	'	'
Combined statutory federal and state income tax rates (in hundredths)	40.90%	40.90%	40.90%	40.90%
Effective book income tax rates (in hundredths)	44.80%	40.70%	37.50%	40.50%

SUPPLEMENTARY_INFORMATION_Deta

SUPPLEMENTARY INFORMATION (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Depreciation and Amortization	'	'	'	'
Property, plant and equipment depreciation	$30,870	$28,648	$89,788	$83,143
Amortization of nuclear plant regulatory assets	16,782	14,272	39,935	35,433
Amortization of other regulatory assets	3,105	3,346	16,785	17,272
Other amortization	4	13	29	38
Total Amortization	19,891	17,631	56,749	52,743
Total Depreciation and Amortization	50,761	46,279	146,537	135,886
Taxes - Other than Income Taxes	'	'	'	'
Connecticut gross earnings	17,780	16,438	54,873	48,290
Local real estate and personal property	12,417	10,866	34,416	29,630
Payroll taxes	2,069	1,117	6,584	4,747
Other	123	81	462	257
Total Taxes - Other than Income Taxes	32,389	28,502	96,335	82,924
Other Income and (Deductions), net	'	'	'	'
Interest income	243	645	1,449	1,720
Allowance for funds used during construction - equity	2,751	1,589	8,085	5,473
Allowance for funds used during construction - debt	1,533	1,427	5,869	5,231
Weather Insurance	0	0	0	3,488
TSO Incentives	0	2,745	0	2,745
Miscellaneous other income and (deductions) - net	626	1,010	315	2,548
Total Other Income and (Deductions), net	$5,153	$7,416	$15,718	$21,205

PENSION_AND_OTHER_BENEFITS_Det

PENSION AND OTHER BENEFITS (Details) (USD $)	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Defined Benefit Plan Disclosure [Line Items]	'		'		'		'
Pension contributions	'		'		$55,000,000		'
Pension Benefit [Member]	'		'		'		'
Components of net periodic benefit cost:	'		'		'		'
Service cost	3,696,000		3,008,000		11,088,000		9,024,000
Interest cost	9,988,000		10,368,000		29,964,000		31,104,000
Expected return on plan assets	-12,863,000		-11,219,000		-38,589,000		-33,657,000
Amortization of:	'		'		'		'
Prior service costs	151,000		162,000		453,000		486,000
Transition obligation	0		0		0		0
Actuarial loss	5,208,000		3,294,000		15,624,000		9,882,000
Settlements (1)	632,000	[1]	0	[1]	632,000	[1]	0	[1]
Net periodic benefit cost	6,812,000		5,613,000		19,172,000		16,839,000
Pension Benefit [Member] | Minimum [Member]	'		'		'		'
Actuarial weighted-average assumptions	'		'		'		'
Discount rate (in hundredths)	4.00%		5.05%		4.00%		5.05%
Average wage increase (in hundredths)	3.50%		3.50%		3.50%		3.50%
Return on plan assets (in hundredths)	7.75%		7.75%		7.75%		7.75%
Pension Benefit [Member] | Maximum [Member]	'		'		'		'
Actuarial weighted-average assumptions	'		'		'		'
Discount rate (in hundredths)	4.25%		5.30%		4.25%		5.30%
Average wage increase (in hundredths)	3.80%		3.80%		3.80%		3.80%
Return on plan assets (in hundredths)	8.00%		8.00%		8.00%		8.00%
Other Postretirement Benefits [Member]	'		'		'		'
Components of net periodic benefit cost:	'		'		'		'
Service cost	481,000		401,000		1,443,000		1,203,000
Interest cost	1,384,000		1,562,000		4,152,000		4,686,000
Expected return on plan assets	-648,000		-626,000		-1,944,000		-1,878,000
Amortization of:	'		'		'		'
Prior service costs	-13,000		-17,000		-39,000		-51,000
Transition obligation	0		98,000		0		294,000
Actuarial loss	444,000		241,000		1,332,000		723,000
Settlements (1)	0	[1]	0	[1]	0	[1]	0	[1]
Net periodic benefit cost	$1,648,000		$1,659,000		$4,944,000		$4,977,000
Actuarial weighted-average assumptions	'		'		'		'
Composite health care trend rate (current year) (in hundredths)	7.50%		8.00%		7.50%		8.00%
Composite health care trend rate (2018 forward) (in hundredths)	5.00%		5.00%		5.00%		5.00%
Other Postretirement Benefits [Member] | Minimum [Member]	'		'		'		'
Actuarial weighted-average assumptions	'		'		'		'
Discount rate (in hundredths)	4.00%		5.05%		4.00%		5.05%
Return on plan assets (in hundredths)	5.56%		5.56%		5.56%		5.56%
Other Postretirement Benefits [Member] | Maximum [Member]	'		'		'		'
Actuarial weighted-average assumptions	'		'		'		'
Discount rate (in hundredths)	4.25%		5.30%		4.25%		5.30%
Return on plan assets (in hundredths)	8.00%		8.00%		8.00%		8.00%
[1]	Reflects settlement charges resulting from a distribution to a former employee upon retirement

RELATED_PARTY_TRANSACTIONS_Det

RELATED PARTY TRANSACTIONS (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
RELATED PARTY TRANSACTIONS [Abstract]	'	'	'	'
Lease payments for office space	$0.40	$0.40	$1.10	$4.40

COMMITMENTS_AND_CONTINGENCIES_

COMMITMENTS AND CONTINGENCIES (Details) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013
	Subcontractor
Connecticut Yankee Atomic Power Company [Member]	'
Site Contingency [Line Items]	'
Percentage stock ownership share in CT Yankee atomic power company (in hundredths)	9.50%
Carrying value of stock in CT Yankee atomic power company	$0.10
DOE spent fuel litigation [Abstract]	'
Damages awarded to CT Yankee for spent fuel related costs	39.7
Entity's share of amount awarded to CT Yankee atomic power company	3.8
Second set of damage claims sent by CT Yankee relating to failure to remove spent atomic fuel	135
Entity's share of second set of damage claims	12.8
Mill River New Haven Connecticut Site [Member]	'
Site Decontamination, Demolition and Remediation Costs [Abstract]	'
Amount placed in escrow for estimated remediation	1.9
Remaining amount of escrow	0.1
New Haven Harbor Station Site [Member]	'
Site Decontamination, Demolition and Remediation Costs [Abstract]	'
Site contingency, liability accrued	3.2
Mill Street Greenfield Massachusetts Site [Member]	'
Site Decontamination, Demolition and Remediation Costs [Abstract]	'
Site contingency, liability accrued	4.3
East Street Site Pittsfield Massachusetts [Member]	'
Site Decontamination, Demolition and Remediation Costs [Abstract]	'
Site contingency, liability accrued	2
Middletown/Norwalk Transmission Project [Member]	'
Middletown/Norwalk Transmission Project [Abstract]	'
Amount sought for change order requests	33.3
Percentage of general contractor mark-up on approved subcontractor change order claims (in hundredths)	10.00%
Amount of general contractor mark up on approved subcontractor change order claims	2.3
Subcontractors responsible for civil construction	2
Revised estimate for change order requests	7.7
Amount in Memorandum of Decision issued by the court for the company to pay to contractor	$1.30

FAIR_VALUE_MEASUREMENTS_Detail

FAIR VALUE MEASUREMENTS (Details) (USD $)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Dec. 31, 2012
		Contract For Difference [Member]	Fair Value, Measurements, Recurring [Member]	Fair Value, Measurements, Recurring [Member]	Fair Value, Measurements, Recurring [Member]	Fair Value, Measurements, Recurring [Member]	Fair Value, Measurements, Recurring [Member]	Fair Value, Measurements, Recurring [Member]	Fair Value, Measurements, Recurring [Member]	Fair Value, Measurements, Recurring [Member]
					Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]	Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]	Significant Other Observable Inputs (Level 2) [Member]	Significant Other Observable Inputs (Level 2) [Member]	Significant Unobservable Inputs (Level 3) [Member]	Significant Unobservable Inputs (Level 3) [Member]
Assets:	'	'	'	'	'	'	'	'	'	'
Derivative assets	'	'	$54,822,000	$79,838,000	$0	$0	$0	$0	$54,822,000	$79,838,000
Noncurrent investments available for sale	'	'	10,725,000	9,902,000	10,725,000	9,902,000	0	0	0	0
Deferred Compensation Plan	'	'	3,604,000	3,745,000	3,604,000	3,745,000	0	0	0	0
Supplemental retirement benefit trust life insurance policies	'	'	7,317,000	6,438,000	0	0	7,317,000	6,438,000	0	0
Total financial assets, fair value	'	'	76,468,000	99,923,000	14,329,000	13,647,000	7,317,000	6,438,000	54,822,000	79,838,000
Liabilities:	'	'	'	'	'	'	'	'	'	'
Derivative liabilities	'	'	202,577,000	255,443,000	0	0	0	0	202,577,000	255,443,000
Long-term debt	'	'	1,757,983,000	1,886,440,000	0	0	1,757,983,000	1,886,440,000	0	0
Total financial liabilities, fair value	'	'	1,960,560,000	2,141,883,000	0	0	1,757,983,000	1,886,440,000	202,577,000	255,443,000
Net fair value assets/(liabilities)	'	'	-1,884,092,000	-2,041,960,000	14,329,000	13,647,000	-1,750,666,000	-1,880,002,000	-147,755,000	-175,605,000
Unobservable input [Abstract]	'	'	'	'	'	'	'	'	'	'
Risk of non-performance, lower range (in hundredths)	'	0.33%	'	'	'	'	'	'	'	'
Risk of non-performance, upper range (in hundredths)	'	0.92%	'	'	'	'	'	'	'	'
Discount rate, lower range (in hundredths)	'	2.02%	'	'	'	'	'	'	'	'
Discount rate, upper range (in hundredths)	'	2.83%	'	'	'	'	'	'	'	'
Forward pricing, lower range (in dollars per MW)	'	1.4	'	'	'	'	'	'	'	'
Forward pricing, upper range (in dollars per MW)	'	9.83	'	'	'	'	'	'	'	'
Changes in fair value of assets and liabilities classified as level 3 [Roll Forward]	'	'	'	'	'	'	'	'	'	'
Net fair value assets/(liabilities), Beginning balance	-175,605,000	'	'	'	'	'	'	'	'	'
Unrealized gains and (losses), net Included in regulatory assets/(liabilities)	28,850,000	'	'	'	'	'	'	'	'	'
Settlements	-1,000,000	'	'	'	'	'	'	'	'	'
Net fair value assets/(liabilities), Ending balance	-147,555,000	'	'	'	'	'	'	'	'	'
Change in unrealized gains (losses), net relating to net fair value assets/(liabilities), still held as of September 30, 2013	28,850,000	'	'	'	'	'	'	'	'	'
Change in regulatory asset/liability balances [Roll Forward]	'	'	'	'	'	'	'	'	'	'
Net regulatory assets/(liabilities), Beginning balance	176,605,000	'	'	'	'	'	'	'	'	'
Unrealized (gains) and losses, net	-28,850,000	'	'	'	'	'	'	'	'	'
Net regulatory assets/(liabilities), Ending balance	$147,755,000	'	'	'	'	'	'	'	'	'

SEGMENT_INFORMATION_Details

SEGMENT INFORMATION (Details) (USD $)	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012		Dec. 31, 2012
Segment Reporting Information [Line Items]	'		'		'		'		'
Operating Revenues	$316,478,000		$322,888,000		$1,183,591,000		$1,063,547,000		'
Purchased power and gas	74,657,000		95,135,000		421,516,000		360,909,000		'
Operation and maintenance	89,810,000		87,281,000		273,539,000		260,887,000		'
Transmission wholesale	28,659,000		26,565,000		65,994,000		59,847,000		'
Depreciation and amortization	50,761,000		46,279,000		146,537,000		135,886,000		'
Taxes - other than income taxes	32,389,000		28,502,000		96,335,000		82,924,000		'
Regulatory disallowances	17,543,000		0		17,543,000		0		'
Operating Income	22,659,000		39,126,000		162,127,000		163,094,000		'
Other Income and (Deductions), net	5,153,000		7,416,000		15,718,000		21,205,000		'
Interest Charges, net	22,399,000		23,353,000		69,533,000		70,335,000		'
Income from Equity Investments	3,930,000		3,421,000		11,590,000		11,823,000		'
Income (Loss) Before Income Taxes	9,343,000		26,610,000		119,902,000		125,787,000		'
Income Taxes	4,186,000		10,835,000		45,004,000		50,924,000		'
Net Income (Loss)	5,157,000		15,775,000		74,898,000		74,863,000		'
Less: Preferred Stock Dividends of Subsidiary, Noncontrolling Interests	13,000		26,000		39,000		65,000		'
Net Income (Loss) attributable to UIL Holdings	5,144,000		15,749,000		74,859,000		74,798,000		'
Total Capital Expenditure	80,188,000	[1]	69,041,000	[1]	224,172,000	[1]	214,240,000	[1]	'
Total Assets	4,865,778,000	[2]	'		4,865,778,000	[2]	'		4,959,367,000	[2]
Electric Distribution Reportable Segment [Member]	'		'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'		'
Operating Revenues	151,369,000		154,165,000		421,959,000		424,060,000		'
Purchased power and gas	37,314,000		43,565,000		105,996,000		118,581,000		'
Operation and maintenance	43,387,000		42,599,000		132,919,000		130,071,000		'
Transmission wholesale	0		0		0		0		'
Depreciation and amortization	28,397,000		25,286,000		72,924,000		66,763,000		'
Taxes - other than income taxes	13,390,000		12,202,000		36,860,000		32,828,000		'
Regulatory disallowances	17,543,000		0		17,543,000		0		'
Operating Income	11,338,000		30,513,000		55,717,000		75,817,000		'
Other Income and (Deductions), net	3,534,000		6,071,000		10,687,000		13,556,000		'
Interest Charges, net	6,088,000		7,242,000		19,834,000		21,732,000		'
Income from Equity Investments	3,930,000		3,421,000		11,590,000		11,823,000		'
Income (Loss) Before Income Taxes	12,714,000		32,763,000		58,160,000		79,464,000		'
Income Taxes	5,607,000		14,597,000		24,464,000		36,163,000		'
Net Income (Loss)	7,107,000		18,166,000		33,696,000		43,301,000		'
Less: Preferred Stock Dividends of Subsidiary, Noncontrolling Interests	0		0		0		0		'
Net Income (Loss) attributable to UIL Holdings	7,107,000		18,166,000		33,696,000		43,301,000		'
Total Capital Expenditure	0	[1]	0	[1]	0	[1]	0	[1]	'
Total Assets	0	[2]	'		0	[2]	'		0	[2]
Electric Transmission Reportable Segment [Member]	'		'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'		'
Operating Revenues	67,830,000		62,932,000		180,412,000		162,729,000		'
Purchased power and gas	0		0		0		0		'
Operation and maintenance	11,532,000		9,840,000		33,212,000		30,791,000		'
Transmission wholesale	28,659,000		26,565,000		65,994,000		59,847,000		'
Depreciation and amortization	4,152,000		3,787,000		12,123,000		10,942,000		'
Taxes - other than income taxes	10,466,000		8,256,000		25,260,000		19,858,000		'
Regulatory disallowances	0		0		0		0		'
Operating Income	13,021,000		14,484,000		43,823,000		41,291,000		'
Other Income and (Deductions), net	746,000		863,000		3,465,000		2,889,000		'
Interest Charges, net	2,763,000		3,148,000		9,104,000		10,042,000		'
Income from Equity Investments	0		0		0		0		'
Income (Loss) Before Income Taxes	11,004,000		12,199,000		38,184,000		34,138,000		'
Income Taxes	3,890,000		3,955,000		13,474,000		10,709,000		'
Net Income (Loss)	7,114,000		8,244,000		24,710,000		23,429,000		'
Less: Preferred Stock Dividends of Subsidiary, Noncontrolling Interests	0		0		0		0		'
Net Income (Loss) attributable to UIL Holdings	7,114,000		8,244,000		24,710,000		23,429,000		'
Total Capital Expenditure	0	[1]	0	[1]	0	[1]	0	[1]	'
Total Assets	0	[2]	'		0	[2]	'		0	[2]
Total Electric Reportable Segments [Member]	'		'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'		'
Operating Revenues	219,199,000		217,097,000		602,371,000		586,789,000		'
Purchased power and gas	37,314,000		43,565,000		105,996,000		118,581,000		'
Operation and maintenance	54,919,000		52,439,000		166,131,000		160,862,000		'
Transmission wholesale	28,659,000		26,565,000		65,994,000		59,847,000		'
Depreciation and amortization	32,549,000		29,073,000		85,047,000		77,705,000		'
Taxes - other than income taxes	23,856,000		20,458,000		62,120,000		52,686,000		'
Regulatory disallowances	17,543,000		0		17,543,000		0		'
Operating Income	24,359,000		44,997,000		99,540,000		117,108,000		'
Other Income and (Deductions), net	4,280,000		6,934,000		14,152,000		16,445,000		'
Interest Charges, net	8,851,000		10,390,000		28,938,000		31,774,000		'
Income from Equity Investments	3,930,000		3,421,000		11,590,000		11,823,000		'
Income (Loss) Before Income Taxes	23,718,000		44,962,000		96,344,000		113,602,000		'
Income Taxes	9,497,000		18,552,000		37,938,000		46,872,000		'
Net Income (Loss)	14,221,000		26,410,000		58,406,000		66,730,000		'
Less: Preferred Stock Dividends of Subsidiary, Noncontrolling Interests	0		0		0		0		'
Net Income (Loss) attributable to UIL Holdings	14,221,000		26,410,000		58,406,000		66,730,000		'
Total Capital Expenditure	41,310,000	[1]	39,584,000	[1]	124,437,000	[1]	134,769,000	[1]	'
Total Assets	2,847,227,000	[2]	'		2,847,227,000	[2]	'		2,875,765,000	[2]
Gas Distribution Reportable Segment [Member]	'		'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'		'
Operating Revenues	97,244,000		105,755,000		581,115,000		476,644,000		'
Purchased power and gas	37,343,000		51,570,000		315,520,000		242,328,000		'
Operation and maintenance	36,271,000		35,788,000		111,496,000		101,944,000		'
Transmission wholesale	0		0		0		0		'
Depreciation and amortization	17,202,000		16,410,000		58,515,000		56,499,000		'
Taxes - other than income taxes	8,410,000		8,011,000		33,769,000		30,111,000		'
Regulatory disallowances	0		0		0		0		'
Operating Income	-1,982,000		-6,024,000		61,815,000		45,762,000		'
Other Income and (Deductions), net	234,000		372,000		-298,000		4,286,000		'
Interest Charges, net	7,507,000		7,070,000		22,415,000		21,281,000		'
Income from Equity Investments	0		0		0		0		'
Income (Loss) Before Income Taxes	-9,255,000		-12,722,000		39,102,000		28,767,000		'
Income Taxes	-2,970,000		-5,423,000		14,770,000		10,807,000		'
Net Income (Loss)	-6,285,000		-7,299,000		24,332,000		17,960,000		'
Less: Preferred Stock Dividends of Subsidiary, Noncontrolling Interests	13,000		26,000		39,000		65,000		'
Net Income (Loss) attributable to UIL Holdings	-6,298,000		-7,325,000		24,293,000		17,895,000		'
Total Capital Expenditure	25,968,000	[1]	22,968,000	[1]	63,771,000	[1]	55,840,000	[1]	'
Total Assets	1,934,249,000		'		1,934,249,000		'		1,993,560,000
Other [Member]	'		'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'		'
Operating Revenues	35,000		36,000		105,000		114,000		'
Purchased power and gas	0		0		0		0		'
Operation and maintenance	-1,380,000		-946,000		-4,088,000		-1,919,000		'
Transmission wholesale	0		0		0		0		'
Depreciation and amortization	1,010,000		796,000		2,975,000		1,682,000		'
Taxes - other than income taxes	123,000		33,000		446,000		127,000		'
Regulatory disallowances	0		0		0		0		'
Operating Income	282,000		153,000		772,000		224,000		'
Other Income and (Deductions), net	639,000		110,000		1,864,000		474,000		'
Interest Charges, net	6,041,000		5,893,000		18,180,000		17,280,000		'
Income from Equity Investments	0		0		0		0		'
Income (Loss) Before Income Taxes	-5,120,000		-5,630,000		-15,544,000		-16,582,000		'
Income Taxes	-2,341,000		-2,294,000		-7,704,000		-6,755,000		'
Net Income (Loss)	-2,779,000		-3,336,000		-7,840,000		-9,827,000		'
Less: Preferred Stock Dividends of Subsidiary, Noncontrolling Interests	0		0		0		0		'
Net Income (Loss) attributable to UIL Holdings	-2,779,000		-3,336,000		-7,840,000		-9,827,000		'
Total Capital Expenditure	12,910,000	[1]	6,489,000	[1]	35,964,000	[1]	23,631,000	[1]	'
Total Assets	84,302,000		'		84,302,000		'		90,042,000
Distribution Segment [Member]	'		'		'		'		'
Net plant in service segregated by segment [Abstract]	'		'		'		'		'
Net plant in service	1,099,100,000		'		1,099,100,000		'		1,058,600,000
Transmission Segment [Member]	'		'		'		'		'
Net plant in service segregated by segment [Abstract]	'		'		'		'		'
Net plant in service	$644,700,000		'		$644,700,000		'		$607,800,000
[1]	Information for segmenting total capital expenditures between Distribution and Transmission is not available.  Total Electric Distribution and Transmission capital expenditures are disclosed in the Total Electric Distribution and Transmission column.
[2]	Information for segmenting total assets between Distribution and Transmission is not available.  Total Electric Distribution and Transmission assets are disclosed in the Total Electric Distribution and Transmission column.  Net plant in service is segregated by segment and, as of September 30, 2013, was $1,099.1 million and $644.7 million for Distribution and Transmission, respectively.  As of December 31, 2012, net plant in service was $1,058.6 million and $607.8 million for Distribution and  Transmission, respectively.