CONSOLIDATED STATEMENT OF INCOME (LOSS) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Operating Revenues (Note F)
Operating Revenues	$ 1,570,447	$ 997,666	$ 896,550
Operation
Purchased power	180,149	242,268	333,339
Natural gas purchased	429,079	81,428	0
Operation and maintenance	382,167	258,282	225,853
Transmission wholesale	77,997	72,169	57,012
Depreciation and amortization (Note F)	167,462	113,946	98,116
Taxes - other than income taxes (Note F)	114,211	78,702	60,062
Acquisition -related costs - (Note A)	0	25,572	0
Total Operating Expenses	1,351,065	872,367	774,382
Operating Income	219,382	125,299	122,168
Other Income and (Deductions), net (Note F), (Note H)	26,932	17,262	5,586
Interest Charges, net
Interest on long-term debt	87,394	50,357	37,297
Other interest, net (Note F)	5,216	1,553	1,286
Interest Charges, gross	92,610	51,910	38,583
Amortization of debt expense and redemption premiums	2,775	1,788	1,817
Total Interest Charges, net	95,385	53,698	40,400
Income Before Income Taxes, Equity Earnings	150,929	88,863	87,354
Income Taxes (Note E)	62,501	35,284	33,096
Income Before Equity Earnings	88,428	53,579	54,258
Income from Equity Investments	11,282	1,278	59
Net Income	99,710	54,857	54,317
Less: Preferred Stock Dividends of Subsidiary, Noncontrolling Interests	54	3	0
Net income attributable to UIL Holdings	$ 99,656	$ 54,854	$ 54,317
Average Number of Common Shares Outstanding - Basic (in shares)	50,609	35,722	28,027
Average Number of Common Shares Outstanding - Diluted (in shares)	50,926	36,083	28,273
Earnings Per Share of Common Stock - Basic: (in dollars per share) (Note A)	$ 1.96	$ 1.53	$ 1.94
Earnings Per Share of Common Stock - Diluted: (in dollars per share) (Note A)	$ 1.95	$ 1.52	$ 1.93
Cash Dividends Declared per share of Common Stock (in dollars per share)	$ 1.728	$ 1.728	$ 1.728