CONSOLIDATED STATEMENTS OF INCOME (USD $) In Thousands, except Per Share data	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Operating revenues:
Electric	$ 119,903	$ 106,249	$ 247,838	$ 219,849	$ 510,899	$ 443,971
Gas	7,303	6,516	28,292	31,076	48,101	52,384
Water	426	436	852	870	1,787	1,774
Other	1,461	1,281	2,839	2,581	5,934	5,170
Total operating revenues	129,093	114,482	279,821	254,376	566,721	503,299
Operating revenue deductions:
Fuel and purchased power	47,228	44,255	101,445	94,939	205,805	188,629
Cost of natural gas sold and transported	2,712	2,265	14,752	17,375	23,991	29,457
Regulated operating expenses	19,085	19,272	38,801	38,189	79,904	75,698
Other operating expenses	649	480	1,123	968	2,106	1,937
Maintenance and repairs	10,540	9,600	19,782	17,407	39,146	33,827
Depreciation and amortization	16,888	13,586	34,221	26,771	66,106	52,853
Provision for income taxes	5,588	4,439	12,857	14,328	28,999	24,338
Other taxes	7,269	6,306	15,859	14,042	29,545	26,390
Total operating revenue deductions	109,959	100,203	238,840	224,019	475,602	433,129
Operating income	19,134	14,279	40,981	30,357	91,119	70,170
Other income and (deductions):
Allowance for equity funds used during construction	70	1,913	70	3,653	954	7,225
Interest income	16	52	40	122	94	202
Benefit/(provision) for other income taxes	9	(46)	33	(91)	61	(308)
Other - non-operating expense, net	(174)	(256)	(460)	(503)	(996)	(997)
Total other income and (deductions)	(79)	1,663	(317)	3,181	113	6,122
Interest charges:
Long-term debt	10,640	10,083	21,273	20,568	42,664	42,106
Trust preferred securities		1,027		2,090		4,215
Short-term debt	16	245	47	490	188	828
Allowance for borrowed funds used during construction	(58)	(2,430)	(81)	(4,845)	(872)	(8,466)
Other	(718)	(352)	(1,672)	(720)	(3,285)	(1,102)
Total interest charges	9,880	8,573	19,567	17,583	38,695	37,581
Net income	$ 9,175	$ 7,369	$ 21,097	$ 15,955	$ 52,537	$ 38,711
Weighted average number of common shares outstanding - basic (in shares)	41,811	40,623	41,738	39,618	41,596	37,645
Weighted average number of common shares outstanding - diluted (in shares)	41,846	40,654	41,774	39,645	41,627	37,665
Total earnings per weighted average share of common stock - basic (in dollars per share)	$ 0.22	$ 0.18	$ 0.51	$ 0.40	$ 1.26	$ 1.03
Total earnings per weighted average share of common stock - diluted (in dollars per share)	$ 0.22	$ 0.18	$ 0.51	$ 0.40	$ 1.26	$ 1.03
Dividends per share of common stock (in dollars per share)	$ 0.32	$ 0.32	$ 0.64	$ 0.64	$ 1.28	$ 1.28