Consolidated Statements of Income (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Operating revenues:
Electric	$ 522,506	$ 482,910	$ 433,133
Gas	46,430	50,885	57,314
Water	1,769	1,805	1,764
Other	6,165	5,676	4,957
Total operating revenues	576,870	541,276	497,168
Operating revenue deductions:
Fuel and purchased power	200,256	199,299	182,028
Cost of natural gas sold and transported	22,760	26,614	35,601
Regulated operating expenses	85,442	79,292	73,086
Other operating expenses	2,098	1,950	1,801
Maintenance and repairs	41,041	36,771	33,012
Loss on plant disallowance	150
Depreciation and amortization	63,537	58,656	51,494
Provision for income taxes	34,071	30,470	19,571
Other taxes	30,581	27,729	26,080
Total operating revenue deductions	479,936	460,781	422,673
Operating income	96,934	80,495	74,495
Other income and (deductions):
Allowance for equity funds used during construction	294	4,538	6,209
Interest income	555	176	217
Provision for other income taxes	(227)	(63)	(311)
Other - non-operating expense, net	(1,283)	(1,039)	(460)
Total other income and (deductions)	(661)	3,612	5,655
Interest charges:
Long-term debt	42,581	41,959	42,084
Trust preferred securities		2,090	4,250
Short-term debt	86	631	1,125
Allowance for borrowed funds used during construction	(218)	(5,636)	(7,924)
Other	(1,147)	(2,333)	(681)
Total interest charges	41,302	36,711	38,854
Net income	$ 54,971	$ 47,396	$ 41,296
Weighted average number of common shares outstanding - basic (in shares)	41,851,759	40,544,802	34,923,526
Weighted average number of common shares outstanding - diluted (in shares)	41,887,428	40,579,521	34,956,264
Total earnings per weighted average share of common stock - basic and diluted (in dollars per share)	$ 1.31	$ 1.17	$ 1.18
Dividends declared per share of common stock (in dollars per share)	$ 0.64	$ 1.28	$ 1.28