Consolidated Statements of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating revenues:
Electric	$ 536,413	$ 510,653	$ 524,275
Gas	50,041	39,849	46,430
Other	7,876	6,595	6,165
Total operating revenues	594,330	557,097	576,870
Operating revenue deductions:
Fuel and purchased power	175,406	178,896	200,256
Cost of natural gas sold and transported	25,795	18,633	22,760
Regulated operating expenses	105,333	94,371	85,442
Other operating expenses	3,142	2,730	2,098
Maintenance and repairs	40,873	40,444	41,041
Loss on plant disallowance	2,409		150
Depreciation and amortization	69,306	60,447	63,537
Provision for income taxes	37,465	34,096	34,071
Other taxes	34,938	31,259	30,581
Total operating revenue deductions	494,667	460,876	479,936
Operating income	99,663	96,221	96,934
Other income and (deductions):
Allowance for equity funds used during construction	3,853	1,147	294
Interest income	566	972	555
Provision for other income taxes	(27)	(63)	(227)
Other - non-operating expense, net	(1,218)	(1,910)	(1,283)
Total other income and (deductions)	3,174	146	(661)
Interest charges:
Long-term debt	40,354	40,192	42,581
Short-term debt	60	187	86
Allowance for borrowed funds used during construction	(2,087)	(781)	(218)
Other	1,065	1,088	(1,147)
Total interest charges	39,392	40,686	41,302
Net income	$ 63,445	$ 55,681	$ 54,971
Weighted average number of common shares outstanding - basic (in shares)	42,781	42,257	41,852
Weighted average number of common shares outstanding - diluted (in shares)	42,803	42,284	41,887
Total earnings per weighted average share of common stock - basic and diluted (in dollars per share)	$ 1.48	$ 1.32	$ 1.31
Dividends declared per share of common stock (in dollars per share)	$ 1.005	$ 1.000	$ 0.640