CONSOLIDATED STATEMENTS OF INCOME (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Operating revenues:
Electric	$ 164,500	$ 150,370	$ 458,355	$ 406,158	$ 588,611	$ 520,265
Gas	4,989	4,952	36,587	33,222	53,406	46,585
Other	2,023	2,164	6,025	5,892	8,008	7,542
Total operating revenues	171,512	157,486	500,967	445,272	650,025	574,392
Operating revenue deductions:
Fuel and purchased power	56,574	44,864	166,518	132,179	209,745	172,283
Cost of natural gas sold and transported	1,208	1,191	18,931	16,229	28,496	23,262
Regulated operating expenses	27,687	26,100	83,253	79,884	108,702	104,024
Other operating expenses	746	805	2,243	2,470	2,915	3,056
Maintenance and repairs	12,004	10,674	33,654	29,764	44,763	39,315
Loss on plant disallowance	86		86	2,409	86	2,409
Depreciation and amortization	18,550	17,735	54,648	51,471	72,483	66,807
Provision for income taxes	13,819	14,197	32,687	28,693	41,460	34,603
Other taxes	9,129	9,024	28,249	26,309	36,878	33,402
Total operating revenue deductions	139,803	124,590	420,269	369,408	545,528	479,161
Operating income	31,709	32,896	80,698	75,864	104,497	95,231
Other income and (deductions):
Allowance for equity funds used during construction	1,799	1,128	4,573	2,521	5,905	3,273
Interest income	4	5	48	522	92	926
Benefit for other income taxes	105	47	203	12	164	201
Other - non-operating expense, net	(313)	(333)	(958)	(912)	(1,263)	(2,119)
Total other income and (deductions)	1,595	847	3,866	2,143	4,898	2,281
Interest charges:
Long-term debt	10,105	10,102	30,316	30,243	40,427	40,194
Short-term debt	46		63	59	64	71
Allowance for borrowed funds used during construction	(972)	(606)	(2,542)	(1,383)	(3,246)	(1,754)
Other	233	251	736	805	996	1,091
Total interest charges	9,412	9,747	28,573	29,724	38,241	39,602
Net income	$ 23,892	$ 23,996	$ 55,991	$ 48,283	$ 71,154	$ 57,910
Weighted average number of common shares outstanding - basic (in shares)	43,367	42,869	43,239	42,715	43,173	42,644
Weighted average number of common shares outstanding - diluted (in shares)	43,413	42,898	43,272	42,737	43,202	42,665
Total earnings per weighted average share of common stock - basic and diluted (in dollars per share)	$ 0.55	$ 0.56	$ 1.29	$ 1.13	$ 1.65	$ 1.36
Dividends declared per share of common stock (in dollars per share)	$ 0.255	$ 0.25	$ 0.765	$ 0.75	$ 1.02	$ 1.00