CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Operating revenues:
Electric	$ 162,412	$ 164,500	$ 431,335	$ 458,355	$ 565,471	$ 588,611
Gas	5,084	4,989	31,181	36,587	46,437	53,406
Other	2,218	2,023	6,299	6,025	8,271	8,008
Total operating revenues	169,714	171,512	468,815	500,967	620,179	650,025
Operating revenue deductions:
Fuel and purchased power	45,795	56,574	133,926	166,518	182,494	209,745
Cost of natural gas sold and transported	1,301	1,208	14,765	18,931	22,860	28,496
Regulated operating expenses	28,437	27,773	84,656	83,339	112,094	108,788
Other operating expenses	879	746	2,474	2,243	3,217	2,915
Maintenance and repairs	11,454	12,004	37,303	33,654	50,424	44,763
Depreciation and amortization	20,090	18,550	60,237	54,648	78,774	72,483
Provision for income taxes	15,850	13,819	28,789	32,687	35,500	41,460
Other taxes	10,125	9,129	30,121	28,249	38,971	36,878
Total operating revenue deductions	133,931	139,803	392,271	420,269	524,334	545,528
Operating income	35,783	31,709	76,544	80,698	95,845	104,497
Other income and (deductions):
Allowance for equity funds used during construction	1,257	1,799	3,469	4,573	5,317	5,905
Interest income	2	4	142	48	145	92
Benefit for other income taxes	586	105	713	203	687	164
Other - non-operating expense, net	(1,751)	(313)	(2,675)	(958)	(3,019)	(1,263)
Total other income	94	1,595	1,649	3,866	3,130	4,898
Interest charges:
Long-term debt	11,001	10,105	32,504	30,316	42,824	40,427
Short-term debt	80	46	247	63	298	64
Allowance for borrowed funds used during construction	(743)	(972)	(2,030)	(2,542)	(2,984)	(3,246)
Other	254	233	780	736	1,033	996
Total interest charges	10,592	9,412	31,501	28,573	41,171	38,241
Net income	$ 25,285	$ 23,892	$ 46,692	$ 55,991	$ 57,804	$ 71,154
Weighted average number of common shares outstanding - basic (in shares)	43,728	43,367	43,629	43,239	43,583	43,173
Weighted average number of common shares outstanding - diluted (in shares)	43,819	43,413	43,721	43,272	43,677	43,202
Total earnings per weighted average share of common stock - basic and diluted (in dollars per share)	$ 0.58	$ 0.55	$ 1.07	$ 1.29
Total earnings per weighted average share of common stock - basic (in dollars per share)					$ 1.33	$ 1.65
Total earnings per weighted average share of common stock - diluted (in dollars per share)					1.32	1.65
Dividends declared per share of common stock (in dollars per share)	$ 0.26	$ 0.255	$ 0.78	$ 0.765	$ 1.04	$ 1.02