CONSOLIDATED STATEMENTS OF INCOME (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Operating revenues:
Electric	$ 140,767	$ 127,026	$ 293,856	$ 255,788	$ 574,481	$ 522,624
Gas	6,989	7,777	31,598	28,270	53,369	46,632
Other	2,026	1,843	4,001	3,728	8,148	6,851
Total operating revenues	149,782	136,646	329,455	287,786	635,998	576,107
Operating revenue deductions:
Fuel and purchased power	54,358	42,013	109,944	87,316	198,034	175,456
Cost of natural gas sold and transported	2,678	3,113	17,723	15,038	28,479	23,321
Regulated operating expenses	27,609	26,647	55,566	53,784	107,115	101,963
Other operating expenses	782	872	1,498	1,665	2,974	3,026
Maintenance and repairs	11,393	9,933	21,650	19,090	43,433	39,613
Loss on plant disallowance				2,409		2,409
Depreciation and amortization	18,157	17,635	36,097	33,736	71,668	64,180
Provision for income taxes	6,694	7,042	18,868	14,496	41,837	35,835
Other taxes	8,609	8,281	19,119	17,284	36,773	32,689
Total operating revenue deductions	130,280	115,536	280,465	244,818	530,313	478,492
Operating income	19,502	21,110	48,990	42,968	105,685	97,615
Other income and (deductions):
Allowance for equity funds used during construction	1,522	867	2,773	1,393	5,234	2,437
Interest income	3	10	44	517	92	1,187
Benefit/(provision) for other income taxes	45	(7)	99	(35)	106	105
Other - non-operating expense, net	(300)	(290)	(645)	(579)	(1,283)	(2,060)
Total other income and (deductions)	1,270	580	2,271	1,296	4,149	1,669
Interest charges:
Long-term debt	10,105	10,190	20,210	20,141	40,424	40,042
Short-term debt	13	12	18	59	18	87
Allowance for borrowed funds used during construction	(830)	(472)	(1,570)	(777)	(2,880)	(1,392)
Other	290	302	504	554	1,015	1,091
Total interest charges	9,578	10,032	19,162	19,977	38,577	39,828
Net income	$ 11,194	$ 11,658	$ 32,099	$ 24,287	$ 71,257	$ 59,456
Weighted average number of common shares outstanding - basic (in shares)	43,236	42,707	43,173	42,636	43,048	42,512
Weighted average number of common shares outstanding - diluted (in shares)	43,269	42,727	43,200	42,652	43,069	42,526
Total earnings per weighted average share of common stock - basic and diluted (in dollars per share)	$ 0.26	$ 0.27	$ 0.74	$ 0.57
Total earnings per weighted average share of common stock - basic (in dollars per share)					$ 1.66	$ 1.40
Total earnings per weighted average share of common stock - diluted (in dollars per share)					$ 1.65	$ 1.40
Dividends declared per share of common stock (in dollars per share)	$ 0.255	$ 0.25	$ 0.51	$ 0.50	$ 1.015	$ 1.00