CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Operating revenues
Electric	$ 216,545	$ 214,426	$ 592,730	$ 575,532
Natural gas	14,266	11,742	89,178	68,064
Other	249	307	742	851
Total operating revenues	231,060	226,475	682,650	644,447
Operating expenses
Electric fuel and purchased power, non-affiliates	4,968	7,516	11,000	15,431
Purchased power, affiliates	106,554	103,572	305,539	301,551
Cost of natural gas sold and transported	7,483	5,656	52,770	39,658
Operating and maintenance expenses	42,521	41,726	127,189	122,718
Conservation program expenses	3,133	3,714	9,243	10,836
Depreciation and amortization	19,359	17,338	57,265	51,440
Taxes (other than income taxes)	6,273	6,218	19,008	18,816
Total operating expenses	190,291	185,740	582,014	560,450
Operating income	40,769	40,735	100,636	83,997
Other (expense) income, net	(61)	(85)	209	375
Allowance for funds used during construction — equity	1,029	(385)	2,755	1,379
Interest charges and financing costs
Interest charges — includes other financing costs of $389, $375, $1,150 and $1,185, respectively	7,191	5,944	20,860	18,003
Allowance for funds used during construction — debt	(471)	(995)	(1,280)	(1,220)
Total interest charges and financing costs	6,720	4,949	19,580	16,783
Income before income taxes	35,017	35,316	84,020	68,968
Income taxes	13,004	13,116	31,778	26,148
Net income	$ 22,013	$ 22,200	$ 52,242	$ 42,820