CONSOLIDATED STATEMENTS OF INCOME (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Operating revenues
Electric	$ 757,565	$ 755,136	$ 708,179
Natural gas	103,100	119,447	118,076
Other	1,177	1,207	1,036
Total operating revenues	861,842	875,790	827,291
Operating expenses
Electric fuel and purchased power, non-affiliates	19,440	20,957	22,222
Purchased power, affiliates	405,016	399,649	377,518
Cost of natural gas sold and transported	61,370	78,208	78,176
Operating and maintenance expenses	167,503	164,323	160,824
Conservation program expenses	14,442	12,883	12,965
Depreciation and amortization	69,234	68,574	63,669
Taxes (other than income taxes)	24,971	23,688	23,096
Total operating expenses	761,976	768,282	738,470
Operating income	99,866	107,508	88,821
Other income, net	476	98	1,265
Allowance for funds used during construction - equity	2,104	1,007	2,253
Interest charges and financing costs
Interest charges - includes other financing costs of $1,574, $1,713 and $1,420, respectively	24,799	24,168	24,517
Allowance for funds used during construction - debt	(1,862)	(175)	(1,039)
Total interest charges and financing costs	22,937	23,993	23,478
Income before income taxes	79,509	84,620	68,861
Income taxes	29,558	33,614	26,112
Net income	$ 49,951	$ 51,006	$ 42,749