CONSOLIDATED STATEMENTS OF INCOME (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating revenues
Electric	$ 789,168	$ 757,565	$ 755,136
Natural gas	132,867	103,100	119,447
Other	1,003	1,177	1,207
Total operating revenues	923,038	861,842	875,790
Operating expenses
Electric fuel and purchased power, non-affiliates	18,129	19,440	20,957
Purchased power, affiliates	416,173	405,016	399,649
Cost of natural gas sold and transported	81,572	61,370	78,208
Operating and maintenance expenses	175,522	167,503	164,323
Conservation program expenses	12,333	14,442	12,883
Depreciation and amortization	76,897	69,234	68,574
Taxes (other than income taxes)	25,231	24,971	23,688
Total operating expenses	805,857	761,976	768,282
Operating income	117,181	99,866	107,508
Other income, net	253	476	98
Allowance for funds used during construction — equity	4,259	2,104	1,007
Interest charges and financing costs
Interest charges — includes other financing costs of $1,538, $1,574 and $1,713, respectively	27,797	24,799	24,168
Allowance for funds used during construction — debt	(1,981)	(1,862)	(175)
Total interest charges and financing costs	25,816	22,937	23,993
Income before income taxes	95,877	79,509	84,620
Income taxes	36,409	29,558	33,614
Net income	$ 59,468	$ 49,951	$ 51,006