CONSOLIDATED STATEMENTS OF INCOME (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Operating revenues
Electric	$ 755,136	$ 708,179	$ 671,703
Natural gas	119,447	118,076	131,555
Other	1,207	1,036	893
Total operating revenues	875,790	827,291	804,151
Operating expenses
Electric fuel and purchased power	420,606	399,740	377,784
Cost of natural gas sold and transported	78,208	78,176	90,318
Operating and maintenance expenses	164,323	160,824	145,748
Conservation program expenses	12,883	12,965	10,679
Depreciation and amortization	68,574	63,669	61,757
Taxes (other than income taxes)	23,688	23,096	23,284
Total operating expenses	768,282	738,470	709,570
Operating income	107,508	88,821	94,581
Other income, net	98	1,265	727
Allowance for funds used during construction - equity	1,007	2,253	1,637
Interest charges and financing costs
Interest charges - includes other financing costs of $1,713, $1,420 and $1,147, respectively	24,168	24,517	24,782
Allowance for funds used during construction - debt	(175)	(1,039)	(818)
Total interest charges and financing costs	23,993	23,478	23,964
Income before income taxes	84,620	68,861	72,981
Income taxes	33,614	26,112	25,618
Net income	$ 51,006	$ 42,749	$ 47,363