CONSOLIDATED STATEMENTS OF INCOME (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Operating revenues:
Electric and water	$ 152,730	$ 157,619	$ 396,546	$ 406,308	$ 514,515	$ 523,177
Gas	4,999	5,052	26,486	33,344	39,571	47,750
Other	1,473	1,613	4,945	4,453	6,657	5,992
Total operating revenues	159,202	164,284	427,977	444,105	560,743	576,919
Operating revenue deductions:
Fuel and purchased power	48,036	54,316	138,792	155,761	183,288	202,835
Cost of natural gas sold and transported	1,251	1,225	11,601	15,977	18,384	23,662
Regulated operating expenses	24,038	23,299	70,230	62,100	93,572	82,895
Other operating expenses	776	507	2,145	1,630	2,763	2,131
Maintenance and repairs	10,972	9,891	30,893	29,673	42,261	40,315
Depreciation and amortization	15,108	14,757	45,111	48,978	59,669	66,240
Provision for income taxes	15,428	15,672	28,185	28,529	33,727	32,737
Other taxes	8,311	8,167	24,166	24,026	30,722	30,408
Total operating revenue deductions	123,920	127,834	351,123	366,674	464,386	481,223
Operating income	35,282	36,450	76,854	77,431	96,357	95,696
Other income and (deductions):
Allowance for equity funds used during construction	292	82	395	152	537	197
Interest income	265	29	568	68	1,055	93
Benefit/(provision) for other income taxes	(49)	20	(251)	53	(531)	67
Other - non-operating expense, net	(274)	(522)	(703)	(981)	(1,005)	(1,273)
Total other income and (deductions)	234	(391)	9	(708)	56	(916)
Interest charges:
Long-term debt	9,950	10,654	30,242	31,927	40,896	42,561
Short-term debt	16	23	175	69	192	96
Allowance for borrowed funds used during construction	(243)	(77)	(410)	(158)	(470)	(177)
Other	251	275	802	(1,396)	1,050	(2,440)
Total interest charges	9,974	10,875	30,809	30,442	41,668	40,040
Net income	$ 25,542	$ 25,184	$ 46,054	$ 46,281	$ 54,745	$ 54,740
Weighted average number of common shares outstanding - basic (in shares)	42,345	41,951	42,197	41,810	42,141	41,734
Weighted average number of common shares outstanding - diluted (in shares)	42,374	41,984	42,220	41,846	42,163	41,771
Total earnings per weighted average share of common stock - basic and diluted (in dollars per share)	$ 0.60	$ 0.60	$ 1.09	$ 1.11	$ 1.30	$ 1.31
Dividends declared per share of common stock (in dollars per share)	$ 0.25	$ 0.00	$ 0.75	$ 0.64	$ 0.75	$ 0.96