Statement of Income (Unaudited) (USD $) In Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Statement of Income [Abstract]
OPERATING REVENUES	$ 107,216	$ 103,562	$ 323,711	$ 312,250
OPERATING EXPENSES:
General and administrative	14,448	13,514	44,497	41,367
Operation and maintenance	20,010	15,921	53,447	48,884
Depreciation	22,515	21,863	67,616	65,766
Regulatory credits	(266)	(431)	(800)	(1,232)
Taxes, other than income taxes	4,427	4,347	15,041	13,407
Total operating expenses	61,134	55,214	179,801	168,192
Operating Income	46,082	48,348	143,910	144,058
Interest income -
Affiliated	2	11	7	20
Other	15	0	16	3
Allowance for equity funds used during construction	598	759	1,005	1,492
Miscellaneous other (expense) income, net	(7)	(144)	(145)	(789)
Total other income - net	608	626	883	726
INTEREST CHARGES:
Interest on long-term debt	11,110	11,110	33,329	33,348
Other interest	492	524	1,506	2,135
Allowance for borrowed funds used during construction	(276)	(337)	(463)	(675)
Total interest charges	11,326	11,297	34,372	34,808
INCOME BEFORE INCOME TAXES	35,364	37,677	110,421	109,976
INCOME TAXES	123	4	118	42
NET INCOME	$ 35,241	$ 37,673	$ 110,303	$ 109,934