Statement of Income (Unaudited) (USD $) In Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Statement of Income [Abstract]
OPERATING REVENUES	$ 106,576	$ 102,578	$ 216,495	$ 208,688
OPERATING EXPENSES:
General and administrative	14,626	13,713	30,049	27,853
Operation and maintenance	18,164	17,462	33,437	32,963
Depreciation	22,543	21,933	45,101	43,903
Regulatory credits	(267)	(341)	(534)	(801)
Taxes, other than income taxes	4,914	4,392	10,614	9,060
Total operating expenses	59,980	57,159	118,667	112,978
Operating Income	46,596	45,419	97,828	95,710
Interest income -
Affiliated	2	5	5	9
Other	1	2	1	3
Allowance for equity funds used during construction	287	456	407	733
Miscellaneous other (expense) income, net	(25)	(25)	(138)	(645)
Total other income - net	265	438	275	100
INTEREST CHARGES:
Interest on long-term debt	11,109	11,110	22,219	22,238
Other interest	504	532	1,014	1,611
Allowance for borrowed funds used during construction	(133)	(201)	(187)	(338)
Total interest charges	11,480	11,441	23,046	23,511
INCOME BEFORE INCOME TAXES	35,381	34,416	75,057	72,299
INCOME TAXES	2	38	(5)	38
NET INCOME	$ 35,379	$ 34,378	$ 75,062	$ 72,261