CONSOLIDATED BALANCE SHEETS (UNAUDITED) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Current assets
Cash and cash equivalents	$ 1,792	$ 1,571
Accounts receivable, net	45,884	51,838
Accounts receivable from affiliates	2,102	0
Accrued unbilled revenues	39,043	48,668
Inventories	18,007	25,703
Regulatory assets	10,354	14,133
Prepaid taxes	23,833	21,841
Deferred income taxes	5,320	0
Prepayments and other	1,731	2,991
Total current assets	148,066	166,745
Property, plant and equipment, net	1,243,438	1,207,698
Other assets
Regulatory assets	228,139	229,910
Other investments	3,043	4,148
Other	3,114	2,970
Total other assets	234,296	237,028
Total assets	1,625,800	1,611,471
Current liabilities
Current portion of long-term debt	1,266	1,286
Short-term debt	79,000	66,000
Notes payable to affiliates	550	500
Accounts payable	21,481	30,897
Accounts payable to affiliates	30,882	23,285
Dividends payable to parent	8,081	8,107
Regulatory liabilities	4,818	16,609
Environmental liabilities	31,674	30,699
Accrued interest	6,500	6,521
Derivative instruments	0	2,514
Other	10,223	11,393
Total current liabilities	194,475	197,811
Deferred credits and other liabilities
Deferred income taxes	255,029	234,222
Deferred investment tax credits	8,786	8,499
Regulatory liabilities	121,062	119,187
Environmental liabilities	78,809	79,399
Customer advances	16,720	15,765
Pension and employee benefit obligations	48,495	60,328
Other	6,525	7,024
Total deferred credits and other liabilities	535,426	524,424
Commitments and contingencies
Capitalization
Long-term debt	368,125	368,083
Common stock - 1,000,000 shares authorized of $100 par value; 933,000 shares outstanding at June 30, 2012 and Dec. 31, 2011, respectively	93,300	93,300
Additional paid in capital	189,233	187,071
Retained earnings	245,717	241,296
Accumulated other comprehensive loss	(476)	(514)
Total common stockholder's equity	527,774	521,153
Total liabilities and equity	$ 1,625,800	$ 1,611,471