CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Plant and property, at original cost:
Electric	$ 2,181,257	$ 2,176,188
Natural gas	70,192	69,851
Other	38,188	37,983
Construction work in progress	82,086	56,347
Total plant and property, Gross	2,371,723	2,340,369
Accumulated depreciation and amortization	694,166	682,737
Total plant and property, Net	1,677,557	1,657,632
Current assets:
Cash and cash equivalents	3,170	3,375
Restricted cash	1,772	4,357
Accounts receivable - trade, net of allowance of $2,109 and $1,388, respectively	48,710	38,874
Accrued unbilled revenues	20,361	23,254
Accounts receivable - other	8,430	13,277
Fuel, materials and supplies	52,140	61,870
Prepaid expenses and other	21,738	21,806
Unrealized gain in fair value of derivative contracts	900	96
Regulatory assets	7,685	6,377
Total current assets	164,906	173,286
Noncurrent assets and deferred charges:
Regulatory assets	237,942	243,958
Goodwill	39,492	39,492
Unamortized debt issuance costs	7,440	7,606
Unrealized gain in fair value of derivative contracts	256	191
Other	8,180	4,204
Total noncurrent assets and deferred charges	293,310	295,451
Total Assets	2,135,773	2,126,369
Capitalization and Liabilities
Common stock, $1 par value, 42,646,040 and 42,484,363 shares issued and outstanding, respectively	42,646	42,484
Capital in excess of par value	631,777	628,199
Retained earnings	49,100	47,115
Total common stockholders' equity	723,523	717,798
Long-term debt (net of current portion):
Obligations under capital lease	4,374	4,441
First mortgage bonds and secured debt	487,550	487,541
Unsecured debt	199,662	199,644
Total long-term debt	691,586	691,626
Total long-term debt and common stockholders' equity	1,415,109	1,409,424
Current liabilities:
Accounts payable and accrued liabilities	50,767	66,559
Current maturities of long-term debt	554	714
Short-term debt	23,000	24,000
Regulatory liabilities	3,542	3,089
Customer deposits	12,238	12,001
Interest accrued	13,163	5,902
Other current liabilities	764
Unrealized loss in fair value of derivative contracts	1,905	3,403
Taxes accrued	8,314	2,992
Total current liabilities	114,247	118,660
Commitments and contingencies (Note 7)
Noncurrent liabilities and deferred credits:
Regulatory liabilities	136,528	134,269
Deferred income taxes	307,660	301,967
Unamortized investment tax credits	18,617	18,897
Pension and other postretirement benefit obligations	121,697	120,808
Unrealized loss in fair value of derivative contracts	3,307	3,819
Other	18,608	18,525
Total noncurrent liabilities and deferred credits	606,417	598,285
Total Capitalization and Liabilities	$ 2,135,773	$ 2,126,369