Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Plant and property, at original cost:
Electric and water	$ 2,176,188	$ 2,074,748
Natural gas	69,851	66,918
Other	37,983	34,984
Construction work in progress	56,347	24,141
Total plant and property, Gross	2,340,369	2,200,791
Accumulated depreciation and amortization	682,737	637,139
Total plant and property, Net	1,657,632	1,563,652
Current assets:
Cash and cash equivalents	3,375	5,408
Restricted cash	4,357	4,357
Accounts receivable - trade, net of allowance of $1,388 and $1,138, respectively	38,874	42,296
Accrued unbilled revenues	23,254	20,326
Accounts receivable - other	13,277	16,269
Fuel, materials and supplies	61,870	62,239
Prepaid expenses and other	21,806	14,629
Unrealized gain in fair value of derivative contracts	96
Regulatory assets	6,377	11,839
Total current assets	173,286	177,363
Noncurrent assets and deferred charges:
Regulatory assets	243,958	227,807
Goodwill	39,492	39,492
Unamortized debt issuance costs	7,606	9,331
Unrealized gain in fair value of derivative contracts	191	2
Other	4,204	4,188
Total noncurrent assets and deferred charges	295,451	280,820
Total assets	2,126,369	2,021,835
Capitalization and liabilities
Common stock, $1 par value, 100,000,000 shares authorized, 42,484,363 and 41,977,725 shares issued and outstanding, respectively	42,484	41,978
Capital in excess of par value	628,199	618,304
Retained earnings	47,115	33,707
Total common stockholders' equity	717,798	693,989
Long-term debt (net of current portion)
Obligations under capital lease	4,441	4,739
First mortgage bonds and secured debt	487,541	487,948
Unsecured debt	199,644	199,572
Total long-term debt	691,626	692,259
Total long-term debt and common stockholders' equity	1,409,424	1,386,248
Current liabilities:
Accounts payable and accrued liabilities	66,559	59,307
Current maturities of long-term debt	714	933
Short-term debt	24,000	12,000
Regulatory liabilities	3,089	3,150
Customer deposits	12,001	11,428
Interest accrued	5,902	5,958
Unrealized loss in fair value of derivative contracts	3,403	4,769
Taxes accrued	2,992	2,634
Total current liabilities	118,660	100,179
Commitments and contingencies (Note 11)
Noncurrent liabilities and deferred credits:
Regulatory liabilities	134,269	125,290
Deferred income taxes	301,967	263,933
Unamortized investment tax credits	18,897	19,226
Pension and other postretirement benefit obligations	120,808	103,371
Unrealized loss in fair value of derivative contracts	3,819	5,081
Other	18,525	18,507
Total noncurrent liabilities and deferred credits	598,285	535,408
Total capitalization and liabilities	$ 2,126,369	$ 2,021,835