Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Utility plant:
Electric plant in service	$ 3,044,963	$ 2,857,913
Less accumulated depreciation and amortization	(1,204,872)	(1,162,483)
Net plant in service	1,840,091	1,695,430
Construction work in progress	251,125	287,358
Nuclear fuel; includes fuel in process of $37,294 and $56,129, respectively	195,317	189,921
Less accumulated amortization	(85,992)	(70,366)
Net nuclear fuel	109,325	119,555
Net utility plant	2,200,541	2,102,343
Current assets:
Cash and cash equivalents	61,948	111,057
Accounts receivable, principally trade, net of allowance for doubtful accounts of $2,799 and $2,906, respectively	97,997	62,900
Accumulated deferred income taxes	14,149	20,292
Inventories, at cost	47,091	42,358
Undercollection of fuel revenues	6,605	0
Prepayments and other	8,990	9,627
Total current assets	236,780	246,234
Deferred charges and other assets:
Decommissioning trust funds	202,907	187,053
Regulatory assets	103,503	101,590
Other	33,661	31,830
Total deferred charges and other assets	340,071	320,473
Total assets	2,777,392	2,669,050
Capitalization:
Common stock, stated value $1 per share, 100,000,000 shares authorized, 65,625,339 and 65,520,551 shares issued, and 121,363 and 84,446 restricted shares, respectively	65,747	65,605
Capital in excess of stated value	313,616	310,994
Retained earnings	995,144	939,131
Accumulated other comprehensive loss, net of tax	(56,162)	(66,084)
Total stockholders equity subtotal before treasury stock	1,318,345	1,249,646
Treasury stock, 25,492,919 shares at cost	(424,647)	(424,647)
Common stock equity	893,698	824,999
Long-term debt	999,598	999,535
Total capitalization	1,893,296	1,824,534
Current liabilities:
Short-term borrowings under the revolving credit facility	15,491	22,155
Accounts payable, principally trade	47,103	61,581
Taxes accrued	31,849	29,248
Interest accrued	14,370	12,127
Overcollection of fuel revenues	2,886	4,643
Other	29,405	21,995
Total current liabilities	141,104	151,749
Deferred credits and other liabilities:
Accumulated deferred income taxes	405,331	358,674
Accrued pension liability	113,842	125,690
Accrued postretirement benefit liability	101,864	99,170
Asset retirement obligation	67,169	62,784
Regulatory liabilities	26,495	22,179
Other	28,291	24,270
Total deferred credits and other liabilities	742,992	692,767
Commitments and contingencies
Total capitalization and liabilities	$ 2,777,392	$ 2,669,050