Condensed Consolidated Balance Sheets (unaudited) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 13,008	$ 4,707	$ 7,924
Restricted cash	0	3,181	2,106
Accounts receivable (less allowances for doubtful accounts of $5,885, $5,519 and $4,232, respectively)	111,840	53,341	97,821
Accounts receivable — related parties	9,431	3,497	7,230
Accrued utility revenues	66,370	18,868	59,036
Inventories	80,675	89,661	61,861
Deferred income taxes	12,317	14,165	22,094
Regulatory assets	361	8,217	3,632
Derivative financial instruments	2,058	43	4,760
Prepaid expenses & other current assets	14,649	15,862	20,948
Total current assets	310,709	211,542	287,412
Property, plant and equipment, at cost (less accumulated depreciation and amortization of $865,852, $853,675 and $826,781, respectively)	1,594,554	1,574,135	1,496,606
Goodwill	182,145	182,145	182,145
Regulatory assets	233,636	236,694	326,996
Other assets	5,626	5,806	5,836
Total assets	2,326,670	2,210,322	2,298,995
Current liabilities:
Current maturities of long-term debt	0	0	133,000
Bank loans	73,500	17,500	73,100
Accounts payable	60,405	51,970	48,762
Accounts payable — related parties	17,250	12,487	8,476
Deferred fuel refunds	7,524	8,283	1,916
Derivative financial instruments	3,272	6,677	35,947
Other current liabilities	131,513	110,596	121,726
Total current liabilities	293,464	207,513	422,927
Long-term debt	642,000	642,000	467,000
Deferred income taxes	440,645	436,810	401,481
Deferred investment tax credits	4,185	4,270	4,526
Pension and postretirement benefit obligations	73,132	72,505	177,094
Other noncurrent liabilities	53,610	55,610	57,498
Total liabilities	1,507,036	1,418,708	1,530,526
Commitments and contingencies (note 8)
Common stockholder’s equity:
Common Stock, $2.25 par value (authorized — 40,000,000 shares; issued and outstanding — 26,781,785 shares)	60,259	60,259	60,259
Additional paid-in capital	470,189	470,098	468,985
Retained earnings	297,417	269,977	266,191
Accumulated other comprehensive loss	(8,231)	(8,720)	(26,966)
Total common stockholder’s equity	819,634	791,614	768,469
Total liabilities and stockholder’s equity	$ 2,326,670	$ 2,210,322	$ 2,298,995