Condensed Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2011
Current assets:
Cash and cash equivalents	$ 7,924	$ 1,259	$ 4,228
Restricted cash	2,106	0	3,066
Accounts receivable (less allowances for doubtful accounts of $4,232, $3,588 and $5,824, respectively)	97,821	47,362	102,332
Accounts receivable — related parties	7,230	4,571	8,534
Accrued utility revenues	59,036	16,911	53,811
Inventories	61,861	67,334	97,451
Deferred income taxes	42,803	46,436	37,779
Regulatory assets	3,632	6,473	8,126
Derivative financial instruments	4,760	5,468	18
Prepaid expenses & other current assets	20,948	29,313	15,720
Total current assets	308,121	225,127	331,065
Property, plant and equipment, at cost (less accumulated depreciation and amortization of $826,781, $815,720 and $793,418, respectively)	1,496,606	1,479,949	1,427,332
Goodwill	182,145	182,145	182,145
Regulatory assets	326,996	331,932	293,365
Other assets	5,836	4,026	4,551
Total assets	2,319,704	2,223,179	2,238,458
Current liabilities:
Current maturities of long-term debt	133,000	133,000	40,000
Bank loans	73,100	9,200	57,700
Accounts payable	48,762	46,754	44,450
Accounts payable — related parties	8,476	10,192	7,024
Deferred fuel refunds	1,916	4,435	5,019
Derivative financial instruments	35,947	36,011	14,697
Other current liabilities	121,726	131,092	163,711
Total current liabilities	422,927	370,684	332,601
Long-term debt	467,000	467,000	600,000
Deferred income taxes	422,190	417,052	355,446
Deferred investment tax credits	4,526	4,612	4,871
Pension and postretirement benefit obligations	177,094	179,056	135,119
Other noncurrent liabilities	57,498	56,262	83,505
Total liabilities	1,551,235	1,494,666	1,511,542
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	468,985	468,692	468,417
Retained earnings	266,191	229,379	221,565
Accumulated other comprehensive loss	(26,966)	(29,817)	(23,325)
Total common stockholder’s equity	768,469	728,513	726,916
Total liabilities and stockholder’s equity	$ 2,319,704	$ 2,223,179	$ 2,238,458