Condensed Consolidated Balance Sheets (unaudited) - USD ($) $ in Thousands	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 9,838	$ 2,819	$ 15,585
Restricted cash	0	583	6,324
Accounts receivable (less allowances for doubtful accounts of $5,518, $3,946 and $5,283, respectively)	97,188	44,692	78,954
Accounts receivable — related parties	1,886	398	2,671
Accrued utility revenues	55,616	12,753	30,776
Inventories	39,693	42,340	49,365
Prepaid income taxes	2,013	1,956	31,465
Regulatory assets	1,635	3,208	3,905
Derivative instruments	7,077	4,263	234
Prepaid expenses & other current assets	26,131	22,009	28,670
Total current assets	241,077	135,021	247,949
Property, plant and equipment, at cost (less accumulated depreciation and amortization of $987,850, $975,374 and $940,655, respectively)	2,071,718	2,023,541	1,870,732
Goodwill	182,145	182,145	182,145
Regulatory assets	391,229	391,933	297,914
Other assets	12,354	10,451	5,428
Total assets	2,898,523	2,743,091	2,604,168
Current liabilities:
Current maturities of long-term debt	39,981	19,986	174,924
Short-term borrowings	98,400	112,500	217,700
Accounts payable	70,703	65,180	51,954
Accounts payable — related parties	11,385	3,995	7,069
Regulatory liability — deferred fuel and power refunds	23,809	22,299	28,083
Derivative instruments	295	310	10,351
Other current liabilities	115,489	109,640	112,528
Total current liabilities	360,062	333,910	602,609
Long-term debt	731,030	651,455	372,945
Deferred income taxes	566,519	550,229	524,287
Deferred investment tax credits	3,189	3,268	3,513
Pension and postretirement benefit obligations	181,809	184,516	132,899
Other noncurrent liabilities	96,178	94,976	58,469
Total liabilities	1,938,787	1,818,354	1,694,722
Commitments and contingencies (Note 7)
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	473,580	473,580	471,952
Retained earnings	456,781	422,516	388,494
Accumulated other comprehensive loss	(30,884)	(31,618)	(11,259)
Total common stockholder’s equity	959,736	924,737	909,446
Total liabilities and stockholder’s equity	$ 2,898,523	$ 2,743,091	$ 2,604,168