Condensed Consolidated Balance Sheets (unaudited) - USD ($) $ in Thousands	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 21,515	$ 10,314	$ 7,289
Restricted cash	3,308	1,190	3,665
Accounts receivable (less allowances for doubtful accounts of $11,694, $9,760 and $6,398, respectively)	117,418	71,507	105,141
Accounts receivable — related parties	498	2,273	1,406
Accrued utility revenues	64,694	13,977	95,854
Inventories	50,798	52,413	49,717
Prepaid income taxes	43,060	53,857	1,977
Regulatory assets	3,267	7,475	605
Derivative instruments	1,070	3,004	678
Prepaid expenses	12,251	9,006	10,402
Other current assets	12,909	8,003	12,664
Total current assets	330,788	233,019	289,398
Property, plant and equipment, at cost (less accumulated depreciation of $1,091,212, $1,074,521 and $1,026,450, respectively)	2,597,546	2,541,768	2,327,664
Goodwill	182,145	182,145	182,145
Regulatory assets	295,496	293,527	362,237
Other assets	18,798	16,117	13,249
Total assets	3,424,773	3,266,576	3,174,693
Current liabilities:
Current maturities of long-term debt	8,786	9,001	144,374
Short-term borrowings	296,000	189,500	181,500
Accounts payable	93,157	87,861	69,697
Accounts payable — related parties	25,063	9,585	13,420
Regulatory liabilities	26,994	40,131	17,091
Derivative instruments	467	0	2,244
Other current liabilities	104,466	114,256	106,177
Total current liabilities	554,933	450,334	534,503
Long-term debt	826,844	828,995	711,242
Deferred income taxes	414,470	400,939	340,772
Pension and postretirement benefit obligations	81,072	81,590	140,224
Regulatory liabilities	346,474	350,044	340,391
Other noncurrent liabilities	67,176	61,386	65,540
Total liabilities	2,290,969	2,173,288	2,132,672
Commitments and contingencies (Note 9)
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	473,580
Retained earnings	626,191	579,778	534,161
Accumulated other comprehensive loss	(26,226)	(20,329)	(25,979)
Total common stockholder’s equity	1,133,804	1,093,288	1,042,021
Total liabilities and stockholder’s equity	$ 3,424,773	$ 3,266,576	$ 3,174,693