Condensed Consolidated Balance Sheets (unaudited) - USD ($) $ in Thousands	Mar. 31, 2019	Sep. 30, 2018	Mar. 31, 2018
Current assets:
Cash and cash equivalents	$ 41,421	$ 10,314	$ 4,710
Restricted cash	837	1,190	1,572
Accounts receivable (less allowances for doubtful accounts of $16,205, $9,760 and $15,582, respectively)	156,634	71,507	169,555
Accounts receivable — related parties	1,999	2,273	1,564
Accrued utility revenues	52,068	13,977	62,343
Inventories	19,942	52,413	19,717
Prepaid income taxes	536	53,857	41
Regulatory assets	1,343	7,475	2,942
Derivative instruments	1,047	3,004	1,014
Prepaid expenses	5,883	9,006	8,746
Other current assets	10,692	8,003	11,451
Total current assets	292,402	233,019	283,655
Property, plant and equipment, at cost (less accumulated depreciation of $1,101,798, $1,074,521 and $1,038,824, respectively)	2,646,983	2,541,768	2,363,373
Goodwill	182,145	182,145	182,145
Regulatory assets	298,026	293,527	358,696
Other assets	18,881	16,117	16,176
Total assets	3,438,437	3,266,576	3,204,045
Current liabilities:
Current maturities of long-term debt	8,546	9,001	6,250
Short-term borrowings	105,000	189,500	135,000
Accounts payable	74,833	87,861	59,870
Accounts payable — related parties	8,881	9,585	11,188
Regulatory liabilities	36,558	40,131	41,154
Other current liabilities	107,722	114,256	126,643
Total current liabilities	341,540	450,334	380,105
Long-term debt	974,779	828,995	827,878
Deferred income taxes	423,377	400,939	339,008
Pension and postretirement benefit obligations	75,626	81,590	136,687
Regulatory liabilities	342,966	350,044	339,567
Other noncurrent liabilities	68,354	61,386	63,784
Total liabilities	2,226,642	2,173,288	2,087,029
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	704,051	579,778	608,344
Accumulated other comprehensive loss	(26,095)	(20,329)	(25,167)
Total common stockholder’s equity	1,211,795	1,093,288	1,117,016
Total liabilities and stockholder’s equity	$ 3,438,437	$ 3,266,576	$ 3,204,045