Condensed Consolidated Balance Sheets (unaudited) - USD ($) $ in Thousands	Mar. 31, 2018	Sep. 30, 2017	Mar. 31, 2017
Current assets:
Cash and cash equivalents	$ 4,710	$ 5,203	$ 4,566
Restricted cash	1,572	3,046	347
Accounts receivable (less allowances for doubtful accounts of $15,582, $4,052 and $9,401, respectively)	169,555	53,720	123,285
Accounts receivable — related parties	1,564	2,807	1,739
Accrued utility revenues	62,343	13,296	36,665
Inventories	19,717	53,309	17,174
Prepaid income taxes	41	7,711	301
Regulatory assets	2,942	8,338	2,309
Derivative instruments	1,014	1,354	2,024
Prepaid expenses & other current assets	20,197	16,406	22,957
Total current assets	283,655	165,190	211,367
Property, plant and equipment, at cost (less accumulated depreciation and amortization of $1,038,824, $1,010,781 and $997,591, respectively)	2,363,373	2,274,548	2,112,013
Goodwill	182,145	182,145	182,145
Regulatory assets	358,696	360,591	392,408
Other assets	16,176	11,541	11,792
Total assets	3,204,045	2,994,015	2,909,725
Current liabilities:
Current maturities of long-term debt	6,250	39,996	59,980
Short-term borrowings	135,000	170,000	48,500
Accounts payable	59,870	71,559	58,095
Accounts payable — related parties	11,188	6,890	11,339
Regulatory liabilities	41,154	12,988	17,186
Derivative instruments	552	1,071	19
Other current liabilities	126,091	110,978	122,947
Total current liabilities	380,105	413,482	318,066
Long-term debt	827,878	711,105	711,066
Deferred income taxes	339,008	635,465	590,964
Deferred investment tax credits	2,791	2,950	3,109
Pension and postretirement benefit obligations	136,687	143,674	179,101
Regulatory liabilities, Noncurrent	339,567	36,242	33,272
Other noncurrent liabilities	60,993	63,192	63,566
Total liabilities	2,087,029	2,006,110	1,899,144
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	473,580	473,580	473,580
Retained earnings	608,344	480,857	506,906
Accumulated other comprehensive loss	(25,167)	(26,791)	(30,164)
Total common stockholder’s equity	1,117,016	987,905	1,010,581
Total liabilities and stockholder’s equity	$ 3,204,045	$ 2,994,015	$ 2,909,725