CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
CASH FLOWS USED IN OPERATING ACTIVITIES
Net income	$ 123,699	$ 34,929
Adjustments to reconcile net income to cash flows from operating activities
Unrealized loss on derivative instruments	34,855	28,302
Gain on sale of available for sale securities, net	(5,332)	(2,581)
Depreciation and amortization	21,854	19,260
Amortization of acquired wholesale energy contracts	3,391	0
Allowance for equity used during construction	(852)	(584)
Allowance for bad debt expense	471	230
Deferred income taxes	(26,264)	16,262
Manufactured gas plant remediation costs	(5,147)	(1,619)
Distributions received from equity investees, net of equity in earnings	(257)	1,101
Cost of removal - asset retirement obligations	(332)	(198)
Contributions to postemployment benefit plans	(1,467)	(1,712)
Tax benefit from stock-based compensation	2,831	1,188
Changes in:
Components of working capital	(189,528)	(150,480)
Other noncurrent assets	13,188	9,823
Other noncurrent liabilities	5,388	15
Cash flows used in operating activities	(23,502)	(46,064)
Expenditures for:
Utility plant	(34,638)	(31,396)
Solar and wind equipment	(18,387)	(46,785)
Real estate properties and other	(1,313)	(171)
Cost of removal	(12,752)	(7,459)
Investments in equity investees	(7,202)	(4,636)
Distribution from equity investees in excess of equity in earnings	793	688
Cash paid related to acquisition	(10,000)	0
Withdrawal from restricted cash construction fund	(43)	0
Proceeds from sale of available for sale securities	6,616	3,218
Cash flows used in investing activities	(76,926)	(86,541)
CASH FLOWS FROM FINANCING ACTIVITIES
Payments of long-term debt	(1,690)	(2,716)
Net proceeds from short-term debt	107,200	162,900
Proceeds from sale-leaseback transaction	7,820	9,587
Payments of common stock dividends	(23,607)	(21,931)
Proceeds from waiver discount issuance of common stock	22,690	0
Proceeds from issuance of common stock	3,846	4,616
Purchases of treasury stock	0	(6,355)
Tax withholding payments related to net settled stock compensation	(13,319)	(4,167)
Cash flows from financing activities	102,940	141,934
Change in cash and cash equivalents	2,512	9,329
Cash and cash equivalents at beginning of period	2,226	37,546
Cash and cash equivalents at end of period	4,738	46,875
CHANGES IN COMPONENTS OF WORKING CAPITAL
Receivables	(192,253)	(152,180)
Inventories	(2,561)	(13,954)
Recovery of gas costs	17,102	(2,472)
Gas purchases payable	43,284	47,772
Prepaid and accrued taxes	(12,418)	7,954
Accounts payable and other	(25,527)	(12,405)
Restricted broker margin accounts	(21,694)	(26,173)
Customers' credit balances and deposits	6,093	616
Other current assets	(1,554)	362
Components of working capital	(189,528)	(150,480)
Cash paid (received) for:
Interest (net of amounts capitalized)	9,758	8,153
Income taxes	(191)	(7,020)
Accrued capital expenditures	$ 26,034	$ 28,442