CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 131,672	$ 180,960	$ 141,970
Adjustments to reconcile net income to cash flows from operating activities
Unrealized loss (gain) on derivative instruments	46,883	(38,681)	28,534
Depreciation and amortization	72,748	61,399	52,742
Impairment loss on investment	0	0	6,351
Allowance for equity used during construction	(4,375)	(3,825)	(1,562)
Allowance for bad debt expense	1,616	2,859	2,504
Deferred income taxes	27,721	45,934	18,421
Manufactured gas plant remediation costs	(8,106)	(6,805)	(4,396)
Distributions received from equity investees, net of equity in earnings	4,534	6,663	2,589
Cost of removal - asset retirement obligations	(403)	(1,034)	(1,153)
Contributions to postemployment benefit plans	(33,359)	(5,778)	(4,953)
Tax benefit from stock based compensation	1,755	881	414
Changes in:
Components of working capital	(123,325)	81,817	85,480
Other noncurrent assets	3,933	38,716	10,484
Other noncurrent liabilities	21,336	27,841	20,724
Cash flows from operating activities	142,630	390,947	358,149
Expenditures for:
Utility plant	(176,067)	(140,797)	(128,254)
Solar and wind equipment	(149,063)	(151,002)	(135,543)
Real estate properties and other	(1,896)	(209)	(1,179)
Cost of removal	(29,066)	(28,078)	(24,312)
Investments in equity investees	(11,176)	(5,780)	(555)
Distributions from equity investees in excess of equity in earnings	2,351	2,620	1,150
Withdrawal from (payment to) from restricted cash construction fund	979	(1,499)	88
Proceeds from sale of investment	0	3,016	0
Proceeds from sale of property	748	0	6,010
Cash flows (used in) investing activities	(363,190)	(321,729)	(282,595)
CASH FLOWS FROM (USED IN) FINANCING ACTIVITIES
Proceeds from issuance of common stock	16,010	37,299	15,373
Tax withholding payments related to net settled stock compensation	(3,547)	(2,146)	(949)
Proceeds from sale-leaseback transaction	7,107	7,216	7,576
Proceeds from long-term debt	275,000	250,000	125,000
Payments of long-term debt	(13,289)	(37,039)	(82,586)
Purchases of treasury stock	(1,008)	(10,589)	(5,522)
Payments of common stock dividends	(82,445)	(76,532)	(70,664)
Net proceeds from (payments of) short-term debt	55,350	(234,650)	(64,600)
Cash flows from (used in) financing activities	253,178	(66,441)	(76,372)
Change in cash and cash equivalents	32,618	2,777	(818)
Cash and cash equivalents at beginning of period	4,928	2,151	2,969
Cash and cash equivalents at end of period	37,546	4,928	2,151
CHANGES IN COMPONENTS OF WORKING CAPITAL
Receivables	11,303	32,529	48,032
Inventories	(45,986)	114,638	43,130
Recovery of gas costs	(39,642)	18,979	13,015
Gas purchases payable	(11,963)	(54,525)	(47,528)
Gas purchases payable - related parties	(411)	202	14
Prepaid and accrued taxes	2,385	(18,161)	21,133
Accounts payable and other	(15,656)	(14,714)	34,716
Restricted broker margin accounts	(38,752)	18,452	(20,758)
Customers’ credit balances and deposits	12,044	(1,545)	(2,058)
Other current assets	3,353	(14,038)	(4,216)
Components of working capital	(123,325)	81,817	85,480
Cash paid (received) for:
Interest (net of amounts capitalized)	31,996	24,208	22,458
Income taxes	(3,516)	28,790	22,447
Accrued capital expenditures	48,881	28,676	9,655
Deferred gain on non-cash exchange of investments	$ 0	$ 24,601	$ 0