CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 180,960	$ 141,970	$ 114,809
Adjustments to reconcile net income to cash flows from operating activities
Unrealized (gain) loss on derivative instruments	(38,681)	28,534	(9,417)
Depreciation and amortization	61,399	52,742	47,310
Impairment loss on investment	0	6,351	0
Allowance for equity used during construction	(3,825)	(1,562)	(2,037)
Allowance for bad debt expense	2,859	2,504	2,627
Deferred income taxes	45,934	18,421	41,075
Manufactured gas plant remediation costs	(6,805)	(4,396)	(6,166)
Equity in earnings of equity investees, net of distributions received	6,663	2,589	3,299
Cost of removal - asset retirement obligations	(1,034)	(1,153)	(1,697)
Contributions to postemployment benefit plans	(5,778)	(4,953)	(26,028)
Changes in:
Components of working capital	81,817	85,480	(60,316)
Other noncurrent assets	38,716	10,484	9,496
Other noncurrent liabilities	25,695	19,775	1,039
Cash flows from operating activities	387,920	356,786	113,994
CASH FLOWS (USED IN) INVESTING ACTIVITIES
Expenditures for Utility plant	(140,797)	(128,254)	(110,482)
Expenditures for Solar and wind equipment	(151,002)	(135,543)	(59,125)
Expenditures for Real estate properties and other	(209)	(1,179)	(1,042)
Expenditures for Cost of removal	(28,078)	(24,312)	(26,601)
Investments in equity investees	(5,780)	(555)	0
Distribution from equity investees in excess of equity in earnings	2,620	1,150	3,079
(Payment to) withdrawal from restricted cash construction fund	(1,499)	88	56
Proceeds from sale of investment	3,016	0	0
Proceeds from sale of property	0	6,010	0
Proceeds from sale of available for sale securities	0	0	482
Cash flows (used in) investing activities	(321,729)	(282,595)	(193,633)
CASH FLOWS (USED IN) FROM FINANCING ACTIVITIES
Proceeds from issuance of common stock	37,299	15,373	37,839
Tax benefit from stock options exercised	881	414	173
Proceeds from sale-leaseback transaction	7,216	7,576	7,076
Proceeds from long-term debt	250,000	125,000	50,000
Payments of long-term debt	(37,039)	(82,586)	(8,953)
Purchases of treasury stock	(10,589)	(5,522)	(26,606)
Payments of common stock dividends	(76,532)	(70,664)	(67,230)
Net (payments of) proceeds from short-term debt	(234,650)	(64,600)	85,800
Cash flows (used in) from financing activities	(63,414)	(75,009)	78,099
Change in cash and cash equivalents	2,777	(818)	(1,540)
Cash and cash equivalents at beginning of period	2,151	2,969	4,509
Cash and cash equivalents at end of period	4,928	2,151	2,969
CHANGES IN COMPONENTS OF WORKING CAPITAL
Receivables	32,529	48,032	(72,244)
Inventories	114,638	43,130	(55,755)
Recovery of gas costs	18,979	13,015	6,100
Gas purchases payable	(54,525)	(47,528)	72,415
Gas purchases payable - related parties	202	14	(16)
Prepaid and accrued taxes	(18,161)	21,133	(8,182)
Accounts payable and other	(14,714)	34,716	726
Restricted broker margin accounts	18,452	(20,758)	15,348
Customers' credit balances and deposits	(1,545)	(2,058)	(24,059)
Other current assets	(14,038)	(4,216)	5,351
Components of working capital	81,817	85,480	(60,316)
Cash paid for:
Interest (net of amounts capitalized)	24,208	22,458	20,414
Income taxes	28,790	22,447	12,039
Accrued capital expenditures	28,676	9,655	(7,103)
Deferred gain on non-cash exchange of investments	$ 24,601	$ 0	$ 0