CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 114,809	$ 92,879	$ 101,299
Adjustments to reconcile net income to cash flows from operating activities:
Unrealized (gain) loss on derivative instruments	(9,417)	35,789	36,876
Depreciation and amortization	47,310	41,643	35,200
Allowance for equity used during construction	(2,037)	(638)	(2,100)
Allowance for bad debt expense	2,627	3,932	4,865
Deferred income taxes	41,075	(5,323)	35,034
Manufactured gas plant remediation costs	(6,166)	(7,965)	(14,115)
Equity in earnings of affiliates, net of distributions received	3,299	6,799	2,791
Cost of removal - asset retirement obligations	(1,697)	(1,196)	(826)
Contributions to postemployment benefit plans	(26,028)	(25,874)	(11,496)
Changes in:
Components of working capital	(60,316)	(95,357)	43,748
Other noncurrent assets	9,496	(20,539)	7,081
Other noncurrent liabilities	1,039	26,931	11,744
Cash flows from operating activities	113,994	51,081	250,101
CASH FLOWS (USED IN) INVESTING ACTIVITIES
Utility plant	(110,482)	(104,277)	(93,624)
Solar equipment	(59,125)	(89,726)	(71,989)
Real estate properties and other	(1,042)	(1,334)	(3,549)
Cost of removal	(26,601)	(12,178)	(8,369)
Investments in equity investees	0	(8,800)	0
Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital	3,079	0	0
Withdrawal from restricted cash construction fund	56	(802)	58
Proceeds from asset sales	0	0	2,396
Proceeds from sale of available-for-sale securities	482	0	0
Cash flows (used in) investing activities	(193,633)	(217,117)	(175,077)
CASH FLOWS FROM (USED IN) FINANCING ACTIVITIES
Proceeds from issuance of common stock	37,839	13,834	13,704
Tax benefit from stock options exercised	173	780	2,007
Proceeds from sale-leaseback transaction	7,076	6,522	5,901
Proceeds from long-term debt	50,000	100,000	97,045
Payments of long-term debt	(8,953)	(8,025)	(130,091)
Purchases of treasury stock	(26,606)	(8,768)	(10,193)
Payments of common stock dividends	(67,230)	(61,688)	(58,650)
Net proceeds of short-term debt	85,800	120,450	11,750
Cash flows from (used in) financing activities	78,099	163,105	(68,527)
Change in cash and cash equivalents	(1,540)	(2,931)	6,497
Cash and cash equivalents at beginning of period	4,509	7,440	943
Cash and cash equivalents at end of period	2,969	4,509	7,440
CHANGES IN COMPONENTS OF WORKING CAPITAL
Receivables	(72,244)	36,670	(49,473)
Inventories	(55,755)	28,814	40,363
Recovery of gas costs	6,100	(11,686)	41,118
Gas purchases payable	72,399	(70,277)	22,289
Prepaid and accrued taxes	(8,182)	23,036	(8,691)
Accounts payable and other	726	(3,418)	4,469
Restricted broker margin accounts	15,348	666	(31,813)
Customers' credit balances and deposits	(24,059)	(65,324)	21,819
Other current assets	5,351	(33,838)	3,667
Components of working capital	(60,316)	(95,357)	43,748
SUPPLEMENTAL DISCLOSURES OF CASH FLOWS INFORMATION
Cash paid for Interest (net of amounts capitalized)	20,414	16,670	17,323
Cash paid for Income taxes	12,039	10,053	5,165
SUPPLEMENTAL SCHEDULE OF NONCASH INVESTING ACTIVITIES
Accrued capital expenditures	$ (7,103)	$ 8,257	$ 9,423