CONDENSED CONSOLIDATED STATEMENT OF CASH FLOWS (Unaudited) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 105,675	$ 111,892
Adjustments to reconcile net income to cash flows from operating activities:
Unrealized loss (gain) on derivative instruments	20,466	(15,353)
Depreciation and amortization	23,024	20,039
Allowance for equity used during construction	(1,333)	(139)
Allowance for bad debt expense	1,341	1,586
Deferred income taxes	14,639	20,920
Manufactured gas plant remediation costs	(3,254)	(4,964)
Equity in earnings of affiliates, net of distributions received	1,835	3,852
Cost of removal - asset retirement obligations	(137)	(368)
Contributions to postemployment benefit plans	(23,102)	(22,982)
Changes in:
Components of working capital	(44,510)	(31,567)
Other noncurrent assets	5,198	11,690
Other noncurrent liabilities	8,539	10,018
Cash flows from operating activities	108,381	104,624
CASH FLOWS (USED IN) INVESTING ACTIVITIES
Utility plant expenditures	(51,376)	(42,380)
Solar equipment expenditures	(24,865)	(61,786)
Real estate properties and other expenditures	(298)	(459)
Cost of removal expenditures	(14,323)	(6,765)
Distribution from equity investees	648	0
Withdrawal from restricted cash construction fund	0	136
Cash flows (used in) investing activities	(90,214)	(111,254)
CASH FLOWS (USED IN) FROM FINANCING ACTIVITIES
Proceeds from issuance of common stock	6,922	7,164
Tax benefit from stock options exercised	79	222
Proceeds from sale-leaseback transaction	7,076	6,522
Payments of long-term debt	(3,833)	(3,371)
Purchases of treasury stock	(1,311)	(4,800)
Payments of common stock dividends	(33,913)	(30,695)
Net proceeds from short-term debt	8,300	31,950
Cash flows (used in) from financing activities	(16,680)	6,992
Change in cash and cash equivalents	1,487	362
Cash and cash equivalents at beginning of period	4,509	7,440
Cash and cash equivalents at end of period	5,996	7,802
CHANGES IN COMPONENTS OF WORKING CAPITAL
Receivables	(245,241)	19,773
Inventories	92,822	118,920
Recovery of gas costs	(542)	(21,177)
Gas purchases payable	88,263	(80,941)
Prepaid and accrued taxes	46,900	47,025
Accounts payable and other	(5,070)	(4,573)
Restricted broker margin accounts	(10,196)	(14,249)
Customers' credit balances and deposits	(30,579)	(82,321)
Other current assets	19,133	(14,024)
Components of working capital	(44,510)	(31,567)
SUPPLEMENTAL DISCLOSURES OF CASH FLOWS INFORMATION
Cash paid for Interest (net of amounts capitalized)	10,207	8,324
Cash paid for Income taxes	4,111	814
SUPPLEMENTAL SCHEDULE OF NONCASH INVESTING ACTIVITIES
Accrued capital expenditures	$ (9,463)	$ 5,041