CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2010
Cash Flows From Operating Activities
Net income (loss)	$ 216,717	$ 207,601	$ 205,839
Adjustments to reconcile net income to net cash provided by operating activities:
Asset impairments	5,288	30,270	0
Gain on sale of discontinued operations	(9,868)	0	0
Depreciation and amortization:
Charged to depreciation and amortization	246,093	233,155	216,960
Charged to other accounts	484	228	173
Deferred income taxes	104,319	117,353	196,731
Stock-based compensation	19,222	11,586	12,655
Debt financing costs	8,147	9,438	11,908
Other	(493)	(961)	(1,245)
Changes in assets and liabilities:
(Increase) decreased in accounts receivable	32,578	(96)	(40,401)
(Increase) decrease in gas stored underground	28,417	27,737	54,014
(Increase) decrease in other current assets	20,989	(38,048)	(18,387)
(Increase) decrease in deferred charges and other assets	(50,055)	(53,519)	14,886
Increase (decrease) in account payable and accrued liabilities	(64,234)	23,904	58,069
Increase (decrease) in other current liabilities	7,889	(57,495)	(48,992)
Increase in deferred credits and other liabilities	21,424	71,691	64,266
Net cash provided by operating activities	586,917	582,844	726,476
Cash Flows From Investing Activities
Capital expenditures	(732,858)	(622,965)	(542,636)
Other, net	(4,625)	(4,421)	(66)
Proceeds from Sale of Productive Assets	128,223	0	0
Net cash used in investing activities	(609,260)	(627,386)	(542,702)
Cash Flows From Financing Activities
Net increase in short-term debt	354,141	83,306	54,268
Net proceeds from issuance of long-term debt	0	394,466	0
Settlement of Treasury lock agreement	0	20,079	0
Unwinding of Treasury lock agreements	0	27,803	0
Repayment of long-term debt	(257,034)	(360,131)	(131)
Cash dividends paid	(125,796)	(124,011)	(124,287)
Repurchase of common stock	(12,535)	0	(100,450)
Repurchase of equity awards	(5,219)	(5,299)	(1,191)
Issuance of common stock	1,606	7,796	8,766
Net cash provided by (used in) financing activities	(44,837)	44,009	(163,025)
Net increase (decrease) in cash and cash equivalents	(67,180)	(533)	20,749
Cash and cash equivalents at beginning of period	131,419	131,952	111,203
Cash and cash equivalents at end of period	$ 64,239	$ 131,419	$ 131,952