CONSOLIDATED STATEMENT OF SHAREHOLDERS' EQUITY (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock [Member]	Additional Paid In Capital [Member]	Accumulated Other Comprehensive Income [Member]	Retained Earnings [Member]
Common shareholders' equity, beginning balance at Sep. 30, 2009	$ 2,176,761	$ 463	$ 1,791,129	$ (20,184)	$ 405,353
Common stock shares outstanding, balance at Sep. 30, 2009		92,551,709
Comprehensive income:
Net income (loss)	205,839				205,839
Unrealized holding gains (losses) on investments, net	1,745			1,745
Treasury Lock Agreements Net	2,030			2,030
Cash Flow Hedges, Net	(6,963)			(6,963)
Repurchase of common stock, amount	(100,450)	(15)	(100,435)
Repurchase of common stock, shares		(2,958,580)
Repurchase of equity awards, amount	(1,191)	(1)	(1,191)
Repurchase of equity awards, shares		(37,365)
Cash dividends	(124,287)				(124,287)
Common stock issued:
Direct stock purchase plan, amount	2,882	1	2,881
Direct stock purchase plan, shares		103,529
Retirement savings plan, amount	2,281	0	2,281
Retirement savings plan, shares		79,722
1998 Long-term incentive plan, amount	8,710	2	8,708
1998 Long-term incentive plan, shares		421,706
Employee stock-based compensation	10,894		10,894
Outside directors stock-for-fee-plan, amount	97		97
Stock Issued During Period Shares Directors Stock For Fee Plan		3,382
Common shareholders' equity, ending balance at Sep. 30, 2010	2,178,348	451	1,714,364	(23,372)	486,905
Common stock shares outstanding, ending balance at Sep. 30, 2010		90,164,103
Comprehensive income:
Net income (loss)	207,601				207,601
Unrealized holding gains (losses) on investments, net	(1,647)			(1,647)
Treasury Lock Agreements Net	(28,689)			(28,689)
Cash Flow Hedges, Net	5,248			5,248
Repurchase of common stock, amount	0	(2)	2
Repurchase of common stock, shares		(375,468)
Repurchase of equity awards, amount	(5,299)		(5,298)
Repurchase of equity awards, shares		(169,793)
Cash dividends	(124,011)				(124,011)
Common stock issued:
Direct stock purchase plan, amount	(54)	0	(54)
Direct stock purchase plan, shares		0
1998 Long-term incentive plan, amount	13,889	3	13,886
1998 Long-term incentive plan, shares		675,255
Employee stock-based compensation	9,958		9,958
Outside directors stock-for-fee-plan, amount	77		77
Stock Issued During Period Shares Directors Stock For Fee Plan		2,385
Common shareholders' equity, ending balance at Sep. 30, 2011	2,255,421	451	1,732,935	(48,460)	570,495
Common stock shares outstanding, ending balance at Sep. 30, 2011		90,296,482
Comprehensive income:
Net income (loss)	216,717				216,717
Unrealized holding gains (losses) on investments, net	3,103			3,103
Treasury Lock Agreements Net	(10,116)			(10,116)
Cash Flow Hedges, Net	7,866			7,866
Repurchase of common stock, amount	(12,535)	(2)	(12,533)
Repurchase of common stock, shares		(387,991)
Repurchase of equity awards, amount	(5,219)	0	(5,219)
Repurchase of equity awards, shares		(153,255)
Cash dividends	(125,796)				(125,796)
Common stock issued:
Direct stock purchase plan, amount	(65)	0	(65)
Direct stock purchase plan, shares		0
1998 Long-term incentive plan, amount	12,037	2	12,519		(484)
1998 Long-term incentive plan, shares		482,289
Employee stock-based compensation	17,752		17,752
Outside directors stock-for-fee-plan, amount	78		78
Stock Issued During Period Shares Directors Stock For Fee Plan		2,375
Common shareholders' equity, ending balance at Sep. 30, 2012	$ 2,359,243	$ 451	$ 1,745,467	$ (47,607)	$ 660,932
Common stock shares outstanding, ending balance at Sep. 30, 2012		90,239,900