Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated other comprehensive income (loss)	Treasury Stock	Total
Balance at Sep. 30, 2013	$ 10,874	$ 288,758	$ 4,105,011	$ 132,530	$ (91,098)	$ 4,446,075
Balance (in shares) at Sep. 30, 2013	108,739,000
Balance (in shares) at Sep. 30, 2013					2,022,000
Comprehensive Income:
Net income (loss)			706,563			706,563
Other comprehensive income (loss)				(49,404)		(49,404)
Dividends declared ($2.625 per share in 2014,$2.75 per share in 2015 and $2.775 per share in 2016)			(285,585)			(285,585)
Exercise of stock options	$ 161	41,911			$ (18,822)	23,250
Exercise of stock options (in shares)	1,613,000				216,000
Tax benefit of stock-based awards		26,616				26,616
Stock issued for vested restricted stock, net of shares withheld for employee taxes	$ 16	(16)			$ (3,049)	$ (3,049)
Stock issued for vested restricted stock, net of shares withheld for employee taxes (in shares)	157,000				38,000
Repurchase of common stock (in shares)						0
Stock-based compensation		26,703				$ 26,703
Balance at Sep. 30, 2014	$ 11,051	383,972	4,525,989	83,126	$ (112,969)	4,891,169
Balance (in shares) at Sep. 30, 2014	110,509,000
Balance (in shares) at Sep. 30, 2014					2,276,000
Comprehensive Income:
Net income (loss)			420,427			420,427
Other comprehensive income (loss)				(84,503)		(84,503)
Dividends declared ($2.625 per share in 2014,$2.75 per share in 2015 and $2.775 per share in 2016)			(298,070)			(298,070)
Exercise of stock options	$ 26	7,223			$ (4,599)	2,650
Exercise of stock options (in shares)	255,000				64,000
Tax benefit of stock-based awards		3,772				3,772
Stock issued for vested restricted stock, net of shares withheld for employee taxes	$ 22	(21)			$ (5,141)	(5,140)
Stock issued for vested restricted stock, net of shares withheld for employee taxes (in shares)	223,000				70,000
Repurchase of common stock					$ (59,654)	$ (59,654)
Repurchase of common stock (in shares)					810,000	810,097
Stock-based compensation		25,195				$ 25,195
Balance at Sep. 30, 2015	$ 11,099	420,141	4,648,346	(1,377)	$ (182,363)	$ 4,895,846
Balance (in shares) at Sep. 30, 2015	110,987,000					110,987,546
Balance (in shares) at Sep. 30, 2015					3,220,000	3,219,631
Comprehensive Income:
Net income (loss)			(56,828)			$ (56,828)
Other comprehensive income (loss)				1,173		1,173
Dividends declared ($2.625 per share in 2014,$2.75 per share in 2015 and $2.775 per share in 2016)			(301,711)			(301,711)
Exercise of stock options	$ 22	6,937			$ (5,919)	1,040
Exercise of stock options (in shares)	220,000				99,000
Tax benefit of stock-based awards		934				934
Stock issued for vested restricted stock, net of shares withheld for employee taxes	$ 19	(3,943)			$ 12	$ (3,912)
Stock issued for vested restricted stock, net of shares withheld for employee taxes (in shares)	193,000				3,000
Repurchase of common stock (in shares)						0
Stock-based compensation		24,383				$ 24,383
Balance at Sep. 30, 2016	$ 11,140	$ 448,452	$ 4,289,807	$ (204)	$ (188,270)	$ 4,560,925
Balance (in shares) at Sep. 30, 2016	111,400,000					111,400,339
Balance (in shares) at Sep. 30, 2016					3,322,000	3,322,423