Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury Stock	Total
Balance at beginning of period 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
Increase (Decrease) in Shareholders' Equity
Net income (loss)			420,427			420,427
Other comprehensive income (loss)				(84,503)		(84,503)
Dividends declared			(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 (in shares)					810,000	810,097
Repurchase of common stock					$ (59,654)	$ (59,654)
Stock-based compensation		25,195				25,195
Balance at end of period 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
Balance (in shares) at Sep. 30, 2015					3,220,000
Increase (Decrease) in Shareholders' Equity
Net income (loss)			(56,828)			(56,828)
Other comprehensive income (loss)				1,173		1,173
Dividends declared			(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 end of period 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
Increase (Decrease) in Shareholders' Equity
Net income (loss)			(128,212)			$ (128,212)
Other comprehensive income (loss)				2,504		2,504
Dividends declared			(305,909)			(305,909)
Exercise of stock options	$ 42	15,738			$ (5,246)	10,534
Exercise of stock options (in shares)	415,000				88,000
Tax benefit of stock-based awards		4,414				4,414
Stock issued for vested restricted stock, net of shares withheld for employee taxes	$ 14	(7,539)			$ 1,677	$ (5,848)
Stock issued for vested restricted stock, net of shares withheld for employee taxes (in shares)	142,000				(57,000)
Repurchase of common stock (in shares)						0
Stock-based compensation		26,183				$ 26,183
Balance at end of period at Sep. 30, 2017	$ 11,196	$ 487,248	$ 3,855,686	$ 2,300	$ (191,839)	$ 4,164,591
Balance (in shares) at Sep. 30, 2017	111,957,000					111,956,875
Balance (in shares) at Sep. 30, 2017					3,353,000	3,352,828