Consolidated Statements of Stockholders' Equity (Deficit) - USD ($) shares in Thousands, $ in Thousands	Total	Cumulative Effect Period of Adoption Adjustment	Common Stock	Common Stock Cumulative Effect Period of Adoption Adjustment	Additional Paid-in Capital	Additional Paid-in Capital Cumulative Effect Period of Adoption Adjustment	Accumulated Earnings (Deficit)	Accumulated Earnings (Deficit) Cumulative Effect Period of Adoption Adjustment	Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) Cumulative Effect Period of Adoption Adjustment
Balance at Sep. 30, 2017	$ (363,616)		$ 1,296				$ (283,076)		$ (81,836)
Balance (in shares) at Sep. 30, 2017			129,585
Increase (Decrease) in Stockholders' Equity
Net earnings	258,047						258,047
Other comprehensive income (loss), net of tax	(8,155)								(8,155)
Repurchases of common stock	$ (166,701)		$ (100)		$ (11,866)		(154,735)
Repurchases of common stock (in shares)	(9,987)		(9,987)
Share-based compensation	$ 10,519		$ 2		10,517
Share-based compensation (in shares)			178
Stock issued for stock options	1,350		$ 1		1,349
Stock issued for stock options (in shares)			150
Balance at Sep. 30, 2018	(268,556)		$ 1,199				(179,764)		(89,991)
Balance (in shares) at Sep. 30, 2018			119,926
Increase (Decrease) in Stockholders' Equity
Net earnings	271,623						271,623
Other comprehensive income (loss), net of tax	(27,296)								(27,296)
Repurchases of common stock	$ (47,434)		$ (36)		(11,336)		(36,062)
Repurchases of common stock (in shares)	(3,562)		(3,562)
Share-based compensation	$ 9,180		$ 2		9,178
Share-based compensation (in shares)			209
Stock issued for stock options	2,160		$ 2		2,158
Stock issued for stock options (in shares)			152
Balance at Sep. 30, 2019	$ (60,323)	$ 76	$ 1,167				55,797	$ 76	(117,287)
Balance (in shares) at Sep. 30, 2019	116,725		116,725
Accounting Standards Update [Extensible List]		us-gaap:AccountingStandardsUpdate201602Member		us-gaap:AccountingStandardsUpdate201602Member		us-gaap:AccountingStandardsUpdate201602Member		us-gaap:AccountingStandardsUpdate201602Member		us-gaap:AccountingStandardsUpdate201602Member
Increase (Decrease) in Stockholders' Equity
Net earnings	$ 113,245						113,245
Other comprehensive income (loss), net of tax	12,584								12,584
Repurchases of common stock	$ (61,357)		$ (46)		(9,302)		(52,009)
Repurchases of common stock (in shares)	(4,702)		(4,702)
Share-based compensation	$ 8,426		$ 1		8,425
Share-based compensation (in shares)			159
Stock issued for stock options	2,792		$ 2		2,790
Stock issued for stock options (in shares)			223
Balance at Sep. 30, 2020	$ 15,443		$ 1,124		$ 1,913		$ 117,109		$ (104,703)
Balance (in shares) at Sep. 30, 2020	112,404		112,405