CONDENSED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Common Stock	Retained Earnings Cumulative effect of accounting standard adoption	Retained Earnings	Accumulated Other Comprehensive Loss Cumulative effect of accounting standard adoption	Accumulated Other Comprehensive Loss	Treasury Stock	Noncontrolling Interest in VIE Cumulative effect of accounting standard adoption	Noncontrolling Interest in VIE	Total
Balance at Sep. 30, 2017	$ 37,850	$ 2,394	$ 794,485	$ (2,394)	$ (106,626)	$ (36,078)
Balance (in shares) at Sep. 30, 2017									27,127
Increase (Decrease) in Stockholders' Equity
Net income (loss)			12,310					$ (274)	$ 12,310
Other comprehensive loss, net of tax					(1,623)				$ (1,623)
Stock issued under equity incentive plans (in shares)									158
Stock issued under employee stock purchase plans, value	1,517
Stock issued under employee stock purchase plans (in shares)									26
Purchase of common stock, value	(2,449)
Purchase of common stock (in shares)									(56)
Share - based compensation	8,090
Equity contribution of noncontrolling interest								24,349
Cash dividends paid			(7,355)
Balance at Sep. 30, 2018	45,008	19,834	801,834		(110,643)	(36,078)	$ 4,655	24,075
Balance (in shares) at Sep. 30, 2018									27,255
Increase (Decrease) in Stockholders' Equity
Net income (loss)			49,694					(9,811)	$ 49,694
Other comprehensive loss, net of tax					(29,050)				$ (29,050)
Stock issued under equity incentive plans (in shares)									145
Stock issued under employee stock purchase plans, value	1,832
Stock issued under employee stock purchase plans (in shares)									32
Purchase of common stock, value	(3,688)
Purchase of common stock (in shares)									(49)
Share - based compensation	15,488
Stock issued under equity offering, net, value	215,832
Stock issued under equity offering, net (in shares)									3,795
Cash dividends paid			(8,414)
Balance at Sep. 30, 2019	274,472	$ (824)	862,948		(139,693)	(36,078)		18,919	$ 980,568
Balance (in shares) at Sep. 30, 2019									31,178
Increase (Decrease) in Stockholders' Equity
Net income (loss)			(3,221)					6,592	$ (3,221)
Other comprehensive loss, net of tax					(9,910)				$ (9,910)
Stock issued under equity incentive plans (in shares)									158
Stock issued under employee stock purchase plans, value	2,493
Stock issued under employee stock purchase plans (in shares)									48
Purchase of common stock, value	(3,707)
Purchase of common stock (in shares)									(55)
Share - based compensation	22,728
Equity contribution of noncontrolling interest								1,892
Cash dividends paid			(8,431)
Balance at Sep. 30, 2020	$ 295,986		$ 850,472		$ (149,603)	$ (36,078)		$ 27,403	$ 988,180
Balance (in shares) at Sep. 30, 2020									31,329