CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Common Stock	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury Stock	Noncontrolling Interest in VIE	Total
Balance at Sep. 30, 2018	$ 45,008	$ 801,834	$ (110,643)	$ (36,078)	$ 24,075
Balance (in shares) at Sep. 30, 2018						27,255
Increase (Decrease) in Stockholders' Equity
Net loss		(15,979)			(5,404)	$ (15,979)
Other comprehensive income (loss), net of tax			487			$ 487
Stock issued under equity incentive plans (in shares)						132
Stock issued under employee stock purchase plans, value	783
Stock issued under employee stock purchase plans (in shares)						15
Purchase of common stock, value	(3,419)
Purchase of common stock (in shares)						(47)
Stock- based compensation	6,358
Cumulative effect of accounting standard adoption		19,834			4,655
Stock issued under equity offering, net, value	215,832
Stock issued under equity offering, net (in shares)						3,795
Cash dividends paid		(4,205)
Other	50	2			(1)
Balance at Mar. 31, 2019	264,612	801,486	(110,156)	(36,078)	23,325
Balance (in shares) at Mar. 31, 2019						31,150
Balance at Dec. 31, 2018	260,141	815,083	(112,642)	(36,078)	24,703
Balance (in shares) at Dec. 31, 2018						31,133
Increase (Decrease) in Stockholders' Equity
Net loss		(9,392)			(1,377)	$ (9,392)
Other comprehensive income (loss), net of tax			2,486			$ 2,486
Stock issued under equity incentive plans (in shares)						3
Stock issued under employee stock purchase plans, value	783
Stock issued under employee stock purchase plans (in shares)						15
Purchase of common stock (in shares)						(1)
Stock- based compensation	3,638
Cash dividends paid		(4,205)
Other	50				(1)
Balance at Mar. 31, 2019	264,612	801,486	(110,156)	(36,078)	23,325
Balance (in shares) at Mar. 31, 2019						31,150
Balance at Sep. 30, 2019	274,472	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 loss		(59,698)			(9,188)	$ (59,698)
Other comprehensive income (loss), net of tax			(8,466)			$ (8,466)
Stock issued under equity incentive plans (in shares)						153
Stock issued under employee stock purchase plans, value	1,169
Stock issued under employee stock purchase plans (in shares)						19
Purchase of common stock, value	(3,660)
Purchase of common stock (in shares)						(54)
Stock- based compensation	9,859
Cumulative effect of accounting standard adoption		(824)
Cash dividends paid		(4,225)
Balance at Mar. 31, 2020	281,840	798,201	(148,159)	(36,078)	9,731	$ 905,535
Balance (in shares) at Mar. 31, 2020						31,296
Balance at Dec. 31, 2019	276,497	841,549	(130,349)	(36,078)	22,909
Balance (in shares) at Dec. 31, 2019						31,274
Increase (Decrease) in Stockholders' Equity
Net loss		(39,123)			(13,178)	$ (39,123)
Other comprehensive income (loss), net of tax			(17,810)			$ (17,810)
Stock issued under equity incentive plans (in shares)						23
Purchase of common stock, value	(39)
Purchase of common stock (in shares)						(1)
Stock- based compensation	5,382
Cash dividends paid		(4,225)
Balance at Mar. 31, 2020	$ 281,840	$ 798,201	$ (148,159)	$ (36,078)	$ 9,731	$ 905,535
Balance (in shares) at Mar. 31, 2020						31,296