CONDENSED CONSOLIDATED STATEMENT OF SHAREHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	COMMON STOCK	CAPITAL IN EXCESS OF PAR VALUE	RETAINED EARNINGS	TREASURY SHARES	ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)	DEFERRED COMPENSATION
Balance (in shares) at Sep. 30, 2019		82,775			35,969
Balance at Sep. 30, 2019	$ 477,763	$ 20,694	$ 519,017	$ 568,516	$ (536,308)	$ (65,916)	$ (28,240)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	10,612			10,612
Dividend	(3,392)			(3,392)
Shares withheld on employee taxes on vested equity awards (in shares)					80
Shares withheld on employee taxes on vested equity awards	(1,758)				$ (1,758)
Amortization of deferred compensation	629						629
Equity awards granted, net (in shares)		182
Equity awards granted, net	0	$ 45	(45)
ESOP allocation of common stock	609		609
Stock-based compensation	3,150		3,150
Stock-based consideration	239		239
Other comprehensive income, net of tax	6,841					6,841
Balance (in shares) at Dec. 31, 2019		82,957			36,049
Balance at Dec. 31, 2019	494,693	$ 20,739	522,970	575,736	$ (538,066)	(59,075)	(27,611)
Balance (in shares) at Sep. 30, 2019		82,775			35,969
Balance at Sep. 30, 2019	477,763	$ 20,694	519,017	568,516	$ (536,308)	(65,916)	(28,240)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	11,507
Other comprehensive income, net of tax	(7,993)
Balance (in shares) at Mar. 31, 2020		83,741			36,310
Balance at Mar. 31, 2020	476,454	$ 20,935	526,988	573,209	$ (543,787)	(73,909)	(26,982)
Balance (in shares) at Dec. 31, 2019		82,957			36,049
Balance at Dec. 31, 2019	494,693	$ 20,739	522,970	575,736	$ (538,066)	(59,075)	(27,611)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	895			895
Dividend	(3,422)			(3,422)
Shares withheld on employee taxes on vested equity awards (in shares)					261
Shares withheld on employee taxes on vested equity awards	(5,721)				$ (5,721)
Amortization of deferred compensation	629						629
Equity awards granted, net (in shares)		784
Equity awards granted, net	0	$ 196	(196)
ESOP allocation of common stock	435		435
Stock-based compensation	3,662		3,662
Stock-based consideration	117		117
Other comprehensive income, net of tax	(14,834)					(14,834)
Balance (in shares) at Mar. 31, 2020		83,741			36,310
Balance at Mar. 31, 2020	476,454	$ 20,935	526,988	573,209	$ (543,787)	(73,909)	(26,982)
Balance (in shares) at Sep. 30, 2020		83,739			27,610
Balance at Sep. 30, 2020	700,151	$ 20,935	583,008	607,518	$ (413,493)	(72,092)	(25,725)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	29,500			29,500
Dividend	(4,469)			(4,469)
Shares withheld on employee taxes on vested equity awards (in shares)					133
Shares withheld on employee taxes on vested equity awards	(2,909)				$ (2,909)
Amortization of deferred compensation	609						609
Equity awards granted, net (in shares)		494
Equity awards granted, net	0	$ 123	(123)
ESOP allocation of common stock	596		596
Stock-based compensation	3,428		3,428
Other comprehensive income, net of tax	13,141					13,141
Balance (in shares) at Dec. 31, 2020		84,233			27,743
Balance at Dec. 31, 2020	740,047	$ 21,058	586,909	632,549	$ (416,402)	(58,951)	(25,116)
Balance (in shares) at Sep. 30, 2020		83,739			27,610
Balance at Sep. 30, 2020	700,151	$ 20,935	583,008	607,518	$ (413,493)	(72,092)	(25,725)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	46,612
Other comprehensive income, net of tax	17,916
Balance (in shares) at Mar. 31, 2021		84,427			27,743
Balance at Mar. 31, 2021	764,431	$ 21,106	591,966	646,444	$ (416,402)	(54,176)	(24,507)
Balance (in shares) at Dec. 31, 2020		84,233			27,743
Balance at Dec. 31, 2020	740,047	$ 21,058	586,909	632,549	$ (416,402)	(58,951)	(25,116)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	17,112			17,112
Dividend	(3,217)			(3,217)
Amortization of deferred compensation	609						609
Equity awards granted, net (in shares)		194
Equity awards granted, net	0	$ 48	(48)
ESOP allocation of common stock	756		756
Stock-based compensation	4,349		4,349
Other comprehensive income, net of tax	4,775					4,775
Balance (in shares) at Mar. 31, 2021		84,427			27,743
Balance at Mar. 31, 2021	$ 764,431	$ 21,106	$ 591,966	$ 646,444	$ (416,402)	$ (54,176)	$ (24,507)