Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Revision of Prior Period Accounting Standards Update Adjustment [Member]	Common Stock [Member]	Number of Warrants [Member]	Common Stock and Additional Paid-In Capital [Member]	Retained Earnings [Member]	Retained Earnings [Member] Revision of Prior Period Accounting Standards Update Adjustment [Member]
Beginning balance at Sep. 30, 2019	$ 425,868				$ 238,504	$ 187,364
Beginning balance (ASU 2018-09 [Member]) at Sep. 30, 2019		$ 259					$ 259
Beginning balance, shares at Sep. 30, 2019			31,413,287	3,600,953
Stock compensation expense	1,320				1,320
Repurchased shares and warrants	(41)				(41)
Repurchased shares and warrants, shares			(5,558)
Warrants converted to common stock			1,612,481	(1,612,481)
Restricted shares issued, shares			18,916
Net income	10,785					10,785
Ending balance at Dec. 31, 2019	438,191				239,783	198,408
Ending balance, shares at Dec. 31, 2019			33,039,126	1,988,472
Beginning balance at Sep. 30, 2019	425,868				238,504	187,364
Beginning balance (ASU 2018-09 [Member]) at Sep. 30, 2019		$ 259					$ 259
Beginning balance, shares at Sep. 30, 2019			31,413,287	3,600,953
Net income	16,089
Ending balance at Jun. 30, 2020	445,494				241,782	203,712
Ending balance, shares at Jun. 30, 2020			35,414,284
Beginning balance at Dec. 31, 2019	438,191				239,783	198,408
Beginning balance, shares at Dec. 31, 2019			33,039,126	1,988,472
Stock compensation expense	1,193				1,193
Repurchased shares and warrants	(160)				(160)
Repurchased shares and warrants, shares			(18,244)
Warrants converted to common stock			1,988,472	(1,988,472)
Restricted shares issued, shares			141,614
Employee share purchases	243				243
Employee share purchases, shares			43,934
Net income	1,885					1,885
Ending balance at Mar. 31, 2020	441,352				241,059	200,293
Ending balance, shares at Mar. 31, 2020			35,194,902
Stock compensation expense	1,020				1,020
Repurchased shares and warrants	(297)				(297)
Repurchased shares and warrants, shares			(88,785)
Restricted shares issued, shares			308,167
Net income	3,419					3,419
Ending balance at Jun. 30, 2020	445,494				241,782	203,712
Ending balance, shares at Jun. 30, 2020			35,414,284
Beginning balance at Sep. 30, 2020	457,859				242,772	215,087
Beginning balance, shares at Sep. 30, 2020			35,526,918
Stock compensation expense	850				850
Repurchased shares and warrants	(19)				(19)
Repurchased shares and warrants, shares			(2,256)
Restricted shares issued, shares			7,500
Issuance of warrants, net of issuance costs	11,489				11,489
Issuance of warrants, net of issuance costs, shares				4,899,497
Net income	14,118					14,118
Ending balance at Dec. 31, 2020	484,297				255,092	229,205
Ending balance, shares at Dec. 31, 2020			35,532,162	4,899,497
Beginning balance at Sep. 30, 2020	457,859				242,772	215,087
Beginning balance, shares at Sep. 30, 2020			35,526,918
Repurchased shares and warrants			$ (1,400)
Net income	24,083
Ending balance at Jun. 30, 2021	494,667				255,497	239,170
Ending balance, shares at Jun. 30, 2021			35,891,029	4,899,497
Beginning balance at Dec. 31, 2020	484,297				255,092	229,205
Beginning balance, shares at Dec. 31, 2020			35,532,162	4,899,497
Stock compensation expense	808				808
Repurchased shares and warrants	(157)				(157)
Repurchased shares and warrants, shares			(14,680)
Restricted shares issued, shares			124,609
Employee share purchases	207				207
Employee share purchases, shares			58,070
Net income	5,689					5,689
Ending balance at Mar. 31, 2021	490,844				255,950	234,894
Ending balance, shares at Mar. 31, 2021			35,700,161	4,899,497
Stock compensation expense	756				756
Repurchased shares and warrants	(1,209)				(1,209)
Repurchased shares and warrants, shares			(122,960)
Restricted shares issued, shares			313,828
Net income	4,276					4,276
Ending balance at Jun. 30, 2021	$ 494,667				$ 255,497	$ 239,170
Ending balance, shares at Jun. 30, 2021			35,891,029	4,899,497