CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss), Net of Tax [Member]	Treasury Stock [Member]
Balance at the beginning of the period at Sep. 30, 2014	$ 174,802	$ 62	$ 95,079	$ 83,797	$ (3,409)	$ (727)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends declared on common stock ($0.52 per share)	(3,493)			(3,493)
Issuance of common shares due to issuance of stock options and restricted stock	378		378
Issuance of common shares due to acquisition	24,303	6	24,297
Issuance of common shares from the sales of equity securities	51,168	14	50,737			417
Stock compensation	258		258
Net change in unrealized gains (losses) on securities, net of income taxes	5,864				5,864
Net income	18,055			18,055
Balance at the end of the period at Sep. 30, 2015	271,335	82	170,749	98,359	2,455	(310)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends declared on common stock ($0.52 per share)	(4,389)			(4,389)
Issuance of common shares due to issuance of stock options and restricted stock	2,357	1	2,046			310
Issuance of common shares due to acquisition	0
Issuance of common shares from the sales of equity securities	11,500	2	11,498
Stock compensation	487		487
Net change in unrealized gains (losses) on securities, net of income taxes	20,465				20,465
Net income	33,220			33,220
Balance at the end of the period at Sep. 30, 2016	334,975	85	184,780	127,190	22,920	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of Accounting Standards Update 2016-09	0		104	(104)
Cash dividends declared on common stock ($0.52 per share)	(4,839)			(4,839)
Issuance of common shares due to issuance of stock options and restricted stock	650		650
Issuance of common shares due to restricted stock	4	4
Issuance of common shares due to acquisition	37,296	7
Issuance of common shares due to ESOP	1,174		1,174
Issuance of common shares from the sales of equity securities	37,296		37,289
Contingent consideration equity earnout due to acquisition	24,142		24,142
Shares repurchased for tax withholdings on stock compensation	(470)		(204)			(266)
Stock compensation	10,401		10,401
Net change in unrealized gains (losses) on securities, net of income taxes	(13,754)				(13,754)
Net income	44,917			44,917
Balance at the end of the period at Sep. 30, 2017	$ 434,496	$ 96	$ 258,336	$ 167,164	$ 9,166	$ (266)