Condensed Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Parent [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]	Noncontrolling Interest [Member]
Beginning Balance at Sep. 30, 2017	$ 434,496	$ 434,496	$ 288	$ 258,144	$ 167,164	$ 9,166	$ (266)	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends declared on common stock	(1,256)	(1,256)			(1,256)
Issuance of common shares due to ESOP	1,606	1,606	1	1,605
Issuance of common shares due to exercise of stock options	1	1	1
Shares repurchased for tax withholdings on stock compensation	(1,671)	(1,671)		(314)			(1,357)
Stock compensation	3,243	3,243		3,243
Total other comprehensive income	(3,384)	(3,384)				(3,384)
Net income	4,670	4,670			4,670
Ending Balance at Dec. 31, 2017	437,705	437,705	290	262,678	170,578	5,782	(1,623)	0
Retained earnings	213,048
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative Effect of New Accounting Principle in Period of Adoption | Accounting Standards Update 2016-01 [Member]					475	(475)
Beginning Balance at Sep. 30, 2018	747,726	744,152	393	565,811	213,048	(33,111)	(1,989)	3,574
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends declared on common stock	(1,970)	(1,970)			(1,970)
Issuance of common shares due to exercise of stock options	54	54		54
Issuance of common shares due to restricted stock	2	2	2
Issuance of common shares due to ESOP	2,010	2,010		2,010
Shares repurchased for tax withholdings on stock compensation	(2,367)	(2,367)	(1)	1			(2,367)	0
Stock compensation	4,280	4,280		4,280
Total other comprehensive income	4,400	4,400				4,400
Net income	16,320	15,398			15,398			922
Net investment by (distribution to) noncontrolling interests	(1,229)							(1,229)
Ending Balance at Dec. 31, 2018	770,728	$ 767,461	$ 394	$ 572,156	$ 228,453	$ (29,186)	$ (4,356)	$ 3,267
Retained earnings	$ 228,453