Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 3,678	$ 9,993
Other comprehensive (loss) income, net of tax:
Unrealized loss on securities available-for-sale	(3,039)	(15,207)
Accretion of unrealized loss on securities reclassified as held-to-maturity	(58)	0
Reclassification adjustment for (loss) gain included in net income	(47)	264
Total other comprehensive (loss) income, net of tax	(3,144)	(14,943)
Derivatives, net of tax
Unrealized gain on swap contracts	164	0
Total derivatives, net of tax	164	0
Employee benefit plans, net of tax:
Amortization of prior service cost included in net income	(43)	(18)
Reclassification adjustment of actuarial net loss included in net income	(103)	5
Change in funded status of retirement obligations	(16,104)	152
Total employee benefit plans, net of tax	(16,250)	139
Total other comprehensive loss	(19,230)	(14,804)
Total comprehensive loss, net of tax	$ (15,552)	$ (4,811)