Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (14,899)
Other comprehensive income (loss)	4,972	$ (6,217)
Ending balance	(9,927)
Unrealized Gains (Losses) on AFS Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	10,150	(2,990)
Other comprehensive income (loss), before reclassifications	(452)	3,527
Amount reclassified from AOCI	0	0
Other comprehensive income (loss)	(452)	3,527
Ending balance	9,698	537
Unrealized Gains (Losses) on Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(25,049)	7,330
Other comprehensive income (loss), before reclassifications	4,715	(9,895)
Amount reclassified from AOCI	709	151
Other comprehensive income (loss)	5,424	(9,744)
Ending balance	(19,625)	(2,414)
AOCI [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(14,899)	4,340
Other comprehensive income (loss), before reclassifications	4,263	(6,368)
Amount reclassified from AOCI	709	151
Other comprehensive income (loss)	4,972	(6,217)
Ending balance	$ (9,927)	$ (1,877)