Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2021	Jun. 30, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			$ (16,505)				$ (16,505)
Other comprehensive income (loss), before reclassifications - AFS Securities	$ 5,703			$ 5,533			(14,091)	$ 15,459
Other comprehensive income (loss), before reclassifications - Cash Flow Hedges	(2,212)			(2,856)			5,743	(21,553)
Amount reclassified from AOCI - AFS Securities	0			0			0	0
Amount reclassified from AOCI - Cash Flow Hedges	2,124			1,710			11,515	3,402
Amount reclassified from AOCI, deferred income taxes	(686)			(549)			(3,717)	(1,092)
Other comprehensive income (loss) - AFS Securities	5,703			5,533			(14,091)	15,459
Other comprehensive income (loss) - Cash Flow Hedges	(88)			(1,146)			17,258	(18,151)
Other comprehensive income (loss)	5,615	$ (7,582)	5,134	4,387	$ (12,051)	$ 4,972
Ending balance	(13,338)						(13,338)
Unrealized Gains (Losses) on AFS Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	3,934		23,728	20,076		10,150	23,728	10,150
Ending balance	9,637	3,934		25,609	20,076		9,637	25,609
Unrealized Gains (Losses) on Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(22,887)		(40,233)	(42,054)		(25,049)	(40,233)	(25,049)
Ending balance	(22,975)	(22,887)		(43,200)	(42,054)		(22,975)	(43,200)
AOCI [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(18,953)		(16,505)	(21,978)		(14,899)	(16,505)	(14,899)
Other comprehensive income (loss), before reclassifications	3,491			2,677			(8,348)	(6,094)
Amount reclassified from AOCI	2,124			1,710			11,515	3,402
Other comprehensive income (loss)	5,615	(7,582)	$ 5,134	4,387	(12,051)	$ 4,972	3,167	(2,692)
Ending balance	$ (13,338)	$ (18,953)		$ (17,591)	$ (21,978)		$ (13,338)	$ (17,591)