Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Jun. 30, 2020	Jun. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			$ (14,899)				$ (14,899)
Other comprehensive income (loss), before reclassifications - AFS Securities	$ 5,533			$ 4,102			15,459	$ 10,690
Other comprehensive income (loss), before reclassifications - Cash Flow Hedges	(2,856)			(11,273)			(21,553)	(27,668)
Amount reclassified from AOCI - AFS Securities	0			0			0	0
Amount reclassified from AOCI - Cash Flow Hedges	1,710			55			3,402	106
Other comprehensive income (loss) - AFS Securities	5,533			4,102			15,459	10,690
Other comprehensive income (loss) - Cash Flow Hedges	(1,146)			(11,218)			(18,151)	(27,562)
Other comprehensive income (loss)	4,387	$ (12,051)	4,972	(7,116)	$ (3,539)	$ (6,217)
Ending balance	(17,591)						(17,591)
Unrealized Gains (Losses) on AFS Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	20,076		10,150	3,598		(2,990)	10,150	(2,990)
Ending balance	25,609	20,076		7,700	3,598		25,609	7,700
Unrealized Gains (Losses) on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(42,054)		(25,049)	(9,014)		7,330	(25,049)	7,330
Ending balance	(43,200)	(42,054)		(20,232)	(9,014)		(43,200)	(20,232)
AOCI [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(21,978)		(14,899)	(5,416)		4,340	(14,899)	4,340
Other comprehensive income (loss), before reclassifications	2,677			(7,171)			(6,094)	(16,978)
Amount reclassified from AOCI	1,710			55			3,402	106
Other comprehensive income (loss)	4,387	(12,051)	$ 4,972	(7,116)	(3,539)	$ (6,217)	(2,692)	(16,872)
Ending balance	$ (17,591)	$ (21,978)		$ (12,532)	$ (5,416)		$ (17,591)	$ (12,532)