Derivative Financial Instruments - Income (loss) Related To Derivative Financial Instruments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Income (loss) related to derivative financial instruments	$ 7,824	$ (7,623)	$ (3,061)	$ (8,408)
Interest rate lock commitments
Income (loss) related to derivative financial instruments	(11,153)	2,757	(14,675)	2,409
Forward mortgage loan sale contracts
Income (loss) related to derivative financial instruments	$ 18,977	$ (10,380)	$ 11,614	$ (10,817)