Mortgage Banking Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Mortgage Banking Income
Origination and sale of mortgage loans (1)	$ 19,367	$ 14,363	$ 62,103	$ 28,989
Net change in fair value of loans held for sale and interest rate lock commitments	(19,570)	3,736	(21,987)	3,272
Realized and unrealized hedging gains (losses)	18,977	(10,380)	11,614	(10,817)
Capitalized residential mortgage loan servicing rights	14,611	1,908	27,483	4,185
Net change in fair value of residential mortgage loan servicing rights	(876)	(1,107)	(3,941)	(1,064)
Provisions for loan repurchases and indemnifications	(111)	(109)	(574)	(231)
Total mortgage banking income	$ 32,398	$ 8,411	$ 74,698	$ 24,334