Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Operating activities
Net (loss) income	$ (680,808)	$ 167,365	$ 157,916
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	26,354	13,655	13,093
Amortization of FDIC indemnification asset	1,012	1,386	2,778
Net loss on sale of securities and other assets	2,851	2,825	5,731
Net gain on sale of loans	(9,910)	(5,680)	(6,829)
Provision for loan and lease losses	118,392	40,947	17,986
Goodwill and intangible assets impairment	742,352	0	0
Provision for (reversal of) loan servicing rights loss	9	(4)	(73)
Stock-based compensation	3,705	4,582	4,419
Originations of residential real estate loans held for sale	(501,947)	(289,973)	(264,514)
Proceeds from sales of residential real estate loans held for sale	506,837	293,758	273,343
Net deferred income taxes	(47,754)	8,124	21,302
Changes in:
Accrued interest receivable	4,040	249	(5,772)
Other assets	(77,271)	(48,524)	(34,209)
Accrued interest payable and other liabilities	(5,398)	2,949	(2,742)
Net cash provided by operating activities	82,464	191,659	182,429
Investing activities
Purchase of securities available for sale	(677,873)	(774,707)	(334,900)
Proceeds from sales of securities available for sale	151,899	175,007	24,971
Proceeds from maturities of securities available for sale	564,123	257,201	254,985
Net increase in loans	(426,156)	(348,479)	(490,804)
Payment of covered losses from FDIC indemnification claims	(47)	(14)	(770)
Purchase of premises and equipment	(6,108)	(15,643)	(13,878)
Proceeds from sale of premises and equipment	44	606	4,599
Proceeds from sale of repossessed property	20,392	9,981	7,468
Purchase of FHLB stock	(113,437)	(89,948)	(64,172)
Proceeds from redemption of FHLB stock	122,483	87,528	79,190
Net cash paid in business acquisition	(4,711)	0	0
Net cash used in investing activities	(369,391)	(698,468)	(533,311)
Financing activities
Net increase in deposits	708,563	567,004	756,145
Net decrease in securities sold under agreements to repurchase and other short-term borrowings	(3,486)	(21,915)	(41,729)
Proceeds from FHLB advances and other long-term borrowings	755,000	810,000	150,000
Repayments on FHLB advances and other long-term borrowings	(900,000)	(745,000)	(518,200)
Common stock repurchased	(39,983)	(94,351)	0
Taxes paid related to net share settlement of equity awards	(1,298)	(1,247)	(4,032)
Dividends paid	(42,456)	(62,904)	(53,002)
Net cash provided by financing activities	476,340	451,587	289,182
Net increase (decrease) in cash and cash equivalents	189,413	(55,222)	(61,700)
Cash and cash equivalents, beginning of period	243,474	298,696	360,396
Cash and cash equivalents, end of period	432,887	243,474	298,696
Supplemental disclosure of cash flow information
Cash payments for interest	85,151	114,891	69,633
Cash payments for income taxes	29,405	46,884	50,020
Supplemental disclosure of noncash investing and financing activities
Loans transferred to repossessed properties	$ (14,088)	$ (25,668)	$ (25,926)