CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 226,068	$ 200,041	$ 257,426
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization, accretion and other, net	9,718	134,103	22,970
Stock-based compensation expense	8,519	9,181	7,914
Provision (release) for credit losses	7,750	17,500	41,500
Loss (gain) on sale of investment securities	(20)	(342)	(33)
Gain on settlements of bank owned life insurance	0	0	(821)
Impairment loss on premises and equipment	992	0	6
Net realized (gain) loss on sales of premises, equipment and real estate owned	(419)	(2,555)	(1,153)
Decrease (increase) in accrued interest receivable	4,238	9,873	(23,131)
Decrease (increase) in federal and state income tax receivable	6,124	18,751	(6,650)
Decrease (increase) in cash surrender value of bank owned life insurance	(7,526)	(6,933)	(5,976)
Decrease (increase) in other assets	(27,885)	148,001	(67,342)
Increase (decrease) in federal and state income tax liabilities	0	0	(3,306)
Increase (decrease) in accrued expenses and other liabilities	9,393	(88,387)	(7,447)
Net cash provided by (used in) operating activities	236,952	439,233	213,957
CASH FLOWS FROM INVESTING ACTIVITIES
Origination of loans and principal repayments, net	973,280	(348,528)	(1,330,399)
Loans purchased	(143,605)	0	(79,965)
FHLB & FRB stock purchase	(496,542)	(602,941)	(654,805)
FHLB & FRB stock redeemed	504,092	669,975	623,058
Available-for-sale securities purchased	(1,482,058)	(549,159)	(376,481)
Principal payments and maturities of available-for-sale securities	561,808	386,564	420,154
Proceeds from sales of available-for-sale investment securities	797	182,682	1,169
Held-to-maturity securities purchased	(261,842)	(47,092)	0
Principal payments and maturities of held-to-maturity securities	53,030	36,013	39,414
Proceeds from sales of real estate owned	2,865	6,802	7,192
Proceeds from settlements of bank owned life insurance	0	0	1,809
Equity method investments purchased	(2,861)	(4,197)	(12,500)
Net cash received (paid) in business combinations	(360)	623,583	(2,590)
Proceeds from sales of loans	0	2,956,856	0
Proceeds from sales of premises and equipment	1,689	1,341	1,090
Premises and equipment purchased and REO improvements	(28,707)	(24,681)	(15,063)
Net cash provided by (used in) investing activities	(318,414)	3,287,218	(1,377,917)
CASH FLOWS FROM FINANCING ACTIVITIES
Net increase (decrease) in customer accounts	63,666	(324,506)	40,759
Proceeds from borrowings	11,019,793	17,037,035	17,175,000
Repayments of borrowings	(12,527,894)	(18,842,525)	(15,650,000)
Principal payments and maturities of senior debt	0	(95,000)	0
Proceeds from stock-based awards	3,943	5,187	1,089
Dividends paid on common stock	(84,639)	(74,267)	(63,792)
Dividends paid on preferred stock	(14,625)	(14,625)	(14,625)
Proceeds from employee stock purchase	842	992	177
Treasury stock purchased	(101,931)	(27,069)	(30,463)
Increase (decrease) in advance payments by borrowers for taxes and insurance	(1,485)	8,780	2,499
Net cash provided by (used by) financing activities	(1,642,330)	(2,325,998)	1,460,644
Increase (decrease) in cash and cash equivalents	(1,723,792)	1,400,453	296,684
Cash and cash equivalents at beginning of year	2,381,102	980,649	683,965
Cash and cash equivalents at end of year	657,310	2,381,102	980,649
Non-cash investing activities
Real estate acquired through foreclosure	5,873	681	121
Non-cash financing activities
Preferred stock dividend payable	3,656	3,656	3,656
Cash paid during the year for
Interest	746,932	739,076	364,386
Income taxes	41,647	20,283	61,245
Summary of non-cash activities related to acquisitions
Fair value of assets and intangibles acquired	0	7,677,177	0
Fair value of liabilities assumed	0	(7,316,380)	0
Net fair value of acquired assets (liabilities)	$ 0	$ 360,797	$ 0