Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2023	Sep. 30, 2022
Statement of Financial Position [Abstract]
Interest-earning deposits	$ 308,127	$ 27,467
Available-for-sale securities, amortized cost	1,624,837	1,768,490
Loans receivable, allowance for credit losses	$ 22,399	$ 16,371
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	100,000,000	100,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	1,400,000,000	1,400,000,000
Common stock, shares issued	136,158,569	138,858,884
Common stock, shares outstanding	136,158,569	138,858,884