CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Statement of Financial Position [Abstract]
Amortized cost, AFS	$ 14,178.0	$ 11,849.0
ACL, AFS	0.4	1.4
Investment securities - HTM, ACL	16.4	7.8
Investment securities - HTM Fair value	$ 1,309.0	$ 1,251.0
Preferred stock, par value (dollars per share)	$ 0.0001	$ 0.0001
Preferred stock, liquidation value (dollars per share)	$ 25	$ 25
Preferred stock, shares authorized (shares)	20,000,000	20,000,000
Preferred stock, shares issued (shares)	30,000	30,000
Preferred stock, shares outstanding (shares)	30,000	30,000
Depository shares issued (shares)	12,000,000	12,000,000
Depository shares outstanding (shares)	12,000,000	12,000,000
Common stock, par value (dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (shares)	200,000,000	200,000,000
Common stock, shares issued (shares)	112,897,807	112,169,523
Treasury stock, at cost (shares)	2,845,201	2,703,218
Loans HFS	$ 2,286.0	$ 1,402.0