Debt Securities Held-to-maturity - Weighted average yield and contractual maturities of debt securities HTM - Parenthetical (Details) - Held To Maturity Debt Securities - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Schedule of Held-to-maturity Securities [Line Items]
Debt securities net unrealized loss remaining in AOCI included in book value for AFS securities transferred to HTM securities	$ 703.0	$ 831.0
Asset Not Pledged as Collateral
Schedule of Held-to-maturity Securities [Line Items]
Debt securities	167.0	1,500.0
Asset pledged as collateral
Schedule of Held-to-maturity Securities [Line Items]
Debt securities	$ 8,100.0	$ 6,900.0