Debt - Narrative (Details) $ in Millions	6 Months Ended
Jun. 30, 2025 USD ($) subsidiaryBusinessTrust class
Debt Instrument [Line Items]
Number of classes of financial instruments \| class	2
Number of business subsidiary trusts \| subsidiaryBusinessTrust	2
Interest Rate Swap
Debt Instrument [Line Items]
Amount of hedged item	$ 20.0
ACST II \| Junior Subordinated Debt, Preferred Securities
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)	3.15%
ACST III
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)	2.00%
Federal Reserve Bank Advances
Debt Instrument [Line Items]
Collateral, at carrying cost	$ 1,000.0
Collateral, at fair value	1,000.0
Federal Home Loan Bank of New York
Debt Instrument [Line Items]
Collateral, at carrying cost	1,000.0
Collateral, at fair value	$ 865.8

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