Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Investment securities:
Estimated fair value	$ 2,361.2	$ 2,358.6
Stockholders' equity:
Nonvoting, noncumulative preferred stock, shares authorized (in shares)	100,000	100,000
Nonvoting, noncumulative preferred stock, shares issued (in shares)	0	0
Nonvoting, noncumulative preferred stock, shares outstanding (in shares)	0	0
Preferred Stock, Shares Outstanding	0	0
Shares outstanding (in shares)	104,909,761	104,585,964
Common Stock, Shares, Issued	104,909,761	104,585,964
Common Stock, Shares Authorized	150,000,000	150,000,000
Common Stock, Par or Stated Value Per Share	$ 0.00001	$ 0.00001