Debt (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Advance from Federal Home Loan Bank	$ 2,067.0	$ 2,327.0
Average fixed rate borrowings in tenors up to one-week
Fixed-to-floating rate (percent)	5.52%
Advance from Federal Home Loan Bank	$ 106.0
5.30% average fixed rate borrowings in tenors up to two-weeks
Fixed-to-floating rate (percent)	5.51%
Advance from Federal Home Loan Bank	$ 100.0
5.01% fixed rate borrowings in tenors up to one-month
Fixed-to-floating rate (percent)	5.50%	4.48%
Advance from Federal Home Loan Bank	$ 925.0	$ 1,500.0
5.11% average fixed rate borrowings in tenors of 2-month
Fixed-to-floating rate (percent)	5.56%
Advance from Federal Home Loan Bank	$ 500.0
5.56% average fixed rate borrowings in tenors of 5-months
Fixed-to-floating rate (percent)	5.56%
Advance from Federal Home Loan Bank	$ 436.0
Variable rate overnight borrowings
Fixed-to-floating rate (percent)		4.60%
Advance from Federal Home Loan Bank		$ 827.0