Borrowings and Financing Activities - Schedule of Debt (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Total FHLB advances	$ 148,983	$ 150,983
Senior notes
Debt Instrument [Line Items]
Total senior notes	1,410,458	1,409,473
Senior notes \| Senior Notes due 2024
Debt Instrument [Line Items]
Total senior notes	446,919	446,631
Senior notes \| Senior Notes due 2025
Debt Instrument [Line Items]
Total senior notes	518,867	518,405
Senior notes \| Senior Notes due 2027
Debt Instrument [Line Items]
Total senior notes	444,672	444,437
FHLB advances
Debt Instrument [Line Items]
2022	66,050	71,050
2023	52,995	52,995
2024	16,954	13,954
2025	9,984	9,984
2027	3,000	3,000
Total FHLB advances	$ 148,983	$ 150,983

Amount of borrowings as of the balance sheet date from the Federal Home Loan Bank, which are primarily used to cover shortages in the required reserve balance and liquidity shortages.

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