Borrowings and Financing Activities - Schedule of Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Total secured borrowings	$ 241,753	$ 155,822
Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate
Debt Instrument [Line Items]
FHLB, floating SOFR advances	$ 13,000	$ 13,000
FHLB, weighted average interest rate	5.51%	3.62%
Senior notes
Debt Instrument [Line Items]
Total senior notes	$ 1,416,687	$ 1,413,504
Senior notes \| Senior Notes due 2024
Debt Instrument [Line Items]
Interest rate on senior notes	4.50%
Total senior notes	$ 448,723	447,805
Senior notes \| Senior Notes due 2025
Debt Instrument [Line Items]
Interest rate on senior notes	6.625%
Total senior notes	$ 521,820	520,305
Senior notes \| Senior Notes due 2027
Debt Instrument [Line Items]
Interest rate on senior notes	4.875%
Total senior notes	$ 446,144	445,394
FHLB advances
Debt Instrument [Line Items]
FHLB advances due 2023, average interest rate	4.666%
FHLB advances due 2024, average interest rate	3.325%
FHLB advances due 2025, average interest rate	2.34%
FHLB advances due 2026, average interest rate	4.469%
FHLB advances due 2027, average interest rate	2.562%
2023	$ 64,745	104,895
2024	32,371	32,371
2025	12,684	9,984
2026	1,835	0
2027	7,887	6,436
Total FHLB advances	119,522	153,686
Mortgage loan financing facilities
Debt Instrument [Line Items]
Total senior notes	$ 122,231	$ 2,136
Mortgage financing facilities, average interest rate	7.05%

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