- Fair value and contractual maturities of the Company's investment securities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Agency RMBS Interest-Only Strips
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	$ 114	$ 143
Agency RMBS Interest-Only Strips | Less than or equal to 10 years
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	0	0
Agency RMBS Interest-Only Strips | More than 10 years and less than or equal to 20 years
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	0	0
Agency RMBS Interest-Only Strips | More than 20 years and less than or equal to 30 years
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	114	143
Agency RMBS Interest-Only Strips | More than 30 years
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	0	0
Agency RMBS Interest-Only Strips accounted for as derivatives, included in MBS
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	1,058	1,565
Agency RMBS Interest-Only Strips accounted for as derivatives, included in MBS | Less than or equal to 10 years
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	0	0
Agency RMBS Interest-Only Strips accounted for as derivatives, included in MBS | More than 10 years and less than or equal to 20 years
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	1,058	1,565
Agency RMBS Interest-Only Strips accounted for as derivatives, included in MBS | More than 20 years and less than or equal to 30 years
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	0	0
Agency RMBS Interest-Only Strips accounted for as derivatives, included in MBS | More than 30 years
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	0	0
Subtotal Agency MBS
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	1,172	1,708
Subtotal Agency MBS | Less than or equal to 10 years
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	0	0
Subtotal Agency MBS | More than 10 years and less than or equal to 20 years
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	1,058	1,565
Subtotal Agency MBS | More than 20 years and less than or equal to 30 years
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	114	143
Subtotal Agency MBS | More than 30 years
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	0	0
Non-Agency CMBS
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	105,358	164,081
Non-Agency CMBS | Less than or equal to 10 years
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	66,384	59,724
Non-Agency CMBS | More than 10 years and less than or equal to 20 years
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	17,644	50,408
Non-Agency CMBS | More than 20 years and less than or equal to 30 years
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	21,171	53,269
Non-Agency CMBS | More than 30 years
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	159	680
Non-Agency RMBS
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	25,652	21,416
Non-Agency RMBS | Less than or equal to 10 years
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	0	0
Non-Agency RMBS | More than 10 years and less than or equal to 20 years
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	0	0
Non-Agency RMBS | More than 20 years and less than or equal to 30 years
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	10,282	7,958
Non-Agency RMBS | More than 30 years
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	15,370	13,458
Non-Agency RMBS Interest-Only Strips
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	2,117	3,965
Non-Agency RMBS Interest-Only Strips | Less than or equal to 10 years
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	0	0
Non-Agency RMBS Interest-Only Strips | More than 10 years and less than or equal to 20 years
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	0	0
Non-Agency RMBS Interest-Only Strips | More than 20 years and less than or equal to 30 years
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	106	472
Non-Agency RMBS Interest-Only Strips | More than 30 years
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	2,011	3,493
Subtotal Non-Agency MBS
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	133,127	189,462
Subtotal Non-Agency MBS | Less than or equal to 10 years
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	66,384	59,724
Subtotal Non-Agency MBS | More than 10 years and less than or equal to 20 years
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	17,644	50,408
Subtotal Non-Agency MBS | More than 20 years and less than or equal to 30 years
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	31,559	61,699
Subtotal Non-Agency MBS | More than 30 years
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	17,540	17,631
Other securities
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	51,648	48,754
Other securities | Less than or equal to 10 years
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	9,255	7,247
Other securities | More than 10 years and less than or equal to 20 years
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	4,266	6,203
Other securities | More than 20 years and less than or equal to 30 years
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	25,653	24,610
Other securities | More than 30 years
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	12,474	10,694
Total mortgage-backed securities and other securities
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	185,947	239,924
Total mortgage-backed securities and other securities | Less than or equal to 10 years
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	75,639	66,971
Total mortgage-backed securities and other securities | More than 10 years and less than or equal to 20 years
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	22,968	58,176
Total mortgage-backed securities and other securities | More than 20 years and less than or equal to 30 years
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	57,326	86,452
Total mortgage-backed securities and other securities | More than 30 years
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	$ 30,014	$ 28,325