Securities Available for Sale - Maturities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Amortized Cost
Amortized Cost, within 1 year	$ 200
Amortized Cost, due after 5 years through 10 years	10,086
Amortized Cost, due after 10 years	193,455
Asset-backed securities related to Structured Program transactions	64,991
Amortized Cost	268,732	$ 159,164
Fair Value
Fair Value, within 1 year	200
Fair Value, due after 5 years through 10 years	10,009
Fair Value, due after 10 years	191,027
Asset-backed securities related to Structured Program transactions	73,694
Fair Value	$ 274,930	142,226
Weighted- average Yield, due within 1 year	0.02%
Weighted- average Yield, due after 5 years through 10 years	0.99%
Weighted- average Yield, due after 10 years	1.54%
Weighted- average Yield	4.39%
U.S. agency residential mortgage-backed securities
Amortized Cost
Amortized Cost, due after 5 years through 10 years	$ 394
Amortized Cost, due after 10 years	115,297
Fair Value
Fair Value, due after 5 years through 10 years	394
Fair Value, due after 10 years	113,500
Fair Value	113,894
Other asset-backed securities
Amortized Cost
Amortized Cost, within 1 year	200
Amortized Cost, due after 5 years through 10 years	926
Amortized Cost, due after 10 years	26,716
Amortized Cost	27,642
Fair Value
Fair Value, within 1 year	200
Fair Value, due after 5 years through 10 years	944
Fair Value, due after 10 years	26,902
Fair Value	27,846	$ 200
Commercial mortgage-backed securities
Amortized Cost
Amortized Cost, due after 5 years through 10 years	4,273
Amortized Cost, due after 10 years	24,690
Amortized Cost	28,963
Fair Value
Fair Value, due after 5 years through 10 years	4,185
Fair Value, due after 10 years	24,459
Fair Value	28,644
U.S. agency securities
Amortized Cost
Amortized Cost, due after 5 years through 10 years	4,023
Amortized Cost, due after 10 years	23,920
Amortized Cost	27,943
Fair Value
Fair Value, due after 5 years through 10 years	4,024
Fair Value, due after 10 years	23,386
Fair Value	27,410
Municipal securities
Amortized Cost
Amortized Cost, due after 5 years through 10 years	470
Amortized Cost, due after 10 years	2,832
Amortized Cost	3,302
Fair Value
Fair Value, due after 5 years through 10 years	462
Fair Value, due after 10 years	2,780
Fair Value	$ 3,242
Asset-backed securities related to Structured Program transactions
Fair Value
Weighted- average Yield	13.40%