Fair Value Measurements - Changes in Level 3 Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Interest-only Strips
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Asset (liability) balance, beginning of period	$ 7,823	$ 12,813
Total net gains (losses) included in:
Net income	144	159
Other comprehensive income (loss)	(181)	(348)
Principal paydowns / settlements	(1,049)	(1,673)
Asset (liability) balance, end of period	6,737	10,951
Unrealized gains (losses) included in other comprehensive income for assets held at the end of the period	(181)	(348)
Originations	0
Swap agreement
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Asset (liability) balance, beginning of period	(66)	(356)
Total net gains (losses) included in:
Net income	0	(1)
Other comprehensive income (loss)	0	0
Principal paydowns / settlements	68	71
Asset (liability) balance, end of period	(286)	(286)
Unrealized gains (losses) included in other comprehensive income for assets held at the end of the period	0	0
Originations	(288)
Investment securities available-for-sale
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation
Asset balance, beginning of period	504	433
Total net gains (losses) included in:
Net income	0	1
Other comprehensive income (loss)	(37)	(31)
Principal paydowns / settlements	0	0
Asset balance, end of period	467	403
Total net gains (losses) included in:
Unrealized gains (losses) included in other comprehensive income for assets held at the end of the period	(37)	$ (31)
Originations	$ 0

Fair Value, Net Assets (Liabilities) Measured On Recurring Basis, Gain (Loss) Included In Earnings [Abstract]

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Unrealized Holding Gain (Loss) Transfers from Available for Sale to Held to Maturity Retained in Accumulated Other Comprehensive Income

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3).

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Amount of gain (loss) recognized in other comprehensive income (OCI) from asset measured at fair value on recurring basis using unobservable input (level 3).

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Amount of issuances of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of settlement of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of gain (loss) recognized in income from derivative asset (liability) after deduction of derivative liability (asset), measured at fair value on recurring basis using unobservable input (level 3).

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Amount of gain (loss) recognized in other comprehensive income from derivative asset (liability) after deduction of derivative liability (asset), measured at fair value on recurring basis using unobservable input (level 3).

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Amount of issuances of financial instrument classified as a derivative asset (liability) after deduction of derivative liability (asset), measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of settlements of financial instrument classified as a derivative asset (liability) after deduction of derivative liability, measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Fair value of financial instrument classified as derivative asset (liability) after deduction of derivative liability (asset), measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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