Fair Value Measurements - Changes in Level 3 Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Interest-only Strips
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Asset (liability) balance, beginning of period	$ 11,811	$ 15,236	$ 12,813	$ 16,835
Total net gains (losses) included in:
Net income	277	610	763	1,975
Other comprehensive income (loss)	(1,211)	(65)	430	246
Acquired		0
Sales				0
Originations		628		2,180
Principal paydowns / settlements	(1,322)	(2,332)	(4,451)	(7,159)
Transfers out of Level 3		0		0
Asset (liability) balance, end of period	9,555	14,077	9,555	14,077
Unrealized gains (losses) included in other comprehensive income for assets held at the end of the period	(1,211)	(65)	430	246
Interest Rate Lock Commitments
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Asset (liability) balance, beginning of period	0	1,402	0	624
Total net gains (losses) included in:
Net income	0	0	0	778
Other comprehensive income (loss)	0	0	0	0
Acquired		0
Sales				0
Originations		0		0
Principal paydowns / settlements	0	0	0	0
Transfers out of Level 3		(1,402)		(1,402)
Asset (liability) balance, end of period	0	0	0	0
Unrealized gains (losses) included in other comprehensive income for assets held at the end of the period	0	0	0	0
Swap agreement
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Asset (liability) balance, beginning of period	(213)	(435)	(356)	(583)
Total net gains (losses) included in:
Net income	0	0	(1)	0
Other comprehensive income (loss)	0	0	0	0
Acquired		0
Sales				0
Originations		0		0
Principal paydowns / settlements	72	79	216	227
Transfers out of Level 3		0		0
Asset (liability) balance, end of period	(141)	(356)	(141)	(356)
Unrealized gains (losses) included in other comprehensive income for assets held at the end of the period	0	0	0	0
Forward loan sales commitments
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Asset (liability) balance, beginning of period	0	(145)	0	(26)
Total net gains (losses) included in:
Net income	0	0	0	(119)
Other comprehensive income (loss)	0	0	0	0
Acquired		0
Sales				0
Originations		0		0
Principal paydowns / settlements	0	0	0	0
Transfers out of Level 3		145		145
Asset (liability) balance, end of period	0	0	0	0
Unrealized gains (losses) included in other comprehensive income for assets held at the end of the period	0	0	0	0
Investment securities available-for-sale
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation
Asset balance, beginning of period	441	3	433	4
Total net gains (losses) included in:
Net income	1	0	3	0
Other comprehensive income (loss)	25	(25)	31	(25)
Acquired		450		450
Sales				0
Originations		0		0
Principal paydowns / settlements	0	0	0	(1)
Transfers out of Level 3		0		0
Asset balance, end of period	467	428	467	428
Total net gains (losses) included in:
Unrealized gains (losses) included in other comprehensive income for assets held at the end of the period	25	(25)	31	(25)
Loans Held for Sale
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation
Asset balance, beginning of period	0	29,211	0	18,070
Total net gains (losses) included in:
Net income	0	0	0	534
Other comprehensive income (loss)	0	0	0	0
Acquired		0
Sales				(164,693)
Originations		0		175,304
Principal paydowns / settlements	0	0	0	(4)
Transfers out of Level 3		(29,211)		(29,211)
Asset balance, end of period	0	0	0	0
Total net gains (losses) included in:
Unrealized gains (losses) included in other comprehensive income for assets held at the end of the period	$ 0	$ 0	$ 0	$ 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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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 purchases 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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Amount of transfers of financial instrument classified as an asset out of level 3 of the fair value hierarchy.

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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 sales 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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Amount of transfers of financial instrument classified as derivative asset (liability) after deduction of derivative liability (asset) out of level 3 of the fair value hierarchy.

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