Fair Value Measurements - Changes in Level 3 Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Total net gains (losses) included in:
Unrealized gains (losses) included in other comprehensive income for assets held at the end of the period	$ 4,500	$ 8,400
Interest-only strips
Total net gains (losses) included in:
Acquired	0	0
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation
Asset (liability) balance, beginning of period	12,813	16,835	$ 21,386
Total net gains (losses) included in:
Net income	1,009	2,568	2,616
Other comprehensive income (loss)	(242)	(262)	1,195
Sales	0	0	0
Originations	0	2,789	4,797
Principal paydowns / settlements	(5,757)	(9,117)	(13,159)
Transfers out of Level 3	0	0
Asset (liability) balance, end of period	7,823	12,813	16,835
Unrealized gains (losses) included in other comprehensive income for assets held at the end of the period	(242)	(262)	1,195
Interest rate lock commitments
Total net gains (losses) included in:
Acquired	0	0
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation
Asset (liability) balance, beginning of period	0	624	223
Total net gains (losses) included in:
Net income	0	778	401
Other comprehensive income (loss)	0	0	0
Sales	0	0	0
Originations	0	0	0
Principal paydowns / settlements	0	0	0
Transfers out of Level 3	0	(1,402)
Asset (liability) balance, end of period	0	0	624
Unrealized gains (losses) included in other comprehensive income for assets held at the end of the period	0	0	0
Swap agreement
Total net gains (losses) included in:
Acquired	0	0
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation
Asset (liability) balance, beginning of period	(356)	(583)	(615)
Total net gains (losses) included in:
Net income	(1)	(68)	(274)
Other comprehensive income (loss)	0	0	0
Sales	0	0	0
Originations	0	0	0
Principal paydowns / settlements	291	295	306
Transfers out of Level 3	0	0
Asset (liability) balance, end of period	(66)	(356)	(583)
Unrealized gains (losses) included in other comprehensive income for assets held at the end of the period	0	0	0
Forward loan sales commitments
Total net gains (losses) included in:
Acquired	0	0
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation
Asset (liability) balance, beginning of period	0	(26)	63
Total net gains (losses) included in:
Net income	0	(119)	(89)
Other comprehensive income (loss)	0	0	0
Sales	0	0	0
Originations	0	0	0
Principal paydowns / settlements	0	0	0
Transfers out of Level 3	0	145
Asset (liability) balance, end of period	0	0	(26)
Unrealized gains (losses) included in other comprehensive income for assets held at the end of the period	0	0	0
Investment securities available-for-sale
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation
Asset (liability) balance, beginning of period	433	4	6
Total net gains (losses) included in:
Net income	3	1	0
Other comprehensive income (loss)	68	(21)	0
Acquired	0	450
Sales	0	0	0
Originations	0	0	0
Principal paydowns / settlements	0	(1)	(2)
Transfers out of Level 3	0	0
Asset (liability) balance, end of period	504	433	4
Total net gains (losses) included in:
Unrealized gains (losses) included in other comprehensive income for assets held at the end of the period	68	(21)	0
Loans held-for-sale
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation
Asset (liability) balance, beginning of period	0	18,070	3,356
Total net gains (losses) included in:
Net income	0	534	454
Other comprehensive income (loss)	0	0	0
Acquired	0	0
Sales	0	(164,693)	(332,288)
Originations	0	175,304	346,560
Principal paydowns / settlements	0	(4)	(12)
Transfers out of Level 3	0	(29,211)
Asset (liability) balance, end of period	0	0	18,070
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

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 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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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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