Fair Values Measurements - Changes in Level 3 Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation
Transfers out of Level 3			$ 0
Interest-only Strips
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Asset (liability) balance, beginning of period	$ 15,236	$ 19,887	16,835	$ 21,386
Transfers out of Level 3	0		0
Total net gains (losses) included in:
Net income	611	732	1,976	1,913
Other comprehensive income (loss)	(65)	246	246	1,015
Acquired	0		0
Sales		0	0	0
Originations	628	0	2,180	3,849
Principal paydowns / settlements	(2,332)	(3,153)	(7,159)	(10,451)
Asset (liability) balance, end of period	14,078	17,712	14,078	17,712
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	1,402	858	624	223
Transfers out of Level 3	(1,402)		(1,402)
Total net gains (losses) included in:
Net income	0	(242)	778	393
Other comprehensive income (loss)	0	0	0	0
Acquired	0		0
Sales		0	0	0
Originations	0	0	0	0
Principal paydowns / settlements	0	0	0	0
Asset (liability) balance, end of period	0	616	0	616
Swap agreement
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Asset (liability) balance, beginning of period	(435)	(441)	(583)	(615)
Transfers out of Level 3	0		0
Total net gains (losses) included in:
Net income	0	(292)	0	(274)
Other comprehensive income (loss)	0	0	0	0
Acquired	0		0
Sales		0	0	0
Originations	0	0	0	0
Principal paydowns / settlements	79	75	227	231
Asset (liability) balance, end of period	(356)	(658)	(356)	(658)
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	(145)	110	(26)	63
Transfers out of Level 3	145		145
Total net gains (losses) included in:
Net income	0	359	(119)	406
Other comprehensive income (loss)	0	0	0	0
Acquired	0		0
Sales		0	0	0
Originations	0	0	0	0
Principal paydowns / settlements	0	0	0	0
Asset (liability) balance, end of period	0	469	0	469
Investment securities carried at fair value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation
Asset balance, beginning of period	3	4	4	6
Transfers out of Level 3	0
Acquired through the Merger	450		450
Total net gains (losses) included in:
Net income	0	0	0	0
Other comprehensive income (loss)	(25)	0	(25)	0
Acquired	0
Sales		0	0	0
Originations	0	0	0	0
Principal paydowns / settlements	0	0	(1)	(2)
Asset balance, end of period	428	4	428	4
Loans Held for Sale
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation
Asset balance, beginning of period	29,211	18,554	18,070	3,356
Transfers out of Level 3	(29,211)		(29,211)
Total net gains (losses) included in:
Net income	0	(184)	534	254
Other comprehensive income (loss)	0	0	0	0
Acquired	0		0
Sales		(97,866)	(164,693)	(232,747)
Originations	0	98,018	175,304	247,667
Principal paydowns / settlements	0	(3)	(4)	(11)
Asset balance, end of period	$ 0	$ 18,519	$ 0	$ 18,519

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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 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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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 purchases 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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