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Securities - Additional Information (Details)		12 Months Ended
	Jan. 01, 2019 USD ($)	Dec. 31, 2019 USD ($) Security	Dec. 31, 2018 USD ($) Security
Schedule Of Investments [Line Items]
Trading securities		$ 0	$ 0
Reclassification from other comprehensive income to retained earnings		(1,440,000)
Equity and other securities, at fair value		8,031,000
Carrying amount of securities pledged as collateral		$ 301,100,000	$ 244,700,000
Minimum
Schedule Of Investments [Line Items]
Percentage of shareholders equity for which securities holdings exceeds for no issuer other than U.S. Government and agencies		10.00%	10.00%
Federal Home Loan Bank Advances
Schedule Of Investments [Line Items]
Carrying amount of securities pledged as collateral		$ 0	$ 0
Public Fund Deposits
Schedule Of Investments [Line Items]
Carrying amount of securities pledged as collateral		240,400,000	197,800,000
Customer Repurchase Agreements
Schedule Of Investments [Line Items]
Carrying amount of securities pledged as collateral		$ 55,700,000	$ 46,900,000
Available-for-sale Securities
Schedule Of Investments [Line Items]
Investment securities with unrealized losses | Security		99	179
Held-to-maturity Securities
Schedule Of Investments [Line Items]
Investment securities with unrealized losses | Security		0	46
ASU 2016-01
Schedule Of Investments [Line Items]
Reclassification from other comprehensive income to retained earnings	$ 1,400,000
Equity and other securities, at fair value			$ 6,600,000
ASU 2017-12
Schedule Of Investments [Line Items]
Reclassification of securities held-to-maturity to securities available-for-sale	$ 94,800,000

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Amount of the cumulative effect on retained earnings net of related income tax effect.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Topic 250
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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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