Investment Securities - Narrative (Details) $ in Thousands	Sep. 30, 2021 USD ($) instrument	Jan. 01, 2021 USD ($)	Dec. 31, 2020 USD ($)
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Accrued interest on investment securities	$ 22,800
Allowance for credit losses	245		$ 0
Gross unrealized losses	16,161		349
Carrying value of securities pledged as collateral	946,200		890,000
Securities sold under repurchase agreements	176,700		167,300
State and municipal
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Allowance for credit losses	245		0
Gross unrealized losses	$ 3,946		246
Number of securities in unrealized loss positions \| instrument	179
State and municipal \| Cumulative effect of ASC 326 adoption
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Allowance for credit losses		$ 245	245
U.S. Government-sponsored mortgage-backed securities
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Allowance for credit losses	$ 0		0
Gross unrealized losses	$ 12,215		$ 103
Number of securities in unrealized loss positions \| instrument	49

Debt Securities, Available-for-sale and Held-to-maturity, Accrued Interest

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Schedule of Available for sale Securities and Held to maturity Securities [Line Items]

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Securities Pledged as Collateral

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Number of investments in debt securities measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount, excluding accrued interest, of allowance for credit loss on investment in debt security measured at amortized cost (held-to-maturity).

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Amount of asset associated with funds outstanding borrowed in the form of a security repurchase agreement between the entity and another party for the sale and repurchase of identical or substantially the same securities at a date certain for a specified price.

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