Investment Securities - Narrative (Details) $ in Thousands	3 Months Ended	12 Months Ended
Jun. 30, 2019 USD ($)	Dec. 31, 2020 USD ($) position	Dec. 31, 2019 USD ($) position	Dec. 31, 2018 USD ($)
Debt Securities, Available-for-sale [Line Items]
Loss upon acquisition of interest-only GNMA securities	$ 7,500	$ 0	$ 7,476	$ 0
Net proceeds from (purchases of) FHLB, Federal Reserve Bank, and other restricted stock		12,846	5,471	16,233
Unrealized gain (loss) on investment securities		1,447	1,299	(1,634)
Proceeds from sale of AFS debt securities		387,810	97,555	476,182
Realized gains from sale of AFS debt securities		$ 20,100	$ 1,000
Realized losses from sale of AFS debt securities				$ 18,700
Number of available for sale debt securities in an unrealized loss position (position) \| position		16	0
Pledged investment securities fair value		$ 18,800	$ 20,400
Interest-only GNMA securities
Debt Securities, Available-for-sale [Line Items]
Loss upon acquisition of interest-only GNMA securities			7,500
Interest-only GNMA securities			$ 16,272
Net proceeds from (purchases of) FHLB, Federal Reserve Bank, and other restricted stock		15,400
Other investments, realized gain		$ 1,000

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Other Investments, Realized Gain

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Amount of realized gain 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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Sum of the carrying amounts as of the date of the latest financial statement presented of securities which are owned but transferred to another party to serve as collateral to partially or fully secure a debt obligation, repurchase agreement or other current or potential obligation, and for which the transferee is not permitted to sell or re-pledge them to an unrelated party.

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Amount of unrealized gain (loss) on investment.

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