Investment Securities - Gross Unrealized Losses on Available-for-sale Securities and the Related Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, fair value	$ 286,129	$ 58,138
Less than 12 months, unrealized losses	(1,359)	(170)
More than 12 months, fair value	0	2,967
More than 12 months, unrealized losses	0	(24)
Fair Value	286,129	61,105
Unrealized Losses	(1,359)	(194)
U.S. Treasury and government sponsored entities
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, fair value	276,140	31,270
Less than 12 months, unrealized losses	(1,315)	(47)
More than 12 months, fair value	0	0
More than 12 months, unrealized losses	0	0
Fair Value	276,140	31,270
Unrealized Losses	(1,315)	(47)
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, fair value	5,013	3,198
Less than 12 months, unrealized losses	(20)	(5)
More than 12 months, fair value	0	0
More than 12 months, unrealized losses	0	0
Fair Value	5,013	3,198
Unrealized Losses	(20)	(5)
Collateralized loan obligations
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, fair value	4,976	23,670
Less than 12 months, unrealized losses	(24)	(118)
More than 12 months, fair value	0	2,967
More than 12 months, unrealized losses	0	(24)
Fair Value	4,976	26,637
Unrealized Losses	$ (24)	$ (142)

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of accumulated unrealized loss on investment in debt security 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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