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Securities - Summary of Amortized Cost and Fair Values of Securities Available-for-sale (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost	$ 1,433,152	$ 1,418,445
Available-for-sale Securities, Gross Unrealized Gains	13,354	29,834
Available-for-sale Securities, Gross Unrealized Losses	(18,901)	(1,049)
Available-for-sale Securities, Fair Value	1,427,605	1,447,230
U.S. Treasury Notes
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost	8,487	23,468
Available-for-sale Securities, Gross Unrealized Gains	91	344
Available-for-sale Securities, Gross Unrealized Losses	0	0
Available-for-sale Securities, Fair Value	8,578	23,812
U.S. Government Agencies
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost	124,244	113,088
Available-for-sale Securities, Gross Unrealized Gains	885	600
Available-for-sale Securities, Gross Unrealized Losses	(1,865)	(137)
Available-for-sale Securities, Fair Value	123,264	113,551
Obligations of States, Municipalities, and Political Subdivisions
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost	101,499	135,513
Available-for-sale Securities, Gross Unrealized Gains	3,725	6,991
Available-for-sale Securities, Gross Unrealized Losses	(164)	(85)
Available-for-sale Securities, Fair Value	105,060	142,419
Agency, Residential Mortgage-Backed Securities
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost	794,856	764,951
Available-for-sale Securities, Gross Unrealized Gains	3,303	13,645
Available-for-sale Securities, Gross Unrealized Losses	(12,986)	(205)
Available-for-sale Securities, Fair Value	785,173	778,391
Non-Agency, Residential Mortgage-Backed Securities
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost	64,645	32,654
Available-for-sale Securities, Gross Unrealized Gains	86	332
Available-for-sale Securities, Gross Unrealized Losses	(722)	(5)
Available-for-sale Securities, Fair Value	64,009	32,981
Agency, Commercial Mortgage-Backed Securities
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost	237,376	244,496
Available-for-sale Securities, Gross Unrealized Gains	3,179	6,046
Available-for-sale Securities, Gross Unrealized Losses	(3,146)	(390)
Available-for-sale Securities, Fair Value	237,409	250,152
Corporate Securities
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost	64,842	59,020
Available-for-sale Securities, Gross Unrealized Gains	2,002	1,850
Available-for-sale Securities, Gross Unrealized Losses	(17)	(102)
Available-for-sale Securities, Fair Value	66,827	60,768
Asset-Backed Securities
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost	37,203	45,255
Available-for-sale Securities, Gross Unrealized Gains	83	26
Available-for-sale Securities, Gross Unrealized Losses	(1)	(125)
Available-for-sale Securities, Fair Value	$ 37,285	$ 45,156

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Amount, before tax, of unrealized gain 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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