Securities - Amortized Cost and Fair Value of Securities Available for Sale and Held for Investment (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Debt securities available-for-sale
Available for sale, amortized cost, total	$ 1,802,563	$ 1,653,658
Available for sale, gross unrealized gains	1,685	11,518
Available for sale, gross unrealized losses	(97,629)	(20,857)
Available for sale, fair value	1,706,619	1,644,319
Debt securities held-to-maturity
Held to maturity, amortized cost, total	747,004	638,640
Held to maturity, gross unrealized gains	15,397	3,828
Held to maturity, gross unrealized losses	(52,909)	(15,070)
Held to maturity, fair value	709,492	627,398
U.S. Treasury securities and obligations of U.S. government agencies
Debt securities available-for-sale
Available for sale, amortized cost, total	6,240	6,466
Available for sale, gross unrealized gains	54	316
Available for sale, gross unrealized losses	(13)	(3)
Available for sale, fair value	6,281	6,779
Mortgage-backed securities and collateralized mortgage obligations of U.S. government-sponsored entities
Debt securities available-for-sale
Available for sale, amortized cost, total	1,335,336	1,234,721
Available for sale, gross unrealized gains	829	8,308
Available for sale, gross unrealized losses	(91,495)	(20,309)
Available for sale, fair value	1,244,670	1,222,720
Debt securities held-to-maturity
Held to maturity, amortized cost, total		638,640
Held to maturity, gross unrealized gains		3,828
Held to maturity, gross unrealized losses		(15,070)
Held to maturity, fair value	709,492	627,398
Private mortgage-backed securities and collateralized mortgage obligations
Debt securities available-for-sale
Available for sale, amortized cost, total	114,286	88,096
Available for sale, gross unrealized gains	284	1,091
Available for sale, gross unrealized losses	(3,274)	(420)
Available for sale, fair value	111,296	88,767
Debt securities held-to-maturity
Held to maturity, fair value	0
Collateralized loan obligations
Debt securities available-for-sale
Available for sale, amortized cost, total	315,168	292,751
Available for sale, gross unrealized gains	0	63
Available for sale, gross unrealized losses	(2,044)	(124)
Available for sale, fair value	313,124	292,690
Debt securities held-to-maturity
Held to maturity, fair value	0
Obligations of state and political subdivisions
Debt securities available-for-sale
Available for sale, amortized cost, total	31,533	31,624
Available for sale, gross unrealized gains	518	1,740
Available for sale, gross unrealized losses	(803)	(1)
Available for sale, fair value	31,248	$ 33,363
Mortgage-backed securities and collateralized mortgage obligations of U.S. government-sponsored entities
Debt securities held-to-maturity
Held to maturity, amortized cost, total	747,004
Held to maturity, gross unrealized gains	15,397
Held to maturity, gross unrealized losses	(52,909)
Held to maturity, fair value	$ 709,492

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

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Amount of accumulated unrecognized gain on investment in debt security measured at amortized cost (held-to-maturity).

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Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity).

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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

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