Securities - Amortized Cost and Fair Value of Securities Available for Sale and Held for Investment (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Securities Available-for-Sale
Available for sale, amortized cost, total	$ 940,765	$ 882,872
Available for sale, gross unrealized gains	8,764	1,306
Available for sale, gross unrealized losses	(2,674)	(18,347)
Available for sale, fair value	946,855	865,831
Debt Securities Held-to-Maturity
Held to maturity, amortized cost	261,369	357,949
Held to maturity, gross unrealized gains	2,717	277
Held to maturity, gross unreazlied losses	(1,873)	(8,331)
Held to maturity, fair value	262,213	349,895
U.S. Treasury securities and obligations of U.S. government agencies
Debt Securities Available-for-Sale
Available for sale, amortized cost, total	9,914	7,200
Available for sale, gross unrealized gains	204	106
Available for sale, gross unrealized losses	(4)	(6)
Available for sale, fair value	10,114	7,300
Mortgage-backed securities and collateralized mortgage obligations of U.S. government sponsored entities
Debt Securities Available-for-Sale
Available for sale, amortized cost, total	604,934	567,753
Available for sale, gross unrealized gains	5,784	300
Available for sale, gross unrealized losses	(1,511)	(14,047)
Available for sale, fair value	609,207	554,006
Debt Securities Held-to-Maturity
Held to maturity, amortized cost	261,369	304,423
Held to maturity, gross unrealized gains	2,717	0
Held to maturity, gross unreazlied losses	(1,873)	(7,324)
Held to maturity, fair value	262,213	297,099
Private mortgage-backed securities and collateralized mortgage obligations
Debt Securities Available-for-Sale
Available for sale, amortized cost, total	56,005	55,569
Available for sale, gross unrealized gains	1,561	560
Available for sale, gross unrealized losses	(5)	(401)
Available for sale, fair value	57,561	55,728
Debt Securities Held-to-Maturity
Held to maturity, amortized cost		21,526
Held to maturity, gross unrealized gains		277
Held to maturity, gross unreazlied losses		(130)
Held to maturity, fair value	0	21,673
Collateralized loan obligations
Debt Securities Available-for-Sale
Available for sale, amortized cost, total	239,364	212,807
Available for sale, gross unrealized gains	7	1
Available for sale, gross unrealized losses	(1,153)	(3,442)
Available for sale, fair value	238,218	209,366
Debt Securities Held-to-Maturity
Held to maturity, amortized cost		32,000
Held to maturity, gross unrealized gains		0
Held to maturity, gross unreazlied losses		(877)
Held to maturity, fair value	0	31,123
Obligations of state and political subdivisions
Debt Securities Available-for-Sale
Available for sale, amortized cost, total	30,548	39,543
Available for sale, gross unrealized gains	1,208	339
Available for sale, gross unrealized losses	(1)	(451)
Available for sale, fair value	$ 31,755	$ 39,431

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 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 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 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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Amount, before other-than-temporary impairment (OTTI) accretion, of investment in debt securities 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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