Securities - Amortized Cost and Estimated Fair Value of Securities - Securities Available-for-sale (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Securities available-for-sale:
Amortized Cost	$ 466,779	$ 393,339
Gross Unrealized Gains	1,032	2,905
Gross Unrealized (Losses)	(8,768)	(4,392)
Total	459,043	391,852
Agency mortgage-backed securities
Securities available-for-sale:
Amortized Cost	311,523	378,339
Gross Unrealized Gains	98	786
Gross Unrealized (Losses)	(8,767)	(4,392)
Total	302,854	374,733
U.S. Treasury
Securities available-for-sale:
Amortized Cost	147,823
Gross Unrealized Gains	930
Total	148,753
Trust preferred securities
Securities available-for-sale:
Amortized Cost		15,000
Gross Unrealized Gains		2,119
Total		$ 17,119
U.S. Government sponsored entities
Securities available-for-sale:
Amortized Cost	7,433
Gross Unrealized Gains	4
Gross Unrealized (Losses)	(1)
Total	$ 7,436

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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