Securities - Amortized Cost and Estimated Fair Value of Securities - Securities Available-for-sale (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Securities available-for-sale:
Amortized Cost	$ 402,537	$ 466,779
Gross Unrealized Gains	2,459	1,032
Gross Unrealized (Losses)	(171)	(8,768)
Total	404,825	459,043
Agency mortgage-backed securities
Securities available-for-sale:
Amortized Cost	283,598	311,523
Gross Unrealized Gains	934	98
Gross Unrealized (Losses)	(171)	(8,767)
Total	284,361	302,854
U.S. Treasury
Securities available-for-sale:
Amortized Cost	118,939	147,823
Gross Unrealized Gains	1,525	930
Total	$ 120,464	148,753
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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