Consolidated Statements of Changes in Stockholders’ Equity (Unaudited ) - USD ($) $ in Thousands	Common Stock	Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Retained Deficit	Treasury Shares	Total
Balance at the beginning of the period at Dec. 31, 2017	$ 387	$ 606,346	$ 19,297	$ (249,847)	$ (200)	$ 375,983
Increase (decrease) in Stockholders' Equity
Stock based employee compensation plan		238				238
New unrealized gain (loss) on investment securities, net of deferred tax expense (benefit)			(21,459)			(21,459)
Net income				10,795		10,795
Balance at the end of the period at Mar. 31, 2018	387	606,584	(2,162)	(239,052)	(200)	365,557
Balance at the beginning of the period at Dec. 31, 2017	387	606,346	19,297	(249,847)	(200)	375,983
Increase (decrease) in Stockholders' Equity
Net income						40,423
Balance at the end of the period at Sep. 30, 2018	387	606,905	(13,949)	(209,424)	(200)	383,719
Balance at the beginning of the period at Mar. 31, 2018	387	606,584	(2,162)	(239,052)	(200)	365,557
Increase (decrease) in Stockholders' Equity
Stock based employee compensation plan		160				160
New unrealized gain (loss) on investment securities, net of deferred tax expense (benefit)			(11,230)			(11,230)
Net income				14,454		14,454
Balance at the end of the period at Jun. 30, 2018	387	606,744	(13,392)	(224,598)	(200)	368,941
Increase (decrease) in Stockholders' Equity
Stock based employee compensation plan		161				161
New unrealized gain (loss) on investment securities, net of deferred tax expense (benefit)			(557)			(557)
Net income				15,174		15,174
Balance at the end of the period at Sep. 30, 2018	387	606,905	(13,949)	(209,424)	(200)	383,719
Balance at the beginning of the period at Dec. 31, 2018	389	607,260	(22,315)	(195,304)	(200)	389,830
Increase (decrease) in Stockholders' Equity
Stock based employee compensation plan		77				77
New unrealized gain (loss) on investment securities, net of deferred tax expense (benefit)			27,752			27,752
Equity distribution		(4,174)				(4,174)
Net income				13,440		13,440
Balance at the end of the period at Mar. 31, 2019	389	603,163	5,437	(181,864)	(200)	426,925
Balance at the beginning of the period at Dec. 31, 2018	389	607,260	(22,315)	(195,304)	(200)	389,830
Increase (decrease) in Stockholders' Equity
Net income						30,370
Balance at the end of the period at Sep. 30, 2019	430	661,357	33,930	(164,934)	(200)	530,583
Balance at the beginning of the period at Mar. 31, 2019	389	603,163	5,437	(181,864)	(200)	426,925
Increase (decrease) in Stockholders' Equity
New unrealized gain (loss) on investment securities, net of deferred tax expense (benefit)			23,407			23,407
Net income				8,618		8,618
Balance at the end of the period at Jun. 30, 2019	389	603,163	28,844	(173,246)	(200)	458,950
Increase (decrease) in Stockholders' Equity
Stock based employee compensation plan		6,785				6,785
New unrealized gain (loss) on investment securities, net of deferred tax expense (benefit)			5,086			5,086
Proceeds from common stock sold in initial public offering, net of offering costs	42	51,557				51,599
Shares cancelled	(1)	1
Retirement of common stock (tax payments on equity compensation)		(149)				(149)
Net income				8,312		8,312
Balance at the end of the period at Sep. 30, 2019	$ 430	$ 661,357	$ 33,930	$ (164,934)	$ (200)	$ 530,583