Consolidated Statement of Changes in Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Treasury Stock [Member]	Accumulated Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Beginning Balance at Dec. 31, 2017						$ 3,612
Comprehensive income:
Net income	$ 16,169
Other comprehensive income:
Unrealized gain (loss) on debt securities, net of tax	(5,848)
Comprehensive income	$ 10,321
Common stock issued upon exercise of options, Shares	15,000
Ending Balance at Mar. 31, 2018						(2,236)
Beginning Balance at Dec. 31, 2018	$ 409,762	$ 205	$ 211,431	$ (22,370)	$ 221,328	(832)
Beginning Balance, Shares at Dec. 31, 2018	20,528,230	20,528,230
Treasury Stock Beginning Balance, Shares at Dec. 31, 2018	(1,258,250)			(1,258,250)
Comprehensive income:
Impact of adoption of ASU 2016-02 | ASU 2016-02 [Member]	$ (1)				(1)
Net income	19,400				19,400
Other comprehensive income:
Unrealized gain (loss) on debt securities, net of tax	5,992					5,992
Change in deferred tax valuation allowance	(198)					(198)
Comprehensive income	25,194
Common stock issued upon exercise of options	$ 20		20
Common stock issued upon exercise of options, Shares	5,000	5,000
Share-based compensation	$ 249		249
Dividends to shareholders	(4,819)				(4,819)
Ending Balance at Mar. 31, 2019	$ 430,405	$ 205	$ 211,700	$ (22,370)	$ 235,908	$ 4,962
Ending Balance, Shares at Mar. 31, 2019	20,533,230	20,533,230
Treasury Stock Ending Balance, Shares at Mar. 31, 2019	(1,258,250)			(1,258,250)