CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS’ EQUITY - USD ($) shares in Thousands, $ in Thousands		Total	Common Stock	Capital Surplus	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Equity, beginning of period (in shares) at Dec. 31, 2016			36,988
Equity, beginning of period at Dec. 31, 2016		$ 430,482	$ 372	$ 382,961	$ 49,127	$ (725)	$ (1,253)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		7,212			7,212
Net change in unrealized gains and losses on available-for-sale securities, net of taxes and reclassification adjustment		(1,024)				(1,024)
Purchase of treasury stock (in shares)			0
Purchase of treasury stock		0					0
Issuance of common stock in connection with exercise of stock options (in shares)			205
Issuance of common stock in connection with exercise of stock options		271		271
Stock-based compensation expense		347		347
Equity, end of period (in shares) at Mar. 31, 2017			37,193
Equity, end of period at Mar. 31, 2017		437,288	$ 372	383,579	56,339	(1,749)	(1,253)
Equity, beginning of period (in shares) at Dec. 31, 2017			37,103
Equity, beginning of period at Dec. 31, 2017		463,795	$ 373	387,891	83,263	(6,479)	(1,253)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Reclassification upon adoption of new accounting standards	[1]	0			1,097	(1,097)
Net income		9,362			9,362
Net change in unrealized gains and losses on available-for-sale securities, net of taxes and reclassification adjustment		(6,686)			0	(6,686)
Issuance of common stock in connection with exercise of stock options (in shares)			238
Issuance of common stock in connection with exercise of stock options		1,218	$ 1	1,217
Stock-based compensation expense		1,189		1,189
Equity, end of period (in shares) at Mar. 31, 2018			37,341
Equity, end of period at Mar. 31, 2018		$ 468,878	$ 374	$ 390,297	$ 93,722	$ (14,262)	$ (1,253)

[1] Adoption of Accounting Standards Updates 2018-02 and 2016-01. See Notes 3 and 14 to interim condensed consolidated financial statements for additional information.