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		20,110			20,110
Other comprehensive income (loss)		(9)				(9)
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)			225
Issuance of common stock in connection with exercise of stock options		456		456
Stock-based compensation expense		702		702
Equity, end of period (in shares) at Jun. 30, 2017			37,213
Equity, end of period at Jun. 30, 2017		451,741	$ 372	384,119	69,237	(734)	(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 | Accounting Standards Update 2018-02	[1]	0			1,396	(1,396)
Reclassification upon adoption of new accounting standards | Accounting Standards Update 2016-01	[1]	(63)			(299)	236
Net income		25,783
Other comprehensive income (loss)		(10,416)				(10,416)
Issuance of common stock in connection with exercise of stock options (in shares)			186
Issuance of common stock in connection with exercise of stock options		1,761	$ 2	1,759
Stock-based compensation expense		2,360		2,360
Cash dividend declared, $0.10 per share		(3,727)			(3,727)
Equity, end of period (in shares) at Jun. 30, 2018			37,289
Equity, end of period at Jun. 30, 2018		$ 479,493	$ 375	$ 392,010	$ 106,416	$ (18,055)	$ (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.