Consolidated Statements of Changes in Shareholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Common Stock [Member]	Accumulated Deferred Compensation [Member]	AOCI Attributable to Parent [Member]	Retained Earnings [Member]	Total
Balance (in shares) at Dec. 31, 2017	26,425
Balance at Dec. 31, 2017	$ 431,734	$ 1,533	$ (16,832)	$ 173,804	$ 590,239
Cumulative effect at Dec. 31, 2017			142	(142)
Adjusted Balance (in shares) at Dec. 31, 2017	26,425
Adjusted Balance at Dec. 31, 2017	$ 431,734	1,533	(16,690)	173,662	590,239
Reclass stranded tax effects resulting from the Tax Cuts and Jobs Act			(3,625)	3,625
Net income for the period				17,506	17,506
Other comprehensive income (loss)			(23,137)		(23,137)
Exercise of stock options (in shares)	166
Exercise of stock options	$ 7,534				7,534
Stock based compensation	525				525
Stock awarded to employees	$ 24				24
Dividends				(10,608)	(10,608)
Balance (in shares) at Mar. 31, 2018	26,591
Balance at Mar. 31, 2018	$ 439,817	1,533	(43,452)	184,185	582,083
Balance (in shares) at Dec. 31, 2017	26,425
Balance at Dec. 31, 2017	$ 431,734	1,533	(16,832)	173,804	590,239
Cumulative effect at Dec. 31, 2017			142	(142)
Adjusted Balance (in shares) at Dec. 31, 2017	26,425
Adjusted Balance at Dec. 31, 2017	$ 431,734	1,533	(16,690)	173,662	590,239
Net income for the period					35,516
Balance (in shares) at Jun. 30, 2018	26,649
Balance at Jun. 30, 2018	$ 443,338	1,533	(49,900)	191,167	586,138
Balance (in shares) at Mar. 31, 2018	26,591
Balance at Mar. 31, 2018	$ 439,817	1,533	(43,452)	184,185	582,083
Net income for the period				18,010	18,010
Other comprehensive income (loss)			(6,448)		(6,448)
Exercise of stock options (in shares)	46
Exercise of stock options	$ 1,949				1,949
Stock based compensation	525				525
Stock awarded to employees	$ 53				53
Dividends				(10,653)	(10,653)
Restricted stock activity (in shares)	20
Restricted stock activity	$ 1,143				1,143
Stock awarded to employees (in shares)	1
Retirement of common stock (in shares)	(9)
Retirement of common stock	$ (149)			(375)	(524)
Balance (in shares) at Jun. 30, 2018	26,649
Balance at Jun. 30, 2018	$ 443,338	1,533	(49,900)	191,167	586,138
Balance (in shares) at Dec. 31, 2018	26,730
Balance at Dec. 31, 2018	$ 448,351	1,395	(39,996)	205,841	615,591
Cumulative effect at Dec. 31, 2018				(2,801)	(2,801)
Adjusted Balance (in shares) at Dec. 31, 2018	26,730
Adjusted Balance at Dec. 31, 2018	$ 448,351	1,395	(39,996)	203,040	612,790
Net income for the period				19,646	19,646
Other comprehensive income (loss)			28,747		28,747
Exercise of stock options (in shares)	120
Exercise of stock options	$ 5,771				5,771
Stock based compensation	541				541
Stock awarded to employees	17				17
Dividends				(10,745)	(10,745)
Restricted stock activity	$ 624	(624)
Shares issued from stock warrant exercise, net of repurchase (in shares)	51
Balance (in shares) at Mar. 31, 2019	26,901
Balance at Mar. 31, 2019	$ 455,304	771	(11,249)	211,941	656,767
Balance (in shares) at Dec. 31, 2018	26,730
Balance at Dec. 31, 2018	$ 448,351	1,395	(39,996)	205,841	615,591
Cumulative effect at Dec. 31, 2018				(2,801)	(2,801)
Adjusted Balance (in shares) at Dec. 31, 2018	26,730
Adjusted Balance at Dec. 31, 2018	$ 448,351	1,395	(39,996)	203,040	612,790
Net income for the period					39,271
Balance (in shares) at Jun. 30, 2019	26,962
Balance at Jun. 30, 2019	$ 459,369	771	13,124	220,173	693,437
Balance (in shares) at Mar. 31, 2019	26,901
Balance at Mar. 31, 2019	$ 455,304	771	(11,249)	211,941	656,767
Net income for the period				19,625	19,625
Other comprehensive income (loss)			24,373		24,373
Exercise of stock options (in shares)	50
Exercise of stock options	$ 2,539				2,539
Stock based compensation	541				541
Stock awarded to employees	$ 48				48
Dividends				(11,041)	(11,041)
Restricted stock activity (in shares)	18
Restricted stock activity	$ 1,073				1,073
Stock awarded to employees (in shares)	1
Retirement of common stock (in shares)	(8)
Retirement of common stock	$ (136)			(352)	(488)
Balance (in shares) at Jun. 30, 2019	26,962
Balance at Jun. 30, 2019	$ 459,369	$ 771	$ 13,124	$ 220,173	$ 693,437