Consolidated Statements of Changes in Shareholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Cumulative Effect, Period of Adoption, Adjustment [Member] Retained Earnings [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member]	Cumulative Effect, Period of Adoption, Adjusted Balance [Member] Common Stock [Member]	Cumulative Effect, Period of Adoption, Adjusted Balance [Member] Deferred Compensation, Share-based Payments [Member]	Cumulative Effect, Period of Adoption, Adjusted Balance [Member] AOCI Attributable to Parent [Member]	Cumulative Effect, Period of Adoption, Adjusted Balance [Member] Retained Earnings [Member]	Cumulative Effect, Period of Adoption, Adjusted Balance [Member]	Common Stock [Member]	Deferred Compensation, Share-based Payments [Member]	AOCI Attributable to Parent [Member]	Retained Earnings [Member]	Total
Balance (in shares) at Dec. 31, 2018			26,730					26,730
Balance at Dec. 31, 2018	$ (2,801)	$ (2,801)	$ 448,351	$ 1,395	$ (39,996)	$ 203,040	$ 612,790	$ 448,351	$ 1,395	$ (39,996)	$ 205,841	$ 615,591
Net income											39,271	39,271
Other comprehensive income										53,120		53,120
Exercise of stock options (in shares)								170
Exercise of stock options								$ 8,310				8,310
Restricted stock activity								1,697	(624)			1,073
Stock based compensation								1,082				1,082
Stock awarded to employees								$ 65				65
Retirement of common stock (in shares)								(8)
Retirement of common stock								$ (136)			(352)	(488)
Dividends											(21,786)	(21,786)
Restricted stock activity (in shares)								18
Stock awarded to employees (in shares)								1
Balance at Jun. 30, 2019								$ 459,369	771	13,124	220,173	693,437
Shares issued from stock warrant exercise, net of repurchase (in shares)								51
Balance (in shares) at Jun. 30, 2019								26,962
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											19,625	19,625
Other comprehensive income										24,373		24,373
Exercise of stock options (in shares)								50
Exercise of stock options								$ 2,539				2,539
Restricted stock activity								1,073				1,073
Stock based compensation								541				541
Stock awarded to employees								$ 48				48
Retirement of common stock (in shares)								(8)
Retirement of common stock								$ (136)			(352)	(488)
Dividends											(11,041)	(11,041)
Restricted stock activity (in shares)								18
Stock awarded to employees (in shares)								1
Balance at Jun. 30, 2019								$ 459,369	771	13,124	220,173	693,437
Balance (in shares) at Jun. 30, 2019								26,962
Balance (in shares) at Dec. 31, 2019			27,062					27,062
Balance at Dec. 31, 2019	$ 52	$ 52	$ 465,460	$ 771	$ 26,051	$ 239,187	$ 731,469	$ 465,460	771	26,051	239,135	731,417
Net income											36,524	36,524
Other comprehensive income										67,681		67,681
Exercise of stock options (in shares)								53
Exercise of stock options								$ 2,838				2,838
Restricted stock activity								1,270	(736)			534
Stock based compensation								1,050				1,050
Stock awarded to employees								$ 66				66
Retirement of common stock (in shares)								(193)
Retirement of common stock								$ (3,333)			(6,533)	(9,866)
Dividends											(22,220)	(22,220)
Restricted stock activity (in shares)								10
Stock awarded to employees (in shares)								1
Balance at Jun. 30, 2020								$ 467,351	35	93,732	246,958	808,076
Balance (in shares) at Jun. 30, 2020								26,933
Balance (in shares) at Mar. 31, 2020								26,932
Balance at Mar. 31, 2020								$ 465,701	771	171	238,903	705,546
Net income											19,562	19,562
Other comprehensive income										93,561		93,561
Exercise of stock options (in shares)								13
Exercise of stock options								$ 572				572
Restricted stock activity								736	(736)
Stock based compensation								525				525
Stock awarded to employees								$ 45				45
Retirement of common stock (in shares)								(13)
Retirement of common stock								$ (228)			(391)	(619)
Dividends											(11,116)	(11,116)
Balance at Jun. 30, 2020								$ 467,351	$ 35	$ 93,732	$ 246,958	$ 808,076
Balance (in shares) at Jun. 30, 2020								26,933