Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Total
Balance at Dec. 31, 2018	$ 315	$ 222,720	$ (75,146)	$ 414,327	$ (12,752)	$ 549,464
Impact of Adoption of Accounting Standards Update	0	0	0	2,716	0	2,716
Net income	0	0	0	7,068	0	7,068
Award of common shares released from Employee Benefit Trust	0	2,086	0	0	0	2,086
Vesting of restricted stock unit awards	0	(5,878)	6,088	(210)	0
Exercise of stock options	0	0	6	(3)	0	3
Stock-based compensation expense	0	3,931	0	0	0	3,931
Repurchase of shares to satisfy tax obligation	0	0	(1,877)	0	0	(1,877)
Dividends on common stock	0	0	0	(6,042)	0	(6,042)
Other comprehensive income (loss)	0	0	0	0	2,210	2,210
Balance at Mar. 31, 2019	315	222,859	(70,929)	417,856	(10,542)	559,559
Balance at Dec. 31, 2018	315	222,720	(75,146)	414,327	(12,752)	549,464
Net income						17,624
Other comprehensive income (loss)					2,136	2,136
Balance at Jun. 30, 2019	315	224,231	(70,913)	422,373	(10,616)	565,390
Balance at Mar. 31, 2019	315	222,859	(70,929)	417,856	(10,542)	559,559
Net income	0	0	0	10,556	0	10,556
Award of common shares released from Employee Benefit Trust	0	81	0	0	0	81
Vesting of restricted stock unit awards	0	(24)	24	0	0	0
Stock-based compensation expense	0	1,315	0	0	0	1,315
Repurchase of shares to satisfy tax obligation	0	0	(8)	0	0	(8)
Dividends on common stock	0	0	0	(6,039)	0	(6,039)
Other comprehensive income (loss)	0	0	0	0	(74)	(74)
Balance at Jun. 30, 2019	315	224,231	(70,913)	422,373	(10,616)	565,390
Balance at Dec. 31, 2019	315	226,691	(71,487)	433,960	(9,807)	579,672
Impact of Adoption of Accounting Standards Update	0	0	0	(875)	0	(875)
Net income	0	0	0	(1,390)	0	(1,390)
Award of common shares released from Employee Benefit Trust	0	1,398	0	0	0	1,398
Vesting of restricted stock unit awards	0	(5,626)	5,782	(156)	0	0
Stock-based compensation expense	0	3,430	0	0	0	3,430
Purchase of treasury shares	0	0	(2,342)	0	0	(2,342)
Repurchase of shares to satisfy tax obligation	0	0	(1,493)	0	0	(1,493)
Dividends on common stock	0	0	0	(6,084)	0	(6,084)
Other comprehensive income (loss)	0	0	0	0	(22,633)	(22,633)
Balance at Mar. 31, 2020	315	225,893	(69,540)	425,455	(32,440)	549,683
Balance at Dec. 31, 2019	315	226,691	(71,487)	433,960	(9,807)	579,672
Net income						16,882
Other comprehensive income (loss)					(13,715)	(13,715)
Balance at Jun. 30, 2020	315	226,901	(69,436)	437,663	(23,522)	571,921
Balance at Mar. 31, 2020	315	225,893	(69,540)	425,455	(32,440)	549,683
Net income	0	0	0	18,272	0	18,272
Award of common shares released from Employee Benefit Trust	0	40	0	0	0	40
Vesting of restricted stock unit awards	0	(133)	134	(1)	0	0
Stock-based compensation expense	0	1,101	0	0	0	1,101
Repurchase of shares to satisfy tax obligation	0	0	(30)	0	0	(30)
Dividends on common stock	0	0	0	(6,063)	0	(6,063)
Other comprehensive income (loss)	0	0	0	0	8,918	8,918
Balance at Jun. 30, 2020	$ 315	$ 226,901	$ (69,436)	$ 437,663	$ (23,522)	$ 571,921