Condensed Consolidated Statements of Changes in Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock Voting and Nonvoting Common Stock	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Loss
Balance, beginning of period at Dec. 31, 2018	$ 288,735		$ 227,587	$ 77,689		$ (16,541)
Balance, beginning of period (Accounting Standards Update 2017-08) at Dec. 31, 2018		$ (821)			$ (821)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	11,817			11,817
Other comprehensive income (loss)	963					963
Dividends declared	(1,231)			(1,231)
Recognition of the fair value of share-based compensation	862		862
Repurchase of common stock	(4,133)		(4,133)
Deferred stock rights and restricted stock units issued in lieu of cash dividends payable on outstanding deferred stock rights and restricted stock units	22		22
Common stock redeemed for the net settlement of share-based awards	(94)		(94)
Balance, end of period at Jun. 30, 2019	296,120		224,244	87,454		(15,578)
Balance, beginning of period at Mar. 31, 2019	294,013		226,235	81,946		(14,168)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	6,121			6,121
Other comprehensive income (loss)	(1,410)					(1,410)
Dividends declared	(613)			(613)
Recognition of the fair value of share-based compensation	383		383
Repurchase of common stock	(2,387)		(2,387)
Deferred stock rights and restricted stock units issued in lieu of cash dividends payable on outstanding deferred stock rights and restricted stock units	13		13
Balance, end of period at Jun. 30, 2019	296,120		224,244	87,454		(15,578)
Balance, beginning of period at Dec. 31, 2019	304,913		219,423	99,681		(14,191)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	9,951			9,951
Other comprehensive income (loss)	(6,947)					(6,947)
Dividends declared	(1,201)			(1,201)
Recognition of the fair value of share-based compensation	1,073		1,073
Deferred stock rights and restricted stock units issued in lieu of cash dividends payable on outstanding deferred stock rights and restricted stock units	15		15
Common stock redeemed for the net settlement of share-based awards	(93)		(93)
Balance, end of period at Jun. 30, 2020	307,711		220,418	108,431		(21,138)
Balance, beginning of period at Mar. 31, 2020	305,127		219,893	105,100		(19,866)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	3,932			3,932
Other comprehensive income (loss)	(1,272)					(1,272)
Dividends declared	(601)			(601)
Recognition of the fair value of share-based compensation	517		517
Deferred stock rights and restricted stock units issued in lieu of cash dividends payable on outstanding deferred stock rights and restricted stock units	8		8
Balance, end of period at Jun. 30, 2020	$ 307,711		$ 220,418	$ 108,431		$ (21,138)