Condensed Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Total
Beginning balance at Dec. 31, 2018	$ 603,804	$ 239	$ (42,655)	$ 350,936	$ 304,566	$ (9,282)
Net income	63,649	0	0	0	63,649	0
Other comprehensive income	28,493	0	0	0	0	28,493
Comprehensive income	92,142	0	0	0	63,649	28,493
Cash dividends paid on common shares	(12,055)	0	0	0	(12,055)	0
Repurchase of common stock	(11,817)	0	(11,817)	0	0	0
Issuance under equity compensation plans, net	(880)	1	0	(881)	0	0
Share-based Payment Arrangement, Noncash Expense	3,016	0	0	3,016	0	0
Shares issued in connection with acquisition	171,885	40	0	171,845	0	0
Ending balance at Sep. 30, 2019	846,095	280	(54,472)	524,916	356,160	19,211
Beginning balance at Jun. 30, 2019	825,501	280	(42,655)	523,454	331,348	13,074
Net income	29,069	0	0	0	29,069	0
Other comprehensive income	6,137	0	0	0	0	6,137
Comprehensive income	35,206	0	0	0	29,069	6,137
Cash dividends paid on common shares	(4,257)	0	0	0	4,257	0
Repurchase of common stock	(11,817)	0	(11,817)	0	0	0
Issuance under equity compensation plans, net	353	0	0	353	0	0
Share-based Payment Arrangement, Noncash Expense	1,109	0	0	1,109	0	0
Ending balance at Sep. 30, 2019	846,095	280	(54,472)	524,916	356,160	19,211
Beginning balance at Dec. 31, 2019	867,185	281	(58,181)	526,599	380,737	17,749
Net income	45,453	0	0	0	45,453	0
Other comprehensive income	14,759	0	0	0	0	14,759
Comprehensive income	60,212	0	0	0	45,453	14,759
Cash dividends paid on common shares	(14,176)	0	0	0	(14,176)	0
Repurchase of common stock	(15,347)	0	(15,347)	0	0	0
Issuance under equity compensation plans, net	(562)	1	0	(563)	0	0
Share-based Payment Arrangement, Noncash Expense	3,069	0	0	3,069	0	0
Reclassification for the adoption of new accounting standards	(18,114)	0	0	0	(18,114)	0
Ending balance at Sep. 30, 2020	882,267	282	(73,528)	529,105	393,900	32,508
Beginning balance at Jun. 30, 2020	867,963	281	(73,528)	527,734	380,667	32,809
Net income	17,951	0	0	0	17,951	0
Other comprehensive income	(301)	0	0	0	0	(301)
Comprehensive income	17,650	0	0	0	17,951	(301)
Cash dividends paid on common shares	(4,718)	0	0	0	(4,718)	0
Issuance under equity compensation plans, net	332	1	0	331	0	0
Share-based Payment Arrangement, Noncash Expense	1,040	0	0	1,040	0	0
Ending balance at Sep. 30, 2020	$ 882,267	$ 282	$ (73,528)	$ 529,105	$ 393,900	$ 32,508