Condensed Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]
Balance at Dec. 31, 2017	$ 548,573	$ 238	$ (23,268)	$ 350,061	$ 225,360	$ (3,818)
Net income	43,172	0	0	0	43,172	0
Other comprehensive income	(7,928)	0	0	0	0	(7,928)
Total comprehensive income	35,244	0	0	0	43,172	(7,928)
Cash dividends paid on common shares	(5,086)	0	0	0	(5,086)	0
Repurchase of common stock	(3,058)	0	(3,058)	0	0	0
Issuance under equity compensation plans, net	(3,220)	1	0	(3,221)	0	0
Share-based Payment Arrangement, Noncash Expense	1,631	0	0	1,631	0	0
Reclassification for the adoption of new accounting standards	0	0	0	0	834	(834)
Balance at Jun. 30, 2018	574,084	239	(26,326)	348,471	264,280	(12,580)
Balance at Mar. 31, 2018	555,015	239	(26,326)	348,092	244,573	(11,563)
Net income	22,251	0	0	0	22,251	0
Other comprehensive income	(1,017)	0	0	0	0	(1,017)
Total comprehensive income	21,234	0	0	0	22,251	(1,017)
Cash dividends paid on common shares	(2,544)	0	0	0	2,544	0
Issuance under equity compensation plans, net	(534)	0	0	(534)	0	0
Share-based Payment Arrangement, Noncash Expense	913	0	0	913	0	0
Balance at Jun. 30, 2018	574,084	239	(26,326)	348,471	264,280	(12,580)
Balance at Dec. 31, 2018	603,804	239	(42,655)	350,936	304,566	(9,282)
Net income	34,580	0	0	0	34,580	0
Other comprehensive income	22,356	0	0	0	0	22,356
Total comprehensive income	56,936	0	0	0	34,580	22,356
Cash dividends paid on common shares	(7,798)	0	0	0	(7,798)	0
Issuance under equity compensation plans, net	(1,233)	1	0	(1,234)	0
Share-based Payment Arrangement, Noncash Expense	1,907	0	0	1,907	0	0
Shares issued in connection with acquisition	171,885	40	0	171,845	0	0
Balance at Jun. 30, 2019	825,501	280	(42,655)	523,454	331,348	13,074
Balance at Mar. 31, 2019	797,835	280	(42,655)	521,761	316,959	1,490
Net income	18,424	0	0	0	18,424	0
Other comprehensive income	11,584	0	0	0	0	11,584
Total comprehensive income	30,008	0	0	0	18,424	11,584
Cash dividends paid on common shares	(4,035)	0	0	0	(4,035)	0
Issuance under equity compensation plans, net	707	0	0	707	0	0
Share-based Payment Arrangement, Noncash Expense	986	0	0	986	0	0
Balance at Jun. 30, 2019	$ 825,501	$ 280	$ (42,655)	$ 523,454	$ 331,348	$ 13,074