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, 2016	$ 387,098	$ 203	$ (6,632)	$ 213,078	$ 182,190	$ (1,741)
Net income	40,661	0	0	0	40,661	0
Other comprehensive income	1,252	0	0	0	0	1,252
Total comprehensive income	41,913	0	0	0	40,661	1,252
Cash dividends paid on common shares	7,709	0	0	0	7,709	0
Repurchase of common stock	16,636	0	16,636	0	0	0
Issuance under equity compensation plans, net	(2,573)	1	0	(2,574)	0	0
Share-based Compensation	2,514	0	0	2,514	0	0
Shares issued in connection with acquisition	141,729	33	0	141,696	0	0
Reclassification for the adoption of new accounting standards	0	0	0	(5,229)	5,229	0
Balance at Sep. 30, 2017	546,336	237	(23,268)	349,485	220,371	(489)
Balance at Dec. 31, 2017	548,573	238	(23,268)	350,061	225,360	(3,818)
Net income	65,688	0	0	0	65,688	0
Other comprehensive income	(11,975)	0	0	0	0	(11,975)
Total comprehensive income	53,713	0	0	0	65,688	(11,975)
Cash dividends paid on common shares	7,866	0	0	0	7,866	0
Repurchase of common stock	6,840	0	6,840	0	0	0
Issuance under equity compensation plans, net	(3,297)	1	0	(3,298)	0	0
Share-based Compensation	2,554	0	0	2,554	0	0
Reclassification for the adoption of new accounting standards	0	0	0	0	834	(834)
Balance at Sep. 30, 2018	$ 586,837	$ 239	$ (30,108)	$ 349,317	$ 284,016	$ (16,627)