Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Retained Earnings	Stock in rabbi trust assumed in acquisition	Rabbi trust obligation	Accumulated Other Comprehensive Income (Loss)
Beginning balance (in shares) at Dec. 31, 2017		29,639,000
Beginning balance at Dec. 31, 2017	$ 692,979	$ 432,794	$ 264,331	$ (3,581)	$ 3,581	$ (4,146)
Net income	89,289		89,289
Cash dividends declared	(11,882)		(11,882)
Change in Rabbi Trust Obligation	$ 0			346	(346)
Stock option exercises (in shares)	29,689	25,000
Stock option exercises	$ 324	$ 324
Stock withheld for payment of taxes (in shares)		(11,000)
Stock withheld for payment of taxes	(406)	$ (406)
Stock-based compensation (in shares)		72,000
Stock-based compensation	1,741	$ 1,741
Other comprehensive income (loss)	(7,815)					(7,815)
Ending balance (in shares) at Dec. 31, 2018		29,725,000
Ending balance at Dec. 31, 2018	764,230	$ 434,453	341,738	(3,235)	3,235	(11,961)
Net income	92,046		92,046
Cash dividends declared	(16,020)		(16,020)
Equity issued related to acquisitions (in shares)		78,000
Equity issued related to acquisition	3,070	$ 3,070
Change in Rabbi Trust Obligation	0			648	(648)
Stock repurchases (in shares)		(282,000)
Stock repurchases	$ (10,000)	$ (10,000)
Stock option exercises (in shares)	9,000	9,000
Stock option exercises	$ 129	$ 129
Stock withheld for payment of taxes (in shares)		(20,000)
Stock withheld for payment of taxes	(702)	$ (702)
Stock-based compensation (in shares)		91,000
Stock-based compensation	2,564	$ 2,564
Other comprehensive income (loss)	$ 17,084					17,084
Ending balance (in shares) at Dec. 31, 2019	29,601,264	29,601,000
Ending balance at Dec. 31, 2019	$ 852,401	$ 429,514	417,764	(2,587)	2,587	5,123
Net income	81,477		81,477
Cash dividends declared	(20,752)		(20,752)
Equity issued related to acquisitions (in shares)		24,000
Equity issued related to acquisition	494	$ 494
Change in Rabbi Trust Obligation	0			344	(344)
Stock repurchases (in shares)		(1,117,000)
Stock repurchases	$ (31,868)	$ (31,868)
Stock option exercises (in shares)	0
Stock withheld for payment of taxes (in shares)		(11,000)
Stock withheld for payment of taxes	$ (307)	$ (307)
Stock-based compensation (in shares)		82,000
Stock-based compensation	2,749	$ 2,749
Other comprehensive income (loss)	$ 9,227					9,227
Ending balance (in shares) at Dec. 31, 2020	28,579,335	28,579,000
Ending balance at Dec. 31, 2020	$ 893,421	$ 400,582	$ 478,489	$ (2,243)	$ 2,243	$ 14,350