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, 2018		29,725,000
Beginning balance at Dec. 31, 2018	$ 764,230	$ 434,453	$ 341,738	$ (3,235)	$ 3,235	$ (11,961)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	71,163		71,163
Cash dividends declared	(10,689)		(10,689)
Change in Rabbi Trust Obligation	0			658	(658)
Equity issued related to acquisition earnout (in shares)		78,000
Equity issued related to acquisition earnout	3,070	$ 3,070
Stock repurchases (in shares)		(282,000)
Stock repurchases	(10,000)	$ (10,000)
Stock option exercises (in shares)		9,000
Stock option exercises	129	$ 129
Stock withheld for payment of taxes (in shares)		(15,000)
Stock withheld for payment of taxes	(558)	$ (558)
Stock-based compensation (in shares)		90,000
Stock-based compensation	2,042	$ 2,042
Other comprehensive income (loss)	15,595					15,595
Ending balance (in shares) at Sep. 30, 2019		29,605,000
Ending balance at Sep. 30, 2019	834,982	$ 429,136	402,212	(2,577)	2,577	3,634
Beginning balance (in shares) at Jun. 30, 2019		29,717,000
Beginning balance at Jun. 30, 2019	815,169	$ 432,533	380,748	(2,866)	2,866	1,888
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	25,019		25,019
Cash dividends declared	(3,555)		(3,555)
Change in Rabbi Trust Obligation	0			289	(289)
Equity issued related to acquisition earnout (in shares)		0
Equity issued related to acquisition earnout	0	$ 0
Stock repurchases (in shares)		(100,000)
Stock repurchases	(3,476)	$ (3,476)
Stock option exercises (in shares)		0
Stock option exercises	0	$ 0
Stock withheld for payment of taxes (in shares)		(12,000)
Stock withheld for payment of taxes	(467)	$ (467)
Stock-based compensation (in shares)		0
Stock-based compensation	546	$ 546
Other comprehensive income (loss)	1,746					1,746
Ending balance (in shares) at Sep. 30, 2019		29,605,000
Ending balance at Sep. 30, 2019	$ 834,982	$ 429,136	402,212	(2,577)	2,577	3,634
Beginning balance (in shares) at Dec. 31, 2019	29,601,264	29,601,000
Beginning balance at Dec. 31, 2019	$ 852,401	$ 429,514	417,764	(2,587)	2,587	5,123
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	57,829		57,829
Cash dividends declared	(15,605)		(15,605)
Change in Rabbi Trust Obligation	0			357	(357)
Equity issued related to acquisition earnout (in shares)		24,000
Equity issued related to acquisition earnout	494	$ 494
Stock repurchases (in shares)		(986,000)
Stock repurchases	(28,701)	$ (28,701)
Stock withheld for payment of taxes (in shares)		(7,000)
Stock withheld for payment of taxes	(178)	$ (178)
Stock-based compensation (in shares)		56,000
Stock-based compensation	2,222	$ 2,222
Other comprehensive income (loss)	$ 12,356					12,356
Ending balance (in shares) at Sep. 30, 2020	28,687,832	28,688,000
Ending balance at Sep. 30, 2020	$ 880,818	$ 403,351	459,988	(2,230)	2,230	17,479
Beginning balance (in shares) at Jun. 30, 2020		28,977,000
Beginning balance at Jun. 30, 2020	867,891	$ 408,699	441,846	(2,217)	2,217	17,346
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	23,297		23,297
Cash dividends declared	(5,155)		(5,155)
Change in Rabbi Trust Obligation	0			(13)	13
Equity issued related to acquisition earnout (in shares)		24,000
Equity issued related to acquisition earnout	494	$ 494
Stock repurchases (in shares)		(306,000)
Stock repurchases	(6,269)	$ (6,269)
Stock withheld for payment of taxes (in shares)		(7,000)
Stock withheld for payment of taxes	(178)	$ (178)
Stock-based compensation (in shares)		0
Stock-based compensation	605	$ 605
Other comprehensive income (loss)	$ 133					133
Ending balance (in shares) at Sep. 30, 2020	28,687,832	28,688,000
Ending balance at Sep. 30, 2020	$ 880,818	$ 403,351	$ 459,988	$ (2,230)	$ 2,230	$ 17,479