Condensed Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Retained Earnings	Accumulated Other Comprehensive (Loss) Income	Common Stock	Treasury Stock	Additional Paid-in Capital
Beginning balance at Dec. 31, 2018	$ 691,618	$ 528,027	$ (3,602)	$ 2,151	$ (56)	$ 165,098
Beginning balance, common stock (in shares) at Dec. 31, 2018				32,256,209
Beginning balance, treasury stock (in shares) at Dec. 31, 2018					(706)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	18,783	18,783
Other comprehensive income (loss)	(1,084)		(1,084)
Treasury shares purchased	(727)				$ (727)
Treasury shares purchased (in shares)					(8,496)
Shares and options issued under stock plans	1,919			$ 5	$ 250	1,664
Shares and options issued under stock plans (in shares)				73,823	3,006
Ending balance at Mar. 31, 2019	710,509	546,810	(4,686)	$ 2,156	$ (533)	166,762
Ending balance, common stock (in shares) at Mar. 31, 2019				32,330,032
Ending balance, treasury stock (in shares) at Mar. 31, 2019					(6,196)
Beginning balance at Dec. 31, 2018	691,618	528,027	(3,602)	$ 2,151	$ (56)	165,098
Beginning balance, common stock (in shares) at Dec. 31, 2018				32,256,209
Beginning balance, treasury stock (in shares) at Dec. 31, 2018					(706)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	38,612
Other comprehensive income (loss)	(2,592)
Ending balance at Jun. 30, 2019	732,345	566,639	(6,194)	$ 2,157	$ 0	169,743
Ending balance, common stock (in shares) at Jun. 30, 2019				32,355,296
Ending balance, treasury stock (in shares) at Jun. 30, 2019					0
Beginning balance at Mar. 31, 2019	710,509	546,810	(4,686)	$ 2,156	$ (533)	166,762
Beginning balance, common stock (in shares) at Mar. 31, 2019				32,330,032
Beginning balance, treasury stock (in shares) at Mar. 31, 2019					(6,196)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	19,829	19,829
Other comprehensive income (loss)	(1,508)		(1,508)
Shares and options issued under stock plans	3,515			$ 1	$ 533	2,981
Shares and options issued under stock plans (in shares)				25,264	6,196
Ending balance at Jun. 30, 2019	732,345	566,639	(6,194)	$ 2,157	$ 0	169,743
Ending balance, common stock (in shares) at Jun. 30, 2019				32,355,296
Ending balance, treasury stock (in shares) at Jun. 30, 2019					0
Beginning balance at Dec. 31, 2019	743,667	590,921	(5,564)	$ 2,161	$ (18,069)	174,218
Beginning balance, common stock (in shares) at Dec. 31, 2019				32,405,796
Beginning balance, treasury stock (in shares) at Dec. 31, 2019					(203,879)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	19,768	19,768
Other comprehensive income (loss)	(2,905)		(2,905)
Treasury shares purchased	(891)				$ (891)
Treasury shares purchased (in shares)					(8,224)
Shares and options issued under stock plans	6,632			$ 3	$ 7,266	(637)
Shares and options issued under stock plans (in shares)				41,619	81,530
Ending balance at Mar. 31, 2020	766,271	610,689	(8,469)	$ 2,164	$ (11,694)	173,581
Ending balance, common stock (in shares) at Mar. 31, 2020				32,447,415
Ending balance, treasury stock (in shares) at Mar. 31, 2020					(130,573)
Beginning balance at Dec. 31, 2019	743,667	590,921	(5,564)	$ 2,161	$ (18,069)	174,218
Beginning balance, common stock (in shares) at Dec. 31, 2019				32,405,796
Beginning balance, treasury stock (in shares) at Dec. 31, 2019					(203,879)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	40,893
Other comprehensive income (loss)	(330)
Ending balance at Jun. 30, 2020	792,523	631,814	(5,894)	$ 2,164	$ (9,634)	174,073
Ending balance, common stock (in shares) at Jun. 30, 2020				32,451,415
Ending balance, treasury stock (in shares) at Jun. 30, 2020					(109,919)
Beginning balance at Mar. 31, 2020	766,271	610,689	(8,469)	$ 2,164	$ (11,694)	173,581
Beginning balance, common stock (in shares) at Mar. 31, 2020				32,447,415
Beginning balance, treasury stock (in shares) at Mar. 31, 2020					(130,573)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	21,125	21,125
Other comprehensive income (loss)	2,575		2,575
Treasury shares purchased	(2,134)				$ (2,134)
Treasury shares purchased (in shares)					(24,281)
Shares and options issued under stock plans	4,686			$ 0	$ 4,194	492
Shares and options issued under stock plans (in shares)				4,000	44,935
Ending balance at Jun. 30, 2020	$ 792,523	$ 631,814	$ (5,894)	$ 2,164	$ (9,634)	$ 174,073
Ending balance, common stock (in shares) at Jun. 30, 2020				32,451,415
Ending balance, treasury stock (in shares) at Jun. 30, 2020					(109,919)