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				32,256,915
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)				79,313	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				32,336,228
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				32,256,915
Beginning balance, treasury stock (in shares) at Dec. 31, 2018					(706)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	59,288
Other comprehensive income/(loss)	(5,453)
Ending balance at Sep. 30, 2019	733,586	587,315	(9,055)	$ 2,160	$ (20,594)	173,760
Ending balance, common stock (in shares) at Sep. 30, 2019				32,401,586
Ending balance, treasury stock (in shares) at Sep. 30, 2019					(232,499)
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				32,336,228
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)				19,068	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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	20,676	20,676
Other comprehensive income/(loss)	(2,861)		(2,861)
Treasury shares purchased	(20,594)				$ (20,594)
Treasury shares purchased (in shares)					(232,499)
Shares and options issued under stock plans	4,020			$ 3		4,017
Shares and options issued under stock plans (in shares)				46,290
Ending balance at Sep. 30, 2019	733,586	587,315	(9,055)	$ 2,160	$ (20,594)	173,760
Ending balance, common stock (in shares) at Sep. 30, 2019				32,401,586
Ending balance, treasury stock (in shares) at Sep. 30, 2019					(232,499)
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	62,461
Other comprehensive income/(loss)	4,347
Ending balance at Sep. 30, 2020	819,443	653,382	(1,217)	$ 2,164	$ (10,046)	175,160
Ending balance, common stock (in shares) at Sep. 30, 2020				32,451,415
Ending balance, treasury stock (in shares) at Sep. 30, 2020					(108,813)
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				$ 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)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	21,568	21,568
Other comprehensive income/(loss)	4,677		4,677
Treasury shares purchased	(2,957)				$ (2,957)
Treasury shares purchased (in shares)					(31,224)
Shares and options issued under stock plans	3,632				$ 2,545	1,087
Shares and options issued under stock plans (in shares)					32,330
Ending balance at Sep. 30, 2020	$ 819,443	$ 653,382	$ (1,217)	$ 2,164	$ (10,046)	$ 175,160
Ending balance, common stock (in shares) at Sep. 30, 2020				32,451,415
Ending balance, treasury stock (in shares) at Sep. 30, 2020					(108,813)