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, 2017	$ 616,881	$ 464,639	$ (1,642)	$ 2,135	$ 0	$ 151,749
Beginning balance, common stock (in shares) at Dec. 31, 2017				32,019,605
Beginning balance, treasury stock (in shares) at Dec. 31, 2017					0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	19,346	19,346
Other comprehensive (loss) income	1,376		1,376
Dividends	1	1
Treasury shares purchased	(786)				$ (786)
Treasury shares purchased (in shares)					(10,454)
Shares and options issued under stock plans	3,072			$ 5	$ 786	2,281
Shares and options issued under stock plans (in shares)				80,505	10,454
Ending balance at Mar. 31, 2018	639,890	483,986	(266)	$ 2,140	$ 0	154,030
Ending balance, common stock (in shares) at Mar. 31, 2018				32,100,110
Ending balance, treasury stock (in shares) at Mar. 31, 2018					0
Beginning balance at Dec. 31, 2017	616,881	464,639	(1,642)	$ 2,135	$ 0	151,749
Beginning balance, common stock (in shares) at Dec. 31, 2017				32,019,605
Beginning balance, treasury stock (in shares) at Dec. 31, 2017					0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	39,025
Other comprehensive (loss) income	(1,519)
Ending balance at Jun. 30, 2018	663,220	503,665	(3,161)	$ 2,148	$ (437)	161,005
Ending balance, common stock (in shares) at Jun. 30, 2018				32,213,094
Ending balance, treasury stock (in shares) at Jun. 30, 2018					(4,408)
Beginning balance at Mar. 31, 2018	639,890	483,986	(266)	$ 2,140	$ 0	154,030
Beginning balance, common stock (in shares) at Mar. 31, 2018				32,100,110
Beginning balance, treasury stock (in shares) at Mar. 31, 2018					0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	19,679	19,679
Other comprehensive (loss) income	(2,895)		(2,895)
Treasury shares purchased	(437)				$ (437)
Treasury shares purchased (in shares)					(4,408)
Shares and options issued under stock plans	6,983			$ 8		6,975
Shares and options issued under stock plans (in shares)				112,984
Ending balance at Jun. 30, 2018	663,220	503,665	(3,161)	$ 2,148	$ (437)	161,005
Ending balance, common stock (in shares) at Jun. 30, 2018				32,213,094
Ending balance, treasury stock (in shares) at Jun. 30, 2018					(4,408)
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 (loss) income	(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 (loss) income	(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 (loss) income	(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