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 (in shares) at Dec. 31, 2017				32,019,605	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 (in shares) at Mar. 31, 2018				32,100,110	0
Beginning balance at Dec. 31, 2018	691,618	528,027	(3,602)	$ 2,151	$ (56)	165,098
Beginning balance (in shares) at Dec. 31, 2018				32,256,209	(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 (in shares) at Mar. 31, 2019				32,330,032	(6,196)