Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	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	78,573	78,573				0
Other comprehensive loss	(1,960)	0	(1,960)			0
Dividends	(15,185)	(15,185)				0
Treasury shares purchased	(1,394)				$ (1,394)	0
Treasury shares purchased (in shares)					(16,755)
Shares and options issued under stock plans	14,703			$ 16	$ 1,338	13,349
Shares and options issued under stock plans (in shares)				237,310	16,049
Ending balance at Dec. 31, 2018	691,618	528,027	(3,602)	$ 2,151	$ (56)	165,098
Ending balance (in shares) at Dec. 31, 2018				32,256,915	(706)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	79,671	79,671				0
Other comprehensive loss	(1,962)		(1,962)			0
Dividends	(16,777)	(16,777)				0
Treasury shares purchased	(21,321)				$ (21,321)	0
Treasury shares purchased (in shares)					(240,995)
Shares and options issued under stock plans	12,438			$ 10	$ 3,308	9,120
Shares and options issued under stock plans (in shares)				148,881	37,822
Ending balance at Dec. 31, 2019	743,667	590,921	(5,564)	$ 2,161	$ (18,069)	174,218
Ending balance (in shares) at Dec. 31, 2019				32,405,796	(203,879)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	84,623	84,623				0
Other comprehensive loss	9,737		9,737			0
Dividends	(18,804)	(18,804)				0
Treasury shares purchased	(13,463)				$ (13,463)	0
Treasury shares purchased (in shares)					(136,629)
Shares and options issued under stock plans	22,473			$ 3	$ 23,659	(1,189)
Shares and options issued under stock plans (in shares)				42,909	264,424
Ending balance at Dec. 31, 2020	$ 828,233	$ 656,740	$ 4,173	$ 2,164	$ (7,873)	$ 173,029
Ending balance (in shares) at Dec. 31, 2020				32,448,705	(76,084)