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, 2016	$ 521,033	$ 388,089	$ (6,849)	$ 2,117	$ 0	$ 137,676
Beginning balance (in shares) at Dec. 31, 2016				31,757,861	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	90,071	90,071
Other comprehensive loss, net of cumulative effect of accounting change	5,150	(57)	5,207
Dividends	(13,464)	(13,464)
Treasury shares purchased	(1,905)				$ (1,905)
Treasury shares purchased (in shares)					(23,182)
Shares and options issued under stock plans and an income tax benefit of $2,546	15,996			$ 18	$ 1,905	14,073
Shares and options issued under stock plans and an income tax benefit (in shares)				261,744	23,182
Ending balance at Dec. 31, 2017	616,881	464,639	(1,642)	$ 2,135	$ 0	151,749
Ending balance (in shares) at Dec. 31, 2017				32,019,605	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	78,573	78,573
Other comprehensive loss, net of cumulative effect of accounting change	(1,960)		(1,960)
Dividends	(15,185)	(15,185)
Treasury shares purchased	(1,394)				$ (1,394)
Treasury shares purchased (in shares)					(16,755)
Shares and options issued under stock plans and an income tax benefit of $2,546	14,703			$ 16	$ 1,338	13,349
Shares and options issued under stock plans and an income tax benefit (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
Other comprehensive loss, net of cumulative effect of accounting change	(1,962)		(1,962)
Dividends	(16,777)	(16,777)
Treasury shares purchased	(21,321)				$ (21,321)
Treasury shares purchased (in shares)					(240,995)
Shares and options issued under stock plans and an income tax benefit of $2,546	12,438			$ 10	$ 3,308	9,120
Shares and options issued under stock plans and an income tax benefit (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)