Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]
Balance at Dec. 31, 2013	$ 331,358	$ 251,627	$ 198	$ 2,016	$ 0	$ 77,517
Balance (in shares) at Dec. 31, 2013				30,225,763	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	52,826	52,826	0	$ 0	$ 0	0
Other comprehensive loss	(2,849)	0	(2,849)	0	0	0
Dividends	(9,251)	(9,251)	0	0	0	0
Treasury shares purchased	(1,068)	0	0	$ 0	$ (1,068)	0
Treasury shares purchased (in shares)				0	(17,497)
Shares and options issued under stock plans and an income tax benefit	20,882	0	0	$ 42	$ 1,068	19,772
Shares and options issued under stock plans and an income tax benefit (in shares)				619,823	17,497
Balance at Dec. 31, 2014	391,898	295,202	(2,651)	$ 2,058	$ 0	97,289
Balance (in shares) at Dec. 31, 2014				30,845,586	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	59,722	59,722	0	$ 0	$ 0	0
Other comprehensive loss	(2,463)	0	(2,463)	0	0	0
Dividends	(10,727)	(10,727)	0	0	0	0
Treasury shares purchased	(1,205)	0	0	$ 0	$ (1,205)	0
Treasury shares purchased (in shares)				0	(20,692)
Shares and options issued under stock plans and an income tax benefit	26,480	0	0	$ 44	$ 1,131	25,305
Shares and options issued under stock plans and an income tax benefit (in shares)				682,863	19,603
Balance at Dec. 31, 2015	463,705	344,197	(5,114)	$ 2,102	$ (74)	122,594
Balance (in shares) at Dec. 31, 2015				31,528,449	(1,089)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	55,972	55,972	0	$ 0	$ 0	0
Other comprehensive loss	(1,735)	0	(1,735)	0	0	0
Dividends	(12,080)	(12,080)	0	0	0	0
Treasury shares purchased	(1,588)	0	0	$ 0	$ (1,588)	0
Treasury shares purchased (in shares)				0	(24,912)
Shares and options issued under stock plans and an income tax benefit	16,759	0	0	$ 15	$ 1,662	15,082
Shares and options issued under stock plans and an income tax benefit (in shares)				229,412	26,001
Balance at Dec. 31, 2016	$ 521,033	$ 388,089	$ (6,849)	$ 2,117	$ 0	$ 137,676
Balance (in shares) at Dec. 31, 2016				31,757,861	0