UNAUDITED CONDENSED CONSOLIDATED STATEMENT OF CHANGES IN STOCKHOLDERS’ EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income	Retained Earnings	Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of new accounting standard (Note C), net of tax of $63	$ (179)				$ (179)
Shares at beginning of period (in shares) at Dec. 31, 2017		71,494				45,167
Balance at beginning of period at Dec. 31, 2017	134,277	$ 715	$ 437,394	$ 100	195,143	$ (499,075)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	41,624				41,624
Issuance for stock-based compensation and dividends, net of forfeitures (in shares)		45
Issuance for stock-based compensation and dividends, net of forfeitures	0	$ 1	525		(526)
Exercise of stock options (in shares)		5				1
Exercise of stock options	0	$ 0	46			$ (46)
Stock-based compensation expense	6,558		6,558
Employee stock purchase plan	405		239			$ 166
Employee stock purchase plan (in shares)						(15)
Dividends ($0.42 per share)	(10,404)				(10,404)
Change in fair value of interest rate swap, net of tax of $275	807			807
Repurchases of common stock (in shares)						330
Repurchases of common stock	(9,141)					$ (9,141)
Shares at end of period (in shares) at Sep. 30, 2018		71,544				45,483
Balance at end of period at Sep. 30, 2018	$ 163,947	$ 716	$ 444,762	$ 907	$ 225,658	$ (508,096)