CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY (Unaudited) - 9 months ended Sep. 30, 2018 - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]
BALANCE at Dec. 31, 2017	$ 135,803	$ 31	$ 69,245	$ (16,359)	$ 83,035	$ (149)
BALANCE (in Shares) at Dec. 31, 2017	30,729	30,729
Impact of change in accounting policy (Note 2)	$ 1,135	$ 0	0	0	1,135	0
Net income	44,933	0	0	0	44,933	0
Share-based compensation expense	7,755	$ 0	7,755	0	0	0
Share-based compensation expense (in Shares)		147
Exercise of stock options	1,939	$ 0	1,939	0	0	0
Exercise of stock options (in Shares)		101
Repurchase of common shares for treasury	(26,304)	$ 0	0	(26,304)	0	0
Cash dividends	(22,667)	0	0	0	(22,667)	0
Employee tax withholdings related to the vesting of equity awards	(1,916)	0	0	(1,916)	0	0
Other comprehensive loss, net of tax	(111)	0	0	0	0	(111)
BALANCE at Sep. 30, 2018	$ 140,567	$ 31	$ 78,939	$ (44,579)	$ 106,436	$ (260)
BALANCE (in Shares) at Sep. 30, 2018	30,977	30,977