CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - 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, 2014	$ 55,515	$ 29	$ 29,992	$ (3,062)	$ 28,552	$ 4
BALANCE (in Shares) at Dec. 31, 2014		28,990
Net income	26,143	$ 0	0	0	26,143	0
Share-based compensation expense	5,468	$ 0	5,468	0	0	0
Share-based compensation expense (in Shares)		296
Exercise of stock options	3,182	$ 0	3,182	0	0	0
Exercise of stock options (in Shares)		335
Equity compensation awards, net	2,750	$ 0	2,750	0	0	0
Cash dividends	(20,504)	0	0	0	(20,504)	0
Employee tax withholdings related to the vesting of equity awards	(2,610)	0	0	(2,610)	0	0
Other comprehensive loss, net of tax	(16)	0	0	0	0	(16)
BALANCE at Dec. 31, 2015	69,928	$ 29	41,392	(5,672)	34,191	(12)
BALANCE (in Shares) at Dec. 31, 2015		29,621
Net income	35,469	$ 0	0	0	35,469	0
Share-based compensation expense	6,970	$ 1	6,969	0	0	0
Share-based compensation expense (in Shares)		296
Exercise of stock options	2,760	$ 0	2,760	0	0	0
Exercise of stock options (in Shares)		286
Equity compensation awards, net	2,936	$ 0	2,936	0	0	0
Cash dividends	(20,861)	0	0	0	(20,861)	0
Employee tax withholdings related to the vesting of equity awards	(2,657)	0	0	(2,657)	0	0
Other comprehensive loss, net of tax	(21)	0	0	0	0	(21)
BALANCE at Dec. 31, 2016	$ 94,524	$ 30	54,057	(8,329)	48,799	(33)
BALANCE (in Shares) at Dec. 31, 2016	30,203	30,203
Net income	$ 57,872	$ 0	0	0	57,872	0
Share-based compensation expense	10,923	$ 1	10,922	0	0	0
Share-based compensation expense (in Shares)		306
Exercise of stock options	4,266	$ 0	4,266	0	0	0
Exercise of stock options (in Shares)		271
Repurchase and retirement of common shares	(2,285)	$ 0	0	0	(2,285)	0
Repurchase and retirement of common shares (in Shares)		(51)
Repurchase of common shares for treasury	(3,485)	$ 0	0	(3,485)	0	0
Cash dividends	(21,351)	0	0	0	(21,351)	0
Employee tax withholdings related to the vesting of equity awards	(4,545)	0	0	(4,545)	0	0
Other comprehensive loss, net of tax	(116)	0	0	0	0	(116)
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