Condensed Consolidated Statement of Changes in Stockholders' Equity - 3 months ended Mar. 31, 2018 - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Treasury Stock	Retained Earnings
Beginning balance (in shares) at Dec. 31, 2017		16,089
Beginning balance at Dec. 31, 2017	$ 179,144	$ 16	$ 233,639	$ (80,795)	$ 26,284
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	5,305		5,305
Issuance of common stock upon exercise of stock option grants (in shares)		77
Issuance of common stock upon exercise of stock option grants	1,166		1,166
Payment of employee withholding tax for net option exercise	(3,051)		(3,051)
Common stock repurchases	(7,003)			(7,003)
Net income	2,616				2,616
Ending balance (in shares) at Mar. 31, 2018		16,166
Ending balance at Mar. 31, 2018	$ 178,177	$ 16	$ 237,059	$ (87,798)	$ 28,900