CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (USD $) In Thousands, except Share data	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]
Beginning Balance at Dec. 31, 2011	$ 146,346	$ 704	$ 601,482	$ (429,288)	$ 0	$ (26,552)
Beginning Balance (in shares) at Dec. 31, 2011		68,165,668
Net income for the year	105,631	0	0	105,631	0	0
Foreign currency translation	248	0	0	0	248	0
Stock-based compensation (in shares)		186,368
Stock-based compensation	4,385	(3)	4,388	0	0	0
Stock repurchase (in shares)		(54,534)
Stock repurchase	(564)	0	0	0	0	(564)
Equity component of convertible senior notes, net of taxes	12,328	0	12,328	0	0	0
Common stock issued in connection with: Stock option exercises (in shares)		81,482
Common stock issued in connection with: Stock option exercises	353	1	352	0	0	0
Ending Balance at Dec. 31, 2012	268,727	702	618,550	(323,657)	248	(27,116)
Ending Balance (in shares) at Dec. 31, 2012		68,378,984
Net income for the year	46,529	0	0	46,529	0	0
Foreign currency translation	(266)	0	0	0	(266)	0
Stock-based compensation (in shares)		62,183
Stock-based compensation	6,822	0	6,822	0	0	0
Stock repurchase (in shares)		(3,665)
Stock repurchase	(35)	0	0	0	0	(35)
Common stock issued in connection with: Stock option exercises (in shares)		85,917
Common stock issued in connection with: Stock option exercises	602	3	599	0	0	0
Ending Balance at Dec. 31, 2013	322,379	705	625,971	(277,128)	(18)	(27,151)
Ending Balance (in shares) at Dec. 31, 2013		68,523,419
Net income for the year	60,930	0	0	60,930	0	0
Foreign currency translation	(619)	0	0	0	(619)	0
Stock-based compensation (in shares)		392,470
Stock-based compensation	7,718	4	7,714	0	0	0
Stock repurchase (in shares)		(113,203)
Stock repurchase	(1,497)	0	0	0	0	(1,497)
Common stock issued in connection with: Stock option exercises (in shares)		195,383
Common stock issued in connection with: Stock option exercises	1,921	0	1,921	0	0	0
Ending Balance at Dec. 31, 2014	$ 390,832	$ 709	$ 635,606	$ (216,198)	$ (637)	$ (28,648)
Ending Balance (in shares) at Dec. 31, 2014		68,998,069