CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (USD $) In Thousands, except Share data, unless otherwise specified	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income	Accumulated Earnings (Deficit)	Total
Balances at Dec. 31, 2011	$ 203,511		$ (13)	$ (97,580)	$ 105,918
Balances (in shares) at Dec. 31, 2011	55,506,120
Increase (Decrease) in Stockholders' Equity
Issuance of common stock upon exercise of options	1,835				1,835
Issuance of common stock upon exercise of options (in shares)	628,394
Issuance of common stock under employee stock purchase plan	851				851
Issuance of common stock under employee stock purchase plan (in shares)	203,389
Issuance of common stock in conjunction with vesting of restricted stock units	278				278
Issuance of common stock in conjunction with vesting of restricted stock units (in shares)	45,810
Stock-based compensation	4,791				4,791
Net income (loss)				(29,781)	(29,781)
Unrealized gain (loss) on available-for-sale securities			44		44
Balances at Dec. 31, 2012	211,266		31	(127,361)	83,936
Balances (in shares) at Dec. 31, 2012	56,383,713
Increase (Decrease) in Stockholders' Equity
Issuance of common stock upon exercise of options	2,782				2,782
Issuance of common stock upon exercise of options (in shares)	621,090				621,090
Issuance of common stock under employee stock purchase plan	966				966
Issuance of common stock under employee stock purchase plan (in shares)	222,062
Issuance of common stock in conjunction with vesting of restricted stock units	765				765
Issuance of common stock in conjunction with vesting of restricted stock units (in shares)	142,818
Stock-based compensation	5,345				5,345
Windfall tax benefit		347			347
Net income (loss)				43,313	43,313
Unrealized gain (loss) on available-for-sale securities			(38)		(38)
Balances at Dec. 31, 2013	221,124	347	(7)	(84,048)	137,416
Balances (in shares) at Dec. 31, 2013	57,369,683				57,369,683
Increase (Decrease) in Stockholders' Equity
Issuance of common stock upon exercise of options	8,370				8,370
Issuance of common stock upon exercise of options (in shares)	1,515,023				1,515,023
Issuance of common stock under employee stock purchase plan	1,536				1,536
Issuance of common stock under employee stock purchase plan (in shares)	177,036
Issuance of common stock in conjunction with vesting of restricted stock units	1,799				1,799
Issuance of common stock in conjunction with vesting of restricted stock units (in shares)	231,686
Stock-based compensation	7,132				7,132
Equity component of convertible debt issued, net of tax		73,272			73,272
Windfall tax benefit		3,190			3,190
Net income (loss)				131,762	131,762
Unrealized gain (loss) on available-for-sale securities			(30)		(30)
Balances at Dec. 31, 2014	$ 239,961	$ 76,809	$ (37)	$ 47,714	$ 364,447
Balances (in shares) at Dec. 31, 2014	59,293,428				59,293,428