Consolidated Statements of Stockholders' Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common stock	Additional paid-in Capital	Accumulated other comprehensive income (loss)	Accumulated deficit
Balance at Dec. 31, 2010	$ 23,479	$ 4	$ 374,528	$ (3)	$ (351,050)
Balance (in shares) at Dec. 31, 2010		42,090,205
Increase (Decrease) in Stockholders' Equity
Issuance of common shares in equity offering, excluding to related parties, net	27,102	1	27,101
Issuance of common shares in equity offering, net (in shares)		5,610,238
Issuance of common shares to related parties	7,734		7,734
Issuance of common shares to related parties (in shares)		1,581,493
Issuance of restricted common shares (in shares)		70,585
Forfeitures of restricted common shares (in shares)		(6,531)
Exercise of stock options	479		479
Exercise of stock options (in shares)		193,818
Compensation expense related to stock options for services	3,354		3,354
Unrealized gain (loss) on marketable securities	6			6
Net loss	(47,380)				(47,380)
Balance at Dec. 31, 2011	14,774	5	413,196	3	(398,430)
Balance (in shares) at Dec. 31, 2011		49,539,808
Increase (Decrease) in Stockholders' Equity
Issuance of common shares in equity offering, excluding to related parties, net	65,107	1	65,106
Issuance of common shares in equity offering, net (in shares)		11,264,102
Issuance of common shares to related parties	53,545	1	53,544
Issuance of common shares to related parties (in shares)		7,762,600
Issuance of restricted common shares (in shares)		45,243
Exercise of stock options	1,141		1,141
Exercise of stock options (in shares)		322,298
Purchase and retirement of common shares from an officer	(32)		(32)
Purchase and retirement of common shares from an officer (in shares)		(3,969)
Compensation expense related to stock options for services	3,322		3,322
Unrealized gain (loss) on marketable securities	(1)			(1)
Net loss	(62,790)				(62,790)
Balance at Dec. 31, 2012	75,066	7	536,277	2	(461,220)
Balance (in shares) at Dec. 31, 2012	68,930,082	68,930,082
Increase (Decrease) in Stockholders' Equity
Issuance of common shares in equity offering, excluding to related parties, net	37,629	1	37,628
Issuance of common shares in equity offering, net (in shares)		10,916,667
Issuance of common shares to related parties	19,437	1	19,436
Issuance of common shares to related parties (in shares)		5,183,333
Issuance of restricted common shares (in shares)		140,000
Forfeitures of restricted common shares (in shares)		(75,000)
Exercise of stock options	1,106		1,106
Exercise of stock options (in shares)		137,424
Compensation expense related to stock options for services	6,030		6,030
Unrealized gain (loss) on marketable securities	15			15
Net loss	(90,192)				(90,192)
Balance at Dec. 31, 2013	$ 49,091	$ 9	$ 600,477	$ 17	$ (551,412)
Balance (in shares) at Dec. 31, 2013	85,232,506	85,232,506