Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Operating activities:
Net loss	$ (21,055)	$ (10,292)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	1,586	1,256
Depreciation and amortization	479	393
Amortization of debt issuance costs and non-cash interest	133	681
Change in fair value of warrant liabilities	4,258	(49)
Change in fair value of embedded derivatives	81	(38)
Changes in operating assets and liabilities:
Trade accounts receivable	(112)	(30)
Inventory, net	223	1,995
Prepaid expenses and other current assets	(1,027)	(431)
Other assets	421	(197)
Accounts payable and accrued expenses	(61)	452
Deferred revenue	0	(8,462)
Net cash used in operating activities	(15,074)	(14,722)
Investing activities:
Purchases of property and equipment	(830)	(111)
Net cash used in investing activities	(830)	(111)
Financing activities:
Proceeds from revolving credit facility	0	5,163
Payments on borrowings of debt	0	(7,013)
Proceeds from exercise of common stock options	0	2
Net cash provided by financing activities	0	(1,848)
Net (decrease) increase in cash and cash equivalents	(15,904)	(16,681)
Cash and cash equivalents at beginning of period	41,228	56,525
Cash and cash equivalents at end of period	$ 25,324	$ 39,844