Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Operating activities:
Net loss	$ (34,389)	$ (27,461)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	3,364	2,794
Restructuring	201	0
Depreciation and amortization	945	790
Amortization of debt issuance costs and non-cash interest	276	797
Change in fair value of warrant liabilities	2,995	42
Change in fair value of embedded derivatives	562	(368)
Changes in operating assets and liabilities:
Trade accounts receivable	1,505	19
Inventory, net	(299)	1,237
Prepaid expenses and other current assets	210	(260)
Other assets	498	(426)
Accounts payable and accrued expenses	(584)	1,832
Restructuring liabilities	146	0
Deferred revenue	0	(8,462)
Net cash used in operating activities	(24,570)	(29,466)
Investing activities:
Purchases of property and equipment	(798)	(291)
Net cash used in investing activities	(798)	(291)
Financing activities:
Proceeds from revolving credit facility	0	9,899
Payments on borrowings of debt	0	(15,040)
Proceeds from exercise of common stock options	0	2
Proceeds from issuance of common stock and common stock warrants	261	345
Net cash provided by (used in) financing activities	261	(4,794)
Net decrease in cash and cash equivalents	(25,107)	(34,551)
Cash and cash equivalents at beginning of period	41,228	56,525
Cash and cash equivalents at end of period	$ 16,121	$ 21,974