Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Operating activities:
Net loss	$ (47,386)	$ (83,903)	$ (73,564)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	6,157	4,809	2,507
Depreciation and amortization	1,599	1,584	1,428
Amortization of debt issuance costs and non-cash interest	2,017	1,793	1,582
Change in fair value of warrant liabilities	(11,811)	(445)	(6,725)
Change in fair value of embedded derivatives	147	240	0
Beneficial conversion feature from issuance of convertible notes	0	0	4,696
Loss on disposal and impairment of property and equipment	9	0	2
Changes in operating assets and liabilities:
Trade accounts receivable	(730)	(439)	(4,474)
Inventory	3,890	1,517	(5,133)
Prepaid expenses and other current assets	163	24	537
Other assets	11	338	(3,976)
Accounts payable and accrued expenses	2,283	4,955	10,866
Deferred rent	(89)	(57)	(48)
Deferred revenue	(8,462)	(10,887)	350
Net cash used in operating activities	(52,202)	(80,471)	(71,952)
Investing activities:
Purchases of property and equipment	(293)	(617)	(3,442)
Net cash used in investing activities	(293)	(617)	(3,442)
Financing activities:
Proceeds from convertible notes, net of issuance costs	0	0	14,957
Proceeds from borrowings of debt and revolving credit facility, net of issuance costs	9,900	39,124	31,072
Payments on borrowings of debt	(25,000)	(825)	(18,178)
Payments on revolving credit facility	(15,051)	(9,477)	0
Proceeds from exercise of common stock options	33	92	71
Proceeds from issuance of common stock and common stock warrants, net of issuance costs	67,316	59,527	51,733
Net cash provided by financing activities	37,198	88,441	79,655
Net (decrease) increase in cash and cash equivalents	(15,297)	7,353	4,261
Cash and cash equivalents at beginning of period	56,525	49,172	44,911
Cash and cash equivalents at end of period	41,228	56,525	49,172
Supplemental disclosure of cash flow information:
Cash paid for interest	5,284	4,186	2,403
Noncash investing and financing activities:
Warrants issued in connection with public offering	20,959	0	0
Asset retirement obligation	286	0	0
Warrants issued in connection with debt	0	866	0
Embedded derivatives related to debt	0	605	0
Purchase of property and equipment in accounts payable	0	123	126
Vesting of early exercised stock options	0	15	59
Conversion of convertible preferred stock to common stock at initial public offering	0	0	149,312
Conversion of convertible notes and related interest to common stock, net of issuance costs	0	0	15,477
Reclassification of convertible preferred stock warrants to common stock warrants	0	0	743
Acquisition of leasehold paid by landlord	$ 0	$ 0	$ 305