Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Operating activities
Net loss	$ (83,903)	$ (73,564)	$ (45,889)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	4,809	2,507	1,026
Depreciation and amortization	1,584	1,428	1,017
Amortization of debt issuance costs and non-cash interest	1,793	1,582	4,297
Change in fair value of warrant liability	(445)	(6,725)	755
Change in fair value of embedded derivatives	240	0	0
Beneficial conversion feature from issuance of convertible notes	0	4,696	3,009
Loss on disposal and impairment of property and equipment	0	2	11
Changes in operating assets and liabilities:
Trade accounts receivable	(439)	(4,474)	0
Inventory	2,042	(5,133)	(13,160)
Prepaid expenses and other current assets	24	537	(1,769)
Other assets	(187)	(3,976)	(176)
Accounts payable and accrued expenses	4,955	10,866	(396)
Deferred rent	(57)	(48)	(86)
Deferred revenue	(10,887)	350	19,000
Net cash used in operating activities	(80,471)	(71,952)	(32,361)
Investing activities:
Purchases of property and equipment	(617)	(3,442)	(2,057)
Net cash used in investing activities	(617)	(3,442)	(2,057)
Financing activities:
Proceeds from issuance of common stock, net of issuance costs	59,527	51,733	0
Proceeds from issuance of convertible preferred stock, net of issuance costs	0	0	54,930
Proceeds from convertible notes, net of issuance costs	0	14,957	14,770
Proceeds from borrowings of debt and revolving credit facility, net of issuance costs	39,124	31,072	0
Payments on borrowings of debt	(825)	(18,178)	(4,691)
Payments on revolving credit facility	(9,477)	0	0
Proceeds from exercise of common stock options	92	71	95
Net cash provided by financing activities	88,441	79,655	65,104
Net increase in cash and cash equivalents	7,353	4,261	30,686
Cash and cash equivalents at beginning of period	49,172	44,911	14,225
Cash and cash equivalents at end of period	56,525	49,172	44,911
Supplemental disclosure of cash flow information:
Cash paid for interest	4,186	2,403	1,894
Noncash investing and financing activities:
Warrants issued in connection with debt	866	0	0
Embedded derivatives related to debt	605	0	0
Purchase of property and equipment in accounts payable	123	126	213
Vesting of early exercised stock options	15	59	54
Conversion of convertible preferred stock to common stock at initial public offering	0	149,312	0
Conversion of convertible notes and related interest to common stock, net of issuance costs	0	15,477	0
Reclassification of convertible preferred stock warrants to common stock warrants	0	743	0
Acquisition of leasehold paid by landlord	0	305	0
Conversion of convertible notes and related interest to convertible preferred stock, net of issuance costs	0	0	15,258
Warrants issued in connection with debt and convertible preferred stock	$ 0	$ 0	$ 3,819