Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Cash flows from operating activities:
Net loss	$ (25,813)	$ (24,431)
Adjustments to reconcile net loss to net cash used in operating activities:
Amortization of purchased premium/discount	23	49
Depreciation of fixed assets	641	824
Non-cash interest expense	3,293	1,915
Compensation expenses associated with stock-based compensation plans	4,353	2,775
Non-cash stock issuance	1,076
Provision for doubtful accounts		(35)
Gain on sale of fixed asset		(110)
Changes in operating assets and liabilities:
Accounts receivable	1,292	(1,363)
Other current assets	80	2,654
Inventory	1,333	(3,130)
Accounts payable and accrued expenses	976	(3,589)
Deferred revenue	(1,381)	(3,053)
Long-term deferred rent	(92)	715
Other	32	153
Net cash used in operating activities	(14,187)	(26,626)
Cash flows from investing activities:
Purchase of investments	(4,002)	(6,057)
Proceeds from maturity of investments	9,000	23,000
Purchase of fixed assets	(497)	(3,834)
Restricted cash		1,266
Proceeds from sale of fixed assets		200
Net cash provided by investing activities	4,501	14,575
Cash flows from financing activities:
Net proceeds from the issuance of common and preferred stock	29,068
Repayment of long-term obligations	(331)	(135)
Proceeds from long-term obligations		1,382
Proceeds from the issuance of common stock under employee stock purchase plan and exercise of stock options	4,069	682
Net cash provided by financing activities	32,806	1,929
Net increase (decrease) in cash and cash equivalents	23,120	(10,122)
Cash and cash equivalents at beginning of the period	20,018	31,468
Cash and cash equivalents at end of the period	43,138	21,346
Supplemental disclosure of cash flow information:
Interest paid	$ 3,057	$ 7,431