Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Cash flows from operating activities:
Net loss	$ (24,431)	$ (21,064)
Adjustments to reconcile net loss to net cash used in operating activities:
Amortization of purchased premium/discount	49	190
Depreciation and amortization of fixed assets and intangible assets	826	973
Non-cash interest expense	1,915	1,612
Compensation expenses associated with stock-based compensation plans	2,775	3,110
Provision for doubtful accounts	(35)	10
Gain on sale of fixed assets	(110)
Changes in operating assets and liabilities:
Accounts receivable	(1,363)	(1,485)
Other current assets	2,654	271
Inventory	(3,130)	(5,075)
Other long-term assets	151	(247)
Accounts payable and accrued expenses	(3,589)	(1,540)
Deferred revenue	(3,053)	(4,010)
Long-term deferred rent	715	(30)
Net cash used in operating activities	(26,626)	(27,285)
Cash flows from investing activities:
Purchase of investments	(6,057)	(3,021)
Proceeds from maturity of investments	23,000	28,502
Purchase of fixed assets	(3,834)	(236)
Restricted cash	1,266	(178)
Proceeds from sale of fixed assets	200
Net cash provided by investing activities	14,575	25,067
Cash flows from financing activities:
Net proceeds from sale of common stock		323
Repayment of long-term obligations	(135)	(1,584)
Proceeds from long-term obligations	1,382
Proceeds from the issuance of common stock under employee stock purchase plan and exercise of stock options	682	159
Net cash provided by (used in) financing activities	1,929	(1,102)
Net decrease in cash and cash equivalents	(10,122)	(3,320)
Cash and cash equivalents at beginning of the period	31,468	18,601
Cash and cash equivalents at end of the period	21,346	15,281
Supplemental disclosure of cash flow information:
Interest paid	$ 7,431	$ 6,923