CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash flows from operating activities
Net income (loss)	$ (30,506)	$ 3,630	$ (38,785)
Adjustments to reconcile net income (loss) to cash used in operating activities:
Depreciation	928	1,298	1,507
Charge for 401(k) company common stock match	397	408	529
Stock-based compensation	3,193	3,807	4,633
Inventory impairment	818	138
Changes in operating assets and liabilities:
Inventory	(1,688)	(3,342)
Accounts receivable	(158)	(693)	(146)
Unbilled receivable	185	(68)	(296)
Due from related parties	24	236	(71)
Prepaid expenses and other assets	(21)	108	68
Accounts payable	(654)	721	273
Accrued expenses	1,383	(34)	(623)
Deferred rent and long-term liabilities	(151)	(154)	(153)
Deferred revenue	(398)	(37,791)	1,333
Net cash used in operating activities	(26,648)	(31,736)	(31,731)
Cash flows from investing activities
Purchase of property and equipment	(373)	(392)	(895)
Proceeds from sale of equipment		12
Change in restricted cash	(25)	28
Purchase of investments	(16,635)	(58,933)	(107,477)
Proceeds from sale and maturity of short-term investments	36,821	84,303	99,464
Net cash provided by (used in) investing activities	19,788	25,018	(8,908)
Cash flows from financing activities
Proceeds from options exercised	14	19	74
Proceeds from public stock offering, net of issuance costs			49,333
Net cash provided by financing activities	14	19	49,407
Effect of exchange rate changes on cash and cash equivalents	(28)	(6)	(17)
Net increase (decrease) in cash and cash equivalents	(6,874)	(6,705)	8,751
Cash and cash equivalents at beginning of period	14,572	21,277	12,526
Cash and cash equivalents at end of period	$ 7,698	$ 14,572	$ 21,277