CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Cash flows from operating activities:
Net loss	$ (20,844)	$ (37,065)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	264	465
Accretion and amortization on investments, net	647	1,264
Gain on sales of property and equipment	(116)	(14)
Loss on write-downs of property and equipment	200
Stock-based compensation for services by non-employees	53	110
Stock-based compensation for employees and directors	2,234	2,753
Amortization related to 401(k) contributions	465	281
Unrealized gain on derivatives	(1)	(34)
Changes in assets and liabilities:
Other current and noncurrent assets	1,248	1,864
Other current liabilities	(8,304)	12
Translation adjustment		16
Net cash used in operating activities	(24,154)	(30,348)
Cash flows from investing activities:
Restricted cash transfer	(1)	(1)
Purchases of property and equipment	(56)	(470)
Proceeds from sales of property and equipment	116	20
Purchases of marketable securities	(40,110)	(35,386)
Proceeds from maturities of marketable securities	50,916	64,124
Net cash provided by investing activities	10,865	28,287
Cash flows from financing activities:
Proceeds from issuance of common stock, net of issuance costs	60	79
Net cash provided by financing activities	60	79
Net decrease in cash and cash equivalents	(13,229)	(1,982)
Cash and cash equivalents at the beginning of the period	22,063	16,105
Cash and cash equivalents at the end of the period	$ 8,834	$ 14,123