CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS CHANGE IN CASH AND CASH EQUIVALENTS (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Cash flows from operating activities:
Net loss	$ (18,739)	$ (24,389)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	251	418
Accretion and amortization on investments, net	669	1,226
Issuance of common stock for acquired in-process research and development	0	594
Issuance of common stock in exchange for services by non-employees	80	270
Stock-based compensation for employees and directors	1,391	6,319
Amortization related to 401(k) contributions	172	235
Loss on equity method investment	0	335
Unrealized gain on fair value of derivatives	(26)	(39)
Changes in assets and liabilities:
Other current and noncurrent assets	1,384	2,157
Other current and noncurrent liabilities	(1,783)	154
Translation adjustment	16	12
Net cash used in operating activities	(16,585)	(12,708)
Cash flows from investing activities:
Purchases of property and equipment	(84)	(124)
Purchases of marketable securities	(17,895)	(51,395)
Proceeds from maturities of marketable securities	37,490	53,523
Net cash provided by investing activities	19,511	2,004
Cash flows from financing activities:
Proceeds from issuances of common stock and warrants, net of issuance costs	0	144
Net cash provided by financing activities	0	144
Net increase (decrease) in cash and cash equivalents	2,926	(10,560)
Cash and cash equivalents at the beginning of the period	16,105	45,972
Cash and cash equivalents at the end of the period	$ 19,031	$ 35,412