CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Cash flows from operating activities:
Net loss	$ (9,097)	$ (41,857)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	1,422	1,317
Non-cash equity-based compensation expense	3,262	7,096
Non-cash income tax benefit	(494)	(396)
Amortization of premium/discount on purchased securities	1,463	1,841
Losses on investments, net	1,471	208
Changes in operating assets and liabilities:
Accounts receivable, net	154	972
Inventories	2,276	1,028
Receivable from collaboration	(14,705)	(430)
Prepaid and other current assets	2,086	2,382
Accounts payable and accrued expenses	(6,546)	1,413
Deferred revenues	(3,048)	(3,305)
Other long-term liabilities	(199)	(172)
Total adjustments	(12,858)	11,954
Net cash used in operating activities	(21,955)	(29,903)
Cash flows from investing activities:
Proceeds from sales or maturities of available-for-sale investments	85,234	71,033
Purchase of available-for-sale investments	(96,178)	(73,912)
Capital expenditures	(47)	(212)
Net cash used in investing activities	(10,991)	(3,091)
Cash flows from financing activities:
Proceeds from the exercise of stock options		10
Proceeds from the issuance of common stock under ESPP	150	294
Net cash provided by financing activities	150	304
Net decrease in cash and cash equivalents	(32,796)	(32,690)
Cash and cash equivalents at beginning of the period	63,474	112,646
Cash and cash equivalents at end of the period	$ 30,678	$ 79,956