CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Cash flows from operating activities:
Net loss	$ (12,416)	$ (22,295)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	551	642
Non-cash equity-based compensation expense	1,685	4,475
Amortization of premium/discount on purchased securities	766	868
Gains on investments, net		(1)
Changes in operating assets and liabilities:
Accounts receivable, net	(346)	(724)
Inventories	2,131	313
Receivable from collaboration	58	(410)
Prepaid and other current assets	548	1,208
Accounts payable and accrued expenses	(2,463)	(3,508)
Deferred revenues	(1,524)	(1,710)
Other long-term liabilities	(97)	(83)
Total adjustments	1,309	1,070
Net cash used in operating activities	(11,107)	(21,225)
Cash flows from investing activities:
Proceeds from sales or maturities of available-for-sale investments	37,504	35,327
Purchase of available-for-sale investments	(52,205)	(49,364)
Capital expenditures	(47)	(76)
Net cash used in investing activities	(14,748)	(14,113)
Cash flows from financing activities:
Proceeds from the exercise of stock options		10
Net cash provided by financing activities		10
Net decrease in cash and cash equivalents	(25,855)	(35,328)
Cash and cash equivalents at beginning of the period	63,474	112,646
Cash and cash equivalents at end of the period	$ 37,619	$ 77,318