Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Cash flows from operating activities
Net loss	$ (115,344)	$ (83,862)	$ (85,302)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	7,583	6,336	5,541
Stock-based compensation	24,916	19,009	20,000
Loss on sale of equipment		33
Forgiveness of notes receivable	16	8	(13)
Changes in operating assets and liabilities:
Receivables	(29)	81	14
Prepaid and other assets	2,288	649	2,741
Accounts payable	3,312	(236)	(1,625)
Accrued personnel related expenses, accrued interest on convertible subordinated notes and accrued liabilities	5,124	3,321	(3,689)
Deferred rent	2,429	1,446	(709)
Deferred revenue	(18,633)	(21,801)	4,589
Other long-term liabilities		(128)	389
Net cash used in operating activities	(88,338)	(75,144)	(58,064)
Cash flows from investing activities
Purchases of property and equipment	(3,628)	(861)	(744)
Purchases of marketable securities	(301,563)	(183,899)	(123,460)
Maturities of marketable securities	231,476	131,855	118,065
Sales of marketable securities	17,321	12,024	5,000
Sale of equipment		12
Release of restricted cash		417	2,500
Additions to notes receivable	(140)
Decrease in notes receivable	715	140	375
Net cash (used in) provided by investing activities	(55,819)	(40,312)	1,736
Cash flows from financing activities
Payments on notes payable and capital leases	(206)	(184)	(131)
Net proceeds from issuances of common stock	25,808	231,429	11,723
Net cash provided by financing activities	25,602	231,245	11,592
Net increase (decrease) in cash and cash equivalents	(118,555)	115,789	(44,736)
Cash and cash equivalents at beginning of period	163,333	47,544	92,280
Cash and cash equivalents at end of period	44,778	163,333	47,544
Supplemental Disclosure of Cash Flow Information
Cash paid for interest	5,195	5,217	5,229
Supplemental Disclosure of Non-Cash Investing Activity
Acquisition cost of property and equipment under capital lease			$ 154