Statements Of Cash Flows (USD $) In Thousands	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010
Cash Flows From Operating Activities:
Net loss	$ (24,291)	$ (59,275)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	614	668
Stock-based compensation expense	9,431	7,892
Amortization of intangible asset	340	340
Other	5	226
Changes in operating assets and liabilities:
Accounts receivable	(3,530)	(3,852)
Prepaid expenses and other assets	(950)	40
Interest receivable on investments	(24)	(60)
Inventory	(154)	(136)
Trade accounts payable	(2,443)	480
Accrued liabilities	1,419	761
Deferred revenue	21,342
Net cash provided by (used in) operating activities	1,759	(52,916)
Cash Flows From Investing Activities:
Acquisition of property and equipment	(77)	(937)
Purchases of investments	(30,299)	(55,050)
Proceeds from maturities of investments	49,972	26,980
Net cash provided by (used in) investing activities	19,596	(29,007)
Cash Flows From Financing Activities:
Proceeds from issuance of common stock associated with stock options and employee stock purchase plan	124	4,138
Proceeds from issuance of common stock, net of issuance costs		32
Net cash provided by financing activities	124	4,170
Net increase (decrease) in cash and cash equivalents	21,479	(77,753)
Cash and cash equivalents, beginning of period	48,164	141,185
Cash and cash equivalents, end of period	69,643	63,432
Supplemental Schedule of Cash and Non-cash Activities:
Deferred revenue in accounts receivable		918
Assets recorded for which payment has not yet occurred		$ 142