Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash flows from operating activities
Net loss	$ (28,323)	$ (23,402)
Adjustments to reconcile net loss to net cash used in operating activities
Non-cash interest expense	234
Remeasurement of convertible preferred stock warrants		(559)
Depreciation and amortization	700	1,201
Stock-based compensation	2,386	1,339
Changes in operating assets and liabilities
Purchased premiums and interest on available-for-sale securities	(291)
Accounts receivable	(531)	1,446
Accounts payable, accrued expenses and other	6,910	(2,356)
Deferred revenues	(3,065)	3,362
Other assets and liabilities, net	784	(434)
Net cash used in operating activities	(21,196)	(19,403)
Cash flows from investing activities
Purchases of available-for-sale securities	(7,090)
Proceeds from maturities of available-for-sale securities	20,950
Purchases of property and equipment	(2,354)	(326)
Other investing activities, net		(100)
Net cash (used in) provided by investing activities	11,506	(426)
Cash flows from financing activities
Proceeds from issuance of common stock	199	148
Proceeds from convertible notes issued by subsidiary, net of issuance costs	274
Other financing activities, net	(62)	(218)
Net cash (used in) provided by financing activities	411	(70)
Net decrease in cash and cash equivalents	(9,279)	(19,899)
Cash and cash equivalents, beginning of period	37,714	50,454
Cash and cash equivalents, end of period	28,435	30,555
Non-cash investing and financing activities
Changes in deferred financing costs included in ending accounts payable, accrued expenses and other		505
Issuance of derivative liability	35
Changes in property and equipment in accounts payable and accrued expenses	(662)
Disposal of fully depreciated assets	50
Supplemental disclosure of cash flows
Cash paid for interest	$ 998