Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Cash flows from operating activities
Net loss	$ (42,881)	$ (30,447)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	3,694	3,912
Loss on disposal of property and equipment	6	26
Unrealized (appreciation) depreciation on equity securities	21,635	(15,971)
Amortization of discount/premium of short term investments	51
Equity in net loss of affiliate	390
Gain on previously held equity investment	(7,415)
Stock-based compensation expense	1,196	520
Contribution of services by shareholder	775	775
Shares issued to nonemployee members of the Board of Directors	85	76
Receivables:
Trade	(112)	(178)
Related parties	(489)	(260)
Other	(184)	933
Prepaid expenses and other	747	(605)
Other assets	(7,547)	311
Accounts payable	722	(582)
Accrued compensation and benefits	(537)	1,273
Other accrued liabilities	39	(754)
Deferred revenue	2,311	7,246
Related party payables	(89)	(249)
Other long term liabilities	(10)	58
Net cash used in operating activities	(27,613)	(33,916)
Cash flows from investing activities
Purchases of short term investments	(95,246)	(1)
Purchases of equity securities		(10,000)
Acquisition of business, net of cash received	512
Purchases of property and equipment	(776)	(6,965)
Proceeds from sale of property and equipment		5
Issuance of related party note receivable	(300)
Proceeds from related party notes receivable	500	34
Net cash used in investing activities	(95,310)	(16,927)
Cash flows from financing activities
Payments of capital lease obligations	(34)	(38)
Proceeds from long term debt	171
Payments of long term debt	(18)
Proceeds from stock option exercises	9	184
Payment of stock issuance costs	(3,148)	(11)
Net cash provided by financing activities	146,980	50,546
Effect of exchange rate changes on cash and cash equivalents	1
Net increase (decrease) in cash and cash equivalents	24,058	(297)
Cash and cash equivalents
Beginning of period	10,403	19,628
End of period	34,461	19,331
Supplemental disclosure of cash flow information
Cash paid during the period for interest	48	6
Significant noncash financing and investing activities
Accretion of dividends on redeemable convertible preferred shares	14,347	10,822
Stock received as consideration for collaboration agreements	3,732	6,588
IPO fees included in accrued expenses	1,526
Series E Redeemable Convertible Preferred Stock [Member]
Cash flows from financing activities
Proceeds from issuance of redeemable convertible preferred shares		50,560
Significant noncash financing and investing activities
Accretion of dividends on redeemable convertible preferred shares	6,383
Series F Redeemable Convertible Preferred Stock [Member]
Cash flows from financing activities
Proceeds from issuance of redeemable convertible preferred shares	150,000
Significant noncash financing and investing activities
Accretion of dividends on redeemable convertible preferred shares	2,139
Subscriptions Payable [Member] | Series E Redeemable Convertible Preferred Stock [Member]
Significant noncash financing and investing activities
Conversion of subscriptions payable into Series E redeemable convertible preferred shares		$ 7,440