Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Cash flows from operating activities
Net loss	$ (91,754)	$ (79,676)	$ (50,159)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities
Non-cash interest expense	78		3,673
Remeasurement of convertible preferred stock warrants	(587)	864	(104)
Depreciation and amortization	3,664	4,596	3,628
Stock-based compensation	6,889	6,952	4,551
Gain on disposal of property and equipment			(26)
Changes in operating assets and liabilities
Purchased premiums and interest on available-for-sale securities	(2,354)
Accounts receivable	(1,841)	(3,681)	(1,975)
Prepaid expenses and other current assets	(2,477)	(3,933)	(571)
Accounts payable, accrued expenses, and other	6,985	8,815	194
Deferred revenues	(5,281)	11,963	12,845
Deferred rent and tax incentives	7,892	1,264	1,567
Other assets and liabilities, net	(1,030)	19	8
Net cash used in operating activities	(79,816)	(52,817)	(26,369)
Cash flows from investing activities
Purchase of available-for-sale securities	(115,665)
Proceeds from maturities and sales of available-for-sale securities	43,880
Purchase of property and equipment	(3,189)	(3,754)	(5,025)
Proceeds from sale of property and equipment			26
Assignment of restricted cash	(628)
Release of restricted cash	381		95
Other investing activities, net		7	4
Net cash used in investing activities	(75,221)	(3,747)	(4,900)
Cash flows from financing activities
Proceeds from initial public offering, net of offering costs	100,025
Proceeds from issuance of convertible preferred stock, net of offering costs		76,949
Proceeds from issuance of common stock	5,427	1,745	294
Principal payment on capital lease obligations	(48)	(443)	(864)
Proceeds from issuance of loans payable, net of issuance costs	41,128
Payments of dividends on Series B convertible preferred stock	(4,235)
Proceeds from issuance of convertible preferred stock of Silver Creek Pharmaceuticals, Inc.			4,165
Deferred financing costs		(1,946)
Net cash provided by financing activities	142,297	76,305	3,595
Net (decrease) increase in cash and cash equivalents	(12,740)	19,741	(27,674)
Cash and cash equivalents, beginning of period	50,454	30,713	58,387
Cash and cash equivalents, end of period	37,714	50,454	30,713
Noncash financing and investing activities
Accrued interest on Series F amount relieved to additional paid-in capital (Note 14)			12,974
Issuance of shares from Series F amount (Note 14)			59,973
Conversion of convertible preferred stock to common stock	268,225
Conversion of convertible preferred stock warrants to common stock warrants	929
Issuance of derivative liability	196
Changes in property and equipment in accounts payable and accrued expenses	412
Disposals of fully depreciated assets	671
Reclassification of deferred financing costs to stockholders' equity	2,748		25
Dividends on Series B convertible preferred stock declared but not paid	28
Supplemental disclosure of cash flows
Cash paid for interest	$ 169	$ 13	$ 55