CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Operating Activities:
Net loss	$ (78,131)	$ (51,401)
Reconciliation of net loss to net cash used in operating activities:
Depreciation and amortization	4,347	2,995
Amortization of net premiums on marketable securities	955	106
Deferred rent	(554)	(302)
Non-cash stock-based compensation	9,278	4,583
Realized gains on marketable securities	0	(615)
Other	140	(13)
Changes in operating assets and liabilities:
Restricted cash	297	1,417
Accounts receivable - billed	5,503	(999)
Accounts receivable - unbilled	963	755
Prepaid expenses and other assets	(6,536)	(3,348)
Accounts payable and accrued expenses	(7,706)	(164)
Deferred revenue	105	(260)
Net cash used in operating activities	(71,339)	(47,246)
Investing Activities:
Capital expenditures	(13,648)	(4,877)
Proceeds from disposal of property and equipment	0	39
Proceeds from maturities of marketable securities	137,107	18,440
Purchases of marketable securities	(154,288)	(160,782)
Net cash used in investing activities	(30,829)	(147,180)
Financing Activities:
Principal payments on capital leases	(49)	(58)
Principal payments on notes payable	(458)	(505)
Changes in restricted cash	(126)	(1)
Cash paid with the Novavax AB acquisition	0	(171)
Net proceeds from sales of common stock	204,275	107,896
Proceeds from the exercise of stock options and employee stock purchases	4,440	2,288
Net cash provided by financing activities	208,082	109,449
Effect of exchange rate on cash and cash equivalents	(105)	(21)
Net increase (decrease) in cash and cash equivalents	105,809	(84,998)
Cash and cash equivalents at beginning of period	32,335	119,471
Cash and cash equivalents at end of period	138,144	34,473
Supplemental disclosure of non-cash activities:
Property and equipment purchases included in accounts payable and accrued expenses	2,390	999
Supplemental disclosure of cash flow information:
Cash payments of interest	$ 79	$ 143