Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Assets, Current
Cash and cash equivalents, fair value	$ 43,604	$ 36,641
Marketable securities	114,066	137,777
Prepaid Expense and Other Assets, Current	3,410	4,368
Total Current Assets	161,080	178,786
Property, Plant and Equipment, Net	10,134	7,893
Deposits and other non-current assets	1,876	1,527
Marketable securities	2,000	1,360
Total Assets	175,090	189,566
Liabilities, Current
Accounts Payable	557	550
Accrued expenses	5,593	6,488
Deferred revenue, current portion	4,914	6,764
Total current liabilities	11,064	13,802
Deferred rent, net of current portion	5,058	4,999
Deferred revenue, net of current portion	35,248	34,818
Other non-current liabilities	1,023	25
Total Liabilities	52,393	53,644
Stockholders' Equity Attributable to Parent
Common stock, $0.001 par value: 120,000,000 shares authorized at March 31, 2017 and December 31, 2016; 25,851,801 and 25,597,912 shares issued and outstanding at March 31, 2017 and December 31, 2016, respectively	26	26
Additional Paid in Capital	229,009	225,963
Accumulated other comprehensive gain	325	(52)
Accumulated deficit	(106,663)	(90,015)
Total stockholders’ deficit	122,697	135,922
Total liabilities, redeemable convertible preferred stock and stockholders’ deficit	$ 175,090	$ 189,566