Condensed Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 53,144	$ 117,773
Short-term investments	172,060	150,892
Receivables from collaborators	73	309
Prepaid expenses and other current assets	4,730	3,733
Total current assets	230,007	272,707
Property and equipment, net	2,732	2,600
Long-term investments	36,803	50,371
Prepaid and other long-term assets	10,007	53
Total assets	279,549	325,731
Current liabilities:
Accounts payable	12,531	3,232
Accrued compensation and employee benefits	2,498	2,569
Accrued and other liabilities	15,284	17,796
Deferred revenue, current portion	9,875	1,958
Total current liabilities	40,188	25,555
Deferred revenue, long-term	29,123	3,253
Other long-term liabilities	1,006	588
Total liabilities	70,317	29,396
Stockholders’ equity:
Preferred stock, $0.001 par value, 5,000,000 shares authorized at September 30, 2014 and December 31, 2013; 0 shares issued and outstanding at September 30, 2014 and December 31, 2013
Common stock, $0.001 par value, 100,000,000 shares authorized at September 30, 2014 and December 31, 2013; 41,501,999 and 40,915,130 shares issued and outstanding at September 30, 2014 and December 31, 2013, respectively	42	41
Additional paid-in capital	592,755	581,911
Accumulated deficit	(383,541)	(285,672)
Accumulated other comprehensive (loss) income	(24)	55
Total stockholders’ equity	209,232	296,335
Total liabilities and stockholders’ equity	$ 279,549	$ 325,731