CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Revenue:
Research and development revenue under collaborative agreements	$ 56,628	$ 37,615	$ 76,177	$ 79,285
Licensing and royalty revenue	448	477	9,060	2,166
Total revenue	57,076	38,092	85,237	81,451
Expenses:
Research, development and patent expenses	59,264	42,631	112,712	80,944
General and administrative	4,462	3,389	8,842	6,811
Total operating expenses	63,726	46,020	121,554	87,755
Loss from operations	(6,650)	(7,928)	(36,317)	(6,304)
Other income (expense):
Investment income	671	589	1,328	967
Interest expense	(4,961)	(4,808)	(9,904)	(9,603)
(Loss) gain on investments, net	(260)	840	137	1,898
Loss before income tax benefit	(11,200)	(11,307)	(44,756)	(13,042)
Income tax (expense) benefit	(881)	1,181	1,395	1,244
Net loss	$ (12,081)	$ (10,126)	$ (43,361)	$ (11,798)
Basic and diluted net loss per share (in dollars per share)	$ (0.10)	$ (0.09)	$ (0.37)	$ (0.11)
Shares used in computing basic net loss per share (in shares)	117,588	108,539	117,359	105,225