Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating activities:
Net loss	$ (30,108)	$ (39,081)	$ (56,948)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation, amortization, and impairment	304	628	886
Gain on disposal of furniture and equipment	(47)
Stock-based compensation expense	4,368	4,167	4,772
Amortization of debt issuance costs	439	439	356
Change in fair value of foreign currency derivative	(5,294)	749	4,000
Changes in operating assets and liabilities:
Receivables from collaborations	2,447	1,269	24,396
Inventory		263	635
Prepaid expenses and other assets	(620)	(623)	626
Deferred collaboration expense	5,133	2,301	1,309
Accounts payable and accrued expenses	(2,049)	2,068	(10,731)
Deferred collaboration revenue	(1,103)	(9,577)	(1,552)
Net cash used in operating activities:	(26,530)	(37,397)	(32,251)
Investing activities:
Acquisition of furniture and equipment	(30)	(113)	(55)
Proceeds from sale furniture and equipment	50
Change in restricted cash	157	317
Purchases of investments	(23,974)	(16,153)	(45,500)
Sales and maturities of investments	20,330	40,833	56,873
Net cash (used in) provided by investing activities:	(3,467)	24,884	11,318
Financing activities:
Sale of common stock, net	23,633	17,805	1,027
Exercise of stock options	1,333	534	278
Employee stock purchase plan sales	124	321	300
Purchases of treasury stock			(61)
Issuance of non-recourse notes payable, net			25,691
Receipt (payment) of foreign currency derivative collateral	5,180	(1,700)	(3,480)
Net cash provided by financing activities:	30,270	16,960	23,755
Increase in cash and cash equivalents	273	4,447	2,822
Cash and cash equivalents at beginning of year	20,891	16,444	13,622
Cash and cash equivalents at end of year	$ 21,164	$ 20,891	$ 16,444