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