Quarterly Financial Information (Unaudited) - Summary of Quarterly Financial Information (Detail) (USD $)
In Thousands, except Per Share data, unless otherwise specified
3 Months Ended 12 Months Ended
Dec. 31, 2013
Sep. 30, 2013
Jun. 30, 2013
Mar. 31, 2013
Dec. 31, 2012
Sep. 30, 2012
Jun. 30, 2012
Mar. 31, 2012
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Quarterly Financial Information Disclosure [Abstract]                      
Revenues $ 10,567 $ 2,389 $ 821 $ 3,554 $ 4,101 $ 5,761 $ 4,210 $ 12,221 $ 17,331 $ 26,293 $ 19,643
Net loss $ (5,429) $ (8,001) $ (12,172) $ (4,506) $ (11,053) $ (9,700) $ (12,276) $ (6,052) $ (30,108) $ (39,081) $ (56,948)
Basic and diluted net loss per share $ (0.09) $ (0.14) $ (0.23) $ (0.09) $ (0.22) $ (0.19) $ (0.25) $ (0.13) $ (0.55) $ (0.79) $ (1.26)