Corporate Partnership, Licensing and Research Funding Agreements (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	3 Months Ended									12 Months Ended
	Dec. 31, 2014		Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013	Dec. 31, 2012
Licensing and Research Funding Agreements [Abstract]
Research and development expense	$ 7,771,000		$ 6,471,000	$ 6,858,000	$ 5,590,000	$ 5,752,000	$ 6,574,000	$ 6,863,000	$ 8,472,000	$ 26,690,000		$ 27,661,000	$ 21,570,000
Exercise price of warrants (in dollars per share)	$ 2.81									$ 2.81
Laboratories del Dr. Esteve, S.A. [Abstract]
Percent of cash upfront and milestone fees payable to Esteve	10.00%									10.00%
Maximum aggregate cash upfront and milestone fees payable to Esteve	20,000,000									20,000,000
Battelle - 2014 Collaboration Agreement [Member]
Licensing and Research Funding Agreements [Abstract]
Research and development expense										300,000
Term of collaboration agreement										10 years
Exercise price of warrants (in dollars per share)	$ 5.00	[1]								$ 5.00	[1]
Maximum royalty paid to Battelle on successful completion of activities										25,000,000
Battelle - 2014 Collaboration Agreement [Member] | Additional Warrants [Member]
Licensing and Research Funding Agreements [Abstract]
Number of warrant shares issuable (in shares)	0.5									0.5
Battelle - 2014 Collaboration Agreement [Member] | Initial Warrants [Member]
Licensing and Research Funding Agreements [Abstract]
Number of warrant shares issuable (in shares)	1.0									1.0
Phillip Morris - License Agreement [Member]
Licensing and Research Funding Agreements [Abstract]
Royalty paid										300,000
Johnson & Johnson - License Agreement [Member]
Licensing and Research Funding Agreements [Abstract]
Potential license fee payable	2,500,000									2,500,000
License fees paid										950,000
Payment of license costs subject to FDA approval													$ 500,000

[1] See Note 12 for further details on the Batelle collaboration.