Basis of Presentation (Details 3) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Cash, Cash Equivalents and Marketable Securities
Cash and cash equivalents	$ 18,130,000	$ 12,416,000	$ 13,245,000	$ 1,707,000
Available-for-sale securities	50,027,000	20,086,000
Net realized gains or losses	0	0
Research and Development
Prepaid research and development costs	$ 3,600,000	$ 900,000
Equipment and furniture and fixtures | Minimum
Property, equipment and depreciation
Estimated useful lives	2 years
Equipment and furniture and fixtures | Maximum
Property, equipment and depreciation
Estimated useful lives	5 years