Equity Transactions (Details) - USD ($)						12 Months Ended
	Oct. 26, 2015	Jul. 24, 2015	Mar. 15, 2014	Feb. 05, 2014	Oct. 15, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Subsequent Event [Line Items]
Authorized but unissued shares of common stock (in shares)						$ 6,000,000
Number of treasury stock retired (in shares)	199,275
Number of treasury stock retired, value	$ (2,600,000)					0
Stock issued, underwritten public offering, value		$ 28,700,000		$ 86,000,000	$ 25,900,000	$ 26,780,068	$ 80,535,401	$ 24,094,530
Stock issued, underwritten public offering, value (in shares)		10,500,000		13,200,000	11,500,000
Common stock per share value (in dollars per share)		$ 2.75		$ 6.50	$ 2.25
Net proceeds from issuance of common stock		$ 26,800,000		$ 80,500,000	$ 24,100,000
Common stock shares outstanding (in shares)				55,300,000		66,480,065	55,921,986
KTB Tumorforschungs GmbH [Member]
Subsequent Event [Line Items]
Stock issued (in shares)			200,000
Fair value of shares issued			$ 800,000