Liquidity and Capital Resources (Details) - USD ($)			3 Months Ended
	Feb. 06, 2016	Feb. 05, 2016	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015	Dec. 31, 2014
Estimated projected expenditure [Line Items]
Cash and cash equivalents			$ 68,162,754	$ 28,052,543	$ 22,261,372	$ 32,218,905
Amount received under long-term loan agreement			24,012,078	$ 0
Hercules Technology Growth Capital, Inc. and Hercules Technology III, L.P. [Member]
Estimated projected expenditure [Line Items]
Maximum borrowing capacity under long-term loan agreement	$ 40,000,000	$ 40,000,000
Amount received under long-term loan agreement	25,000,000	$ 25,000,000
Remaining borrowing capacity of long term loan	$ 15,000,000
Currently projected expenditures for clinical programs			63,000,000
Milestone payment to licensor			1,500,000
Interest and payments on term loan			3,100,000
Hercules Technology Growth Capital, Inc. and Hercules Technology III, L.P. [Member] | Aldoxorubicin [Member]
Estimated projected expenditure [Line Items]
Currently projected expenditures for clinical programs			32,600,000
Hercules Technology Growth Capital, Inc. and Hercules Technology III, L.P. [Member] | Other Programs [Member]
Estimated projected expenditure [Line Items]
Currently projected expenditures for clinical programs			5,600,000
Hercules Technology Growth Capital, Inc. and Hercules Technology III, L.P. [Member] | General Operation [Member]
Estimated projected expenditure [Line Items]
Currently projected expenditures for clinical programs			5,400,000
Hercules Technology Growth Capital, Inc. and Hercules Technology III, L.P. [Member] | Other General and Administrative Expenses [Member]
Estimated projected expenditure [Line Items]
Currently projected expenditures for clinical programs			$ 16,300,000