Fair Value Measurements (Details 3) - USD ($) $ in Thousands		12 Months Ended
	Oct. 06, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Warrants Not Settleable in Cash, Fair Value Disclosure			$ 5,497
Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Warrants, Acquired From Acquisition	$ 5,552		4,914
Gain on Sale of Investments		$ 2,532	1,402	$ 530
Proceeds from Issuance of Warrants		(3,093)	(1,894)	(1,529)
Stock and Warrants Issued During Period, Value, Preferred Stock and Warrants		$ 1,407	1,911	363
Equity Warrants Transfers to Available For Sale Securities			(836)	2
Warrants Not Settleable in Cash, Fair Value Disclosure			$ 5,497	$ 4,914