Fair Value Measurements (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Financial Assets:
Warrant assets	$ 1,013	$ 1,900
Marketable investments	2,621	5,286
Financial Liabilities:
Warrant liability	189	259
Tribute Warrant [Member] | Fair Value, Inputs, Level 1 [Member]
Financial Assets:
Marketable investments	1,057	2,429
Tribute Warrant [Member] | Fair Value, Inputs, Level 3 [Member]
Financial Assets:
Warrant assets	1,013	1,900
Marketable investments	1,564	2,857
Financial Liabilities:
Warrant liability	189	259
Warrant Liability [Member]
Financial Liabilities:
Warrant liability	189	259	$ 421
Marketable Securities [Member] | Tribute Warrant [Member]
Financial Assets:
Warrant assets	1,013	1,900
Marketable investments	2,621	5,286
Financial Liabilities:
Warrant liability	$ 189	$ 259