Fair Value of Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Assets
Marketable securities - mutual and exchange traded funds	$ 1,256	$ 2,700
Investments	10,070	10,345
Liabilities
Fair value of warrant liabilities	135	82
Hoth [Member]
Assets
Investments		9,214
Quoted prices in active markets (Level 1) [Member]
Assets
Marketable securities - mutual and exchange traded funds	1,256	2,700
Investments	8,939
Liabilities
Fair value of warrant liabilities
Significant other observable inputs (Level 2) [Member]
Assets
Marketable securities - mutual and exchange traded funds
Investments
Liabilities
Fair value of warrant liabilities
Significant unobservable inputs (Level 3) [Member]
Assets
Marketable securities - mutual and exchange traded funds
Investments		9,214
Liabilities
Fair value of warrant liabilities		82
Significant unobservable inputs (Level 3) [Member] | Hoth [Member]
Assets
Investments		$ 9,214
Significant unobservable inputs (Level 3) [Member] | Other investments [Member]
Liabilities
Fair value of warrant liabilities	$ 135