Summary of Significant Accounting Policies (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Summary of Significant Accounting Policies [Line Items]
Short-term investments - debt securities	$ 93,756,000			$ 33,642,000
Investment in common stock	4,116,000			5,395,000
Investment warrants	1,367,000			2,064,000
Patent acquisition expenses	0	$ 4,000,000
Available-for-sale Securities, Amortized Cost Basis	93,464,000			33,643,000
Debt Securities, Available-for-sale, Unrealized Gain	294,000			18,000
Debt Securities, Available-for-sale, Unrealized Loss	(2,000)			(19,000)
Available-for-sale Securities, Gross Unrealized Gain	302,000			45,000
Available-for-sale Securities, Gross Unrealized Loss	(8,000)			(423,000)
Available-for-sale Securities	94,587,000			36,654,000
Investments at fair value	5,483,000			7,459,000
Unrealized Gain (Loss) on Investments - Common Stock	7,605,000	(33,450,000)
Unrealized Gain (Loss) on Investment - Warrants	(697,000)	(7,647,000)
Fair Value of Profits Interest	591,000			591,000
Non-cash stock compensation - profits interests	0	(1,728,000)
Change in fair value of investment, net	6,908,000	(41,097,000)
Loss on Sale of Investments	(5,590,000)	$ 0		(19,100,000)
Available-for-sale Equity Securities, Amortized Cost Basis	829,000			3,389,000
Trading Securities, Unrealized Holding Gain	8,000			27,000
Available-for-sale Equity Securities, Gross Unrealized Loss			$ (6,000)	(404,000)
Short-term investments - equity securities	831,000			3,012,000
Available-for-sale Securities, Amortized Cost Basis	$ 94,293,000			37,032,000
Effective tax rate	(8.00%)	1.00%
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	$ (4,084,000)	$ (31,920,000)
Minimum [Member]
Summary of Significant Accounting Policies [Line Items]
Useful life of patents and patent rights	1 year
Maximum [Member]
Summary of Significant Accounting Policies [Line Items]
Useful life of patents and patent rights	5 years
Fair Value, Inputs, Level 1 [Member]
Summary of Significant Accounting Policies [Line Items]
Short-term investments	$ 4,947,000			8,407,000
Fair Value, Inputs, Level 2 [Member]
Summary of Significant Accounting Policies [Line Items]
Short-term investments	$ 95,123,000			$ 35,706,000