Investments - Schedule of Available-for-sale Securities Reconciliation (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 11,563,000	$ 1,625,000
Unrealized Gain	1,000
Unrealized Loss	(40,000)	(11,000)
Fair Value	11,524,000	1,614,000
Short-term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	1,285,000	115,000
Unrealized Gain	1,000
Unrealized Loss
Fair Value	1,286,000	115,000
Short-term Investments [Member] | U.S. Treasury Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	1,065,000	40,000
Unrealized Gain	1,000
Unrealized Loss
Fair Value	1,066,000	40,000
Short-term Investments [Member] | Corporate Bonds and Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	220,000	25,000
Unrealized Gain
Unrealized Loss
Fair Value	220,000	25,000
Short-term Investments [Member] | Government Agency Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost		50,000
Unrealized Gain
Unrealized Loss
Fair Value		50,000
Long-term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	10,278,000	1,510,000
Unrealized Gain
Unrealized Loss	(40,000)	(11,000)
Fair Value	10,238,000	1,499,000
Long-term Investments [Member] | U.S. Treasury Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	3,718,000	1,027,000
Unrealized Gain
Unrealized Loss	(14,000)	(7,000)
Fair Value	3,704,000	1,020,000
Long-term Investments [Member] | Corporate Bonds and Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	2,630,000	383,000
Unrealized Gain
Unrealized Loss	(14,000)	(3,000)
Fair Value	2,616,000	380,000
Long-term Investments [Member] | Government Agency Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	3,930,000	100,000
Unrealized Gain
Unrealized Loss	(12,000)	(1,000)
Fair Value	$ 3,918,000	$ 99,000