Investments and Fair Value Measurements (Details) - USD ($)	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Dec. 31, 2018
Cash, cash equivalents and investments [Abstract]
Cash	$ 27,837,000	$ 27,837,000	$ 16,526,000
Cash equivalents [Abstract]
Total cash and cash equivalents	27,837,000	27,837,000	16,526,000
Amortized Cost	10,641,000	10,641,000	22,930,000
Cash, cash equivalents and investments, amortized costs	38,478,000	38,478,000	39,456,000
Gross Unrealized Gain	7,000	7,000
Gross Unrealized (Loss)	(13,000)	(13,000)	(84,000)
Fair Value	10,635,000	10,635,000	22,846,000
Cash, cash equivalents and investments, amortized costs		38,472,000	39,372,000
Contractual maturities on investments, amortized cost basis [Abstract]
Due within 1 year	6,109,000	6,109,000	22,210,000
Due after 1 through 5 years	4,532,000	4,532,000	720,000
Investments, amortized cost	10,641,000	10,641,000	22,930,000
Contractual maturities on investments, fair value basis [Abstract]
Due within 1 year	6,116,000	6,116,000	22,129,000
Due after 1 through 5 years	4,519,000	4,519,000	717,000
Investments, fair value	10,635,000	10,635,000	22,846,000
Transfers between fair value measurements	0	0
Total Investments
Cash equivalents [Abstract]
Amortized Cost	10,641,000	10,641,000	22,930,000
Gross Unrealized Gain	7,000	7,000
Gross Unrealized (Loss)	(13,000)	(13,000)	(84,000)
Fair Value	10,635,000	10,635,000	22,846,000
Contractual maturities on investments, amortized cost basis [Abstract]
Investments, amortized cost	10,641,000	10,641,000	22,930,000
Contractual maturities on investments, fair value basis [Abstract]
Investments, fair value	10,635,000	10,635,000	22,846,000
Certificates of Deposit [Member]
Cash equivalents [Abstract]
Amortized Cost	3,600,000	3,600,000	4,508,000
Gross Unrealized Gain	2,000	2,000
Gross Unrealized (Loss)			(27,000)
Fair Value	3,602,000	3,602,000	4,481,000
Contractual maturities on investments, amortized cost basis [Abstract]
Investments, amortized cost	3,600,000	3,600,000	4,508,000
Contractual maturities on investments, fair value basis [Abstract]
Investments, fair value	3,602,000	3,602,000	4,481,000
Corporate Bonds [Member]
Cash equivalents [Abstract]
Amortized Cost	7,041,000	7,041,000	18,422,000
Gross Unrealized Gain	5,000	5,000
Gross Unrealized (Loss)	(13,000)	(13,000)	(57,000)
Fair Value	7,033,000	7,033,000	18,365,000
Contractual maturities on investments, amortized cost basis [Abstract]
Investments, amortized cost	7,041,000	7,041,000	18,422,000
Contractual maturities on investments, fair value basis [Abstract]
Investments, fair value	$ 7,033,000	$ 7,033,000	$ 18,365,000