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Marketable Securities and Fair Value Disclosures (Details Textual) - USD ($)	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Transfers of assets between fair value hierarchy levels	$ 0
Fair Value Measurements, Recurring | Level 1 | Money Market Funds | Commercial paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents consisting of money market funds and commercial paper	$ 8,100,000	$ 7,700,000

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Fair value assets between hierarchy levels transfers amount.

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- Definition

Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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