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Marketable Securities (Details) - USD ($)	Jun. 30, 2017	Dec. 31, 2016
Available-for-sale securities held
Amortized Cost	$ 32,519,000	$ 44,070,000
Unrealized Gains	0	4,000
Unrealized Losses	(17,000)	(8,000)
Fair Value	32,502,000	44,066,000
Maturities
Available-for-sale securities with remaining maturities greater than one year	0
U.S. government agency securities and treasuries
Available-for-sale securities held
Amortized Cost	32,519,000	42,516,000
Unrealized Gains	0	4,000
Unrealized Losses	(17,000)	(8,000)
Fair Value	$ 32,502,000	42,512,000
Corporate debt securities
Available-for-sale securities held
Amortized Cost		1,554,000
Unrealized Gains		0
Unrealized Losses		0
Fair Value		$ 1,554,000

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Available-for-sale debt securities maturing greater than one year.

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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