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Marketable Securities and Fair Value Disclosures - Summary of Marketable securities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 3,052
Fair Value	3,050
Short-term available-for-sale securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,052	$ 13,778
Gross Unrealized Losses	(2)	(16)
Fair Value	3,050	13,762
Short-term available-for-sale securities | Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,052	13,778
Gross Unrealized Losses	(2)	(16)
Fair Value	$ 3,050	13,762
Long-term available-for-sale securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		2,355
Gross Unrealized Gains		3
Gross Unrealized Losses		(6)
Fair Value		2,352
Long-term available-for-sale securities | Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		2,355
Gross Unrealized Gains		3
Gross Unrealized Losses		(6)
Fair Value		$ 2,352

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

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