Marketable Securities - Summary of Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available For Sale Securities [Line Items]
Marketable securities, Amortized Cost Basis	$ 35,039	$ 38,728
Marketable securities, Unrealized Gains	2	3
Marketable securities, Unrealized Loses	(164)	(163)
Marketable securities, Aggregate Fair Value	34,877	38,568
Short-Term Marketable Securities
Schedule of Available For Sale Securities [Line Items]
Marketable securities, Amortized Cost Basis	20,040	12,988
Marketable securities, Unrealized Gains	2
Marketable securities, Unrealized Loses	(48)	(17)
Marketable securities, Aggregate Fair Value	19,994	12,971
Less: Cash equivalents	(723)	(1,580)
Short-Term Marketable Securities \| Money Market Accounts
Schedule of Available For Sale Securities [Line Items]
Marketable securities, Amortized Cost Basis	723	1,580
Marketable securities, Aggregate Fair Value	723	1,580
Short-Term Marketable Securities \| Corporate Debt Securities
Schedule of Available For Sale Securities [Line Items]
Marketable securities, Amortized Cost Basis	20,040	12,988
Marketable securities, Unrealized Gains	2
Marketable securities, Unrealized Loses	(48)	(17)
Marketable securities, Aggregate Fair Value	19,994	12,971
Long-Term Marketable Securities
Schedule of Available For Sale Securities [Line Items]
Marketable securities, Amortized Cost Basis	14,999	25,740
Marketable securities, Unrealized Gains		3
Marketable securities, Unrealized Loses	(116)	(146)
Marketable securities, Aggregate Fair Value	14,883	25,597
Long-Term Marketable Securities \| Corporate Debt Securities
Schedule of Available For Sale Securities [Line Items]
Marketable securities, Amortized Cost Basis	14,999	25,740
Marketable securities, Unrealized Gains		3
Marketable securities, Unrealized Loses	(116)	(146)
Marketable securities, Aggregate Fair Value	$ 14,883	$ 25,597

This item represents the cost of debt securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
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-Publisher FASB
-Name Accounting Standards Codification
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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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