Investments - Schedule of Available-for-sale Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Investment [Line Items]
Amortized Cost	$ 72,682	$ 58,595
Gross Unrealized Gains	0	7
Gross Unrealized Losses	(73)	(83)
Fair Value	72,609	58,519
Certificates of deposit
Investment [Line Items]
Amortized Cost	12,410	7,257
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	12,410	7,257
US Treasury securities
Investment [Line Items]
Amortized Cost	7,041	8,553
Gross Unrealized Gains	0	1
Gross Unrealized Losses	(16)	(10)
Fair Value	7,025	8,544
US Agency securities
Investment [Line Items]
Amortized Cost	4,516	4,514
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(17)	(13)
Fair Value	4,499	4,501
Commercial paper
Investment [Line Items]
Amortized Cost	5,141
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Fair Value	5,141
Asset-backed securities
Investment [Line Items]
Amortized Cost	5,027	5,554
Gross Unrealized Gains	0	3
Gross Unrealized Losses	(1)	0
Fair Value	5,026	5,557
Corporate notes and bonds
Investment [Line Items]
Amortized Cost	38,547	32,717
Gross Unrealized Gains	0	3
Gross Unrealized Losses	(39)	(60)
Fair Value	$ 38,508	$ 32,660

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- Definition

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
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- Definition

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

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-Publisher FASB
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-Topic 320
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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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This item represents the cost of debt and equity 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.

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