Income Taxes - Effective Income Tax Rate Reconciliation (Details)	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Statutory tax rate	35.00%	35.00%
Permanent differences	(6.40%)	(1.50%)
Other	(0.50%)	(0.40%)
General business credits	15.10%	2.40%
Change in valuation allowance	15.60%	(35.50%)
Tax Reform - tax rate change	(58.80%)	0.00%
Effective tax rate	0.00%	0.00%

Effective Income Tax Reconciliation, Permanent Differences, Percent

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Effective Income Tax Reconciliation, Tax Credit, General Business Credits, Percent

+ References

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
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-Section S99
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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
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-Name Accounting Standards Codification
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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to changes in the valuation allowance for deferred tax assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 13
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-Name Accounting Standards Codification
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-Section S99
-Paragraph 1
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