Income Taxes - Carryforwards (Details) $ in Millions	Dec. 31, 2017 USD ($)
State
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 32.0
Income tax credit carryforwards	0.9
Switzerland
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 0.8

Amount of operating loss carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32559-109319

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The amount of the tax credit carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

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