Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Examination [Line Items]
Cumulative amount of earnings	$ 400,000
Valuation allowance, deferred tax asset, Increase (Decrease), amount	34,200,000
Interest and penalties related to uncertain tax positions	0.0
Potential benefits, which if recognized, would affect the effective tax rate.	0	$ 400,000	$ 100,000
We Are Cloud, Inc
Income Tax Examination [Line Items]
Net operating loss carryforwards	3,000,000
FRANCE
Income Tax Examination [Line Items]
Net operating loss carryforwards	9,700,000
Domestic Tax Authority
Income Tax Examination [Line Items]
Net operating loss carryforwards	464,500,000
Research and development credit carryforwards	7,400,000
State and Local Jurisdiction
Income Tax Examination [Line Items]
Net operating loss carryforwards	218,400,000
Research and development credit carryforwards	$ 8,300,000