Net Loss per Share - Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Numerator:
Net loss	$ (25,281)	$ (12,335)	$ (45,875)	$ (24,774)
Accretion of preferred stock to redemption value	(159,453)	3,323	(199,492)	(8,324)
Net loss attributable to common stockholders	$ (184,734)	$ (9,012)	$ (245,367)	$ (33,098)
Denominator:
Weighted-average common shares outstanding - basic and diluted	44,759,435	10,255,078	28,104,372	10,116,021
Net loss per share attributable to common stockholders - basic and diluted	$ (4.13)	$ (0.88)	$ (8.73)	$ (3.27)

The amount of net income or loss for the period per each share in instances when basic and diluted earnings per share are the same amount and reported as a single line item on the face of the financial statements. Basic earnings per share is the amount of net income or loss for the period per each share of common stock or unit outstanding during the reporting period. Diluted earnings per share includes the amount of net income or loss for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities; of income (loss) available to common shareholders.

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Amount of decrease to net income for accretion of temporary equity to its redemption value to derive net income apportioned to common stockholders.

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Average number of shares or units issued and outstanding that are used in calculating basic and diluted earnings per share (EPS).

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