Preferred Stock - Tabular Disclosure (Details) - USD ($) $ in Thousands	Jun. 30, 2018	May 07, 2018	Dec. 31, 2017
Convertible preferred stock
Convertible preferred stock, shares authorized (in shares)	25,000,000
Convertible preferred stock, shares issued (in shares)	0
Convertible preferred stock, shares outstanding (in shares)	0
Series A convertible preferred stock
Convertible preferred stock
Convertible preferred stock, shares authorized (in shares)	0	8,800,000	8,800,000
Convertible preferred stock, shares issued (in shares)	0	4,212,191	3,851,806
Convertible preferred stock, shares outstanding (in shares)	0	4,212,191	3,851,806
Convertible preferred stock	$ 0	$ 1,721	$ 1,510
Convertible preferred stock, common stock issuable upon conversion (in shares)		1,709,063
Redeemable convertible preferred stock
Convertible preferred stock
Convertible preferred stock, shares authorized (in shares)	0	94,101,207	94,101,207
Convertible preferred stock, shares issued (in shares)	0	88,741,194	88,741,194
Convertible preferred stock, shares outstanding (in shares)	0	88,741,194	88,741,194
Convertible preferred stock	$ 0	$ 532,696	$ 333,204
Convertible preferred stock, liquidation preference, value		$ 272,506	$ 272,506
Convertible preferred stock, common stock issuable upon conversion (in shares)		44,370,560
Redeemable convertible preferred stock, Series B
Convertible preferred stock
Convertible preferred stock, shares authorized (in shares)		24,673,917
Convertible preferred stock, shares issued (in shares)		24,665,856
Convertible preferred stock, shares outstanding (in shares)		24,665,856
Convertible preferred stock		$ 10,442
Convertible preferred stock, liquidation preference, value		$ 22,534
Convertible preferred stock, common stock issuable upon conversion (in shares)		12,332,924
Redeemable convertible preferred stock, Series C
Convertible preferred stock
Convertible preferred stock, shares authorized (in shares)		13,283,366
Convertible preferred stock, shares issued (in shares)		10,105,400
Convertible preferred stock, shares outstanding (in shares)		10,105,400
Convertible preferred stock		$ 9,540
Convertible preferred stock, liquidation preference, value		$ 11,447
Convertible preferred stock, common stock issuable upon conversion (in shares)		5,052,697
Redeemable convertible preferred stock, Series D
Convertible preferred stock
Convertible preferred stock, shares authorized (in shares)		11,876,688
Convertible preferred stock, shares issued (in shares)		11,541,688
Convertible preferred stock, shares outstanding (in shares)		11,541,688
Convertible preferred stock		$ 109,646
Convertible preferred stock, liquidation preference, value		$ 34,500
Convertible preferred stock, common stock issuable upon conversion (in shares)		5,770,841
Redeemable convertible preferred stock, Series E
Convertible preferred stock
Convertible preferred stock, shares authorized (in shares)		12,219,202
Convertible preferred stock, shares issued (in shares)		12,219,202
Convertible preferred stock, shares outstanding (in shares)		12,219,202
Convertible preferred stock		$ 116,082
Convertible preferred stock, liquidation preference, value		$ 48,999
Convertible preferred stock, common stock issuable upon conversion (in shares)		6,109,588
Redeemable convertible preferred stock, Series E-1
Convertible preferred stock
Convertible preferred stock, shares authorized (in shares)		6,415,146
Convertible preferred stock, shares issued (in shares)		4,739,463
Convertible preferred stock, shares outstanding (in shares)		4,739,463
Convertible preferred stock		$ 45,025
Convertible preferred stock, liquidation preference, value		$ 3,991
Convertible preferred stock, common stock issuable upon conversion (in shares)		2,369,729
Redeemable convertible preferred stock, Series F
Convertible preferred stock
Convertible preferred stock, shares authorized (in shares)		25,632,888
Convertible preferred stock, shares issued (in shares)		25,469,585
Convertible preferred stock, shares outstanding (in shares)		25,469,585
Convertible preferred stock		$ 241,961
Convertible preferred stock, liquidation preference, value		$ 151,035
Convertible preferred stock, common stock issuable upon conversion (in shares)		12,734,781

Number of shares issued for each share of convertible preferred stock that is converted.

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Carrying amount, attributable to parent, of an entity's issued and outstanding stock which is not included within permanent equity. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. Includes stock with a put option held by an ESOP and stock redeemable by a holder only in the event of a change in control of the issuer.

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The aggregate liquidation preference (or restrictions) of stock classified as temporary equity that has a preference in involuntary liquidation considerably in excess of the par or stated value of the shares. The liquidation preference is the difference between the preference in liquidation and the par or stated values of the share. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. If convertible, the issuer does not control the actions or events necessary to issue the maximum number of shares that could be required to be delivered under the conversion option if the holder exercises the option to convert the stock to another class of equity. If the security is a warrant or a rights issue, the warrant or rights issue is considered to be temporary equity if the issuer cannot demonstrate that it would be able to deliver upon the exercise of the option by the holder in all cases. Includes stock with put option held by ESOP and stock redeemable by holder only in the event of a change in control of the issuer.

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The maximum number of securities classified as temporary equity that are permitted to be issued by an entity's charter and bylaws. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. If convertible, the issuer does not control the actions or events necessary to issue the maximum number of shares that could be required to be delivered under the conversion option if the holder exercises the option to convert the stock to another class of equity. If the security is a warrant or a rights issue, the warrant or rights issue is considered to be temporary equity if the issuer cannot demonstrate that it would be able to deliver upon the exercise of the option by the holder in all cases. Includes stock with put option held by ESOP and stock redeemable by holder only in the event of a change in control of the issuer.

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