Convertible Preferred Stock (Details) $ / shares in Units, $ in Thousands				1 Months Ended					12 Months Ended
	Oct. 09, 2018 shares	Sep. 19, 2018	Apr. 30, 2017 $ / shares	Sep. 30, 2018	Oct. 31, 2017 $ / shares shares	Aug. 31, 2017 shares	Jul. 31, 2017 $ / shares shares	May 31, 2017 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares	May 31, 2019 $ / shares
Class of Stock [Line Items]
Stock split, conversion ratio		0.7378		0.7378
Share price of stock issued (in usd per share) | $ / shares												$ 71.00
Preferred stock, convertible, conversion price | $ / shares			$ 10.1338					$ 9.8329
Deemed dividend related to repurchase of convertible preferred stock | $									$ 1,100
Incremental common shares attributable to dilutive effect of conversion of preferred stock									253,361
Repurchase of shares | $										$ 172	$ 7,222
Common Stock
Class of Stock [Line Items]
Stock repurchased during period (in shares)						131,243	1,588,065
Treasury stock acquired, average cost per share | $ / shares							$ 10.23887
Percentage of the original price per share of Series E convertible preferred stock							90.00%
Series E Convertible Preferred Stock
Class of Stock [Line Items]
Issuance of convertible preferred stock, net of issuance costs (in shares)					796,346
Share price of stock issued (in usd per share) | $ / shares					$ 0.00001
Series A Convertible Preferred Stock
Class of Stock [Line Items]
Stock repurchased during period (in shares)										666,920	666,920
Treasury stock acquired, average cost per share | $ / shares										$ 8.00	$ 8.00
Deemed dividend related to repurchase of convertible preferred stock | $									$ 0	$ 0	$ 4,716
Repurchase of shares | $											$ 5,335
Common Stock
Class of Stock [Line Items]
Conversion of convertible preferred stock to common stock upon initial public offering (in shares)									58,264,577
Stock repurchased during period (in shares)										31,681	1,719,308
Issuance of convertible preferred stock, net of issuance costs (in shares)	7,636
SoftBank | Series E Convertible Preferred Stock
Class of Stock [Line Items]
Shares purchased in joint venture (in shares)								38,174,246
Sale of stock, price (usd per share) | $ / shares								$ 8.3936
Aggregate purchase price | $								$ 320,400
Threshold percentage of new shares issued								35.00%
Threshold period after initial closing to issue new shares								70 years