Balance Sheet Components - Property and Equipment, Net (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Gross property and equipment	$ 151,370		$ 151,370		$ 113,109
Less accumulated depreciation and amortization	(58,885)		(58,885)		(39,899)
Total property and equipment, net	92,485		92,485		73,210
Depreciation and amortization expense	7,700	$ 5,000	20,800	$ 13,000
Servers—network infrastructure
Property, Plant and Equipment [Line Items]
Gross property and equipment	75,362		75,362		57,089
Buildings
Property, Plant and Equipment [Line Items]
Gross property and equipment	13,035		13,035		13,035
Construction in progress
Property, Plant and Equipment [Line Items]
Gross property and equipment	7,690		7,690		14,848
Capitalized internal-use software
Property, Plant and Equipment [Line Items]
Gross property and equipment	27,966		27,966		16,344
Depreciation and amortization expense	1,800	$ 1,000	4,600	$ 2,100
Office and computer equipment
Property, Plant and Equipment [Line Items]
Gross property and equipment	12,033		12,033		6,552
Office furniture
Property, Plant and Equipment [Line Items]
Gross property and equipment	5,668		5,668		3,573
Software
Property, Plant and Equipment [Line Items]
Gross property and equipment	990		990		847
Leasehold improvements
Property, Plant and Equipment [Line Items]
Gross property and equipment	8,395		8,395		772
Asset retirement obligation
Property, Plant and Equipment [Line Items]
Gross property and equipment	$ 231		$ 231		$ 49