Goodwill and Intangible Assets, Net - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Finite Lived Intangible Assets [Line Items]
Weighted-average remaining useful lives of acquired intangible assets			4 years 4 months 24 days
Amortization Expense	$ 16.5	$ 34.1	$ 6.0	$ 10.6
Trademarks, Branding and Domain Names [Member]
Finite Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets	$ 6.1		$ 6.1		$ 6.1
Weighted-average remaining useful lives of acquired intangible assets			6 years 3 months 18 days
Developed Technology [Member]
Finite Lived Intangible Assets [Line Items]
Weighted-average remaining useful lives of acquired intangible assets			4 years
Noncompetition Agreements [Member]
Finite Lived Intangible Assets [Line Items]
Weighted-average remaining useful lives of acquired intangible assets			1 year 6 months