Property and Equipment, net - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Property, Plant and Equipment [Line Items]
Amortization and depreciation expense related to property and equipment other than website development costs	$ 7.1	$ 6.4	$ 18.9	$ 12.4
Capitalization of website development costs	15.4	10.3	27.9	20.3
Amortization of website development costs and intangible assets included in technology and development	13.1	11.0	24.9	22.0
Technology and development \| Software Development
Property, Plant and Equipment [Line Items]
Amortization of website development costs and intangible assets included in technology and development	$ 6.0	$ 3.6	$ 11.4	$ 7.0

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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Additions made to capitalized computer software costs during the period.

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Amount of expense charged against earnings to allocate the cost of tangible and intangible assets over their remaining economic lives, classified as other.

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