Additional tax liability, unremitted foreign earnings.

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Number of customers.

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Significant accounting policies.

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Amount charged to advertising expense for the period, which are expenses incurred with the objective of increasing revenue for a specified brand, product or product line.

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Amount before accumulated amortization of capitalized costs for computer software, including but not limited to, acquired and internally developed computer software.

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- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

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Expected dividends to be paid to holders of the underlying shares or financial instruments (expressed as a percentage of the share or instrument's price).

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Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to repatriation of foreign earnings.

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Amount of cumulative effect of the change in accounting principle or new accounting pronouncement on retained earnings or other components of equity or net assets in the statement of financial position as of the beginning of the earliest period presented.

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Amount of the effect of a change in accounting principle on net income.

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Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

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Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017 USD ($) Customer Segment	Dec. 31, 2016 USD ($) Customer	Dec. 31, 2015 USD ($) Customer	Oct. 10, 2017 USD ($)	Jan. 01, 2017 USD ($)
Significant Accounting Policies [Line Items]
Advertising costs	$ 107,200,000	$ 75,500,000	$ 64,400,000
Expected dividend yield	0.00%
Valuation allowance related to deferred tax assets	$ 4,803,000	1,610,000
Tax liability related to one-time tax on unremitted foreign earnings	363,000
Additional tax liability, unremitted foreign earnings	0
Goodwill	589,862,000	436,455,000	396,220,000	$ 153,407,000
Goodwill Impairment	$ 0	$ 0	$ 0
Number of reportable segment \| Segment	1
ASU 2017-04
Significant Accounting Policies [Line Items]
Goodwill Impairment	$ 0
ASU 2016-09
Significant Accounting Policies [Line Items]
Cumulative-effect adjustment for previously unrecognized excess tax benefits					$ 2,600,000
ASU 2016-09 \| Income Tax (Benefit) Expense
Significant Accounting Policies [Line Items]
Recognized excess tax benefits from stock-based compensation	$ 7,100,000
Customer Concentration Risk \| Revenue
Significant Accounting Policies [Line Items]
Number of customers accounted \| Customer	0	0	0
Concentration risk percentage	1.00%	1.00%	1.00%
Customer Concentration Risk \| Accounts receivable
Significant Accounting Policies [Line Items]
Number of customers accounted \| Customer	0	0	0
Concentration risk percentage	10.00%	10.00%	10.00%
Developed software
Significant Accounting Policies [Line Items]
Capitalized cost	$ 26,000,000	$ 15,600,000	$ 8,000,000
Tax Cuts and Jobs Act
Significant Accounting Policies [Line Items]
Tax liability related to one-time tax on unremitted foreign earnings	363,000
Tax Cuts and Jobs Act \| U K Subsidiary
Significant Accounting Policies [Line Items]
Tax liability related to one-time tax on unremitted foreign earnings	$ 363,000