For contingent consideration arrangements recognized in connection with a business combination, this element represents an estimate of the high-end of the potential range (undiscounted) of the consideration which may be paid.

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Amount of liability recognized arising from contingent consideration in a business combination.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
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-Publisher FASB
-Name Accounting Standards Codification
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-Publisher FASB
-Name Accounting Standards Codification
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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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Measure of dispersion, in percentage terms (for instance, the standard deviation or variance), for a given stock price.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Paragraph 2
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Interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value. For example, but not limited to, weighted average cost of capital (WACC), cost of capital, cost of equity and cost of debt.

+ References

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Amount of gain (loss) recognized on the income statement for financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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- Definition

Amount of purchases of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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-Publisher FASB
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Amount of settlements of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Summary of Significant Accounting Policies - Fair Value Measurements (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Acquisitions that have maximum payouts	$ 139,500,000		$ 139,500,000
Fair Value, Inputs, Level 3 \| Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration, liability	70,900,000		70,900,000		$ 19,500,000
Fair Value, Inputs, Level 3 \| Fair Value, Measurements, Recurring \| Acquisition Without Maximum Earn-out
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration, liability	1,000,000		1,000,000
Contingent consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration, additions from new business combinations	51,100,000	$ 3,300,000	51,100,000	$ 18,700,000
Contingent consideration, payments	0	0	0
Change in fair value of contingent consideration	$ 0	$ 0	$ 0	$ 0
Contingent consideration \| Fair Value, Inputs, Level 3 \| Fair Value, Measurements, Recurring \| Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value inputs discount rate			1.10%
Fair value inputs expected volatility rate			25.00%
Contingent consideration \| Fair Value, Inputs, Level 3 \| Fair Value, Measurements, Recurring \| Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value inputs discount rate			1.80%
Fair value inputs expected volatility rate			29.60%