Business Segment Information - Reconciliation of Segment Profit to Income Before Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Reconciliation of segment profit to income before income taxes
Income before income taxes	$ 40,961	$ 44,975	$ 70,713	$ 84,838
Stock compensation expense	9,320	10,323	27,405	31,834
Changes in fair value of contingent consideration	148	(834)	451	(631)
Non-controlling interest segment (profit) loss		(788)		59
Depreciation and amortization	33,047	28,189	97,302	82,896
Interest expense	8,990	7,663	26,034	16,711
Interest and other income	(4,139)	(1,781)	(9,978)	(3,801)
Segment Profit	$ 88,327	$ 87,747	$ 211,927	$ 211,906

The noncontrolling portion of segment profit that is excluded from the computation of segment profit.

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- Definition

Non-GAAP measure representing aggregate segment revenue less cost of goods and services, other operating and non-operating expenses, and non-controlling interest.

+ References

No definition available.

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- Definition

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

+ References

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- Definition

Amount of increase (decrease) in the value of a contingent consideration liability, including, but not limited to, differences arising upon settlement.

+ References

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-Publisher FASB
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- Definition

The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.

+ References

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- Definition

Amount of income (loss) from continuing operations before deduction of income tax expense (benefit) and income (loss) attributable to noncontrolling interest, and addition of income (loss) from equity method investments.

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- Definition

The amount of interest income and other income recognized during the period. Included in this element is interest derived from investments in debt securities, cash and cash equivalents, and other investments which reflect the time value of money or transactions in which the payments are for the use or forbearance of money and other income from ancillary business-related activities (that is, excluding major activities considered part of the normal operations of the business).

+ References

No definition available.

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- Definition

Amount of the cost of borrowed funds accounted for as interest expense.

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- References

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