Supplemental Cash Flow Information (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash Flow Supplemental Disclosures [Line Items]
Interest paid	$ 3,065	$ 5,773	$ 3,362
Income taxes net of refunds	115,301	$ 48,056	$ 99,006
Common stock issued for Alert Labs Inc.	$ 6,846

The amount of cash paid during the current period to foreign, federal, state, and local authorities as taxes on income, net of any cash received during the current period as refunds for the overpayment of taxes.

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Amount of cash paid for interest, including, but not limited to, capitalized interest and payment to settle zero-coupon bond attributable to accreted interest of debt discount and debt instrument with insignificant coupon interest rate in relation to effective interest rate of borrowing attributable to accreted interest of debt discount; classified as operating and investing activities.

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Value of stock issued pursuant to acquisitions during the period.

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Cash Flow Supplemental Disclosures [Line Items]

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