Income Taxes - Reconciliation of Beginning and Ending Balance of Total Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of beginning and ending balance of total unrecognized tax benefits
Balance, beginning period	$ 27,648	$ 18,440	$ 11,737
Gross increases - tax positions in prior year	3,721	398	1,122
Gross decreases - tax positions in prior period	(2,896)	0	(50)
Gross increases - tax positions in current period	5,796	8,810	5,673
Gross decreases - tax positions in current period	0	0	0
Lapse of statute of limitations	(1,078)	0	(42)
Settlements	(5,600)	0	0
Balance, end of period	$ 27,591	$ 27,648	$ 18,440

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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- Definition

Amount of unrecognized tax benefits.

+ References

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Amount of decrease in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return.

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Amount of decrease in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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Amount of decrease in unrecognized tax benefits resulting from settlements with taxing authorities.

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Amount of increase in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return.

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Amount of increase in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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Amount of decrease in unrecognized tax benefits resulting from lapses of applicable statutes of limitations.

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