Income taxes - uncertain tax positions for liabilities associated with unrecognized tax benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	$ 9,336	$ 15,054	$ 34,381
Increase in unrecognized tax benefits related to prior years	0	0	0
Decrease in unrecognized tax benefits related to prior years	0	0	(13,083)
Unrecognized tax benefits related to the current year	899	895	705
Reductions in unrecognized tax benefits due to settlements	0	0	(2,121)
Reductions in unrecognized tax benefits due to lapse of applicable statute of limitations	(1,955)	(6,813)	(4,840)
Increase (decrease) in unrecognized tax benefits due to foreign currency translation	(174)	200	12
Ending balance	$ 8,106	$ 9,336	$ 15,054

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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Amount of unrecognized tax benefits.

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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 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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