Income taxes - Uncertain tax positions for liabilities associated with unrecognized tax benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	$ 7,561	$ 8,106	$ 9,336
Increase in unrecognized tax benefits related to prior years	1,286	351	0
Decrease in unrecognized tax benefits related to prior years	0	(201)	0
Unrecognized tax benefits related to the current year	0	1,237	899
Reductions in unrecognized tax benefits due to lapse of applicable statute of limitations	(1,864)	(1,881)	(1,955)
Increase (decrease) in unrecognized tax benefits due to foreign currency translation	247
Increase (decrease) in unrecognized tax benefits due to foreign currency translation		(51)	(174)
Ending balance	$ 7,230	$ 7,561	$ 8,106

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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 45
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-URI http://asc.fasb.org/extlink&oid=120406818&loc=SL37586934-109318

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- Definition

Amount of decrease in unrecognized tax benefits resulting from foreign currency translation.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
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-Topic 740
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-Paragraph 15A
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Amount of decrease in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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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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