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Income taxes - Narrative (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Effective tax rate (in percentage)	17.30%	22.60%	21.90%	22.30%
Unrecognized tax benefits	$ 28,385		$ 28,385		$ 34,300
Unrecognized tax benefits that would impact effective tax rate	28,385		28,385
Unrecognized tax benefits, interest on income taxes accrued	2,883		2,883		6,369
Accrued penalties	$ 869		869		900
Unrecognized tax benefits, excluding exchange rate differences for interest recognized			$ (3,400)		$ 662

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Unrecognized tax benefits interest on income taxes expense benefit.

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
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Amount of unrecognized tax benefits.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 45
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Amount of statutory penalties accrued for a tax position claimed or expected to be claimed by the entity, in its tax return.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
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-Paragraph 15
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Amount of interest expense accrued for an underpayment of income taxes.

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The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate.

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