Income taxes - uncertain tax positions for liabilities associated with unrecognized tax benefits (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	$ 55,771us-gaap_UnrecognizedTaxBenefits	$ 62,108us-gaap_UnrecognizedTaxBenefits	$ 75,026us-gaap_UnrecognizedTaxBenefits
Increase in unrecognized tax benefits related to prior years	0	0	1,110
Decrease in unrecognized tax benefits related to prior years	0	0	(6,134)
Unrecognized tax benefits related to the current year	910	1,838	4,256
Reductions in unrecognized tax benefits due to settlements	(132)	0	(8,816)
Reductions in unrecognized tax benefits due to lapse of applicable statute of limitations	(3,235)	(8,433)	(3,503)
Increase (decrease) in unrecognized tax benefits due to foreign currency translation	(2,230)	258	169
Ending balance	$ 51,084us-gaap_UnrecognizedTaxBenefits	$ 55,771us-gaap_UnrecognizedTaxBenefits	$ 62,108us-gaap_UnrecognizedTaxBenefits

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Amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Unrecognized Tax Benefit

-URI http://asc.fasb.org/extlink&oid=6527854

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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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-Publisher FASB

-Name Accounting Standards Codification

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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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The net amount of all increases and decreases in unrecognized tax benefits for the period.

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

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