Income taxes (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended
Jun. 29, 2014
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	$ 57,324
Additions based on tax positions related to the current year	3,744
Additions for tax positions of prior years	75
Reductions for tax positions of prior years	(4,315)
Reductions due to lapse of statutes of limitations	(574)
Ending balance	$ 56,254

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

+ References

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-Name Accounting Standards Codification

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

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