Income taxes (Uncertain Tax Positions) (Details) $ in Thousands	12 Months Ended
Dec. 31, 2016 USD ($)
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning Balance	$ 8,410
Additional based on tax positions related to prior years	1,785
Additional based on tax positions related to current year	6,103
Reduction based on tax positions related to prior years	0
Lapse of statute of limitations	(2,078)
Ending Balance	14,220
Deferred tax benefits on uncertain tax position related to U.S. and non-U.S. income tax	0
Net balance at December 31, 2016	$ 14,220

Deferred Tax Assets, Uncertain Tax Position Domestic and Foreign Tax

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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- Definition

Amount of unrecognized tax benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=65882285&loc=SL6600010-109319

Reference 2: 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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- Definition

Amount of decrease in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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- Definition

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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- Definition

Amount of increase in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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- Definition

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

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- Definition

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

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