Employee benefit plans - Summary of Actuarial Assumptions Used to Benefit Obligations (Detail) (Foreign Pension Plan Defined Benefit [Member])	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Foreign Pension Plan Defined Benefit [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Discount rate	3.70%	4.90%
Increase in future compensation levels	3.10%	3.10%	3.00%

Expected rate of compensation increases (for pay-related plans).

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (k)(2)

-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph j

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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Data Type:	num:percentItemType
Balance Type:	na
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