Commitments and contingencies - Settlement of litigation (Details) (Infringement litigation of "Cipriani", USD $) In Thousands, unless otherwise specified	1 Months Ended
Mar. 31, 2012	Dec. 31, 2012
Infringement litigation of "Cipriani"
Litigation settlement
Amount received from defendants	$ 3,947
Amount receivable from defendants in installments	9,833
Period for receivable amount from defendants in installments (in years)	5 years
Amount receivable from defendants not yet recognized		$ 5,224

Cash received for the settlement of litigation during the current period.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 27

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 25

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3536-108585

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration