Summary of significant accounting policies - Property, Plant and Equipment (Details)	3 Months Ended
Mar. 31, 2014
Minimum
Property, Plant and Equipment [Line Items]
Useful life - years	3 years
Maximum
Property, Plant and Equipment [Line Items]
Useful life - years	15 years

Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

No definition available.

Name:	us-gaap_PropertyPlantAndEquipmentUsefulLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration