Estimated Useful Life (Detail)	6 Months Ended
Jun. 30, 2012
Machinery and equipment \| Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	3 years
Machinery and equipment \| Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	7 years
Track on leased properties
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	4 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