Segment Information - Additional Information (Detail)	3 Months Ended							12 Months Ended
	Mar. 31, 2013 Segment	Mar. 31, 2013 Customer Concentration Risk Sales Revenue, Goods, Net Customer	Mar. 31, 2012 Customer Concentration Risk Sales Revenue, Goods, Net Customer	Mar. 31, 2013 Geographic Concentration Risk Sales Revenue, Goods, Net Country	Mar. 31, 2012 Geographic Concentration Risk Sales Revenue, Goods, Net	Mar. 31, 2012 Geographic Concentration Risk Sales Revenue, Goods, Net GERMANY	Mar. 31, 2013 Geographic Concentration Risk Assets, Total Country	Dec. 31, 2012 Geographic Concentration Risk Assets, Total Country
Segment Reporting Information
Number of operating segments	1
Number Of Individual Country accounted for 10% or more of total revenues				0
Individual Country accounted for 10% or more of total revenues					Germany
Concentration of risk, percentage						10.40%
Number Of Individual Customer accounted for 10% or more of total consolidated revenues		0	0
Number Of Individual country accounted for 10% or more of total consolidated assets							0	0