Derivatives and Hedging (Details)	12 Months Ended
	Dec. 31, 2012
Cash flow hedges
Foreign Exchange Risk Management
Foreign currency exposures, maximum average hedging period	2 years
Interest Rate Risk Management
Interest rate fluctuations, maximum hedging period	2 years
Cash flow hedges | Maximum
Foreign Exchange Risk Management
Foreign currency exposures, hedging period	5 years
Not designated as hedging instrument
Foreign Exchange Risk Management
Foreign currency exposures, maximum hedging period	1 year