Short-term Debt and Credit Lines (Revolving Loan Facility and Credit Lines) (Details)			12 Months Ended
	Dec. 31, 2014 USD ($)	Apr. 30, 2014 USD ($)	Dec. 31, 2014 Line of Credit	Apr. 30, 2014 Line of Credit USD ($)	Dec. 31, 2013 Line of Credit	May 31, 2013 Line of Credit USD ($)	May 31, 2012 Line of Credit USD ($)	May 30, 2012 Line of Credit USD ($)	Apr. 30, 2014 Foreign Line of Credit USD ($)	Dec. 31, 2014 Revolving Credit Facility Euro-Based Revolving Loan Facility USD ($)	Dec. 31, 2014 Revolving Credit Facility Euro-Based Revolving Loan Facility EUR (€)	Dec. 31, 2013 Revolving Credit Facility Euro-Based Revolving Loan Facility USD ($)	Dec. 31, 2013 Revolving Credit Facility Euro-Based Revolving Loan Facility EUR (€)	Dec. 31, 2014 Revolving Credit Facility Line of Credit EUR (€)
Line of Credit Facility
Revolving loan facility										$ 4,500,000		$ 4,800,000
Maximum borrowing capacity				105,000,000.0			125,000,000.0	90,000,000.0		4,800,000	4,000,000	5,500,000	4,000,000	37,500,000.0
Interest rate (as a percent)			1.25%		1.25%					1.51%	1.51%	1.72%	1.72%
Line of credit period (in years)			3 years
Expected decrease in line of credit facility						16,700,000
Maximum amount issuable		70,000,000.0							5,000,000.0
Current borrowing capacity	$ 33,600,000