Derivatives Derivatives not designated as hedging instrument under Generally Accepted Accounting Principals (Details) - Cross Currency Swap € in Thousands	Dec. 31, 2018 EUR (€)
Derivatives designated as hedging instruments
Derivative [Line Items]
Derivative, Notional Amount	€ 174,000
Derivatives not designated as hedging instruments
Derivative [Line Items]
Derivative, Notional Amount	€ 0