Debt (Private Placement Notes) (Details) - Unsecured debt - EUR (€)	Dec. 31, 2018	Dec. 31, 2017	Oct. 31, 2013	Jun. 30, 2012	Jul. 27, 2010
Debt Instrument [Line Items]
Debt instrument, face amount			€ 355,000,000	€ 325,000,000
5.00% Notes due 2020
Debt Instrument [Line Items]
Debt instrument, face amount					€ 200,000,000
Interest rate, stated percentage	5.00%	5.00%			5.00%
3.40% Notes due 2022
Debt Instrument [Line Items]
Debt instrument, face amount				€ 150,000,000
Interest rate, stated percentage	3.40%	3.40%		3.40%
4.00% Notes due 2027
Debt Instrument [Line Items]
Debt instrument, face amount				€ 75,000,000
Interest rate, stated percentage	4.00%	4.00%		4.00%
4.00% Notes due 2032
Debt Instrument [Line Items]
Debt instrument, face amount				€ 100,000,000
Interest rate, stated percentage	4.00%	4.00%		4.00%
3.75% Notes due 2033
Debt Instrument [Line Items]
Debt instrument, face amount			€ 100,000,000
Interest rate, stated percentage	3.75%	3.75%	3.75%
3.15% Notes due 2023
Debt Instrument [Line Items]
Debt instrument, face amount			€ 130,000,000
Interest rate, stated percentage	3.15%	3.15%	3.15%
3.15% Notes due 2023
Debt Instrument [Line Items]
Debt instrument, face amount			€ 125,000,000
Interest rate, stated percentage	3.15%	3.15%	3.15%