Financial Instruments - Derivatives and Hedging (Details) € in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2017 EUR (€)	Dec. 31, 2016 USD ($)
Foreign Exchange Forward
Derivative Instruments, Gain (Loss) [Line Items]
Derivative notional amount	$ 31.8		$ 42.0
Derivative remaining maturity	1 year
Embedded Derivative Financial Instruments
Derivative Instruments, Gain (Loss) [Line Items]
Derivative notional amount	$ 9.7		9.9
Commodity Contract
Derivative Instruments, Gain (Loss) [Line Items]
Derivative liability, current			0.0
Notes Payable to Banks | USD Notes | Interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Derivative notional amount	$ 1,140.0
Interest rate swap rate (as a percent)	1.96%	1.96%
Notes Payable to Banks | Euro Notes | Interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Derivative notional amount | €		€ 279
Interest rate swap rate (as a percent)	1.20%	1.20%
Not Designated as Hedging Instrument | Foreign Exchange Forward
Derivative Instruments, Gain (Loss) [Line Items]
Derivative notional amount	$ 615.0		$ 552.0
Derivative remaining maturity	1 year
Designated as Hedging Instrument | Interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) to be reclassified during next 12 months	$ 2.8