Financial Instruments and Fair Value Measurement - Narrative (Details)	12 Months Ended
	Dec. 31, 2017 USD ($) derivate investment	Dec. 31, 2016 USD ($) investment	Dec. 31, 2015 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments carried at fair value	$ 72,200,000	$ 67,600,000
Purchase of trading securities held-for-investment	2,100,000	1,400,000
Proceeds from the sale of trading securities held-for-investment	$ 300,000	1,600,000
Number of foreign exchange contracts held (foreign_exchange_contract) | derivate	46
Hedge ineffectiveness with respect to forward exchange cash flow hedges	$ 0	0	$ 0
Long-term debt	987,100,000	990,500,000
Long-term debt, fair value	1,013,200,000	$ 1,017,800,000
Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, notional amount	400,000.0
Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, notional amount	$ 1,500,000.0
Unobservable inputs for which little or no market data exists (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of available-for-sale securities (investment) | investment	1	1
Customer Concentration Risk
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Concentration risk, percentage	40.00%