Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

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Amount before tax of foreign currency transaction realized and unrealized gain (loss) recognized in the income statement.

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The net gain (loss) during the reporting period due to ineffectiveness in interest rate cash flow hedges. Recognized in earnings.

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Financial Instruments (Narrative) (Details) - USD ($)	12 Months Ended
Financial Instruments (Narrative) (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2017	Jun. 08, 2015
Derivatives, Fair Value [Line Items]
Amount of cash flow hedge ineffectiveness	$ 0
Foreign exchange contract
Derivatives, Fair Value [Line Items]
Derivative amount	157,300,000	$ 130,500,000
Realized and unrealized foreign currency transaction gain (loss)	(8,000,000)	(6,300,000)	$ 700,000
Interest rate swap 2
Derivatives, Fair Value [Line Items]
Derivative amount	$ 1,000,000,000.0	$ 750,000,000
1.00% Notes
Derivatives, Fair Value [Line Items]
Debt instrument, interest rate (as a percent)	1.00%
1.625% Notes
Derivatives, Fair Value [Line Items]
Debt instrument, interest rate (as a percent)	1.625%	1.625%
Convertible Debt \| 1.00% Notes
Derivatives, Fair Value [Line Items]
Debt instrument, interest rate (as a percent)	1.00%	1.00%			1.00%
Convertible Debt \| 1.625% Notes
Derivatives, Fair Value [Line Items]
Debt instrument, interest rate (as a percent)	1.625%	1.625%		1.625%