Derivative Financial Instruments (Schedule Of Notional Amounts Of Outstanding Derivative Positions (Details) - Dec. 31, 2017 € in Millions, £ in Millions, kr in Millions, R$ in Millions, $ in Millions, $ in Millions, $ in Millions, $ in Millions	USD ($)	EUR (€)	GBP (£)	CAD ($)	BRL (R$)	NOK (kr)	SGD ($)	AUD ($)
Foreign exchange forward | Australian dollar | Notional amount bought
Derivative [Line Items]
Derivative, notional amount	$ 122.3							$ 156.5
Foreign exchange forward | Brazilian real | Notional amount bought
Derivative [Line Items]
Derivative, notional amount	236.7				R$ 783.1
Foreign exchange forward | British pound | Notional amount bought
Derivative [Line Items]
Derivative, notional amount	191.9		£ 142.0
Foreign exchange forward | Canadian dollar | Notional amount sold
Derivative [Line Items]
Derivative, notional amount	144.9			$ 181.9
Foreign exchange forward | Euro | Notional amount bought
Derivative [Line Items]
Derivative, notional amount	425.6	€ 354.9
Foreign exchange forward | Norwegian krone | Notional amount bought
Derivative [Line Items]
Derivative, notional amount	226.3
Foreign exchange forward | Norwegian krone | Notional amount sold
Derivative [Line Items]
Derivative, notional amount | kr						kr 1,857.5
Foreign exchange forward | Singapore dollar | Notional amount bought
Derivative [Line Items]
Derivative, notional amount	87.0						$ 116.2
Foreign exchange forward | U.S. dollar | Notional amount sold
Derivative [Line Items]
Derivative, notional amount	647.6
Embedded derivative financial instruments | Norwegian krone | Notional amount sold
Derivative [Line Items]
Derivative, notional amount	35.3					kr 290.1
Embedded derivative financial instruments | U.S. dollar | Notional amount bought
Derivative [Line Items]
Derivative, notional amount	$ 32.8