Taxation (Unrecognized Tax Benefits) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Reconciliation of Unrecognized Tax Benefits
Balance at January 1,	$ 355.2	[1]	$ 278.7	[1]	$ 265.5
Increases based on tax positions related to the current year	20.3		56.8		20.5
Decreases based on tax positions taken in the current year	0		(0.5)		0
Increases for tax positions taken in prior years	64.2		34.5		0.4
Decreases for tax positions taken in prior years	(211.0)		(0.8)		(3.3)
Decreases resulting from settlements with the taxing authorities	(9.4)		0		(10.6)
Decreases as a result of expiration of the statute of limitations	(0.6)		(0.6)		(0.3)
Foreign currency translation adjustments	(10.9)	[2]	(12.9)	[2]	6.5	[2]
Balance at December 31,	207.8	[1]	355.2	[1]	278.7	[1]
Income Tax Contingency [Line Items]
Income tax penalties and interest expense	(103.1)		0.4		5.1
Income tax penalties and interest expense accrued	25.8		112.2		119.6
Unrecognized tax benefits that would impact effective tax rate if recognized	181.0		355.0		278.0
Future decrease in the unrecognized tax benefit	25
Repayment from the Canadian revenue authorities	417.0		0		0
Canadian revenue authorities
Income Tax Contingency [Line Items]
Income tax penalties and interest expense	289.4
Net tax credit following the settlement of certain tax position with the Canadian revenue authorities	235
Repayment from the Canadian revenue authorities	$ 417.0

[1] (2) Approximately $181 million (2013: $355 million, 2012: $278 million) of which would affect the effective tax rate if recognized

[2] Recognized within Other Comprehensive Income