Accumulated Other Comprehensive Income (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2014
Accumulated Other Comprehensive Income (Loss)
As at January 1, 2014	$ 110.2
Other comprehensive income, net of tax	(79.4)
As at September 30, 2014	30.8
Foreign currency translation adjustment
Accumulated Other Comprehensive Income (Loss)
As at January 1, 2014	110.4
Other Comprehensive income before reclassification	(75.9)
Gain transferred to the income statement (within Other income/(expense),net) on disposal of available-for-sale-securities	0
Other comprehensive income, net of tax	(75.9)
As at September 30, 2014	34.5
Unrealized holding gain/(loss) on available-for-sale securities
Accumulated Other Comprehensive Income (Loss)
As at January 1, 2014	(0.2)
Other Comprehensive income before reclassification	5.6
Gain transferred to the income statement (within Other income/(expense),net) on disposal of available-for-sale-securities	(9.1)
Other comprehensive income, net of tax	(3.5)
As at September 30, 2014	(3.7)
Accumulated other comprehensive income
Accumulated Other Comprehensive Income (Loss)
As at January 1, 2014	110.2
Other Comprehensive income before reclassification	(70.3)
Gain transferred to the income statement (within Other income/(expense),net) on disposal of available-for-sale-securities	(9.1)
Other comprehensive income, net of tax	(79.4)
As at September 30, 2014	$ 30.8