Accumulated Other Comprehensive Income (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014
Accumulated Other Comprehensive Income (Loss)
As at January 1, 2014	$ 110.2
Other comprehensive income, net of tax	2.6
As at March, 2014	112.8
Foreign currency translation adjustment
Accumulated Other Comprehensive Income (Loss)
As at January 1, 2014	110.4
Other Comprehensive income before reclassification	(1.7)
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	(1.7)
As at March, 2014	108.7
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	7.5
Gain transferred to the income statement (within Other income/(expense),net) on disposal of available-for-sale-securities	(3.2)
Other comprehensive income, net of tax	4.3
As at March, 2014	4.1
Accumulated other comprehensive income
Accumulated Other Comprehensive Income (Loss)
As at January 1, 2014	110.2
Other Comprehensive income before reclassification	5.8
Gain transferred to the income statement (within Other income/(expense),net) on disposal of available-for-sale-securities	(3.2)
Other comprehensive income, net of tax	2.6
As at March, 2014	$ 112.8