Accumulated Other Comprehensive Income (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Accumulated Other Comprehensive Income (Loss)
As at January 1, 2013			$ 86.9
Net current period other comprehensive income - Available for sale securities	1.5	3.1	(0.2)	6.0
As at June 30, 2013	52.2		52.2
Foreign currency translation adjustment
Accumulated Other Comprehensive Income (Loss)
As at January 1, 2013			85.1
Other Comprehensive income before reclassification			(34.5)
Amounts reclassified from accumulated other comprehensive income			0
Net current period other comprehensive income- Foreign Currency			(34.5)
As at June 30, 2013	50.6		50.6
Unrealized holding gain/(loss) on available-for-sale securities
Accumulated Other Comprehensive Income (Loss)
As at January 1, 2013			1.8
Other Comprehensive income before reclassification			(2.1)
Net current period other comprehensive income - Available for sale securities			(0.2)
Gain recognized in the income statement (within Other (expense)/income) on disposal of available-for-sale securities			1.9
As at June 30, 2013	1.6		1.6
Accumulated other comprehensive income
Accumulated Other Comprehensive Income (Loss)
As at January 1, 2013			86.9
Net current period other comprehensive income - Available for sale securities			(0.2)
Other Comprehensive income before reclassification			(36.6)
Gain recognized in the income statement (within Other (expense)/income) on disposal of available-for-sale securities			1.9
Net current period other comprehensive income			(34.7)
As at June 30, 2013	$ 52.2		$ 52.2