Consolidated Statements of Changes in Equity (USD $) In Millions, except Share data	Total	EBT	Share Buy-back Program	Common stock	Additional paid-in capital	Treasury stock	Treasury stock EBT	Treasury stock Share Buy-back Program	Accumulated other comprehensive income	Retained earnings/(accumulated deficit)
As at Dec. 31, 2009	$ 1,912.5			$ 55.6	$ 2,677.6	$ (347.4)			$ 149.1	$ (622.4)
Shares as at Dec. 31, 2009				561,500,000
Net income	588.0									588.0
Foreign currency translation	(51.3)								(51.3)
Options exercised	2.1			0.1	2.0
Option exercised (in shares)				700,000
Share-based compensation	62.2				62.2
Tax benefit associated with exercise of stock options	2.9				2.9
Shares issued by EBT					1.7
Shares repurchased							(1.7)
Shares released by EBT to satisfy exercise of stock options	9.1						73.0			(63.9)
Unrealized holding gain (loss) on available-for-sale securities, net of taxes	(13.6)								(13.6)
Realized gain on divestment of available-for-sale securities, net of taxes	0
Other than temporary impairment of available-for-sale securities, net of taxes	1.5								1.5
Dividends	(62.0)									(62.0)
As at Dec. 31, 2010	2,451.4			55.7	2,746.4	(276.1)			85.7	(160.3)
Shares as at Dec. 31, 2010				562,200,000
Net income	865.0									865.0
Foreign currency translation	(24.0)								(24.0)
Options exercised	0.7				0.7
Option exercised (in shares)				300,000
Share-based compensation	76.8				76.8
Tax benefit associated with exercise of stock options	29.4				29.4
Shares repurchased	(151.8)						(151.8)
Shares released by EBT to satisfy exercise of stock options	12.7						140.7			(128.0)
Unrealized holding gain (loss) on available-for-sale securities, net of taxes	16.2								16.2
Realized gain on divestment of available-for-sale securities, net of taxes	(20.0)								(20.0)
Other than temporary impairment of available-for-sale securities, net of taxes	2.4								2.4
Dividends	(73.8)									(73.8)
As at Dec. 31, 2011	3,185.0			55.7	2,853.3	(287.2)			60.3	502.9
Shares as at Dec. 31, 2011	562,500,000			562,500,000
Net income	745.4									745.4
Foreign currency translation	23.7								23.7
Options exercised	0.1				0.1
Share-based compensation	88.0				88.0
Tax benefit associated with exercise of stock options	40.1				40.1
Shares repurchased		(99.3)	(106.5)				(99.3)	(106.5)
Shares released by EBT to satisfy exercise of stock options	16.1						182.6			(166.5)
Unrealized holding gain (loss) on available-for-sale securities, net of taxes	2.9								2.9
Realized gain on divestment of available-for-sale securities, net of taxes	0
Other than temporary impairment of available-for-sale securities, net of taxes	0
Dividends	(86.3)									(86.3)
As at Dec. 31, 2012	$ 3,809.2			$ 55.7	$ 2,981.5	$ (310.4)			$ 86.9	$ 995.5
Shares as at Dec. 31, 2012	562,500,000			562,500,000