Common Shares (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Common Shares
Common shares, shares authorized	800,000,000	800,000,000	800,000,000
Common shares, par value (in dollars per share)	$ 0.001	$ 0.001	$ 0.001
Common shares, shares issued	318,813,000	317,042,000	315,034,000
Issuance of common shares for stock options exercised, net of surrender of unexercised stock options (in shares)	1,100,000	1,100,000	700,000
Preferred shares, shares authorized	25,000,000	25,000,000
Preferred shares, par value (in dollars per share)	$ 0.001	$ 0.001
Proceeds from stock options exercised	$ 17.4	$ 11.6	$ 8.2
Repurchase surrendered unexercised vested options surrendered to satisfy exercise price and related tax withholding obligations	21
Anthony g petrello
Common Shares
Issuance of common shares for stock options exercised, net of surrender of unexercised stock options (in shares)	807,142	82,138	136,818
Value of surrendered unexercised vested stock options	$ 79.6	$ 7.6	$ 77.0
Officers and directors
Common Shares
Restricted stock awarded to executive officers, key employees & directors	944,015	1,096,379	538,496
Restricted shares awarded, average market price (in dollars per share)	$ 20.69	$ 27.32	$ 22.15