Common Shares (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Common Shares
Common shares, shares authorized	800,000,000	800,000,000
Common shares, par value (in dollars per share)	$ 0.001	$ 0.001
Common shares, shares issued	323,710,583	318,813,500
Preferred shares, shares issued	0
Shares purchased	0	0	0
Issuance of common shares for stock options exercised, net of surrender of unexercised stock options (in shares)	5,383,000	(3,625,000)	11,605,000
Preferred shares, shares authorized	25,000,000
Preferred shares, par value (in dollars per share)	$ 0.001
Proceeds from stock options exercised	$ 5,400,000	$ 17,400,000	$ 11,600,000
Amount paid to repurchase surrendered unexercised vested options to satisfy exercise price and related tax withholding obligations		21,000,000
Common stock dividend declared (in dollars per share)	$ 0.04
Cash dividends paid	47,168,000
Officers and directors
Common Shares
Restricted stock awarded to executive officers, key employees & directors	4,847,376	944,015	1,096,379
Restricted shares awarded, average market price (in dollars per share)	$ 16.28	$ 20.69	$ 27.32
Employees
Common Shares
Issuance of common shares for stock options exercised, net of surrender of unexercised stock options (in shares)	1,284	807,142	82,138
Value of surrendered unexercised vested stock options		$ 79,600,000	$ 7,600,000