Common Shares (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Common Shares (Textual) [Abstract]
Common shares, shares authorized	800,000,000	800,000,000
Common shares, par value	$ 0.001	$ 0.001
Common shares, shares issued	317,042,000	315,034,000
Preferred shares, shares authorized	25,000,000	25,000,000
Preferred shares, par value	$ 0.001	$ 0.001
Repurchase of treasury shares	0	0	0
Preferred shares, shares issued	0	0
Restricted shares awarded, average market price	$ 27.32	$ 22.15	$ 11.55
Vested options exercised by employees , shares	(1,116,000)	700,000	1,500,000
Proceeds from issuance of common shares	$ 11,605,000	$ 8,201,000	$ 11,249,000
Anthony G Petrello [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Issuance of common shares for stock options exercised	82,138	110,805	218,835
Value of surrendered unexercised vested stock options	7,600,000	24,500,000	5,600,000
Officers And Directors [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Restricted stock awarded to executive officers, key employees & directors	1,096,379	538,496	85,000
Gene M Isenberg [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Issuance of common shares for stock options exercised		22,385
Value of surrendered unexercised vested stock options		$ 50,100,000