Net Income (Loss) Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Numerator [Abstract]
Net income (loss)	$ 486,706		$ 180,123		$ 1,022,994		$ (502,648)
Dividends on preferred shares	(15,405)		(14,352)		(46,216)		(31,614)
Net income (loss) available to common shareholders	$ 471,301		$ 165,771		$ 976,778		$ (534,262)
Denominator [Abstract]
Weighted Average Number Of Shares Outstanding Basic	61,837,328		67,743,296		63,679,114		67,788,427
Share options and other	769,500	[1]	438,700	[1]	605,000	[1]	0	[1]
Weighted average number of common shares and common share equivalents outstanding	62,606,761		68,181,982		64,284,125		67,788,427
Basic net income (loss)	$ 7.62		$ 2.45		$ 15.34		$ (7.88)
Diluted net income (loss)	$ 7.53		$ 2.43		$ 15.19		$ (7.88)
Share options excluded from computation of weighted average number of common share and common share equivalents outstanding	1,233,300		2,996,100
Weighted Average Number Of Potentially Dilutive Common Shares And Common Share Equivalents Outstanding							785,200

[1] At September 30, 2012 and 2011, share based awards to purchase 1,233.3 thousand and 2,996.1 thousand common shares, respectively, were excluded from the calculation of diluted weighted average number of common shares and common share equivalents outstanding because their exercise prices were greater than the average market price of the common shares. In addition, dilutive securities, in the form of share options and other, of 785.2 thousand shares were not included in the weighted average number of common shares and common share equivalents outstanding for the purpose of computing the diluted net loss per share because to do so would have been anti-dilutive for the nine months ended September 30, 2011.