Unaudited Condensed Consolidated Statements of Shareholders' Equity (USD $) In Thousands	Total	[CommonStockMember]	[PreferredStockMember]	[AdditionalPaidInCapitalMember]	[AccumulatedOtherComprehensiveIncomeMember]	[RetainedEarningsMember]	[TreasuryStockMember]
Balance at beginning of period at Dec. 31, 2010		$ 84,033	$ 20,800	$ 3,419,864	$ 4,056	$ 4,761,178	$ (1,083,012)
Net income (loss)	(806,956)					(806,956)
Dividends on common shares						(37,145)
Dividends on preferred shares	(8,631)					(8,631)
Issuance of common shares		238		9,565
Change in currency translation adjustment	37,781				37,781
Change in other accumulated comprehensive loss	(235)				(235)
Repurchase of common shares							(226,703)
Balance at end of period at Mar. 31, 2011	6,174,833	84,271	20,800	3,429,429	41,602	3,908,446	(1,309,715)
Balance at beginning of period at Dec. 31, 2011	6,467,542	84,767	35,750	3,803,796	(12,644)	4,035,103	(1,479,230)
Net income (loss)	360,141					360,141
Dividends on common shares						(40,543)
Dividends on preferred shares	(15,405)					(15,405)
Issuance of common shares		173		11,260
Change in currency translation adjustment	17,207				17,207
Change in other accumulated comprehensive loss	(1,111)				(1,111)
Repurchase of common shares							(12,393)
Balance at end of period at Mar. 31, 2012	$ 6,786,871	$ 84,940	$ 35,750	$ 3,815,056	$ 3,452	$ 4,339,296	$ (1,491,623)