Consolidated Statements of Shareholders' Equity (USD $) In Thousands	Total	Common Shares [Member]	Preferred shares	Additional Paid-in Capital [Member]	Accumulated other comprehensive (loss) income [Member]	Accumulated other comprehensive (loss) income [Member] Currency translation adjustment [Member]	Accumulated other comprehensive (loss) income [Member] Unfunded pension obligation [Member]	Accumulated other comprehensive (loss) income [Member] Unrealized gains losses on investments [Member]	Retained Earnings [Member]	Common shares held in treasury [Member]	Noncontrolling Interest Member
Balance at beginning of year at Dec. 31, 2010		$ 84,033	$ 20,800	$ 3,419,864	$ 4,056	$ 16,101	$ (19,159)	$ 7,114	$ 4,761,178	$ (1,083,012)
Issuance of common shares		734		37,160
Issuance of preferred shares			14,950	346,772
Redemption of preferred shares			0	0
Change in currency translation adjustment	(11,834)					(11,834)
Change in unfunded pension obligation	(3,917)						(3,917)
Change in unrealized losses on investments, net of tax	(949)							(949)
Net income (loss)	(520,291)								(520,291)
Net income attributable to noncontrolling interests	0								0
Dividends on common shares									(158,764)
Dividends on preferred shares	(47,020)								(47,020)
Loss on redemption of preferred shares	0								0
Repurchase of common shares										(396,218)
Noncontrolling interests											0
Total shareholders' equity	6,467,542
Balance at end of year at Dec. 31, 2011	6,467,542	84,767	35,750	3,803,796	(12,644)	4,267	(23,076)	6,165	4,035,103	(1,479,230)
Issuance of common shares		693		58,048
Issuance of preferred shares			0	0
Redemption of preferred shares			0	0
Change in currency translation adjustment	28,488					28,488
Change in unfunded pension obligation	(4,294)						(4,294)
Change in unrealized losses on investments, net of tax	(953)							(953)
Net income (loss)	1,134,514								1,134,514
Net income attributable to noncontrolling interests	0								0
Dividends on common shares									(155,993)
Dividends on preferred shares	(61,622)								(61,622)
Loss on redemption of preferred shares	0								0
Repurchase of common shares										(532,927)
Noncontrolling interests	0
Total shareholders' equity	6,933,496
Balance at end of year at Dec. 31, 2012	6,933,496	85,460	35,750	3,861,844	10,597	32,755	(27,370)	5,212	4,952,002	(2,012,157)	0
Issuance of common shares		1,197		77,783
Issuance of preferred shares			10,000	231,265
Redemption of preferred shares			(11,600)	(269,265)
Change in currency translation adjustment	(31,778)					(31,778)
Change in unfunded pension obligation	9,861						9,861
Change in unrealized losses on investments, net of tax	(918)							(918)
Net income (loss)	673,442								673,442
Net income attributable to noncontrolling interests	9,434								(9,434)
Dividends on common shares									(142,217)
Dividends on preferred shares	(57,861)								(57,861)
Loss on redemption of preferred shares	(9,135)								(9,135)
Repurchase of common shares										(695,304)
Noncontrolling interests	56,627
Total shareholders' equity	6,766,159
Balance at end of year at Dec. 31, 2013	$ 6,709,532	$ 86,657	$ 34,150	$ 3,901,627	$ (12,238)	$ 977	$ (17,509)	$ 4,294	$ 5,406,797	$ (2,707,461)	$ 56,627