Condensed Consolidated Statements of Shareholders' Equity (USD $) In Thousands	Total	Common Shares [Member]	Preferred shares	Additional Paid-in Capital [Member]	Accumulated other comprehensive loss [Member]	Accumulated other comprehensive loss [Member] Currency translation adjustment [Member]	Accumulated other comprehensive loss [Member] Unfunded pension obligation [Member]	Accumulated other comprehensive loss [Member] Unrealized gains losses on investments [Member]	Retained Earnings [Member]	Common shares held in treasury [Member]	Noncontrolling Interest Member
Balance at beginning of period at Dec. 31, 2012		$ 85,460	$ 35,750	$ 3,861,844	$ 10,597	$ 32,755	$ (27,370)	$ 5,212	$ 4,952,002	$ (2,012,157)
Issuance of common shares		552		21,937
Issuance of preferred shares			10,000	231,265
Redemption of preferred shares			(11,600)	(269,265)
Change in currency translation adjustment	(19,830)					(19,830)
Change in unfunded pension obligation, net of tax	996						996
Change in unrealized losses on investments, net of tax	(233)							(233)
Net income	234,370								234,370
Net income attributable to noncontrolling interests	0								0
Dividends on common shares									(37,365)
Dividends on preferred shares	(14,699)								(14,699)
Loss on redemption of preferred shares	(9,135)								(9,135)
Repurchase of common shares										(159,775)
Total shareholders' equity	6,947,558
Balance at end of period at Mar. 31, 2013	6,910,714	86,012	34,150	3,845,781	(8,470)	12,925	(26,374)	4,979	5,125,173	(2,171,932)	36,844
Balance at beginning of period 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)
Issuance of common shares		222		5,720
Issuance of preferred shares			0	0
Redemption of preferred shares			0	0
Change in currency translation adjustment	(15,223)					(15,223)
Change in unfunded pension obligation, net of tax	(1)						(1)
Change in unrealized losses on investments, net of tax	(225)							(225)
Net income	312,887								312,887
Net income attributable to noncontrolling interests	3,044								(3,044)
Dividends on common shares									(34,588)
Dividends on preferred shares	(14,184)								(14,184)
Loss on redemption of preferred shares	0								0
Repurchase of common shares										(180,168)
Noncontrolling interests	59,671
Total shareholders' equity	6,840,599
Balance at end of period at Mar. 31, 2014	$ 6,780,928	$ 86,879	$ 34,150	$ 3,907,347	$ (27,687)	$ (14,246)	$ (17,510)	$ 4,069	$ 5,667,868	$ (2,887,629)	$ 59,671