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 gain 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		905		48,278
Issuance of preferred shares			10,000	231,265
Redemption of preferred shares			(11,600)	(269,265)
Change in currency translation adjustment	(31,344)					(31,344)
Change in unfunded pension obligation, net of tax	866						866
Change in unrealized losses on investments, net of tax	(463)							(463)
Net income	59,982								59,982
Net income attributable to noncontrolling interests	1,183								(1,183)
Dividends on common shares									(73,800)
Dividends on preferred shares	(29,494)								(29,494)
Loss on redemption of preferred shares	(9,135)								(9,135)
Repurchase of common shares										(491,551)
Noncontrolling interests											48,319
Total shareholders' equity	6,415,276
Balance at end of period at Jun. 30, 2013	6,366,957	86,365	34,150	3,872,122	(20,344)	1,411	(26,504)	4,749	4,898,372	(2,503,708)
Balance at beginning of period at Mar. 31, 2013
Change in currency translation adjustment	(11,514)
Change in unfunded pension obligation, net of tax	(130)
Change in unrealized losses on investments, net of tax	(230)
Net income	(174,388)
Net income attributable to noncontrolling interests	1,183
Dividends on preferred shares	(14,796)
Loss on redemption of preferred shares	0
Noncontrolling interests											48,319
Total shareholders' equity	6,415,276
Balance at end of period at Jun. 30, 2013	6,366,957				(20,344)
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		450		26,841
Issuance of preferred shares			0	0
Redemption of preferred shares			0	0
Change in currency translation adjustment	1,797					1,797
Change in unfunded pension obligation, net of tax	(10)						(10)
Change in unrealized losses on investments, net of tax	(447)							(447)
Net income	586,678								586,678
Net income attributable to noncontrolling interests	4,995								(4,995)
Dividends on common shares									(68,291)
Dividends on preferred shares	(28,367)								(28,367)
Loss on redemption of preferred shares	0								0
Repurchase of common shares										(313,141)
Noncontrolling interests	47,356										47,356
Total shareholders' equity	6,957,403
Balance at end of period at Jun. 30, 2014	6,910,047	87,107	34,150	3,928,468	(10,898)	2,774	(17,519)	3,847	5,891,822	(3,020,602)
Balance at beginning of period at Mar. 31, 2014
Change in currency translation adjustment	17,020
Change in unfunded pension obligation, net of tax	(9)
Change in unrealized losses on investments, net of tax	(222)
Net income	273,792
Net income attributable to noncontrolling interests	1,951
Dividends on preferred shares	(14,184)
Loss on redemption of preferred shares	0
Noncontrolling interests	47,356										47,356
Total shareholders' equity	6,957,403
Balance at end of period at Jun. 30, 2014	$ 6,910,047				$ (10,898)