Condensed Consolidated Statements of Shareholders' Equity (USD $) In Thousands, unless otherwise specified	Total	Common Shares [Member]	Preferred shares	Additional Paid-in Capital [Member]	Accumulated other comprehensive loss [Member]	Foreign Currency translation adjustment [Member]	Unfunded pension obligation [Member]	Unrealized gain (loss) on investment [Member]	Retained Earnings [Member]	Common shares held in treasury [Member]	Noncontrolling Interest [Member]
Balance at beginning of period at Dec. 31, 2013		$ 86,657	$ 34,150	$ 3,901,627	$ (12,238)	$ 977	$ (17,509)	$ 4,294	$ 5,406,797	$ (2,707,461)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common shares		222		1,101
Stock compensation expense, net of taxes paid				4,619
Change in currency translation adjustment						(15,223)
Change in net unrealized gain on designated net investment hedges						0
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)
Reissuance of common shares									0	0
Dividends on common shares									(34,588)
Dividends on preferred shares	(14,184)								(14,184)
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)
Balance at beginning of period at Dec. 31, 2014	7,048,910	87,237	34,150	3,949,665	(34,083)	(7,915)	(29,576)	3,408	6,270,811	(3,258,870)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common shares		0		0
Stock compensation expense, net of taxes paid				9,800
Change in currency translation adjustment						(5,063)
Change in net unrealized gain on designated net investment hedges						2,559
Change in unfunded pension obligation, net of tax	(436)						(436)
Change in unrealized losses on investments, net of tax	(217)							(217)
Net income	248,099								248,099
Net income attributable to noncontrolling interests	(2,182)								(2,182)
Reissuance of common shares									26,917	(29,227)
Dividends on common shares									(33,185)
Dividends on preferred shares	(14,184)								(14,184)
Repurchase of common shares										(59,266)
Noncontrolling interests	57,683										57,683
Total shareholders' equity	7,254,828
Balance at end of period at Mar. 31, 2015	$ 7,197,145	$ 87,237	$ 34,150	$ 3,959,465	$ (37,240)	$ (10,419)	$ (30,012)	$ 3,191	$ 6,442,442	$ (3,288,909)