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]	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		450		11,183
Stock compensation expense, net of taxes paid				15,658
Change in currency translation adjustment						1,797
Change in net unrealized gain on designated net investment hedges						0
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)
Reissuance of common shares									0	0
Dividends on common shares									(68,291)
Dividends on preferred shares	(28,367)								(28,367)
Repurchase of common shares										(313,141)
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)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Noncontrolling interests											$ 47,356
Total shareholders' equity	6,957,403
Noncontrolling interests	55,501
Total shareholders' equity	7,104,411
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				15,825
Change in currency translation adjustment						(4,148)
Change in net unrealized gain on designated net investment hedges						9,745
Change in unfunded pension obligation, net of tax	(1,327)						(1,327)
Change in unrealized losses on investments, net of tax	(431)							(431)
Net income	159,543								159,543
Net income attributable to noncontrolling interests	(2,536)								(2,536)
Reissuance of common shares									(34,874)	43,461
Dividends on common shares									(66,609)
Dividends on preferred shares	(28,367)								(28,367)
Repurchase of common shares										(59,266)
Balance at end of period at Jun. 30, 2015	7,079,926	$ 87,237	$ 34,150	$ 3,965,490	$ (30,244)	$ (2,318)	$ (30,903)	$ 2,977	$ 6,297,968	$ (3,274,675)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Noncontrolling interests	2,217										$ 2,217
Total shareholders' equity	$ 7,082,143