CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (USD $) In Thousands	Total	Parent [Member]	Preferred shares [Member]	Common shares (par value) [Member]	Additional paid-in capital [Member]	Unrealized appreciation on available for sale investments, net of tax [Member]	Cumulative foreign currency translation adjustments, net of tax [Member]	Accumulated other comprehensive income [Member]	Retained earnings [Member]	Treasury shares, at cost [Member]	Noncontrolling interest [Member]
Total shareholders' equity at Dec. 31, 2012			$ 502,843	$ 2,146	$ 2,179,034	$ 348,328	$ 14,294	$ 362,622	$ 4,497,789	$ (1,764,673)
Shares issued			225,000	26	2,777
Cost of treasury shares reissued					(3,984)					3,984
Issue costs on newly issued preferred shares					(6,551)
Value of shares repurchased and retired during the period			(100,000)		3,081				(3,081)
Stock options exercised					12,017
Share-based compensation expense					26,830
Unrealized gains (losses) arising during the period, net of reclassification adjustment	(319,340)					(319,340)
Non-credit portion of OTTI losses	0					0
Foreign currency translation adjustments	(18,527)						(18,527)
Net income	395,280								395,280
Net income attributable to noncontrolling interests	0								0
Preferred share dividends									(16,938)
Common share dividends									(59,363)
Shares repurchased for treasury										(359,025)
Total shareholders' equity at Jun. 30, 2013	5,561,947	5,561,947	627,843	2,172	2,213,204	28,988	(4,233)	24,755	4,813,687	(2,119,714)	0
Total shareholders' equity at Dec. 31, 2013	5,867,962		627,843	2,174	2,240,125	124,945	(7,120)	117,825	5,062,706	(2,232,711)
Shares issued			0	15	2,549
Cost of treasury shares reissued					(11,524)					11,524
Issue costs on newly issued preferred shares					0
Value of shares repurchased and retired during the period			0		0				0
Stock options exercised					2,134
Share-based compensation expense					27,800
Unrealized gains (losses) arising during the period, net of reclassification adjustment	148,390					148,390
Non-credit portion of OTTI losses	0					0
Foreign currency translation adjustments	6,449						6,449
Net income	350,729								350,729
Net income attributable to noncontrolling interests	(2,795)								(2,795)
Preferred share dividends									(20,044)
Common share dividends									(59,397)
Shares repurchased for treasury										(318,082)
Total shareholders' equity at Jun. 30, 2014	$ 6,008,505	$ 5,955,710	$ 627,843	$ 2,189	$ 2,261,084	$ 273,335	$ (671)	$ 272,664	$ 5,331,199	$ (2,539,269)	$ 52,795