CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (USD $) In Thousands	Total	Preferred shares - Series A, B and C [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]	Supplemental Executive Retirement Plans (SERPs) [Member]	Accumulated other comprehensive income [Member]	Retained earnings [Member]	Treasury shares, at cost [Member]
Balance at beginning of period at Dec. 31, 2010		$ 500,000	$ 1,934	$ 2,059,708	$ 161,802	$ 16,829	$ (1,810)	$ 176,821	$ 4,267,608	$ (1,381,101)
Shares issued (gross)		0	173	1,447
Value of shares repurchased and retired during the period		0		0					0
Shares issued (costs)				0
Stock options exercised				4,001
Share-based compensation expense				20,059
Unrealized gains arising during the period, net of reclassification adjustment	37,385				37,385
Non-credit portion of OTTI losses	(215)				(215)
Foreign currency translation adjustments	4,142					4,142
Net change in benefit plan assets and obligations recognized in equity							0
Net income (loss)	(264,254)								(264,254)
Series A, B and C preferred share dividends									(18,438)
Common share dividends									(61,521)
Shares repurchased for treasury										(14,810)
Balance at end of period at Jun. 30, 2011	5,332,939	500,000	2,107	2,085,215	198,972	20,971	(1,810)	218,133	3,923,395	(1,395,911)
Balance at beginning of period at Dec. 31, 2011	5,444,079	500,000	2,125	2,105,386	116,096	13,784	(1,718)	128,162	4,155,392	(1,446,986)
Shares issued (gross)		400,000	16	1,053
Value of shares repurchased and retired during the period		(397,157)		7,093					(14,009)
Shares issued (costs)				(6,456)
Stock options exercised				945
Share-based compensation expense				45,446
Unrealized gains arising during the period, net of reclassification adjustment	114,851				114,851
Non-credit portion of OTTI losses	0				0
Foreign currency translation adjustments	(2,074)					(2,074)
Net change in benefit plan assets and obligations recognized in equity							0
Net income (loss)	324,905								324,905
Series A, B and C preferred share dividends									(20,746)
Common share dividends									(62,137)
Shares repurchased for treasury										(137,969)
Balance at end of period at Jun. 30, 2012	$ 5,697,840	$ 502,843	$ 2,141	$ 2,153,467	$ 230,947	$ 11,710	$ (1,718)	$ 240,939	$ 4,383,405	$ (1,584,955)