Unaudited Consolidated Statements of Changes in Shareholders' Equity (USD $) In Thousands	Total	Non-Cumulative Preferred Shares	Common Shares	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Common Shares Held in Treasury, at Cost
Balance at beginning of year at Dec. 31, 2011		$ 325,000	$ 549	$ 161,419	$ 4,796,655	$ 153,923	$ (845,472)
Shares issued - Series C		325,000
Common shares issued, net			7	4,553
Issue costs on Series C preferred shares				(9,398)
Shares repurchased - Series A and B		(325,000)		10,612	(10,612)
Exercise of stock options				4,822
Amortization of share-based compensation				23,930
Other				1,687
Net income	384,524				384,524
Dividends declared on preferred shares	(14,110)				(14,110)
Change in unrealized appreciation (decline) in value of investments, net of deferred income tax						41,620
Portion of other-than-temporary impairment losses recognized in other comprehensive income, net of deferred income tax	(511)					(511)
Foreign currency translation adjustments, net of deferred income tax	(1,935)					(1,935)
Shares repurchased for treasury							(6,947)
Balance at end of period at Jun. 30, 2012	5,020,316	325,000	556	197,625	5,156,457	193,097	(852,419)
Balance at beginning of year at Dec. 31, 2012	5,168,878	325,000	561	227,778	5,354,361	287,017	(1,025,839)
Common shares issued, net			3	5,362
Exercise of stock options				6,022
Amortization of share-based compensation				31,466
Other				2,327
Net income	433,416				433,416
Dividends declared on preferred shares	(10,969)				(10,969)
Change in unrealized appreciation (decline) in value of investments, net of deferred income tax						(302,708)
Portion of other-than-temporary impairment losses recognized in other comprehensive income, net of deferred income tax	(2)					(2)
Foreign currency translation adjustments, net of deferred income tax	(33,629)					(33,629)
Shares repurchased for treasury							(65,848)
Balance at end of period at Jun. 30, 2013	$ 5,234,318	$ 325,000	$ 564	$ 272,955	$ 5,776,808	$ (49,322)	$ (1,091,687)