Industry Segments (Financial Information of Company Operating Segments) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012
Segment Reporting Information [Line Items]
Earned Premiums	$ 1,282,515		$ 1,147,357		$ 2,514,634		$ 2,247,008
Investment Income and Funds	143,737		161,250		279,666		318,869
Other Revenues	144,710		107,140		283,431		228,575
Total revenues	1,570,962		1,415,747		3,077,731		2,794,452
Pre-Tax Income (Loss)	158,706		148,439		318,929		335,742
Net Income (Loss)	115,957		108,838		232,572		244,156
Net investment gains, before tax	33,058		24,286		53,027		71,777
Net investment gains, net of tax	21,488		15,850		34,468		46,932
Intersegment Eliminations and Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Earned Premiums	0		0		0	[1]	0	[1]
Investment Income and Funds	(32)		949		3,540	[1]	7,464	[1]
Other Revenues	84,000		55,818		176,016	[1]	105,885	[1]
Total revenues	83,968	[1]	56,767	[1]	179,556	[1]	113,349	[1]
Pre-Tax Income (Loss)	(64,021)		(61,723)		(125,440)	[1]	(116,983)	[1]
Net Income (Loss)	(38,782)		(40,335)		(76,426)	[1]	(76,177)	[1]
Insurance-Domestic Segment [Member]
Segment Reporting Information [Line Items]
Earned Premiums	925,997		846,734		1,810,375		1,656,803
Insurance-Domestic Segment [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Earned Premiums	925,997		846,734		1,810,375		1,656,803
Investment Income and Funds	107,562		120,656		205,359		232,742
Other Revenues	27,652		27,036		54,388		50,913
Total revenues	1,061,211		994,426		2,070,122		1,940,458
Pre-Tax Income (Loss)	152,334		144,640		293,684		292,375
Net Income (Loss)	106,478		103,435		205,886		209,315
Insurance-International Segment [Member]
Segment Reporting Information [Line Items]
Earned Premiums	180,192		154,501		351,311		298,386
Insurance-International Segment [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Earned Premiums	180,192		154,501		351,311		298,386
Investment Income and Funds	13,171		11,194		25,232		21,525
Other Revenues	0		0		0		0
Total revenues	193,363		165,695		376,543		319,911
Pre-Tax Income (Loss)	12,583		13,782		34,965		29,481
Net Income (Loss)	9,092		9,833		24,569		20,945
Reinsurance-Global Segment [Member]
Segment Reporting Information [Line Items]
Earned Premiums	176,326		146,122		352,948		291,819
Reinsurance-Global Segment [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Earned Premiums	176,326		146,122		352,948		291,819
Investment Income and Funds	23,036		28,451		45,535		57,138
Other Revenues	0		0		0		0
Total revenues	199,362		174,573		398,483		348,957
Pre-Tax Income (Loss)	24,752		27,454		62,693		59,092
Net Income (Loss)	$ 17,681		$ 20,055		$ 44,075		$ 43,141

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