Industry Segments (Financial Information of Company Operating Segments) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Segment Reporting Information [Line Items]
Earned Premiums	$ 1,417,645		$ 1,282,515		$ 2,781,257		$ 2,514,634
Investment Income and Funds	138,729		143,737		307,440		279,666
Other Revenues	240,615		144,710		415,198		283,431
Total revenues	1,796,989		1,570,962		3,503,895		3,077,731
Pre-Tax Income (Loss)	263,454		158,706		511,039		318,929
Net Income (Loss)	179,961		115,957		349,634		232,572
Net investment gains	109,168		33,058		161,922		53,027
Net investment gains, net of tax	70,959		21,488		105,249		34,468
Intersegment Eliminations and Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Earned Premiums	0	[1]	0	[1]	0	[1]	0	[1]
Investment Income and Funds	6,772	[1]	(32)	[1]	13,116	[1]	3,540	[1]
Other Revenues	104,462	[1]	84,000	[1]	197,525	[1]	176,016	[1]
Total revenues	111,234	[1]	83,968	[1]	210,641	[1]	179,556	[1]
Pre-Tax Income (Loss)	(59,945)	[1]	(64,021)	[1]	(117,120)	[1]	(125,440)	[1]
Net Income (Loss)	(39,110)	[1]	(38,782)	[1]	(76,623)	[1]	(76,426)	[1]
Insurance-Domestic Segment [Member]
Segment Reporting Information [Line Items]
Earned Premiums	1,041,745		925,997		2,045,252		1,810,375
Insurance-Domestic Segment [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Earned Premiums	1,041,745		925,997		2,045,252		1,810,375
Investment Income and Funds	103,073		107,562		221,210		205,359
Other Revenues	26,985		27,652		55,751		54,388
Total revenues	1,171,803		1,061,211		2,322,213		2,070,122
Pre-Tax Income (Loss)	176,855		152,334		379,040		293,684
Net Income (Loss)	121,834		106,478		259,870		205,886
Insurance-International Segment [Member]
Segment Reporting Information [Line Items]
Earned Premiums	201,868		180,192		387,192		351,311
Insurance-International Segment [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Earned Premiums	201,868		180,192		387,192		351,311
Investment Income and Funds	11,276		13,171		27,928		25,232
Other Revenues	0		0		0		0
Total revenues	213,144		193,363		415,120		376,543
Pre-Tax Income (Loss)	11,510		12,583		29,257		34,965
Net Income (Loss)	8,253		9,092		20,721		24,569
Reinsurance-Global Segment [Member]
Segment Reporting Information [Line Items]
Earned Premiums	174,032		176,326		348,813		352,948
Reinsurance-Global Segment [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Earned Premiums	174,032		176,326		348,813		352,948
Investment Income and Funds	17,608		23,036		45,186		45,535
Other Revenues	0		0		0		0
Total revenues	191,640		199,362		393,999		398,483
Pre-Tax Income (Loss)	25,866		24,752		57,940		62,693
Net Income (Loss)	$ 18,025		$ 17,681		$ 40,417		$ 44,075

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