Industry Segments (Financial Information of Company Operating Segments) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Segment Reporting Information [Line Items]
Earned Premiums		$ 1,493,041	$ 1,417,645	$ 2,965,054	$ 2,781,257
Investment Income and Funds		127,583	138,729	251,822	307,440
Other Revenues		169,141	240,615	317,568	415,198
Total revenues		1,789,765	1,796,989	3,534,444	3,503,895
Pre-Tax Income (Loss)		178,187	263,454	346,904	511,039
Net Income (Loss)		123,035	179,961	241,342	349,634
Net investment gains		27,557	109,168	46,601	161,922
Net investment gains, net of tax		17,911	70,959	30,290	105,249
Intersegment Eliminations and Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Earned Premiums	[1]	0	0	0	0
Investment Income and Funds	[1]	6,253	6,772	14,367	13,116
Other Revenues	[1]	117,199	104,462	221,007	197,525
Total revenues	[1]	123,452	111,234	235,374	210,641
Pre-Tax Income (Loss)	[1]	(59,962)	(59,945)	(118,720)	(117,120)
Net Income (Loss)	[1]	(39,799)	(39,110)	(78,410)	(76,623)
Insurance-Domestic Segment [Member]
Segment Reporting Information [Line Items]
Earned Premiums		1,159,653	1,041,745	2,277,195	2,045,252
Insurance-Domestic Segment [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Earned Premiums		1,159,653	1,041,745	2,277,195	2,045,252
Investment Income and Funds		93,114	103,073	175,766	221,210
Other Revenues		24,385	26,985	49,960	55,751
Total revenues		1,277,152	1,171,803	2,502,921	2,322,213
Pre-Tax Income (Loss)		175,953	176,855	342,819	379,040
Net Income (Loss)		120,578	121,834	235,488	259,870
Insurance-International Segment [Member]
Segment Reporting Information [Line Items]
Earned Premiums		191,729	201,868	385,463	387,192
Insurance-International Segment [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Earned Premiums		191,729	201,868	385,463	387,192
Investment Income and Funds		10,150	11,276	26,582	27,928
Other Revenues		0	0	0	0
Total revenues		201,879	213,144	412,045	415,120
Pre-Tax Income (Loss)		7,517	11,510	28,820	29,257
Net Income (Loss)		5,518	8,253	20,647	20,721
Reinsurance-Global Segment [Member]
Segment Reporting Information [Line Items]
Earned Premiums		141,659	174,032	302,396	348,813
Reinsurance-Global Segment [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Earned Premiums		141,659	174,032	302,396	348,813
Investment Income and Funds		18,066	17,608	35,107	45,186
Other Revenues		0	0	0	0
Total revenues		159,725	191,640	337,503	393,999
Pre-Tax Income (Loss)		27,122	25,866	47,384	57,940
Net Income (Loss)		$ 18,827	$ 18,025	$ 33,327	$ 40,417

[1] Corporate and eliminations represent corporate revenues and expenses that are not allocated to business segments.