Industry Segments (Identifiable Assets by Segment) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013		Dec. 31, 2012
Segment Reporting, Asset Reconciling Item [Line Items]
Consolidated Assets	$ 20,211,542		$ 20,155,896
Operating Segments [Member] | Reinsurance-Global Segment [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Consolidated Assets	2,965,565		3,337,937
Operating Segments [Member] | Insurance-International Segment [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Consolidated Assets	1,449,188		1,541,365
Operating Segments [Member] | Insurance-Domestic Segment [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Consolidated Assets	14,849,126		14,661,476
Intersegment Eliminations and Corporate, Non-Segment [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Consolidated Assets	$ 947,663	[1]	$ 615,118	[1]

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