Industry Segments (Identifiable Assets by Segment) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012
Segment Reporting, Asset Reconciling Item [Line Items]
Consolidated Assets	$ 20,523,719		$ 20,155,896
Operating Segments [Member] | Reinsurance-Global Segment [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Consolidated Assets	3,090,334		3,337,937
Operating Segments [Member] | Insurance-International Segment [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Consolidated Assets	1,451,487		1,541,365
Operating Segments [Member] | Insurance-Domestic Segment [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Consolidated Assets	15,097,667		14,661,476
Intersegment Eliminations and Corporate, Non-Segment [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Consolidated Assets	$ 884,231	[1]	$ 615,118	[1]

[1]