Industry Segments (Identifiable Assets by Segment) (Details) - USD ($) $ in Thousands		Sep. 30, 2016	Dec. 31, 2015
Segment Reporting, Asset Reconciling Item [Line Items]
Consolidated Assets		$ 23,345,656	$ 21,724,156
Operating Segments [Member] | Reinsurance-Global Segment [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Consolidated Assets		2,585,307	2,441,340
Operating Segments [Member] | Insurance-Domestic Segment [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Consolidated Assets		18,972,237	18,063,730
Intersegment Eliminations and Corporate, Non-Segment [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Consolidated Assets	[1]	$ 1,788,112	$ 1,219,086

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