Derivative Instruments (Consolidated Balance Sheets And Fair Value Of The Principal Derivative Instruments) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Other Assets
Derivative Assets [Abstract]
Gross Amounts of Recognized Assets	$ 10,635	$ 12,328
Gross Amounts Offset in the Balance Sheet	2,941	1,661
Net Amounts of Assets Presented in the Balance Sheet	7,694	10,667
Collateral	310	310
Net Amount	7,384	10,357
Other Assets \| Interest Rate Futures
Derivative Assets [Abstract]
Gross Amounts of Recognized Assets	468	897
Gross Amounts Offset in the Balance Sheet	468	62
Net Amounts of Assets Presented in the Balance Sheet	0	835
Collateral	0	0
Net Amount	0	835
Other Assets \| Foreign Currency Forward Contracts, Underwriting and Non-investment Operations
Derivative Assets [Abstract]
Gross Amounts of Recognized Assets	5,740	9,612
Gross Amounts Offset in the Balance Sheet	1,737	1,179
Net Amounts of Assets Presented in the Balance Sheet	4,003	8,433
Collateral	0	0
Net Amount	4,003	8,433
Other Assets \| Foreign Currency Forward Contracts, Investment Operations
Derivative Assets [Abstract]
Gross Amounts of Recognized Assets	3,959	1,013
Gross Amounts Offset in the Balance Sheet	648	338
Net Amounts of Assets Presented in the Balance Sheet	3,311	675
Collateral	0	0
Net Amount	3,311	675
Other Assets \| Credit Default Swaps
Derivative Assets [Abstract]
Gross Amounts of Recognized Assets	468	806
Gross Amounts Offset in the Balance Sheet	88	82
Net Amounts of Assets Presented in the Balance Sheet	380	724
Collateral	310	310
Net Amount	70	414
Other Liabilities
Derivative Liabilities [Abstract]
Gross Amounts of Recognized Liabilities	3,521	6,419
Gross Amounts Offset in the Balance Sheet	2,172	510
Net Amounts of Liabilities Presented in the Balance Sheet	1,349	5,909
Collateral	759	2,502
Net Amount	590	3,407
Other Liabilities \| Interest Rate Futures
Derivative Liabilities [Abstract]
Gross Amounts of Recognized Liabilities	1,037	74
Gross Amounts Offset in the Balance Sheet	468	62
Net Amounts of Liabilities Presented in the Balance Sheet	569	12
Collateral	569	12
Net Amount	0	0
Other Liabilities \| Foreign Currency Forward Contracts, Underwriting and Non-investment Operations
Derivative Liabilities [Abstract]
Gross Amounts of Recognized Liabilities	1,319	2,204
Gross Amounts Offset in the Balance Sheet	967	28
Net Amounts of Liabilities Presented in the Balance Sheet	352	2,176
Collateral	0	0
Net Amount	352	2,176
Other Liabilities \| Foreign Currency Forward Contracts, Investment Operations
Derivative Liabilities [Abstract]
Gross Amounts of Recognized Liabilities	724	1,557
Gross Amounts Offset in the Balance Sheet	649	338
Net Amounts of Liabilities Presented in the Balance Sheet	75	1,219
Collateral	0	0
Net Amount	75	1,219
Other Liabilities \| Credit Default Swaps
Derivative Liabilities [Abstract]
Gross Amounts of Recognized Liabilities	251	94
Gross Amounts Offset in the Balance Sheet	88	82
Net Amounts of Liabilities Presented in the Balance Sheet	163	12
Collateral	0	0
Net Amount	163	12
Other Liabilities \| Weather Contract
Derivative Liabilities [Abstract]
Gross Amounts of Recognized Liabilities	190	2,490
Gross Amounts Offset in the Balance Sheet	0	0
Net Amounts of Liabilities Presented in the Balance Sheet	190	2,490
Collateral	190	2,490
Net Amount	$ 0	$ 0

Amount of obligation to return cash collateral under master netting arrangements offset against derivative assets.

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