Derivative Instruments (Consolidated Balance Sheets And Fair Value Of The Principal Derivative Instruments) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Other Assets
Derivative Assets
Gross Amounts of Recognized Assets	$ 20,963	$ 10,635
Gross Amounts Offset in the Balance Sheet	7,970	2,941
Net Amounts of Assets Presented in the Balance Sheet	12,993	7,694
Collateral	600	310
Net Amount	12,393	7,384
Other Assets \| Interest Rate Contracts
Derivative Assets
Gross Amounts of Recognized Assets	2,079	468
Gross Amounts Offset in the Balance Sheet	2,043	468
Net Amounts of Assets Presented in the Balance Sheet	36	0
Collateral	0	0
Net Amount	36	0
Other Assets \| Foreign Currency Forward Contracts, Underwriting and Non-investment Operations
Derivative Assets
Gross Amounts of Recognized Assets	16,646	5,740
Gross Amounts Offset in the Balance Sheet	5,808	1,737
Net Amounts of Assets Presented in the Balance Sheet	10,838	4,003
Collateral	0	0
Net Amount	10,838	4,003
Other Assets \| Foreign Currency Forward Contracts, Investment Operations
Derivative Assets
Gross Amounts of Recognized Assets	1,774	3,959
Gross Amounts Offset in the Balance Sheet	106	648
Net Amounts of Assets Presented in the Balance Sheet	1,668	3,311
Collateral	290	0
Net Amount	1,378	3,311
Other Assets \| Credit Default Swaps
Derivative Assets
Gross Amounts of Recognized Assets	464	468
Gross Amounts Offset in the Balance Sheet	13	88
Net Amounts of Assets Presented in the Balance Sheet	451	380
Collateral	310	310
Net Amount	141	70
Other Liabilities
Derivative Liabilities
Gross Amounts of Recognized Liabilities	9,194	3,521
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	3,577	2,172
Net Amounts of Liabilities Presented in the Balance Sheet	5,617	1,349
Collateral	552	759
Net Amount	5,065	590
Other Liabilities \| Interest Rate Contracts
Derivative Liabilities
Gross Amounts of Recognized Liabilities	2,571	1,037
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	2,043	468
Net Amounts of Liabilities Presented in the Balance Sheet	528	569
Collateral	528	569
Net Amount	0	0
Other Liabilities \| Foreign Currency Forward Contracts, Underwriting and Non-investment Operations
Derivative Liabilities
Gross Amounts of Recognized Liabilities	6,377	1,319
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	1,415	967
Net Amounts of Liabilities Presented in the Balance Sheet	4,962	352
Collateral	0	0
Net Amount	4,962	352
Other Liabilities \| Foreign Currency Forward Contracts, Investment Operations
Derivative Liabilities
Gross Amounts of Recognized Liabilities	208	724
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	106	649
Net Amounts of Liabilities Presented in the Balance Sheet	102	75
Collateral	0	0
Net Amount	102	75
Other Liabilities \| Credit Default Swaps
Derivative Liabilities
Gross Amounts of Recognized Liabilities	14	251
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	13	88
Net Amounts of Liabilities Presented in the Balance Sheet	1	163
Collateral	0	0
Net Amount	1	163
Other Liabilities \| Weather Contract
Derivative Liabilities
Gross Amounts of Recognized Liabilities	24	190
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	0	0
Net Amounts of Liabilities Presented in the Balance Sheet	24	190
Collateral	24	190
Net Amount	$ 0	$ 0

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

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