Derivative Instruments (Consolidated Balance Sheets And Fair Value Of The Principal Derivative Instruments) (Details) - Not Designated as Hedging Instrument - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Other Assets
Derivative Assets
Gross Amounts of Recognized Assets	$ 8,809	$ 6,968
Gross Amounts Offset in the Balance Sheet	2,427	1,662
Net Amounts of Assets Presented in the Balance Sheet	6,382	5,306
Collateral	420	0
Net Amount	5,962	5,306
Other Assets | Interest Rate Futures
Derivative Assets
Gross Amounts of Recognized Assets	2,781	1,059
Gross Amounts Offset in the Balance Sheet	1,645	937
Net Amounts of Assets Presented in the Balance Sheet	1,136	122
Collateral	0	0
Net Amount	1,136	122
Other Assets | Foreign Currency Forward Contracts, Underwriting and Non-investment Operations
Derivative Assets
Gross Amounts of Recognized Assets	4,677	4,645
Gross Amounts Offset in the Balance Sheet	508	82
Net Amounts of Assets Presented in the Balance Sheet	4,169	4,563
Collateral	0	0
Net Amount	4,169	4,563
Other Assets | Foreign Currency Forward Contracts, Investment Operations
Derivative Assets
Gross Amounts of Recognized Assets	244	1,007
Gross Amounts Offset in the Balance Sheet	168	599
Net Amounts of Assets Presented in the Balance Sheet	76	408
Collateral	0	0
Net Amount	76	408
Other Assets | Credit Default Swaps
Derivative Assets
Gross Amounts of Recognized Assets	1,107	257
Gross Amounts Offset in the Balance Sheet	106	44
Net Amounts of Assets Presented in the Balance Sheet	1,001	213
Collateral	420	0
Net Amount	581	213
Other Liabilities
Derivative Liabilities
Gross Amounts of Recognized Liabilities	3,619	5,481
Gross Amounts Offset in the Balance Sheet	1,919	1,661
Net Amounts of Liabilities Presented in the Balance Sheet	1,700	3,820
Collateral Pledged	419	1,803
Net Amount	1,281	2,017
Other Liabilities | Interest Rate Futures
Derivative Liabilities
Gross Amounts of Recognized Liabilities	1,865	2,293
Gross Amounts Offset in the Balance Sheet	1,645	937
Net Amounts of Liabilities Presented in the Balance Sheet	220	1,356
Collateral Pledged	220	1,356
Net Amount	0	0
Other Liabilities | Foreign Currency Forward Contracts, Underwriting and Non-investment Operations
Derivative Liabilities
Gross Amounts of Recognized Liabilities	1,129	1,891
Gross Amounts Offset in the Balance Sheet	0	81
Net Amounts of Liabilities Presented in the Balance Sheet	1,129	1,810
Collateral Pledged	0	0
Net Amount	1,129	1,810
Other Liabilities | Foreign Currency Forward Contracts, Investment Operations
Derivative Liabilities
Gross Amounts of Recognized Liabilities	200	806
Gross Amounts Offset in the Balance Sheet	168	599
Net Amounts of Liabilities Presented in the Balance Sheet	32	207
Collateral Pledged	0	0
Net Amount	32	207
Other Liabilities | Credit Default Swaps
Derivative Liabilities
Gross Amounts of Recognized Liabilities	425	491
Gross Amounts Offset in the Balance Sheet	106	44
Net Amounts of Liabilities Presented in the Balance Sheet	319	447
Collateral Pledged	199	447
Net Amount	$ 120	$ 0