Fair Value Disclosures (Summary Of Gains (Losses) Due To Changes In Instrument Specific Credit Risk For Loans and Other Receivables And Loan Commitments Measured At Fair Value Under Fair Value Option) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Financial Instruments [Line Items]
Loans and other receivables	$ 2,628	$ (5,127)
Financial Instruments Sold
Financial Instruments [Line Items]
Loans	250	(27)
Loan commitments	(129)	871
Long-term Debt
Financial Instruments [Line Items]
Loan commitments	(16,202)	(16,040)
Other changes in fair value	$ 41,154	$ 3,417