Borrowings (Summary Of Securities Sold Under Agreements To Repurchase And Other Borrowings) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets Sold under Agreements to Repurchase [Line Items]
Total securities sold under agreements to repurchase	$ 588,269	$ 740,526
Fed funds purchased	55,000	209,000
Securities sold under agreements to repurchase and other borrowings	643,269	949,526
Original maturity of one year or less [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Total securities sold under agreements to repurchase	288,269	340,526
Original maturity of greater than one year, non-callable [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Total securities sold under agreements to repurchase	$ 300,000	$ 400,000
Securities Sold under Agreements to Repurchase [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Rate (as a percent)	1.66%	1.82%
Securities Sold under Agreements to Repurchase [Member] | Original maturity of one year or less [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Rate (as a percent)	0.17%	0.16%
Securities Sold under Agreements to Repurchase [Member] | Original maturity of greater than one year, non-callable [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Rate (as a percent)	3.10%	3.09%
Federal Funds Purchased [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Rate (as a percent)	1.37%	0.46%
Federal Funds Purchased and Securities Sold under Agreements to Repurchase [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Rate (as a percent)	1.64%	1.53%