Borrowings (Summary Of Securities Sold Under Agreements To Repurchase And Other Borrowings) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	$ 437,749	$ 440,431
Fed funds purchased	825,000	600,000
Securities sold under agreements to repurchase and other borrowings	$ 1,262,749	$ 1,040,431
Securities Sold under Agreements to Repurchase [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.51%	0.91%
Federal Funds Purchased [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.17%	1.59%
Federal Funds Purchased and Securities Sold under Agreements to Repurchase [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.29%	1.30%
Original maturity of one year or less [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	$ 237,749	$ 240,431
Original maturity of one year or less [Member] | Securities Sold under Agreements to Repurchase [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.24%	0.19%
Original maturity of greater than one year, non-callable [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	$ 200,000	$ 200,000
Original maturity of greater than one year, non-callable [Member] | Securities Sold under Agreements to Repurchase [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.84%	1.78%