Borrowings (Summary Of Securities Sold Under Agreements To Repurchase And Other Borrowings) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Assets Sold under Agreements to Repurchase [Line Items]
Amount	$ 2,300,000	$ 3,500,000
Securities sold under agreements to repurchase
Assets Sold under Agreements to Repurchase [Line Items]
Amount	$ 478,122	$ 440,431
Rate	0.35%	0.91%
Fed funds purchased
Assets Sold under Agreements to Repurchase [Line Items]
Amount	$ 823,700	$ 600,000
Rate	0.08%	1.59%
Securities sold under agreements to repurchase and other borrowings
Assets Sold under Agreements to Repurchase [Line Items]
Amount	$ 1,301,822	$ 1,040,431
Rate	0.18%	1.30%
Original maturity of one year or less | Securities sold under agreements to repurchase
Assets Sold under Agreements to Repurchase [Line Items]
Amount	$ 278,122	$ 240,431
Rate	0.19%	0.19%
Original maturity of greater than one year, non-callable | Securities sold under agreements to repurchase
Assets Sold under Agreements to Repurchase [Line Items]
Amount	$ 200,000	$ 200,000
Rate	0.57%	1.78%