Securities Sold Under Agreements To Repurchase (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Securities sold under agreements to repurchase average	$ 370.0	$ 299.6	$ 282.6
Securities sold under agreements to repurchase maximum outstanding	$ 398.4	$ 336.8	$ 315.4