Income Taxes (Summary Of The Tax Years By Jurisdiction That Remain Subject To Examination By Taxing Authorities) (Details)	12 Months Ended
	Dec. 31, 2020
Minimum [Member] | United States Federal [Member]
Tax years open	2017
Maximum [Member] | United States Federal [Member]
Tax years open	2020
Various U.S. States [Member] | Minimum [Member]
Tax years open	2016
Various U.S. States [Member] | Maximum [Member]
Tax years open	2020
Canada [Member] | Minimum [Member]
Tax years open	2004
Canada [Member] | Maximum [Member]
Tax years open	2020