Income Taxes (Schedule Of Principal Components Of Net Deferred Tax Liability) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Deferred Tax Liabilities
Accelerated depreciation and other property differences	$ 2,339.3	$ 2,516.9
Other regulatory assets	331.8	381.5
Total Deferred Tax Liabilities	2,671.1	2,898.4
Deferred Tax Assets
Other regulatory liabilities and deferred investment tax credits (including TCJA)	287.8	336.1
Pension and other postretirement/postemployment benefits	118.1	152.1
Net operating loss carryforward and AMT credit carryforward	602.1	765.9
Environmental liabilities	22.6	25.4
Other accrued liabilities	41.5	35.3
Other, net	128.4	98.3
Total Deferred Tax Assets	1,200.5	1,413.1
Net Deferred Tax Liabilities	$ 1,470.6	$ 1,485.3