Income Taxes (Schedule Of Income Taxes (Benefit)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes [Abstract]
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued	$ 1.0	$ 0.1
Current Federal, Income taxes (benefit)	166.0	217.0	$ 158.0
Deferred Federal Income taxes (benefit)	146.0	(4.0)	(32.0)
Federal Income taxes (benefit) total	312.0	213.0	126.0
Current State, Income taxes (benefit)	24.0	27.0	14.0
Deferred State, Income taxes (benefit)	8.0	(4.0)	2.0
State Income taxes (benefit) total	32.0	23.0	16.0
Income Tax Expense (Benefit), Total	$ 344.0	$ 236.0	$ 142.0