Income Taxes (Difference In Income Tax Expense And Expected Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Expected rate of federal income tax expense	35.00%	35.00%	35.00%
Federal income tax expense at the 'expected' rate of 35%	$ 305.6	$ 276.4	$ 289.1
State income taxes, net of federal benefit	21.5	20.0	21.6
Transition tax	6.5	0.0	0.0
Effect of 2018 deferred rate change	(30.8)	0.0	0.0
Other, net	(8.3)	(6.1)	(1.0)
Income tax expense	$ 294.5	$ 290.3	$ 309.7
Effective income tax rate	33.70%	36.80%	37.50%