Income Taxes (Unrecognized Tax Benefits) (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Unrecognized tax benefits
Reserve for unrecognized tax benefits, including interest and penalties	$ 35.9	$ 36.6	$ 38.9
Amounts that would affect the effective tax rate if recognized	35.9	36.6	38.9
Federal tax effect for unrecognized tax benefits	7.5
Accrual of interest and penalties related to uncertain tax positions	5.0	5.1	5.1
Tax expense related to an increase in liabilities for interest and penalties	2.2	$ 2.7	$ 2.3
Reduction of unrecognized tax benefits due to lapse of statute of limitations and settlements over the next twelve months	$ 6.0
Open tax year	2017