Income Taxes (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Investments, Owned, Federal Income Tax Note [Line Items]
Corporate Federal Income Tax Rate	21.00%
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount	$ (2.0)	$ 47.0	$ 0.0
Deferred Tax Assets, Tax Deferred Expense, Other	45.0
Effect of Change in Tax Rate, Early Adoption	25.0
Deferred Tax Assets, Valuation Allowance, amount	1.0
Unrecognized Tax Benefits, Decreases Resulting from Prior Period Tax Positions	0.0	$ 0.0	$ 0.0
Effective income tax rate reconciliation, at federal statutory income tax rate		35.00%
Deferred Tax Assets, Valuation Allowance	0.0	$ 2.0
Deferred Tax Assets Net Operating Loss And Tax Credit Carry Forward Expiring Through Two Thousand Thirty		2.0
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	7.0	5.0
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued	$ 1.0	$ 0.1