Summary of Significant Accounting Policies (New Accounting Pronouncements) (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Effective Income Tax Rate Reconciliation, Equity in Earnings (Losses) of Unconsolidated Subsidiary, Amount	$ 8.0	$ 6.0	$ 10.0
Accounting Standards Update 2016-13 [Member]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	(15.0)
Adjustments for New Accounting Pronouncement [Member]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	(55.2)
Accounting Standards Update 2018-02 [Member]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	0.0	3.0	(18.0)
AOCI Attributable to Parent [Member] | Accounting Standards Update 2018-02 [Member]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification		$ 4.0	$ (157.0)