New Accounting Standards (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2020	[1]	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Shareholders' deficit	$ 867.2		$ 983.8	$ 896.8	$ 714.7
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Shareholders' deficit	$ 360.5		(2,138.9)	$ (2,234.3)	(2,320.3)
Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Shareholders' deficit			2.0		41.1
Cumulative Effect, Period of Adoption, Adjustment | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Shareholders' deficit			2.0		$ 41.1
Cumulative Effect, Period of Adoption, Adjustment | Retained Earnings | Accounting Standards Update 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Shareholders' deficit			$ 2.0

[1] The number of shares of Common Stock (par value $0.01 per share) outstanding at December 31, 2020 was 101.34.