Unconsolidated Affiliates Accounted For Under The Equity Method (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Unconsolidated Affiliates Accounted For Under The Equity Method [Abstract]
Investment income from equity-method investments	$ 0.0	$ 0.0	$ 0.1
Equity-method investments	$ 7.4	$ 8.0

Amount of income (loss) for proportionate share of equity method investee's income (loss).

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Name:	us-gaap_IncomeLossFromEquityMethodInvestments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration