Stock-Based Compensation and Other Employee Benefit Plans (Restricted Shares) (Narrative) (Details) - USD ($) $ in Millions		12 Months Ended
Dec. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Restricted Shares [Member]
Stock-Based Compensation and Other Employee Benefit Plans [Line Items]
Stock-based compensation awards, unearned compensation	$ 37.9	$ 37.9
Stock-based compensation awards, unearned compensation, weighted average expected recognition period (in years)	2 years 1 month 6 days
Stock-based compensation, vested awards, intrinsic value		$ 16.8	$ 25.0	$ 16.6
Unvested stock awards (in shares)	1,845,341	1,845,341	1,221,593	1,270,233
Restricted Stock Units [Member]
Stock-Based Compensation and Other Employee Benefit Plans [Line Items]
Unvested stock awards (in shares)	2,300	2,300	0	18,700

Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Amount of cost to be recognized for nonvested award under share-based payment arrangement. Excludes share and unit options.

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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