Long-Term Incentive Compensation (Summary of Equity-Classified Performance Units Activity) (Details) - Performance units - $ / shares	1 Months Ended	12 Months Ended
May 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Number of Shares
Number of Shares/Units, Unvested shares/units at January 1 (in shares)		178,000	598,000	1,084,000
Number of Shares/Units, Granted (in shares)		0	0	0
Number of Shares/Units, Vested (in shares)		(178,000)	(378,000)	(290,000)
Number of Shares/Units, Forfeited (in shares)		0	(42,000)	(196,000)
Number of Shares/Units, Unvested shares/units at December 31 (in shares)		0	178,000	598,000
Weighted Average Fair Value
Weighted Average Fair Value, Unvested shares/units at January 1 (in dollars per share)		$ 10.47	$ 10.01	$ 10.12
Weighted Average Fair Value, Granted (in dollars per share)		0	0	0
Weighted Average Fair Value, Vested (in dollars per share)		10.47	9.59	10.47
Weighted Average Fair Value, Forfeited (in dollars per share)		0	10.47	9.94
Weighted Average Fair Value, Unvested shares/units at December 31 (in dollars per share)		$ 0	$ 10.47	$ 10.01
Vesting period for stock awards from grant date	3 years	3 years	3 years	3 years
Minimum
Number of Shares
Number of Shares/Units, Granted (in shares)		0	0	0
Maximum
Number of Shares
Number of Shares/Units, Granted (in shares)		2	2	2
Workforce Reduction
Number of Shares
Number of Shares/Units, Forfeited (in shares)			(41,761)	(144,927)

Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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