Stock-Based Compensation (Summary of Equity-Classified Performance Units Activity) (Details) - Performance Units [Member] - $ / shares	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares/Units, Unvested shares/units at January 1, 2018	1,084,000	719,000	407,000
Number of Shares/Units, Granted		1,197,000	1,503,000
Number of Shares/Units, Vested	(290,000)	(325,000)	(889,000)
Number of Shares/Units, Forfeited	(196,000)	(507,000)	(302,000)
Number of Shares/Units, Unvested shares/units at December 31, 2018	598,000	1,084,000	719,000
Weighted Average Fair Value, Unvested shares/units at January 1, 2018	$ 10.12	$ 11.46	$ 36.65
Weighted Average Fair Value, Granted		10.47	8.60
Weighted Average Fair Value, Vested	10.47	12.21	12.78
Weighted Average Fair Value, Forfeited	9.94	9.53	11.26
Weighted Average Fair Value, Unvested shares/units at December 31, 2018	$ 10.01	$ 10.12	$ 11.46
Share-based Compensation Award, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period for stock awards from grant date		3 years
Workforce Reduction [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares/Units, Vested			(22,918)
Number of Shares/Units, Forfeited	(144,927)		(87,595)
Executive Management [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares/Units, Vested			(37,590)
Number of Shares/Units, Forfeited			(195,834)

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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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Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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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 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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The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

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

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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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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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