Stock-Based Compensation (Summary of Restricted Stock Activity) (Details) - Restricted Stock [Member] - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested shares/units at January 1, Number of Shares	3,321,000	7,222,000	2,376,000
Granted, Number of Shares/Units	5,055,000	81,000	5,822,000
Vested, Number of Shares/Units	(1,380,000)	(3,817,000)	(873,000)
Forfeited, Number of Shares/Units	(742,000)	(165,000)	(103,000)
Unvested shares/units at December 31, Number of Shares	6,254,000	3,321,000	7,222,000
Unvested shares/units at January 1, Weighted Average Fair Value	$ 11.85	$ 13.24	$ 34.00
Granted, Weighted Average Fair Value	8.38	8.56	8.07
Vested, Weighted Average Fair Value	13.28	11.34	33.33
Forfeited, Weighted Average Fair Value	10.04	12.05	29.14
Unvested shares at December 31, Weighted Average Fair Value	$ 8.85	$ 11.85	$ 13.24
Workforce Reduction [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vested, Number of Shares/Units		(2,059,626)
Executive Management [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vested, Number of Shares/Units		(151,575)