Share-Based Compensation - Stock Option Activity Table (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding, beginning balance (in shares options)	18,096
Granted (in shares options)	1,000
Exercised (in shares options)	0
Expired (in shares options)	(451)
Forfeited (in shares options)	(554)
Outstanding, ending balance (in shares options)	18,091	18,096
Weighted Average Exercise Price Per Share
Outstanding, beginning (in dollars per share)	$ 7.20
Granted (in dollars per share)	2.97
Exercised (in dollars per share)	0
Expired (in dollars per share)	6.57
Forfeited (in dollars per share)	3.82
Outstanding, ending (in dollars per share)	$ 7.09	$ 7.20
Weighted average contract life, outstanding	6 years 4 months 20 days	7 years 1 month 24 days
Aggregate intrinsic value, outstanding	$ 0	$ 0
Aggregate intrinsic value, exercised	$ 0
Exercisable (in shares options)	13,030
Weighted average exercise price, exercisable (in dollars per share)	$ 8.29
Weighted average contract life, exercisable (in years)	5 years 7 months 2 days
Aggregate intrinsic value, exercisable	$ 0