Long-term Incentive Compensation (Summary of Liability-Classified Performance Cash Awards ) (Details) - Performance units - $ / shares shares in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Number of Units
Beginning balance (in shares)	5,142
Granted (in shares)	6,172
Vested (in shares)	0
Forfeited (in shares)	(2,300)
Ending balance (in shares)	9,014
Weighted Average Fair Value
Beginning balance (in dollars per share)	$ 2.42
Granted (in dollars per share)	1.41
Vested (in dollars per share)	0
Forfeited (in dollars per share)	3.06
Ending balance (in dollars per share)	$ 2.10
Vesting period	3 years	3 years	3 years