Long-Term Incentive Compensation (Summary of Equity-Classified Stock Option Activity) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Number of Shares
Number of Options, Outstanding at January 1 (in shares)	4,635,000	5,178,000	6,020,000
Number of Options, Granted (in shares)	0	0	0
Number of Options, Exercised (in shares)	0	0	0
Number of Options, Forfeited or expired (in shares)	(785,000)	(543,000)	(842,000)
Number of Options, Outstanding at December 31 (in shares)	3,850,000	4,635,000	5,178,000
Weighted Average Exercise Price
Weighted Average Exercise Price, Outstanding at January 1 (in dollars per share)	$ 15.26	$ 17.06	$ 19.43
Weighted Average Exercise Price, Granted (in dollars per share)	0	0	0
Weighted Average Exercise Price, Exercised (in dollars per share)	0	0	0
Weighted Average Exercise Price, Forfeited or expired (in dollars per share)	24.46	32.38	33.99
Weighted Average Exercise Price, Outstanding at December 31 (in dollars per share)	$ 13.39	$ 15.26	$ 17.06