Share-Based Compensation - Stock Option Activity Table (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	1 Months Ended	12 Months Ended
	Feb. 09, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding, beginning balance (in shares)	20	90	90
Granted (in shares)	0	0	5
Exercised (in shares)	0	0	0
Expired (in shares)	(1)	(23)	(2)
Forfeited (in shares)	(19)	(47)	(3)
Outstanding, ending balance (in shares)	0	20	90	90
Weighted Average Exercise Price Per Share
Outstanding, beginning balance (in usd per share)	$ 1,429.11	$ 1,420.9	$ 1,440.18
Granted (in usd per share)	0	0	594.00
Exercised (in usd per share)	0	0	0
Expired (in usd per share)	741.86	914.50	1,272.94
Forfeited (in usd per share)	1,452.4	1,666.21	793.40
Outstanding, ending balance (in usd per share)	$ 0	$ 1,429.11	$ 1,420.9	$ 1,440.18
Options outstanding, weighted average contract life		4 years 3 months 7 days	5 years 8 months 12 days	7 years 1 month 24 days
Options outstanding, aggregate intrinsic value	$ 0	$ 0	$ 0	$ 0
Options exercised, aggregate intrinsic value	$ 0	$ 0	$ 0
Options exercisable, shares underlying options (in shares)	0	19	65
Options exercisable, average exercise price per share (in usd per share)	$ 0	$ 1,439.55	$ 1,656.14
Options exercisable, weighted average contract life		4 years 4 months 6 days	4 years 10 months 9 days
Options exercisable, aggregate intrinsic value	$ 0	$ 0	$ 0