Debt - Schedule of Carrying Values and Fair Values of Debt Outstanding (Parenthetical) (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Feb. 16, 2021
Senior notes | 5.125% Senior Secured Notes due 2023
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Interest rate		5.125%	5.125%
Debt instrument maturity year		2023
Senior notes | 4.000% Notes due 2027
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Interest rate	4.00%	4.00%
Debt instrument maturity year	2027	2027
Unsecured debt | 7.950% Debentures due 2025
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Interest rate	7.95%	7.95%
Debt instrument maturity year	2025	2025
Unsecured debt | 8.375% Debentures due 2027
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Interest rate	8.375%	8.375%
Debt instrument maturity year	2027	2027