Fair Value of Assets and Liabilities - Carrying Value and Estimated Fair Value of Financial Instruments (Parenthetical) (Details)	Sep. 30, 2021	Dec. 31, 2020
5.875% Senior Notes due 2022
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Stated interest rate	5.875%	5.875%
5.125% Senior Notes due 2023
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Stated interest rate	5.125%	5.125%
5.875% Senior Notes due 2024
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Stated interest rate	5.875%	5.875%
6.00% Senior Notes due 2026
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Stated interest rate	6.00%	6.00%
6.50% Exchangeable Senior Notes due 2026
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Stated interest rate	6.50%