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Debt - Schedule of Long-Term Debt (Details) - USD ($) $ in Millions | Dec. 31, 2021 | Sep. 30, 2021 | Sep. 02, 2021 | Jan. 15, 2021 | Dec. 31, 2020 | May 21, 2020 | Apr. 24, 2020 | Apr. 06, 2020
--- | --- | --- | --- | --- | --- | --- | --- | ---
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Other | $ (18) |  |  |  | $ (12) |  |  |
Long-term debt | 4,232 |  |  |  | 5,075 |  |  |
Less: amount due within one year | 5 |  |  |  | 376 |  |  |
Total long-term debt | 4,227 |  |  |  | $ 4,699 |  |  |
5.400% Notes, due 2021 |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Long- term debt, interest rate |  |  |  | 5.40% | 5.40% | 5.40% |  | 5.40%
Amount outstanding | 0 |  |  |  | $ 361 |  |  |
5.870% Notes, due 2022 |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Long- term debt, interest rate |  |  |  |  | 5.87% | 5.87% |  |
Amount outstanding | $ 0 |  |  |  | $ 476 |  |  |
5.125% Notes, due 2024 |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Long- term debt, interest rate | 5.125% | 5.125% |  |  |  |  |  |
Amount outstanding | $ 1,150 |  |  |  | 1,250 |  |  |
6.875% Notes, due 2025 |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Long- term debt, interest rate | 6.875% |  | 6.875% |  |  |  | 6.875% |
Amount outstanding | $ 600 |  |  |  | 1,200 |  |  |
5.900% Notes, due 2027 |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Long- term debt, interest rate | 5.90% |  |  |  |  |  |  |
Amount outstanding | $ 625 |  |  |  | 625 |  |  |
6.750% Bonds, due 2028 |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Long- term debt, interest rate | 6.75% |  |  |  |  |  |  |
Amount outstanding | $ 300 |  |  |  | 300 |  |  |
3.000% Notes due 2029 |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Long- term debt, interest rate | 3.00% |  |  |  |  |  |  |
Amount outstanding | $ 700 |  |  |  | 0 |  |  |
5.950% Notes, due 2037 |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Long- term debt, interest rate | 5.95% |  |  |  |  |  |  |
Amount outstanding | $ 625 |  |  |  | 625 |  |  |
4.750% Iowa Finance Authority Loan, due 2042 |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Long- term debt, interest rate | 4.75% |  |  |  |  |  |  |
Amount outstanding | $ 250 |  |  |  | $ 250 |  |  |

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