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Long-term Debt and Finance Leases - Schedule of Long-term Debt and Finance Leases (Details) $ / shares in Units, $ in Millions |  | 12 Months Ended |  |  |  |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Jan. 29, 2021 $ / shares | Dec. 31, 2020 USD ($) $ / shares | Dec. 31, 2019 USD ($) $ / shares | Dec. 02, 2020 | Mar. 11, 2020 | May 28, 2019 | May 24, 2019 | May 14, 2019 | Dec. 07, 2017 | Aug. 02, 2016 | May 23, 2016
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  | $ 8,855 | $ 6,042 |  |  |  |  |  |  |  |
Finance leases |  | 4 | 0 |  |  |  |  |  |  |  |
Subtotal long-term debt and finance leases (including current maturities) |  | 8,859 | 6,042 |  |  |  |  |  |  |  |
Less current maturities |  | (1) | (88) |  |  |  |  |  |  |  |
Less debt issuance costs |  | (93) | (65) |  |  |  |  |  |  |  |
Discounts |  | (74) | (86) |  |  |  |  |  |  |  |
Total long-term debt and finance leases |  | 8,691 | 5,803 |  |  |  |  |  |  |  |
Debt Instrument, Unamortized Discount [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total discounts |  | (74) | (86) |  |  |  |  |  |  |  |
Recourse Debt |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  | 8,855 | 6,008 |  |  |  |  |  |  |  |
Recourse Debt | Senior Notes, due 2026 |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  | $ 1,000 | 1,000 |  |  |  |  |  |  |  |
Interest rate, stated percentage |  | 7.25% |  |  |  |  |  |  |  |  | 7.25%
Recourse Debt | Senior Notes, due 2027 |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  | $ 1,230 | 1,230 |  |  |  |  |  |  |  |
Interest rate, stated percentage |  | 6.625% |  |  |  |  |  |  |  | 6.625% |
Recourse Debt | Senior Notes, due 2028 |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  | $ 821 | 821 |  |  |  |  |  |  |  |
Interest rate, stated percentage |  | 5.75% |  |  |  |  |  |  | 5.75% |  |
Recourse Debt | Senior Notes, due 2029 |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  | $ 733 | 733 |  |  |  |  |  |  |  |
Interest rate, stated percentage |  | 5.25% |  |  |  |  | 5.25% | 5.25% |  |  |
Recourse Debt | Senior Notes, due 2029 |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  | $ 500 | 0 |  |  |  |  |  |  |  |
Interest rate, stated percentage |  | 3.375% |  | 3.375% |  |  |  |  |  |  |
Recourse Debt | 3.625% Senior Unsecured Notes Due 2031 [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  | $ 1,030 | 0 |  |  |  |  |  |  |  |
Interest rate, stated percentage |  | 3.625% |  | 3.625% |  |  |  |  |  |  |
Recourse Debt | Convertible Senior Notes Due 2048 |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  | $ 575 | 575 |  |  |  |  |  |  |  |
Discounts |  | $ (72) | $ (85) |  |  |  |  |  |  |  |
Interest rate, stated percentage |  | 2.75% |  |  |  |  |  |  |  |  |
Effective rate |  | 5.19% | 5.05% |  |  |  |  |  |  |  |
Conversion price per common share (in usd per share) | $ / shares |  | $ 46.24 | $ 47.74 |  |  |  |  |  |  |  |
Conversion ratio |  | 0.0216242 | 0.0209479 |  |  |  |  |  |  |  |
Debt Instrument, Unamortized Discount [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total discounts |  | $ (72) | $ (85) |  |  |  |  |  |  |  |
Recourse Debt | Convertible Senior Notes Due 2048 | Subsequent Event |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Conversion price per common share (in usd per share) | $ / shares | $ 45.94 |  |  |  |  |  |  |  |  |  |
Conversion ratio | 0.02177 |  |  |  |  |  |  |  |  |  |
Debt discount amortization period | 4 years 8 months 12 days |  |  |  |  |  |  |  |  |  |
Recourse Debt | Senior Secured First Lien Notes, due 2024 |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  | $ 600 | 600 |  |  |  |  |  |  |  |
Interest rate, stated percentage |  | 3.75% |  |  |  | 2.75% |  |  |  |  |
Recourse Debt | Senior Secured First Lien Notes, due 2025 |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  | $ 500 | 0 |  |  |  |  |  |  |  |
Interest rate, stated percentage |  | 2.00% |  | 2.00% |  |  |  |  |  |  |
Recourse Debt | Senior Secured First Lien Notes, due 2027 |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  | $ 900 | 0 |  |  |  |  |  |  |  |
Interest rate, stated percentage |  | 2.45% |  | 2.45% |  |  |  |  |  |  |
Recourse Debt | Senior Secured First Lien Notes, due 2029 |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  | $ 500 | 500 |  |  |  |  |  |  |  |
Interest rate, stated percentage |  | 4.45% |  |  |  | 4.45% |  |  |  |  |
Recourse Debt | Tax-exempt bonds |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  | $ 466 | 466 |  |  |  |  |  |  |  |
Recourse Debt | Tax-exempt bonds | Minimum |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate, stated percentage |  | 1.25% |  |  | 1.30% |  |  |  |  |  |
Recourse Debt | Tax-exempt bonds | Maximum |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest rate, stated percentage |  | 4.75% |  |  |  |  |  |  |  |  |
Recourse Debt | Senior Secured First Lien Notes, due 2024, 2025, 2027 and 2029 |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Discounts |  | $ (2) | (1) |  |  |  |  |  |  |  |
Debt Instrument, Unamortized Discount [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total discounts |  | (2) | (1) |  |  |  |  |  |  |  |
Line of Credit | Revolving Credit Facility | Revolving Credit Facility |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  | $ 0 | 83 |  |  |  |  |  |  |  |
Line of Credit | Revolving Credit Facility | Revolving Credit Facility | LIBOR |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Basis spread on variable rate (as a percent) |  | 1.75% |  |  |  |  |  |  |  |  |
Non Recourse Debt |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  | $ 0 | 34 |  |  |  |  |  |  |  |
Non Recourse Debt | Other |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  | $ 0 | $ 34 |  |  |  |  |  |  |  |

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