Debt and Capital Leases - Schedule of Long-term Debt and Capital Leases (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Debt amount	$ 6,656	$ 6,691
Capital leases	1	1
Subtotal long-term debt and capital leases (including current maturities)	6,657	6,692
Less current maturities	(124)	(72)
Less debt issuance costs	(69)	(70)
Discounts	(98)	(101)
Total long-term debt and capital leases	6,366	6,449
Recourse Debt
Debt Instrument [Line Items]
Debt amount	6,519	6,523
Recourse Debt \| Senior Notes, due 2024
Debt Instrument [Line Items]
Debt amount	$ 733	733
Interest rate, stated percentage	6.25%
Recourse Debt \| Senior Notes, due 2026
Debt Instrument [Line Items]
Debt amount	$ 1,000	1,000
Interest rate, stated percentage	7.25%
Recourse Debt \| Senior Notes, due 2027
Debt Instrument [Line Items]
Debt amount	$ 1,230	1,230
Interest rate, stated percentage	6.625%
Recourse Debt \| Senior Notes, due 2028
Debt Instrument [Line Items]
Debt amount	$ 821	821
Interest rate, stated percentage	5.75%
Recourse Debt \| Convertible Senior Notes, due 2048
Debt Instrument [Line Items]
Debt amount	$ 575	575
Interest rate, stated percentage	2.75%
Recourse Debt \| Term loan facility, due 2023
Debt Instrument [Line Items]
Debt amount	$ 1,694	1,698
Recourse Debt \| Term loan facility, due 2023 \| LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	1.75%
Recourse Debt \| Tax-exempt bonds
Debt Instrument [Line Items]
Debt amount	$ 466	466
Recourse Debt \| Tax-exempt bonds \| Minimum
Debt Instrument [Line Items]
Interest rate, stated percentage	4.125%
Recourse Debt \| Tax-exempt bonds \| Maximum
Debt Instrument [Line Items]
Interest rate, stated percentage	6.00%
Non Recourse Debt
Debt Instrument [Line Items]
Debt amount	$ 137	168
Non Recourse Debt \| Agua Caliente Borrower 1, due 2038
Debt Instrument [Line Items]
Debt amount	$ 83	86
Interest rate, stated percentage	5.43%
Non Recourse Debt \| Midwest Generation, due 2019
Debt Instrument [Line Items]
Debt amount	$ 20	48
Interest rate, stated percentage	4.39%
Non Recourse Debt \| Other
Debt Instrument [Line Items]
Debt amount	$ 34	$ 34

Sum of the carrying values as of the balance sheet date of all debt, including all short-term borrowings, long-term debt, and capital lease obligations.

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