Long-Term Debt (Schedule of Debt) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Debt	$ 13,596	$ 13,913
Less: Unamortized deferred debt issuance costs and note premium	(164)	(169)
Less: Current maturities	(204)	(33)
Long-term debt	13,392	13,880
Senior Secured Notes at 6.25, Due 2023 [Member]
Debt Instrument [Line Items]
Debt	3,100	3,100
Junior-Priority Secured Notes due 2023 [Member]
Debt Instrument [Line Items]
Debt	1,770
Junior-Priority Secured Notes due 2024 [Member]
Debt Instrument [Line Items]
Debt	1,355
Receivables Facility [Member]
Debt Instrument [Line Items]
Debt		565
ABL Credit Agreement [Member]
Debt Instrument [Line Items]
Debt	698
Secured Debt [Member] | Credit Facility, Term Loan G [Member]
Debt Instrument [Line Items]
Debt		1,037
Secured Debt [Member] | Credit Facility, Term Loan H [Member]
Debt Instrument [Line Items]
Debt	1,622	1,903
Senior Notes [Member] | Senior Notes at 8.0, Due 2019 [Member]
Debt Instrument [Line Items]
Debt	155	1,925
Senior Notes [Member] | Senior Notes at 7.125, Due 2020 [Member]
Debt Instrument [Line Items]
Debt	121	1,200
Senior Notes [Member] | Senior Notes at 6.875, Due 2022 [Member]
Debt Instrument [Line Items]
Debt	2,632	3,000
Senior Secured Notes [Member] | Senior Secured Notes at 5.125, Due 2021 [Member]
Debt Instrument [Line Items]
Debt	1,000	1,000
Senior Secured Notes [Member] | Senior Secured Notes at 8.625, Due 2024 [Member]
Debt Instrument [Line Items]
Debt	1,033
Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Debt	231	304
Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt	$ 43	$ 48