Fair Value of Financial Instruments (Schedule of Estimated Fair Value of Financial Instruments, by Balance Sheet Grouping) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Assets:
Investments in equity securities	$ 131	$ 137
Available-for-sale securities	95	93
Trading securities	11	11
Carrying Amount [Member]
Assets:
Cash and cash equivalents	277	196
Investments in equity securities	131	137
Available-for-sale securities	95	93
Trading securities	11	11
Carrying Amount [Member] | Credit Facility, Type of Debt [Member] | Credit Facility, Name [Member]
Liabilities:
Credit Facility, Fair Value Disclosure		1,602
Carrying Amount [Member] | Senior Notes [Member] | Senior Notes at 8.0, Due 2019 [Member]
Liabilities:
Notes Payable, Fair Value Disclosure	155	155
Carrying Amount [Member] | Senior Notes [Member] | Senior Notes at 7.125, Due 2020 [Member]
Liabilities:
Notes Payable, Fair Value Disclosure	121	121
Carrying Amount [Member] | Senior Notes [Member] | Senior Notes at 6.875, Due 2022 [Member]
Liabilities:
Notes Payable, Fair Value Disclosure	2,596	2,593
Carrying Amount [Member] | Senior Secured Notes [Member] | Senior Secured Notes at 5.125, Due 2021 [Member]
Liabilities:
Notes Payable, Fair Value Disclosure	985	984
Carrying Amount [Member] | Senior Secured Notes [Member] | Senior Secured Notes at 6.25, Due 2023 [Member]
Liabilities:
Notes Payable, Fair Value Disclosure	3,069	3,067
Carrying Amount [Member] | Senior Secured Notes [Member] | Senior Secured Notes at 8.625, Due 2024 [Member]
Liabilities:
Notes Payable, Fair Value Disclosure	1,022	1,021
Carrying Amount [Member] | Senior Secured Notes [Member] | Senior Secured Notes at 8.0, Due 2026 [Member]
Liabilities:
Notes Payable, Fair Value Disclosure	1,572
Carrying Amount [Member] | Junior-Priority Secured Notes [Member] | Junior-Priority Secured Notes Due 2023 [Member]
Liabilities:
Notes Payable, Fair Value Disclosure	1,751	1,750
Carrying Amount [Member] | Junior-Priority Secured Notes [Member] | Junior-Priority Secured Notes Due 2024 [Member]
Liabilities:
Notes Payable, Fair Value Disclosure	1,339	1,338
Carrying Amount [Member] | Receivables Facility and Other Debt, Type [Member] | ABL Facility and Other Debt [Member]
Liabilities:
Notes Payable, Fair Value Disclosure	762	734
Estimated Fair Value [Member]
Assets:
Cash and cash equivalents	277	196
Investments in equity securities	131	137
Available-for-sale securities	95	93
Trading securities	11	11
Estimated Fair Value [Member] | Credit Facility, Type of Debt [Member] | Credit Facility, Name [Member]
Liabilities:
Credit Facility, Fair Value Disclosure		1,564
Estimated Fair Value [Member] | Senior Notes [Member] | Senior Notes at 8.0, Due 2019 [Member]
Liabilities:
Notes Payable, Fair Value Disclosure	153	146
Estimated Fair Value [Member] | Senior Notes [Member] | Senior Notes at 7.125, Due 2020 [Member]
Liabilities:
Notes Payable, Fair Value Disclosure	115	100
Estimated Fair Value [Member] | Senior Notes [Member] | Senior Notes at 6.875, Due 2022 [Member]
Liabilities:
Notes Payable, Fair Value Disclosure	1,745	1,175
Estimated Fair Value [Member] | Senior Secured Notes [Member] | Senior Secured Notes at 5.125, Due 2021 [Member]
Liabilities:
Notes Payable, Fair Value Disclosure	983	934
Estimated Fair Value [Member] | Senior Secured Notes [Member] | Senior Secured Notes at 6.25, Due 2023 [Member]
Liabilities:
Notes Payable, Fair Value Disclosure	2,919	2,819
Estimated Fair Value [Member] | Senior Secured Notes [Member] | Senior Secured Notes at 8.625, Due 2024 [Member]
Liabilities:
Notes Payable, Fair Value Disclosure	1,034	1,025
Estimated Fair Value [Member] | Senior Secured Notes [Member] | Senior Secured Notes at 8.0, Due 2026 [Member]
Liabilities:
Notes Payable, Fair Value Disclosure	1,536
Estimated Fair Value [Member] | Junior-Priority Secured Notes [Member] | Junior-Priority Secured Notes Due 2023 [Member]
Liabilities:
Notes Payable, Fair Value Disclosure	1,444	1,380
Estimated Fair Value [Member] | Junior-Priority Secured Notes [Member] | Junior-Priority Secured Notes Due 2024 [Member]
Liabilities:
Notes Payable, Fair Value Disclosure	1,011	976
Estimated Fair Value [Member] | Receivables Facility and Other Debt, Type [Member] | ABL Facility and Other Debt [Member]
Liabilities:
Notes Payable, Fair Value Disclosure	$ 762	$ 734