Long-Term Debt (Schedule of Debt) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Debt	$ 15,244	$ 16,785
Current maturities of long-term debt	(455)	(229)
Long-term debt	14,789	16,556
Secured Debt [Member] | Credit Facility, Term Loan A [Member]
Debt Instrument [Line Items]
Debt	745	844
Secured Debt [Member] | Credit Facility, Term Loan F [Member]
Debt Instrument [Line Items]
Debt	1,435	1,671
Secured Debt [Member] | Credit Facility, Term Loan G [Member]
Debt Instrument [Line Items]
Debt	1,510	1,568
Secured Debt [Member] | Credit Facility, Term Loan H [Member]
Debt Instrument [Line Items]
Debt	2,776	2,884
Line of Credit [Member] | Credit Facility, Revolving Credit Loans [Member]
Debt Instrument [Line Items]
Debt	(10)	147
Senior Notes [Member] | Senior Notes at 8.0, Due 2019 [Member]
Debt Instrument [Line Items]
Debt	1,920	1,992
Senior Notes [Member] | Senior Notes at 7.125, Due 2020 [Member]
Debt Instrument [Line Items]
Debt	1,189	1,186
Senior Notes [Member] | Senior Notes at 6.875, Due 2022 [Member]
Debt Instrument [Line Items]
Debt	2,932	2,921
Senior Secured Notes [Member] | Senior Secured Notes At 5.125 Due 2018 [Member]
Debt Instrument [Line Items]
Debt	698	1,587
Senior Secured Notes [Member] | Senior Secured Notes at 5.125, Due 2021 [Member]
Debt Instrument [Line Items]
Debt	972	967
Receivables Facility [Member] | Receivables Facility, Name [Member]
Debt Instrument [Line Items]
Debt	675	699
Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Debt	328	227
Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt	$ 74	$ 92