Debt (Schedule of long-term debt instruments) (Details) - USD ($)	3 Months Ended
Mar. 31, 2021	Dec. 31, 2020
Debt Instrument
Finance leases	$ 131,000,000	$ 135,000,000
Total debt	9,082,000,000	9,682,000,000
Less short-term portion	(585,000,000)	(704,000,000)
Total long-term debt	8,497,000,000	8,978,000,000
Term loan facility expiring 2025
Debt Instrument
Long-term debt	$ 969,000,000	971,000,000
Annual repayment rate	1.00%
Line of Credit \| $3.75 billion ABL Facility expiring 2024
Debt Instrument
Maximum borrowing capacity	$ 3,750,000,000
Long-term debt	491,000,000	977,000,000
Borrowing capacity, net of letters of credit	3,191,000,000
Letters of credit	$ 60,000,000
Interest rate at March 31, 2021	1.30%
Average month-end debt outstanding	$ 624,000,000
Weighted-average interest rate on average debt outstanding	1.30%
Maximum month-end debt outstanding	$ 774,000,000
Senior notes \| 5 7/8 percent Senior Notes due 2026
Debt Instrument
Stated interest rate	5.875%
Long-term debt	$ 999,000,000	999,000,000
Senior notes \| 5 1/2 percent Senior Notes due 2027
Debt Instrument
Stated interest rate	5.50%
Long-term debt	$ 994,000,000	994,000,000
Senior notes \| 3 7/8 percent Senior Secured Notes due 2027
Debt Instrument
Stated interest rate	3.875%
Long-term debt	$ 742,000,000	742,000,000
Senior notes \| 4 7/8 percent Senior Notes due 2028
Debt Instrument
Stated interest rate	4.875%
Long-term debt	$ 1,655,000,000	1,654,000,000
Senior notes \| 4 7/8 percent Senior Notes due 2028
Debt Instrument
Stated interest rate	4.875%
Long-term debt	$ 4,000,000	4,000,000
Senior notes \| 5 1/4 percent Senior Notes due 2030
Debt Instrument
Stated interest rate	5.25%
Long-term debt	$ 743,000,000	742,000,000
Senior notes \| 4 percent Senior Notes due 2030
Debt Instrument
Stated interest rate	4.00%
Long-term debt	$ 742,000,000	742,000,000
Senior notes \| 3 7/8 percent Senior Notes due 2031
Debt Instrument
Stated interest rate	3.875%
Long-term debt	$ 1,088,000,000	1,088,000,000
Line of Credit \| Accounts Receivable Securitization Facility expiring 2021
Debt Instrument
Long-term debt	524,000,000	$ 634,000,000
Borrowing capacity, net of letters of credit	$ 276,000,000
Interest rate at March 31, 2021	1.40%
Average month-end debt outstanding	$ 603,000,000
Weighted-average interest rate on average debt outstanding	1.40%
Maximum month-end debt outstanding	$ 644,000,000
Collateral amount	787,000,000
Line of Credit \| Term loan facility
Debt Instrument
Borrowing capacity, net of letters of credit	$ 0
Interest rate at March 31, 2021	1.90%
Average month-end debt outstanding	$ 977,000,000
Weighted-average interest rate on average debt outstanding	1.90%
Maximum month-end debt outstanding	$ 978,000,000

Debt Instrument, Annual Repayment Rate

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- Definition

Amount of short-term and long-term debt and lease obligation.

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- Definition

Amount of short-term debt and current maturity of long-term debt and capital lease obligations due within one year or the normal operating cycle, if longer.

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- Definition

Amount of assets pledged to secure a debt instrument.

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Contractual interest rate for funds borrowed, under the debt agreement.

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- Definition

Present value of lessee's discounted obligation for lease payments from finance lease.

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The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

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Average amount borrowed under the credit facility during the period.

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The effective interest rate at the end of the reporting period.

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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Maximum month-end amount borrowed under the credit facility during the period.

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Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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- Definition

Amount of long-term debt and lease obligation, classified as noncurrent.

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- Definition

Weighted average interest rate of short-term debt outstanding calculated at point in time.

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