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

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Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount of unamortized debt discount (premium) and debt issuance costs.

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Represents the aggregate of total long-term debt, including current maturities and short-term debt.

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Weighted average interest rate of debt outstanding.

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The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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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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Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

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Debt (Summary of Long-Term Debt) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Oct. 15, 2019	Sep. 13, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Debt at face value	$ 3,550			$ 3,075
Net unamortized discounts and debt issuance costs	(34)			(27)
Total debt	3,516			3,048
Short-term debt	(25)			(50)
Long-term debt	3,491			2,998
Tax-exempt bonds due April 2020 and April 2021, at 1.850% and 1.885% at December 31, 2019, and 2018, respectively
Debt Instrument [Line Items]
Long-term debt, gross	$ 75			$ 75
Interest rate, stated percentage	1.85%			1.885%
Senior Notes
Debt Instrument [Line Items]
Short-term debt			$ (400)
Senior Notes \| 2.646% Senior Notes due February 2020
Debt Instrument [Line Items]
Long-term debt, gross	$ 0			$ 300
Interest rate, stated percentage	2.646%	2.646%
Senior Notes \| 2.450% Senior Notes due December 2024
Debt Instrument [Line Items]
Long-term debt, gross	$ 300			0
Interest rate, stated percentage	2.45%
Senior Notes \| 3.605% Senior Notes due February 2025
Debt Instrument [Line Items]
Long-term debt, gross	$ 500			500
Interest rate, stated percentage	3.605%
Senior Notes \| 3.550% Senior Notes due October 2026
Debt Instrument [Line Items]
Long-term debt, gross	$ 500			500
Interest rate, stated percentage	3.55%
Senior Notes \| 3.750% Senior Notes due March 2028
Debt Instrument [Line Items]
Long-term debt, gross	$ 500			500
Interest rate, stated percentage	3.75%
Senior Notes \| 3.150% Senior Notes due December 2029
Debt Instrument [Line Items]
Long-term debt, gross	$ 600			0
Interest rate, stated percentage	3.15%
Senior Notes \| 4.680% Senior Notes due February 2045
Debt Instrument [Line Items]
Long-term debt, gross	$ 450			450
Interest rate, stated percentage	4.68%
Senior Notes \| 4.900% Senior Notes due October 2046
Debt Instrument [Line Items]
Long-term debt, gross	$ 625			625
Interest rate, stated percentage	4.90%
Revolving credit facility due January 2019 and October 2021 at weighted-average rate of 3.669% at year-end 2018
Debt Instrument [Line Items]
Credit facility	$ 0			$ 125
Weighted average interest rate				3.669%