Contractual interest rate for funds borrowed, under the debt 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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Debt - Summary (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018	May 17, 2018	Sep. 22, 2016	May 26, 2015
Debt Instrument [Line Items]
Long-term debt	$ 3,663	$ 3,662
Senior Notes \| 3.3% Senior Notes, due 2020
Debt Instrument [Line Items]
Long-term debt	$ 698	698
Stated interest rate (as a percent)	3.30%
Unamortized debt discount and issuance costs	$ 2
Senior Notes \| 4.0% Senior Notes, due 2025
Debt Instrument [Line Items]
Long-term debt	$ 693	693
Stated interest rate (as a percent)	4.00%				4.00%
Unamortized debt discount and issuance costs	$ 7
Senior Notes \| 4.4% Senior Notes, due 2026
Debt Instrument [Line Items]
Long-term debt	$ 893	892
Stated interest rate (as a percent)	4.40%
Unamortized debt discount and issuance costs	$ 7
Senior Notes \| 2.95% Senior Notes, due 2027
Debt Instrument [Line Items]
Long-term debt	$ 493	493
Stated interest rate (as a percent)	2.95%			2.95%
Unamortized debt discount and issuance costs	$ 7
Senior Notes \| 6.55% Senior Notes, due 2037
Debt Instrument [Line Items]
Long-term debt	$ 396	396
Stated interest rate (as a percent)	6.55%
Unamortized debt discount and issuance costs	$ 4
Senior Notes \| 4.5% Senior Notes, due 2048
Debt Instrument [Line Items]
Long-term debt	$ 490	$ 490
Stated interest rate (as a percent)	4.50%		4.50%
Unamortized debt discount and issuance costs	$ 10