Financing (Senior Notes) (Narrative) (Details) $ in Billions	3 Months Ended
Mar. 31, 2018 USD ($) d Rate
Financing
Unsecured senior notes description	The Company has issued a cumulative $2.7 billion aggregate principal amount of unsecured senior notes, which are due between 2021 and 2027, with UMB Bank, N.A. as trustee. Interest on the senior notes, ranging from 3.550% to 4.875%, is payable semi-annually and is computed on the basis of a 360-day year.
Debt instrument covenant description	Each of the senior notes is subject to certain customary covenants, with which the Company complied as of March 31, 2018.
Senior notes [Member]
Financing
Aggregate principle of unsecured senior notes \| $	$ 2.7
Number of days in annual interest calculation period \| d	360
Minimum [Member] \| Senior notes [Member]
Financing
Senior notes maturity, year	2021
Interest rate of senior notes	3.55%
Maximum [Member] \| Senior notes [Member]
Financing
Senior notes maturity, year	2027
Interest rate of senior notes	4.875%

The year when the debt instrument is scheduled to be fully repaid.

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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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