Debt Obligations (0.875% Senior Unsecured Notes Due 2030) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Debt Instrument [Line Items]
Proceeds from issuances of long-term debt, net of issuance costs	$ 644	$ 0
Increase in carrying amount	$ (680)
3.875% senior unsecured notes repaid on March 16, 2020
Debt Instrument [Line Items]
Stated rate	3.875%
Senior Notes \| 0.875% Senior Unsecured Notes Due 2030
Debt Instrument [Line Items]
Stated rate	0.875%
Senior Notes \| 3.875% senior unsecured notes repaid on March 16, 2020
Debt Instrument [Line Items]
Stated rate	3.875%
Increase in carrying amount	$ (671)

Payments (Accretions) And Other of Long-term Debt

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- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

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.

+ References

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- Definition

The cash inflow from a borrowing with the highest claim on the assets of the entity in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle, if longer).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3255-108585

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