Investments (Schedule of Held-to-Maturity Securities) (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value		$ 0
Commercial Paper [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	$ 3
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	0
Commercial Paper [Member] \| Maximum
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss	1
Short-term Investments [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity investment securities	27	14
Fair Value	27	14
Short-term Investments [Member] \| Corporate And Other Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity investment securities	7	14
Fair Value	7	14
Short-term Investments [Member] \| Commercial Paper [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity investment securities	20	0
Fair Value	$ 20	$ 0

Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity), in unrealized loss position.

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-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
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Fair value of investment in debt security measured at amortized cost (held-to-maturity), in unrealized loss position.

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Fair value of investment in debt security measured at amortized cost (held-to-maturity), in continuous unrealized loss position for less than 12 months.

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Amount of investment in debt security measured at amortized cost (held-to-maturity), classified as current.

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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

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