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Marketable and Other Securities Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Marketable Securities [Line Items]
Sale proceeds from investments classified as available-for-sale and sold prior to maturity	$ 611	$ 920
Lyft, Inc. [Member] | Level 3 [Member] | Other assets [Member]
Marketable Securities [Line Items]
Fair value of equity securities	1,200		$ 884
Lyft, Inc. [Member] | Level 3 [Member] | Interest Income and Other Non-Operating Income [Member]
Marketable Securities [Line Items]
Unrealized gain on securities	$ 285

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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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