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Marketable and Other Securities - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Marketable Securities [Line Items]
Sale proceeds from investments classified as available-for-sale and sold prior to maturity	$ 486	$ 1,000	$ 1,100	$ 2,000
Lyft, Inc. [Member] | Level 3 [Member] | Other assets [Member]
Marketable Securities [Line Items]
Fair value of equity securities	1,100		1,100		$ 884
Lyft, Inc. [Member] | Level 3 [Member] | Interest Income and Other Non-Operating Income [Member]
Marketable Securities [Line Items]
Unrealized gain (loss) on securities	$ (65)	$ 142	$ 220	$ 142

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