We classify our cash equivalents and marketable debt securities within Level 1 or Level 2 because we use quoted market prices or alternative pricing sources and models utilizing market observable inputs to determine their fair value. Certain other assets are classified within Level 3 because factors used to develop the estimated fair value are unobservable inputs that are not supported by market activity.

The following tables summarize our assets measured at fair value on a recurring basis and the classification by level of input within the fair value hierarchy (in millions):


			Fair Value Measurement at Reporting Date Using
	September 30, 2024		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Cash	$	6,529
Cash equivalents:
Money market funds	36,172		$	36,172	$	—	$	—
U.S. government and agency securities	696		696		—		—

Time deposits	290		—		290		—
Corporate debt securities	165		—		165		—
Total cash and cash equivalents	43,852		36,868		455		—
Marketable securities:
U.S. government securities	11,314		11,314		—		—
U.S. government agency securities	2,998		2,998		—		—
Corporate debt securities	12,736		—		12,736		—

Total marketable securities	27,048		14,312		12,736		—
Restricted cash equivalents	1,153		1,153		—		—
Other assets	102		—		—		102
Total	$	72,155	$	52,333	$	13,191	$	102


			Fair Value Measurement at Reporting Date Using
	December 31, 2023		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Cash	$	6,265
Cash equivalents:
Money market funds	32,910		$	32,910	$	—	$	—
U.S. government and agency securities	2,206		2,206		—		—

Time deposits	261		—		261		—
Corporate debt securities	220		—		220		—
Total cash and cash equivalents	41,862		35,116		481		—
Marketable securities:
U.S. government securities	8,439		8,439		—		—
U.S. government agency securities	3,498		3,498		—		—
Corporate debt securities	11,604		—		11,604		—

Total marketable securities	23,541		11,937		11,604		—
Restricted cash equivalents	857		857		—		—
Other assets	101		—		—		101
Total	$	66,361	$	47,910	$	12,085	$	101

The following tables summarize our available-for-sale marketable debt securities and cash equivalents with unrealized losses as of September 30, 2024 and December 31, 2023, aggregated by major security type and the length of time that individual securities have been in a continuous loss position (in millions):


	September 30, 2024
	Less than 12 months				12 months or greater				Total
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
U.S. government securities	$	1,140	$	(2)	$	4,744	$	(126)	$	5,884	$	(128)
U.S. government agency securities	123		—		2,407		(63)		2,530		(63)
Corporate debt securities	504		(1)		7,031		(209)		7,535		(210)
Total	$	1,767	$	(3)	$	14,182	$	(398)	$	15,949	$	(401)


	December 31, 2023
	Less than 12 months				12 months or greater				Total
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
U.S. government securities	$	336	$	(1)	$	7,041	$	(275)	$	7,377	$	(276)
U.S. government agency securities	71		—		3,225		(164)		3,296		(164)
Corporate debt securities	647		(3)		10,125		(491)		10,772		(494)
Total	$	1,054	$	(4)	$	20,391	$	(930)	$	21,445	$	(934)

Our non-marketable equity securities accounted for using the measurement alternative are measured at fair value on a non-recurring basis and are classified within Level 3 of the fair value hierarchy because we use significant unobservable inputs to estimate their fair value. During the three and nine months ended September 30, 2024 and 2023, changes in the fair value recorded for these non-marketable equity securities were not material.