Cash, Cash Equivalents, and Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2015

Investments, Debt and Equity Securities [Abstract]

The following table summarizes, by major security type, our cash, cash equivalents, and marketable securities that are measured at fair value on a recurring basis and are categorized using the fair value hierarchy (in millions):



	December 31, 2015
	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Total Estimated Fair Value
Cash	$	6,201	$	—	$	—		$	6,201
Level 1 securities:
Money market funds	8,025		—		—			8,025
Equity securities	4		11		—			15
Level 2 securities:
Foreign government and agency securities	49		—		—			49
U.S. government and agency securities	5,171		1		(5		)	5,167
Corporate debt securities	479		—		(2		)	477
Asset-backed securities	118		—		(1		)	117
Other fixed income securities	42		—		—			42
	$	20,089	$	12	$	(8	)	$	20,093
Less: Restricted cash, cash equivalents, and marketable securities (1)								(285		)
Total cash, cash equivalents, and marketable securities								$	19,808



	December 31, 2014
	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Total Estimated Fair Value
Cash	$	4,155	$	—	$	—		$	4,155
Level 1 securities:
Money market funds	10,718		—		—			10,718
Equity securities	2		2		—			4
Level 2 securities:
Foreign government and agency securities	80		—		—			80
U.S. government and agency securities	2,407		1		(2		)	2,406
Corporate debt securities	401		1		(1		)	401
Asset-backed securities	69		—		—			69
Other fixed income securities	33		—		—			33
	$	17,865	$	4	$	(3	)	$	17,866
Less: Restricted cash, cash equivalents, and marketable securities (1)								(450		)
Total cash, cash equivalents, and marketable securities								$	17,416

___________________

(1)

We are required to pledge or otherwise restrict a portion of our cash, cash equivalents, and marketable securities as collateral for standby and trade letters of credit, guarantees, debt, real estate leases, and amounts due to third-party sellers in certain jurisdictions. We classify cash, cash equivalents, and marketable securities with use restrictions of less than twelve months as “Accounts receivable, net and other” and of twelve months or longer as non-current “Other assets” on our consolidated balance sheets. See “Note 7—Commitments and Contingencies.”

Realized Gain (Loss) on Investments

The following table summarizes gross gains and gross losses realized on sales of available-for-sale marketable securities (in millions):



	Year Ended December 31,
	2015		2014		2013
Realized gains	$	2	$	8	$	6
Realized losses	7		5		7

Investments Classified by Contractual Maturity Date

The following table summarizes the contractual maturities of our cash equivalents and marketable fixed-income securities as of December 31, 2015 (in millions):



	Amortized Cost		Estimated Fair Value
Due within one year	$	12,533	$	12,531
Due after one year through five years	1,086		1,084
Due after five years through ten years	96		95
Due after ten years	169		167
Total	$	13,884	$	13,877