Investments - (Tables)

12 Months Ended

Dec. 31, 2020

Investments, Debt and Equity Securities [Abstract]

Amortized cost, gross unrealized gains, gross unrealized losses and estimated fair values of available-for-sale investments by type of security

The amortized cost, gross unrealized gains, gross unrealized losses and fair values of interest-bearing securities, all of which are considered available-for-sale, by type of security were as follows (in millions):


Types of securities as of December 31, 2020	Amortized cost		Gross unrealized gains		Gross unrealized losses		Fair values
U.S. Treasury notes	$	129	$	1	$	—	$	130
U.S. Treasury bills	4,948		—		—		4,948
Corporate debt securities:
Financial	—		—		—		—
Industrial	—		—		—		—
Other	—		—		—		—
Residential-mortgage-backed securities	—		—		—		—

Money market mutual funds	4,765		—		—		4,765
Other short-term interest-bearing securities	2		—		—		2
Total available-for-sale investments	$	9,844	$	1	$	—	$	9,845


Types of securities as of December 31, 2019	Amortized cost		Gross unrealized gains		Gross unrealized losses		Fair values
U.S. Treasury notes	$	359	$	1	$	—	$	360
U.S. Treasury bills	—		—		—		—
Corporate debt securities:
Financial	1,108		13		—		1,121
Industrial	824		10		—		834
Other	195		3		—		198
Residential-mortgage-backed securities	181		1		—		182

Money market mutual funds	5,250		—		—		5,250
Other short-term interest-bearing securities	289		—		—		289


Total available-for-sale investments	$	8,206	$	28	$	—	$	8,234

Fair values of available-for-sale investments by classification in the Consolidated Balance Sheets

The fair values of available-for-sale investments by location in the Consolidated Balance Sheets were as follows (in millions):


	December 31,
Consolidated Balance Sheets locations	2020		2019
Cash and cash equivalents	$	5,464	$	5,360
Marketable securities	4,381		2,874

Total available-for-sale investments	$	9,845	$	8,234

Fair values of available-for-sale interest-bearing security investments by contractual maturity

The fair values of available-for-sale investments by contractual maturity, except for mortgage- and asset-backed securities that do not have a single maturity date, were as follows (in millions):


	December 31,
Contractual maturities	2020		2019
Maturing in one year or less	$	9,795	$	5,629
Maturing after one year through three years	50		2,304
Maturing after three years through five years	—		119


Residential-mortgage-backed securities	—		182
Total available-for-sale investments	$	9,845	$	8,234