Financial Instruments and Fair Value Measurements

12 Months Ended

Dec. 31, 2020

Investments, Debt and Equity Securities [Abstract]

Financial Instruments and Fair Value Measurements

Cash and Cash Equivalents and Investments

The following tables summarize our cash and available-for-sale securities by significant investment category at December 31, 2020 and 2019 (in thousands):


	December 31, 2020
	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value		Cash and Cash Equivalents		Current Marketable Securities		Non- Current Marketable Securities
Cash and cash equivalents	$	2,623,849	$	1	$	—	$	2,623,850	$	2,623,850	$	—	$	—
Available-for-sale:
Certificates of deposit	238,774		49		(4)		238,819		—		215,389		23,430
U.S. treasury securities	491,549		69		—		491,618		—		491,618		—
Debt securities of U.S. government agencies and corporate entities	1,888,022		4,294		(147)		1,892,169		—		1,276,751		615,418
	$	5,242,194	$	4,413	$	(151)	$	5,246,456	$	2,623,850	$	1,983,758	$	638,848


	December 31, 2019
	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value		Cash and Cash Equivalents		Current Marketable Securities		Non- Current Marketable Securities
Cash and cash equivalents	$	225,874	$	—	$	—	$	225,874	$	225,874	$	—	$	—
Available-for-sale:
Certificates of deposit	82,028		79		(6)		82,101		10,002		69,197		2,902
U.S. treasury securities	117,891		260		(2)		118,149		—		110,186		7,963
Debt securities of U.S. government agencies and corporate entities	834,187		2,708		(32)		836,863		—		687,741		149,122
	$	1,259,980	$	3,047	$	(40)	$	1,262,987	$	235,876	$	867,124	$	159,987

The amortized cost and estimated fair value of marketable securities, by contractual maturity at December 31, 2020 and 2019 are as follows (in thousands):


	December 31, 2020
	Amortized Cost		Estimated Fair Value
Due in one year or less	$	1,980,963	$	1,983,758
Due after one year through five years	637,382		638,848
Total	$	2,618,345	$	2,622,606
	December 31, 2019
	Amortized Cost		Estimated Fair Value
Due in one year or less	$	864,958	$	867,124
Due after one year through five years	159,148		159,987
Total	$	1,024,106	$	1,027,111

In accordance with our investment policy, we place investments in investment grade securities with high credit quality issuers, and generally limit the amount of credit exposure to any one issuer. We evaluate securities for impairment at the end of each reporting period. We did not record any impairment charges related to our available-for-sale securities during the years ended December 31, 2020, 2019 and 2018. We did not recognize any credit losses related allowance to available-for-sale securities as of the years ended December 31, 2020 and 2019.

The following table summarizes the amount of gross unrealized losses and the estimated fair value for our available-for-sale securities in an unrealized loss position by length of time the securities have been in an unrealized loss position at December 31, 2020 and 2019 (in thousands):


	Less than 12 Months				12 Months or More				Total
	Gross Unrealized Losses		Estimated Fair Value		Gross Unrealized Losses		Estimated Fair Value		Gross Unrealized Losses		Estimated Fair Value
As of December 31, 2020:
Certificates of deposit	$	(4)	$	81,524	$	—	$	—	$	(4)	$	81,524
Debt securities of U.S. government agencies and corporate entities	(148)		507,016		—		—		(148)		507,016
Total	$	(152)	$	588,540	$	—	$	—	$	(152)	$	588,540

As of December 31, 2019:
Certificates of deposit	$	(6)	$	12,822	$	—	$	—	$	(6)	$	12,822
U.S. treasury securities	(2)		9,979		—		—		(2)		9,979
Debt securities of U.S. government agencies and corporate entities	(32)		62,360		—		—		(32)		62,360
Total	$	(40)	$	85,161	$	—	$	—	$	(40)	$	85,161

At December 31, 2020 and 2019, we held 108 and 19 individual available-for-sale securities, respectively, out of our total investment portfolio that were in a continuous unrealized loss position for less than 12 months. We neither intend to sell these investments nor conclude that we are more-likely-than-not that we will have to sell them before recovery of their carrying values. We also believe that we will be able to collect both principal and interest amounts due to us at maturity.

Assets and Liabilities Measured at Fair Value on a Recurring Basis

The following tables summarize our financial assets measured at fair value on a recurring basis as of December 31, 2020 and 2019 (in thousands):


	Fair Value at December 31, 2020		Fair Value Measurement Using
			Level 1		Level 2
Assets:
Money market funds	$	620,947	$	620,947	$	—
Certificates of deposit	238,819		—		238,819
U.S. treasury securities	491,618		—		491,618
Debt securities of U.S. government agencies and corporate entities	1,892,169		—		1,892,169
Derivative instruments (Note 7)	293		—		293
Total	$	3,243,846	$	620,947	$	2,622,899


	Fair Value at December 31, 2019		Fair Value Measurement Using
			Level 1		Level 2
Assets:
Certificates of deposit	$	82,101	$	—	$	82,101
U.S. treasury securities	118,149		—		118,149
Debt securities of U.S. government agencies and corporate entities	836,863		—		836,863
Total	$	1,037,113	$	—	$	1,037,113

During the years ended December 31, 2020 and 2019, we did not have any financial liabilities measured at fair value on a recurring basis and did not have non-financial assets or liabilities measured at fair value on a recurring basis.