Marketable Securities

12 Months Ended

Dec. 31, 2020

Investments, Debt and Equity Securities [Abstract]

Marketable securities as of December 31, 2020 and 2019 consist of both available-for-sale debt securities of investment grade issuers (see below and Note 5) as well as equity securities of publicly traded companies (see Note 5).

The following tables summarize the Company's investments in available-for-sale debt securities:


	Amortized		Unrealized				Fair
As of December 31, 2020	Cost Basis		Gains		Losses		Value
Corporate bonds	$	3,053.0	$	37.5	$	(0.2)	$	3,090.3
U.S. government and government agency obligations	127.6		1.3		—		128.9
Sovereign bonds	65.2		1.1		—		66.3
Commercial paper	276.0		0.1		—		276.1
Certificates of deposit	127.4		0.1		—		127.5
	$	3,649.2	$	40.1	$	(0.2)	$	3,689.1

As of December 31, 2019
Corporate bonds	$	3,960.5	$	27.8	$	(0.2)	$	3,988.1
U.S. government and government agency obligations	54.3		0.2		(0.1)		54.4
Sovereign bonds	26.9		0.4		—		27.3
Commercial paper	92.3		—		—		92.3
Certificates of deposit	72.3		0.1		—		72.4
	$	4,206.3	$	28.5	$	(0.3)	$	4,234.5

The Company classifies its investments in available-for-sale debt securities based on their contractual maturity dates. The available-for-sale debt securities listed as of December 31, 2020 mature at various dates through October 2025. The fair values of available-for-sale debt security investments by contractual maturity consist of the following:


	As of December 31,
	2020		2019
Maturities within one year	$	1,393.3	$	1,596.5
Maturities after one year through five years	2,295.8		2,638.0
	$	3,689.1	$	4,234.5

Unrealized losses of our available-for-sale debt securities that had been in a continuous loss position, for both less than and greater than 12 months, were not material for the years ended December 31, 2020 and 2019.

Realized gains on sales of marketable securities for the year ended December 31, 2020 were $29.0 million and realized gains were not material for the years ended December 31, 2019 and 2018. Realized losses on sales of marketable securities were not material for the years ended December 31, 2020 and 2018 and there were no realized losses for the year ended December 31, 2019.

With respect to marketable securities, for the years ended December 31, 2020, 2019, and 2018, amounts reclassified from Accumulated other comprehensive income (loss) into Other income (expense), net were related to realized gains and losses on sales of available-for-sale debt securities (as described above).