Marketable Securities (Tables)

6 Months Ended

Jun. 30, 2020

Investments, Debt and Equity Securities [Abstract]

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


	Amortized		Unrealized						Fair
As of June 30, 2020	Cost Basis		Gains		Losses		Value
Corporate bonds	$	2,393.2	$	41.9	$	(0.7)	$	2,434.4
U.S. government and government agency obligations	81.6		1.1		—		82.7
Sovereign bonds	27.0		1.2		—		28.2
Commercial paper	283.1		0.6		—		283.7
Certificates of deposit	105.4		0.1		—		105.5
	$	2,890.3	$	44.9	$	(0.7)	$	2,934.5

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

Marketable Securities, Based on Contractual Maturity Dates

The fair values of available-for-sale debt security investments by contractual maturity consist of the following:


	June 30,		December 31,
	2020		2019
Maturities within one year	$	1,152.0	$	1,596.5
Maturities after one year through five years	1,779.6		2,638.0
Maturities after five years	2.9		—
	$	2,934.5	$	4,234.5

Fair Value and Unrealized Losses of Marketable Securities

The following table shows the fair value of the Company's available-for-sale debt securities that have unrealized losses, aggregated by investment category and length of time that the individual securities have been in a continuous loss position.


	Less than 12 Months					12 Months or Greater					Total
As of June 30, 2020	Fair Value		Unrealized Loss		Fair Value	Unrealized Loss	Fair Value		Unrealized Loss
Corporate bonds	$	247.9	$	(0.7)	—	—	$	247.9	$	(0.7)

As of December 31, 2019
Corporate bonds	$	257.2	$	(0.2)	—	—	$	257.2	$	(0.2)
U.S. government and government agency obligations	17.3		(0.1)		—	—	17.3		(0.1)
	$	274.5	$	(0.3)	—	—	$	274.5	$	(0.3)