Cash, Cash Equivalents, and Marketable Debt Securities (Tables)

12 Months Ended

Dec. 31, 2019

Cash Cash Equivalents And Short Term Investments [Abstract]

Schedule of Cash and Available-For-Sale Debt Securities by Major Asset Category

The following table shows the Company’s cash and available-for-sale (AFS) debt securities by major asset category at December 31, 2019 (in millions):

	Adjusted Cost Basis		Fair Value (c)		Cash and Cash Equivalents		Short-Term Marketable Debt Securities		Long-Term Marketable Debt Securities
Cash and cash equivalents	$	675.6	$	675.6	$	675.6	$	—	$	—
Level 1 (a):
Money market funds		0.1		0.1		0.1		—		—
U.S. Treasury securities		27.1		27.1		3.1		11.5		12.5
Subtotal		27.2		27.2		3.2		11.5		12.5
Level 2 (b):
Certificates of deposit		3.9		3.9		—		3.9		—
Commercial paper		5.6		5.6		0.7		4.9		—
U.S. government agency securities		7.0		7.0		—		3.0		4.0
Corporate debt securities		106.2		106.2		—		64.6		41.6
Subtotal		122.7		122.7		0.7		76.4		45.6
Total	$	825.5	$	825.5	$	679.5	$	87.9	$	58.1

Schedule of Market Value of Marketable Debt Securities with Continuous Unrealized Losses

The market value of marketable debt securities with continuous unrealized losses as of December 31, 2019 was as follows (in millions):

	2019
	Continuous Unrealized Losses
	Less than 12 Months		12 Months or Greater		Total
Fair value of marketable debt securities	$	78.1	$	—	$	78.1
Unrealized losses	$	—	$	—	$	—