Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

Schedule of Fair Value Hierarchy for Financial Assets

The following table summarizes financial assets that we measured at fair value on a recurring basis as of December 31, 2019, classified in accordance with the fair value hierarchy:

	Fair Value Measurements Using
(In millions)	Level 1		Level 2		Level 3		Total
Cash equivalents	$	110.1	$	144.9	$	—	$	255.0
Debt securities, available for sale:
U.S. government agencies	—		676.0		—		676.0
Commercial paper	—		248.2		—		248.2
Corporate debt	—		162.9		—		162.9
Total debt securities, available for sale	—		1,087.1		—		1,087.1
Other assets (1)	0.7		—		—		0.7
Total assets measured at fair value on a recurring basis	$	110.8	$	1,232.0	$	—	$	1,342.8

⁽¹⁾ Includes assets which are held pursuant to a deferred compensation plan for our executives, which consist mainly of mutual funds.

The following table summarizes financial assets that we measured at fair value on a recurring basis as of December 31, 2018, classified in accordance with the fair value hierarchy:

	Fair Value Measurements Using
(In millions)	Level 1		Level 2		Level 3		Total
Cash equivalents	$	199.3	$	66.7	$	—	$	266.0
Equity investment in Tandem Diabetes Care, Inc.	38.0		—		—		38.0
Debt securities, available for sale:
U.S. government agencies	—		173.1		—		173.1
Commercial paper	—		36.2		—		36.2
Corporate debt	—		1.3		—		1.3
Total debt securities, available for sale	—		210.6		—		210.6
Total assets measured at fair value on a recurring basis	$	237.3	$	277.3	$	—	$	514.6

Schedule of Fair Value of Senior Convertible Notes

The fair value, based on trading prices (Level 1), of our Senior Convertible Notes were as follows as of the dates indicated:

	Fair Value Measurements Using Level 1
(In millions)	December 31, 2019		December 31, 2018
0.75% Senior Convertible Notes due 2022	$	890.8	$	540.2
0.75% Senior Convertible Notes due 2023	1,260.0		859.6
Total fair value of outstanding senior convertible notes	$	2,150.8	$	1,399.8

For more information on the carrying values of our 2022 Notes and 2023 Notes, see Note 5, “Debt.”