XML 56 R33.htm IDEA: XBRL DOCUMENT v3.20.4
Fair Value Measurements - Fair Value Hierarchy of Financial Assets (Details) - USD ($)
$ in Millions
Dec. 31, 2020
Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents $ 641.5 $ 255.0
Debt securities, available-for-sale 1,890.1 1,087.1
Other assets 3.4 0.7
Total assets measured at fair value on a recurring basis 2,535.0 1,342.8
Level 1    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents 491.5 110.1
Debt securities, available-for-sale 0.0 0.0
Other assets 3.4 0.7
Total assets measured at fair value on a recurring basis 494.9 110.8
Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents 150.0 144.9
Debt securities, available-for-sale 1,890.1 1,087.1
Other assets 0.0 0.0
Total assets measured at fair value on a recurring basis 2,040.1 1,232.0
Level 3    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents 0.0 0.0
Debt securities, available-for-sale 0.0 0.0
Other assets 0.0 0.0
Total assets measured at fair value on a recurring basis 0.0 0.0
U.S. government agencies    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Debt securities, available-for-sale 1,570.4 676.0
U.S. government agencies | Level 1    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Debt securities, available-for-sale 0.0 0.0
U.S. government agencies | Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Debt securities, available-for-sale 1,570.4 676.0
U.S. government agencies | Level 3    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Debt securities, available-for-sale 0.0 0.0
Commercial paper    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Debt securities, available-for-sale 258.8 248.2
Commercial paper | Level 1    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Debt securities, available-for-sale 0.0 0.0
Commercial paper | Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Debt securities, available-for-sale 258.8 248.2
Commercial paper | Level 3    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Debt securities, available-for-sale 0.0 0.0
Corporate debt    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Debt securities, available-for-sale 60.9 162.9
Corporate debt | Level 1    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Debt securities, available-for-sale 0.0 0.0
Corporate debt | Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Debt securities, available-for-sale 60.9 162.9
Corporate debt | Level 3    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Debt securities, available-for-sale $ 0.0 $ 0.0