XML 47 R31.htm IDEA: XBRL DOCUMENT v3.23.3
Fair Value Measurements - Fair Value Hierarchy for Financial Assets (Details) - USD ($)
$ in Millions
Sep. 30, 2023
Dec. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]    
Cash equivalents $ 390.8 $ 420.7
Debt securities, available-for-sale 2,596.6 1,813.9
Other assets 13.7 10.2
Total assets measured at fair value on a recurring basis 3,001.1 2,244.8
U.S. government agencies    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]    
Debt securities, available-for-sale 1,819.0 1,530.7
Commercial paper    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]    
Debt securities, available-for-sale 387.3 119.4
Corporate debt    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]    
Debt securities, available-for-sale 390.3 163.8
Level 1    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]    
Cash equivalents 360.9 375.9
Debt securities, available-for-sale 0.0 0.0
Other assets 13.7 10.2
Total assets measured at fair value on a recurring basis 374.6 386.1
Level 1 | U.S. government agencies    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]    
Debt securities, available-for-sale 0.0 0.0
Level 1 | Commercial paper    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]    
Debt securities, available-for-sale 0.0 0.0
Level 1 | Corporate debt    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]    
Debt securities, available-for-sale 0.0 0.0
Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]    
Cash equivalents 29.9 44.8
Debt securities, available-for-sale 2,596.6 1,813.9
Other assets 0.0 0.0
Total assets measured at fair value on a recurring basis 2,626.5 1,858.7
Level 2 | U.S. government agencies    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]    
Debt securities, available-for-sale 1,819.0 1,530.7
Level 2 | Commercial paper    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]    
Debt securities, available-for-sale 387.3 119.4
Level 2 | Corporate debt    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]    
Debt securities, available-for-sale 390.3 163.8
Level 3    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]    
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
Level 3 | U.S. government agencies    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]    
Debt securities, available-for-sale 0.0 0.0
Level 3 | Commercial paper    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]    
Debt securities, available-for-sale 0.0 0.0
Level 3 | Corporate debt    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]    
Debt securities, available-for-sale $ 0.0 $ 0.0