v3.26.1
Fair Value Measurements - Fair Value of Financial Assets by Level (Details) - USD ($)
$ in Millions
Mar. 31, 2026
Dec. 31, 2025
Financial Assets:    
Cash Equivalents: $ 1,105.3 $ 1,336.1
Marketable Securities: 9,563.7  
Marketable Securities 9,563.7 8,779.1
Money market funds - restricted cash 1.4 1.4
Total Financial Assets 10,670.4 10,116.6
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]    
Amortized Cost 9,707.2 8,914.4
Unrealized Gains 8.1 27.5
Unrealized Losses (19.5) (1.5)
Fair Value 9,695.8 8,940.4
Commercial paper    
Financial Assets:    
Marketable Securities: 311.1 83.0
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]    
Amortized Cost 374.8 112.8
Unrealized Gains 0.0 0.0
Unrealized Losses 0.0 0.0
Fair Value 374.8 112.8
U.S. government notes    
Financial Assets:    
Marketable Securities: 2,728.1 2,854.3
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]    
Amortized Cost 2,777.5 2,970.4
Unrealized Gains 2.8 8.8
Unrealized Losses (3.8) 0.0
Fair Value 2,776.5 2,979.2
Corporate bonds    
Financial Assets:    
Marketable Securities: 5,059.7 4,329.7
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]    
Amortized Cost 5,066.3 4,321.2
Unrealized Gains 4.7 16.0
Unrealized Losses (11.3) (0.9)
Fair Value 5,059.7 4,336.3
Municipal bonds    
Financial Assets:    
Marketable Securities: 14.5 14.5
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]    
Amortized Cost 14.5 14.5
Unrealized Gains 0.0 0.0
Unrealized Losses 0.0 0.0
Fair Value 14.5 14.5
Agency securities    
Financial Assets:    
Marketable Securities: 1,450.3 1,497.6
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]    
Amortized Cost 1,474.1 1,495.5
Unrealized Gains 0.6 2.7
Unrealized Losses (4.4) (0.6)
Fair Value 1,470.3 1,497.6
Money market funds    
Financial Assets:    
Cash Equivalents: 973.2 1,174.8
Commercial paper    
Financial Assets:    
Cash Equivalents: 63.7 29.8
Corporate bonds    
Financial Assets:    
Cash Equivalents: 0.0 6.6
U.S. government notes    
Financial Assets:    
Cash Equivalents: 48.4 124.9
Agency securities    
Financial Assets:    
Cash Equivalents: 20.0 0.0
Level I    
Financial Assets:    
Cash Equivalents: 1,021.6 1,299.7
Marketable Securities 2,728.1 2,854.3
Money market funds - restricted cash 1.4 1.4
Total Financial Assets 3,751.1 4,155.4
Level I | Commercial paper    
Financial Assets:    
Marketable Securities: 0.0 0.0
Level I | U.S. government notes    
Financial Assets:    
Marketable Securities: 2,728.1 2,854.3
Level I | Corporate bonds    
Financial Assets:    
Marketable Securities: 0.0 0.0
Level I | Municipal bonds    
Financial Assets:    
Marketable Securities: 0.0 0.0
Level I | Agency securities    
Financial Assets:    
Marketable Securities: 0.0 0.0
Level I | Money market funds    
Financial Assets:    
Cash Equivalents: 973.2 1,174.8
Level I | Commercial paper    
Financial Assets:    
Cash Equivalents: 0.0 0.0
Level I | Corporate bonds    
Financial Assets:    
Cash Equivalents: 0.0 0.0
Level I | U.S. government notes    
Financial Assets:    
Cash Equivalents: 48.4 124.9
Level I | Agency securities    
Financial Assets:    
Cash Equivalents: 0.0 0.0
Level II    
Financial Assets:    
Cash Equivalents: 83.7 36.4
Marketable Securities 6,835.6 5,924.8
Money market funds - restricted cash 0.0 0.0
Total Financial Assets 6,919.3 5,961.2
Level II | Commercial paper    
Financial Assets:    
Marketable Securities: 311.1 83.0
Level II | U.S. government notes    
Financial Assets:    
Marketable Securities: 0.0 0.0
Level II | Corporate bonds    
Financial Assets:    
Marketable Securities: 5,059.7 4,329.7
Level II | Municipal bonds    
Financial Assets:    
Marketable Securities: 14.5 14.5
Level II | Agency securities    
Financial Assets:    
Marketable Securities: 1,450.3 1,497.6
Level II | Money market funds    
Financial Assets:    
Cash Equivalents: 0.0 0.0
Level II | Commercial paper    
Financial Assets:    
Cash Equivalents: 63.7 29.8
Level II | Corporate bonds    
Financial Assets:    
Cash Equivalents: 0.0 6.6
Level II | U.S. government notes    
Financial Assets:    
Cash Equivalents: 0.0 0.0
Level II | Agency securities    
Financial Assets:    
Cash Equivalents: 20.0 0.0
Level III    
Financial Assets:    
Cash Equivalents: 0.0 0.0
Marketable Securities 0.0 0.0
Money market funds - restricted cash 0.0 0.0
Total Financial Assets 0.0 0.0
Level III | Commercial paper    
Financial Assets:    
Marketable Securities: 0.0 0.0
Level III | U.S. government notes    
Financial Assets:    
Marketable Securities: 0.0 0.0
Level III | Corporate bonds    
Financial Assets:    
Marketable Securities: 0.0 0.0
Level III | Municipal bonds    
Financial Assets:    
Marketable Securities: 0.0 0.0
Level III | Agency securities    
Financial Assets:    
Marketable Securities: 0.0 0.0
Level III | Money market funds    
Financial Assets:    
Cash Equivalents: 0.0 0.0
Level III | Commercial paper    
Financial Assets:    
Cash Equivalents: 0.0 0.0
Level III | Corporate bonds    
Financial Assets:    
Cash Equivalents: 0.0 0.0
Level III | U.S. government notes    
Financial Assets:    
Cash Equivalents: 0.0 0.0
Level III | Agency securities    
Financial Assets:    
Cash Equivalents: $ 0.0 $ 0.0