Fair Value Measurements - Fair Value of Financial Assets (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Financial Assets:
Cash Equivalents:	$ 1,336.1	$ 1,741.9
Marketable Securities:	8,779.1
Marketable Securities	8,779.1	5,541.1
Money market funds - restricted cash	1.4	1.4
Total Financial Assets	10,116.6	7,284.4
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost	8,914.4	5,580.3
Unrealized Gains	27.5	8.7
Unrealized Losses	(1.5)	(13.5)
Fair Value	8,940.4	5,575.5
Commercial paper
Financial Assets:
Marketable Securities:	83.0	48.8
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost	112.8	48.8
Unrealized Gains	0.0	0.0
Unrealized Losses	0.0	0.0
Fair Value	112.8	48.8
U.S. government notes
Financial Assets:
Marketable Securities:	2,854.3	1,921.5
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost	2,970.4	1,954.8
Unrealized Gains	8.8	2.7
Unrealized Losses	0.0	(4.6)
Fair Value	2,979.2	1,952.9
Corporate bonds
Financial Assets:
Marketable Securities:	4,329.7	2,593.6
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost	4,321.2	2,595.7
Unrealized Gains	16.0	4.4
Unrealized Losses	(0.9)	(6.5)
Fair Value	4,336.3	2,593.6
Municipal bonds
Financial Assets:
Marketable Securities:	14.5	0.0
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost	14.5	0.0
Unrealized Gains	0.0	0.0
Unrealized Losses	0.0	0.0
Fair Value	14.5	0.0
Agency securities
Financial Assets:
Marketable Securities:	1,497.6	977.2
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost	1,495.5	981.0
Unrealized Gains	2.7	1.6
Unrealized Losses	(0.6)	(2.4)
Fair Value	1,497.6	980.2
Level I
Financial Assets:
Cash Equivalents:	1,299.7	1,738.9
Marketable Securities	2,854.3	1,921.5
Money market funds - restricted cash	1.4	1.4
Total Financial Assets	4,155.4	3,661.8
Level I | Commercial paper
Financial Assets:
Marketable Securities:	0.0	0.0
Level I | U.S. government notes
Financial Assets:
Marketable Securities:	2,854.3	1,921.5
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 II
Financial Assets:
Cash Equivalents:	36.4	3.0
Marketable Securities	5,924.8	3,619.6
Money market funds - restricted cash	0.0	0.0
Total Financial Assets	5,961.2	3,622.6
Level II | Commercial paper
Financial Assets:
Marketable Securities:	83.0	48.8
Level II | U.S. government notes
Financial Assets:
Marketable Securities:	0.0	0.0
Level II | Corporate bonds
Financial Assets:
Marketable Securities:	4,329.7	2,593.6
Level II | Municipal bonds
Financial Assets:
Marketable Securities:	14.5	0.0
Level II | Agency securities
Financial Assets:
Marketable Securities:	1,497.6	977.2
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
Level III | Agency securities
Financial Assets:
Marketable Securities:	0.0	0.0
Money market funds
Financial Assets:
Cash Equivalents:	1,174.8	1,707.5
Money market funds | Level I
Financial Assets:
Cash Equivalents:	1,174.8	1,707.5
Money market funds | Level II
Financial Assets:
Cash Equivalents:	0.0	0.0
Money market funds | Level III
Financial Assets:
Cash Equivalents:	0.0	0.0
Commercial paper
Financial Assets:
Cash Equivalents:	29.8	0.0
Commercial paper | Level I
Financial Assets:
Cash Equivalents:	0.0	0.0
Commercial paper | Level II
Financial Assets:
Cash Equivalents:	29.8	0.0
Commercial paper | Level III
Financial Assets:
Cash Equivalents:	0.0	0.0
Corporate bonds
Financial Assets:
Cash Equivalents:	6.6	0.0
Corporate bonds | Level I
Financial Assets:
Cash Equivalents:	0.0	0.0
Corporate bonds | Level II
Financial Assets:
Cash Equivalents:	6.6	0.0
Corporate bonds | Level III
Financial Assets:
Cash Equivalents:	0.0	0.0
Agency securities
Financial Assets:
Cash Equivalents:	0.0	3.0
Agency securities | Level I
Financial Assets:
Cash Equivalents:	0.0	0.0
Agency securities | Level II
Financial Assets:
Cash Equivalents:	0.0	3.0
Agency securities | Level III
Financial Assets:
Cash Equivalents:	0.0	0.0
U.S. government notes
Financial Assets:
Cash Equivalents:	124.9	31.4
U.S. government notes | Level I
Financial Assets:
Cash Equivalents:	124.9	31.4
U.S. government notes | Level II
Financial Assets:
Cash Equivalents:	0.0	0.0
U.S. government notes | Level III
Financial Assets:
Cash Equivalents:	$ 0.0	$ 0.0