Condensed Consolidated Statements Of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024
Cash flows from operating activities:
Net income	$ 619.5	$ 594.2
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation of property and equipment	24.5	28.1
Stock-based compensation	51.8	45.2
Investment Income, Amortization of Discount	(8.2)	(16.6)
Other Noncash Income (Expense)	(2.4)	(2.1)
Changes in operating assets and liabilities
Other assets	(3.2)	(18.2)
Other Liabilities	20.6	(31.9)
Deferred revenues	80.1	52.9
Deferred Income Taxes	14.0	15.3
Net cash provided by operating activities	801.5	671.1
Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract]
Proceeds from maturities and sales of marketable securities	412.5	1,009.6
Purchases of marketable securities	(393.6)	(684.0)
Purchases of property and equipment	(18.3)	(18.6)
Net cash used in investing activities	0.6	307.0
Cash flows from financing activities:
Payments for Repurchase of Common Stock	627.2	963.3
Repayments of Debt, Maturing in More than Three Months	(500.0)	0.0
Proceeds from Debt, Net of Issuance Costs	493.3	0.0
Payments of Dividends	(144.1)	0.0
Proceeds from employee stock purchase plans	(12.3)	(12.3)
Share Repurchase Program, Excise Tax, Payable	(11.6)	0.0
Net cash used in financing activities	(777.3)	(951.0)
Effect of Exchange Rate on Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	0.1	0.1
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	24.9	27.2
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, beginning of period	212.1	245.5
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, end of period	237.0	272.7
Supplemental cash flow disclosures:
Cash paid for interest	55.4	49.5
Cash paid for income taxes, net of refunds received	$ 169.3	$ 187.1