Condensed Consolidated Statements Of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024
Cash flows from operating activities:
Net income	$ 406.7	$ 392.9
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation of property and equipment	17.2	19.1
Stock-based compensation	33.4	29.4
Investment Income, Amortization of Discount	(4.8)	(11.1)
Other Noncash Income (Expense)	(1.4)	(1.6)
Changes in operating assets and liabilities
Other assets	(19.9)	(19.2)
Other Liabilities	(24.8)	(58.8)
Deferred revenues	75.5	42.6
Deferred Income Taxes	9.1	21.2
Net cash provided by operating activities	493.8	417.7
Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract]
Proceeds from maturities and sales of marketable securities	396.8	727.6
Purchases of marketable securities	(278.6)	(468.1)
Purchases of property and equipment	(13.6)	(13.0)
Net cash used in investing activities	104.6	246.5
Cash flows from financing activities:
Repayments of Short-Term Debt, Maturing in Three Months or Less	(500.0)	0.0
Proceeds from Debt, Net of Issuance Costs	493.3	0.0
Payments for Repurchase of Common Stock	408.5	660.2
Payments of Dividends	(72.1)	0.0
Payment of excise tax on repurchase of common stock	(11.6)	0.0
Proceeds from employee stock purchase plans	(7.9)	(8.3)
Net cash used in financing activities	(491.0)	(651.9)
Effect of Exchange Rate on Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	0.1	(0.3)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	107.5	12.0
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	319.6	257.5
Supplemental cash flow disclosures:
Cash paid for interest	42.3	36.4
Cash paid for income taxes, net of refunds received	$ 149.4	$ 138.6