Condensed Consolidated Statements Of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Cash flows from operating activities:
Net income	$ 178.7	$ 157.5
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation of property and equipment	11.6	11.9
Stock-based compensation	13.8	14.2
Other Noncash Income (Expense)	2.9	(0.6)
Changes in operating assets and liabilities
Other assets	1.9	8.3
Accounts payable and accrued liabilities	11.6	(14.9)
Deferred revenues	41.8	28.3
Deferred Income Taxes	2.5	1.2
Net cash provided by operating activities	259.0	207.1
Net Cash Provided by (Used in) Investing Activities [Abstract]
Proceeds from maturities and sales of marketable securities	562.0	696.0
Purchases of marketable securities	(146.5)	(164.9)
Purchases of property and equipment	(5.7)	(6.6)
Net cash used in investing activities	409.8	524.5
Cash flows from financing activities:
Proceeds from employee stock purchase plans	8.0	8.2
Payments for Repurchase of Common Stock	230.5	204.6
Net cash used in financing activities	(222.5)	(196.4)
Effect of Exchange Rate on Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	(0.2)	(0.1)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	446.1	535.1
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, beginning of period	379.0	228.8
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, end of period	825.1	763.9
Supplemental cash flow disclosures:
Cash paid for interest	13.1	13.1
Cash paid for income taxes, net of refunds received	$ 18.3	$ 2.2