Condensed Consolidated Statements Of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Cash flows from operating activities:
Net income	$ 364.4	$ 324.8
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation of property and equipment	22.9	23.8
Stock-based compensation	29.5	27.9
Other Noncash Income (Expense)	7.3	(1.5)
Changes in operating assets and liabilities
Other assets	(1.0)	1.1
Accounts payable and accrued liabilities	(48.7)	(55.4)
Deferred revenues	41.5	28.2
Deferred Income Taxes	3.0	0.1
Net cash provided by operating activities	404.3	352.0
Net Cash Provided by (Used in) Investing Activities [Abstract]
Proceeds from maturities and sales of marketable securities	721.3	1,057.4
Purchases of marketable securities	(697.6)	(465.2)
Purchases of property and equipment	(12.2)	(12.8)
Net cash used in investing activities	11.5	579.4
Cash flows from financing activities:
Proceeds from employee stock purchase plans	8.0	8.2
Payments for Repurchase of Common Stock	453.4	556.1
Net cash used in financing activities	(445.4)	(547.9)
Effect of Exchange Rate on Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	(0.2)	(0.7)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	(29.8)	382.8
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	349.2	611.6
Supplemental cash flow disclosures:
Cash paid for interest	36.4	36.4
Cash paid for income taxes, net of refunds received	$ 132.4	$ 113.3