Condensed Consolidated Statements Of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Cash flows from operating activities:
Net income	$ 494.3	$ 454.7
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation of property and equipment	35.2	35.6
Stock-based compensation	44.2	41.0
Other Noncash Income (Expense)	(0.7)	(5.4)
Changes in operating assets and liabilities
Other assets	(2.5)	(19.7)
Accounts payable and accrued liabilities	(26.8)	(5.5)
Deferred revenues	82.1	94.9
Deferred Income Taxes	(13.0)	(5.5)
Net cash provided by operating activities	614.2	600.9
Net Cash Provided by (Used in) Investing Activities [Abstract]
Proceeds from maturities and sales of marketable securities	1,475.0	2,246.1
Purchases of marketable securities	(909.3)	(2,421.7)
Purchases of property and equipment	(19.7)	(39.5)
Net cash used in investing activities	546.0	(215.1)
Cash flows from financing activities:
Proceeds from employee stock purchase plans	12.3	12.4
Repayments of Debt, Maturing in More than Three Months	0.0	(750.0)
Payments for Repurchase of Common Stock	834.0	536.8
Proceeds from Debt, Net of Issuance Costs	0.0	741.1
Net cash used in financing activities	(821.7)	(533.3)
Effect of Exchange Rate on Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	(1.4)	(0.6)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	337.1	(148.1)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, beginning of period	228.8	410.6
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, end of period	565.9	262.5
Supplemental cash flow disclosures:
Cash paid for interest	49.6	61.8
Cash paid for income taxes, net of refunds received	$ 159.6	$ 132.2