Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 341.8	$ 213.5
Adjustments to reconcile net income to net cash provided by operating activities:
Stock-based compensation	143.0	130.4
Amortization of deferred contract costs	99.8	78.5
Depreciation and amortization	52.1	45.9
Amortization of investment premiums (discounts)	0.2	(4.7)
Other	5.8	5.0
Changes in operating assets and liabilities:
Accounts receivable—net	(3.1)	60.5
Inventory	(31.0)	(25.2)
Prepaid expenses and other current assets	(4.6)	(6.3)
Deferred contract costs	(143.9)	(113.1)
Deferred tax assets	4.4	11.5
Other assets	(2.0)	(0.8)
Accounts payable	(4.2)	(6.2)
Accrued liabilities	16.5	(16.6)
Accrued payroll and compensation	19.5	(9.5)
Other liabilities	10.3	(1.0)
Deferred revenue	282.6	255.7
Net cash provided by operating activities	787.2	617.6
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of investments	(776.3)	(1,072.4)
Sales of investments	141.4	19.7
Maturities of investments	730.3	695.0
Purchases of property and equipment	(93.6)	(45.0)
Payments made in connection with business combination, net of cash acquired	(9.2)	0.0
Other	(0.4)	0.0
Net cash used in investing activities	(7.8)	(402.7)
CASH FLOWS FROM FINANCING ACTIVITIES:
Repurchase and retirement of common stock	(1,046.0)	(117.6)
Proceeds from issuance of common stock	18.2	41.8
Taxes paid related to net share settlement of equity awards	(86.5)	(76.0)
Payments of debt assumed in connection with business combination	(4.1)	0.0
Other	(1.2)	0.0
Net cash used in financing activities	(1,119.6)	(151.8)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(340.2)	63.1
CASH AND CASH EQUIVALENTS—Beginning of period	1,222.5	1,112.4
CASH AND CASH EQUIVALENTS—End of period	882.3	1,175.5
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Operating lease liabilities arising from obtaining right-of-use assets	14.7	12.6
Cash paid to settle liability incurred for repurchase of common stock	0.0	4.2
NON-CASH INVESTING AND FINANCING ACTIVITIES:
Transfers of evaluation units from inventory to property and equipment	14.8	16.3
Liability for purchase of property and equipment	26.1	20.1
Liability incurred for repurchase of common stock	$ 0.0	$ 4.0