Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 216.1	$ 131.5
Adjustments to reconcile net income to net cash provided by operating activities:
Stock-based compensation	93.7	88.0
Amortization of deferred contract costs	64.5	51.0
Depreciation and amortization	35.4	30.9
Amortization of investment premiums (discounts)	(0.4)	(3.0)
Other	5.5	0.5
Changes in operating assets and liabilities:
Accounts receivable—net	44.5	41.5
Inventory	(17.9)	(5.5)
Prepaid expenses and other current assets	(15.2)	(5.4)
Deferred contract costs	(91.1)	(72.4)
Deferred tax assets	13.0	(4.4)
Other assets	0.7	2.4
Accounts payable	9.7	(14.6)
Accrued liabilities	6.5	(13.1)
Accrued payroll and compensation	8.9	(7.9)
Other liabilities	5.6	(2.8)
Deferred revenue	186.9	179.7
Net cash provided by operating activities	566.4	396.4
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of investments	(399.3)	(748.1)
Sales of investments	130.0	15.1
Maturities of investments	548.1	384.9
Purchases of property and equipment	(58.5)	(27.5)
Payments made in connection with business combination, net of cash acquired	(3.1)	0.0
Other	(0.4)	0.0
Net cash provided by (used in) investing activities	216.8	(375.6)
CASH FLOWS FROM FINANCING ACTIVITIES:
Repurchase and retirement of common stock	(1,046.0)	(94.2)
Proceeds from issuance of common stock	15.7	39.6
Taxes paid related to net share settlement of equity awards	(58.9)	(56.5)
Other	(0.1)	0.0
Net cash used in financing activities	(1,089.3)	(111.1)
NET DECREASE IN CASH AND CASH EQUIVALENTS	(306.1)	(90.3)
CASH AND CASH EQUIVALENTS—Beginning of period	1,222.5	1,112.4
CASH AND CASH EQUIVALENTS—End of period	916.4	1,022.1
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Operating lease liabilities arising from obtaining right-of-use assets	5.9	4.9
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	10.2	9.9
Liability for purchase of property and equipment	24.9	9.9
Liability incurred for repurchase of common stock	$ 0.0	$ 1.0