Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flow from operating activities
Net income (loss)	$ 56.8	$ (29.1)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	79.6	91.9
Stock-based compensation	116.4	123.7
Net gains on equity investments	(17.5)	(7.4)
Amortization of deferred commissions	10.8	8.1
Other	(0.1)	(7.6)
Changes in operating assets and liabilities:
Trade and other receivables, net	(8.8)	(8.5)
Prepaid expenses and other current assets	(22.4)	(18.5)
Other assets	33.1	26.2
Accounts payable	(12.8)	(1.8)
Accrued and other current liabilities	(24.7)	10.5
Accrued compensation and benefits	(30.3)	(24.8)
Deferred revenue	28.7	28.0
Other non-current liabilities	(26.2)	(27.2)
Tenant improvement allowance reimbursement	16.6	28.5
Net cash provided by operating activities	199.2	192.0
Cash flow from investing activities
Capital expenditures	(53.9)	(63.4)
Business combinations, net of cash acquired	0.0	(171.6)
Purchases of short-term investments	(429.2)	(389.7)
Proceeds from sales of short-term investments	145.3	181.0
Proceeds from maturities of short-term investments	138.9	161.6
Other	9.3	11.6
Net cash used in investing activities	(189.6)	(270.5)
Cash flow from financing activities
Shares repurchased for tax withholdings on release of restricted stock units and awards	(44.0)	(48.1)
Proceeds from issuance of common stock, net of repurchases	1.5	2.0
Principal payments on finance lease obligations	(43.4)	(50.6)
Common stock repurchases	(139.8)	0.0
Other	(0.5)	(0.7)
Net cash used in financing activities	(226.2)	(97.4)
Effect of exchange rate changes on cash and cash equivalents	(0.6)	0.2
Change in cash and cash equivalents	(217.2)	(175.7)
Cash and cash equivalents - beginning of period	551.3	519.3
Cash and cash equivalents - end of period	334.1	343.6
Supplemental cash flow data:
Property and equipment acquired under finance leases	$ 64.4	$ 75.4