Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (168,700)	$ (208,193)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	71,238	76,238
Stock-based compensation	113,593	117,162
Non-cash interest expense related to convertible senior notes	35,480	35,768
Deferred income taxes	91	(661)
Other	6,836	463
Changes in operating assets and liabilities, net of business acquisitions:
Accounts receivable	36,148	5,929
Inventories	1,576	29
Prepaid expenses and other assets	13,476	4,824
Accounts payable	(17,292)	2,127
Accrued liabilities	(4,902)	1,206
Accrued compensation	26,763	2,448
Deferred revenue	(80,952)	(2,172)
Other long-term liabilities	(9,854)	(7,146)
Net cash provided by operating activities	23,501	28,022
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment and demonstration units	(22,198)	(38,615)
Purchases of short-term investments	(305,180)	(493,038)
Proceeds from maturities of short-term investments	355,820	502,100
Purchase of investment in privately held company	(1,000)	0
Proceeds from sales of short-term investments	28,208	0
Business acquisitions, net of cash acquired	(12,948)	(127,249)
Lease deposits	68	637
Net cash provided by (used in) investing activities	42,770	(156,165)
CASH FLOWS FROM FINANCING ACTIVITIES:
Repurchase of convertible senior notes	(96,392)	0
Payment related to shares withheld for taxes	(8,802)	0
Proceeds from employee stock purchase plan	12,300	12,315
Proceeds from exercise of equity awards	6,270	3,159
Net cash provided by (used in) financing activities	(86,624)	15,474
Net change in cash and cash equivalents	(20,353)	(112,669)
Cash and cash equivalents, beginning of period	334,603	409,829
Cash and cash equivalents, end of period	314,250	297,160
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Cash paid for income taxes	3,961	3,981
Cash paid for interest	6,962	6,962
SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING AND FINANCING ACTIVITIES:
Common stock issued in connection with acquisitions	0	119,682
Purchases of property and equipment and demonstration units in accounts payable and accrued liabilities	$ 2,031	$ 4,438