Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (129,582)	$ (142,698)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	47,738	48,102
Stock-based compensation	73,224	80,474
Non-cash interest expense related to convertible senior notes	24,367	23,700
Deferred income taxes	154	(18)
Other	6,608	637
Changes in operating assets and liabilities, net of business acquisitions:
Accounts receivable	50,320	32,860
Inventories	(15)	(243)
Prepaid expenses and other assets	13,137	3,959
Accounts payable	(12,971)	4,415
Accrued liabilities	(6,073)	(3,566)
Accrued compensation	11,910	(8,704)
Deferred revenue	(81,721)	(24,830)
Other long-term liabilities	(6,862)	(4,564)
Net cash provided by provided by (used in) operating activities	(9,766)	9,524
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment and demonstration units	(17,556)	(28,240)
Purchases of short-term investments	(106,631)	(258,104)
Proceeds from maturities of short-term investments	277,749	311,905
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	87	426
Net cash provided by (used in) investing activities	167,909	(101,262)
CASH FLOWS FROM FINANCING ACTIVITIES:
Repurchase of convertible senior notes	(96,392)	0
Payment related to shares withheld for taxes	(8,039)	0
Proceeds from employee stock purchase plan	12,300	12,315
Proceeds from exercise of equity awards	3,731	1,495
Net cash provided by provided by (used in) financing activities	(88,400)	13,810
Net change in cash and cash equivalents	69,743	(77,928)
Cash and cash equivalents, beginning of period	334,603	409,829
Cash and cash equivalents, end of period	404,346	331,901
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Cash paid for income taxes	1,449	2,682
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	$ 2,348	$ 6,531