Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (115,342)	$ (129,581)
Less: income from discontinued operations	70,254	58,222
Loss from continuing operations	(185,596)	(187,803)
Adjustments to reconcile loss from continuing operations to net cash provided by (used in) operating activities:
Depreciation and amortization	46,648	37,684
Stock-based compensation	72,173	52,802
Non-cash interest expense related to convertible senior notes	22,907	24,367
Deferred income taxes	(114)	154
Other	20	1,166
Changes in operating assets and liabilities, net of business acquisitions:
Accounts receivable	17,294	25,910
Prepaid expenses and other assets	6,323	5,089
Accounts payable	4,331	(6,203)
Accrued liabilities	(1,540)	(5,046)
Accrued compensation	(13,616)	14,245
Deferred revenue	13,072	(29,157)
Other long-term liabilities	(4,914)	(5,701)
Net cash used in operating activities - continuing operations	(23,012)	(72,493)
Net cash provided by operating activities - discontinued operations	67,317	62,727
Net cash provided by (used in) operating activities	44,305	(9,766)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment and demonstration units	(13,497)	(14,037)
Purchases of short-term investments	(512,642)	(106,631)
Proceeds from maturities of short-term investments	264,160	277,749
Purchase of investment in privately held company	0	(1,000)
Proceeds from sales of short-term investments	0	28,208
Business acquisitions, net of cash acquired	50	(6,284)
Lease deposits	725	34
Net cash provided by (used in) investing activities - continuing operations	(261,204)	178,039
Net cash used in investing activities - discontinued operations	(10,039)	(10,130)
Net cash provided by (used in) investing activities	(271,243)	167,909
CASH FLOWS FROM FINANCING ACTIVITIES:
Repurchase of convertible senior notes	0	(96,392)
Share repurchases	(68,334)	0
Series A convertible preferred stock issuance costs	(9,075)	0
Dividends on series A convertible preferred stock	8,993	0
Payment related to shares withheld for taxes	(9,725)	(8,039)
Proceeds from employee stock purchase plan	12,335	12,300
Proceeds from exercise of equity awards	3,600	3,731
Net cash used in financing activities	(62,206)	(88,400)
Net change in cash and cash equivalents	(289,144)	69,743
Cash and cash equivalents, beginning of period	676,454	334,603
Cash and cash equivalents, end of period	387,310	404,346
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Cash paid for income taxes	3,581	1,449
Cash paid for interest	6,480	6,962
SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING AND FINANCING ACTIVITIES:
Purchases of property and equipment and demonstration units in accounts payable and accrued liabilities	3,735	2,348
Dividend on series A convertible preferred stock	9,075	0
Accretion of series A convertible preferred stock	$ 82	$ 0