Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Cash flow from operating activities:
Net income	$ 79,666	$ 49,139
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization expense	25,773	26,752
Bad debt expense	493	247
Loss on disposal of property and equipment	5	12
Stock-based compensation	37,856	56,218
Amortization of premiums on marketable securities	1,127	2,985
Deferred income taxes	(15,599)	(15,962)
Changes in operating assets and liabilities:
Accounts receivable	9,788	15,665
Prepaid expenses and other assets	(1,412)	(5,460)
Accounts payable	841	200
Accrued liabilities	3,968	9,912
Deferred revenues	12,504	21,033
Net cash provided by operating activities	155,010	160,741
Cash flow from investing activities:
Purchases of marketable securities	(178,788)	(255,051)
Sales and maturities of marketable securities	290,949	295,336
Purchases of property and equipment	(12,391)	(20,089)
Proceeds from disposal of property and equipment	0	6
Purchases of intangible assets	(120)	(1,080)
Net cash provided by investing activities	99,650	19,122
Cash flow from financing activities:
Repurchases of common stock	(212,839)	(94,919)
Proceeds from exercise of stock options	23,161	10,948
Payments for taxes related to net share settlement of equity awards	(12,853)	(24,194)
Proceeds from issuance of common stock through employee stock purchase plan	4,445	0
Principal payments under finance lease obligations	0	(90)
Net cash used in financing activities	(198,086)	(108,255)
Net increase in cash, cash equivalents and restricted cash	56,574	71,608
Cash, cash equivalents and restricted cash at beginning of period	138,528	75,332
Cash, cash equivalents and restricted cash at end of period	$ 195,102	$ 146,940