Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating Activities
Net income	$ 32,194	$ 61,338	$ 37,729
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	61,067	53,559	51,350
Loss on disposal of property and equipment	267	445	133
Share-based compensation expense	44,697	34,049	28,885
Deferred income taxes	(6,546)	(1,339)	(5,705)
Amortization of operating lease right-of-use assets	10,528	10,562	0
Amortization of debt issuance costs	1,597	2,204	2,292
Amortization of discount on convertible senior notes	4,766	0	0
Changes in operating assets and liabilities:
Accounts receivable and unbilled receivables	36,842	(21,540)	(6,192)
Inventories	12,359	(8,123)	(6,763)
Prepaid expenses	(2,081)	2,909	(308)
Other current assets	(6,408)	(2,010)	1,170
Investment in sales-type leases	(2,882)	(3,699)	(1,680)
Prepaid commissions	(8,057)	(2,719)	(4,711)
Other long-term assets	(7,675)	4,528	(7,077)
Accounts payable	(6,300)	7,893	(9,154)
Accrued compensation	11,595	2,495	14,419
Accrued liabilities	4,374	3,045	8,223
Deferred revenues	7,620	5,445	3,020
Operating lease liabilities	(9,543)	(10,040)	0
Other long-term liabilities	7,456	6,006	(1,665)
Net cash provided by operating activities	185,870	145,008	103,966
Investing Activities
Software development for external use	(32,024)	(45,770)	(30,677)
Purchases of property and equipment	(22,842)	(15,894)	(23,697)
Business acquisition	(225,000)	0	0
Net cash used in investing activities	(279,866)	(61,664)	(54,374)
Financing Activities
Proceeds from revolving credit facility	150,000	0	0
Repayment of debt and revolving credit facility	(200,000)	(90,000)	(77,000)
Payments for debt issuance costs for revolving credit facility	(550)	(2,321)	0
Proceeds from issuance of convertible senior notes, net of issuance costs	559,665	0	0
Purchase of convertible note hedge	(100,625)	0	0
Proceeds from sale of warrants	51,290	0	0
At the market equity offering, net of offering costs	0	37,806	39,567
Proceeds from issuances under stock-based compensation plans	54,270	40,706	30,611
Employees’ taxes paid related to restricted stock units	(8,738)	(9,670)	(6,775)
Stock repurchases	(53,035)	0	0
Change in customer funds, net	3,992	0	0
Net cash provided by (used in) financing activities	456,269	(23,479)	(13,597)
Effect of exchange rate changes on cash and cash equivalents	437	153	(1,227)
Net increase in cash, cash equivalents, and restricted cash	362,710	60,018	34,768
Cash, cash equivalents, and restricted cash at beginning of period	127,210	67,192	32,424
Cash, cash equivalents, and restricted cash at end of period	489,920	127,210	67,192
Reconciliation of cash, cash equivalents, and restricted cash to the Consolidated Balance Sheets:
Cash, cash equivalents, and restricted cash at end of period	127,210	127,210	67,192
Supplemental cash flow information
Cash paid for interest	522	3,582	7,487
Cash paid for taxes, net of refunds	10,343	7,761	3,489
Supplemental disclosure of non-cash activities
Unpaid purchases of property and equipment	405	913	1,123
Transfers between inventory and property and equipment, net	0	1,552	2,032
Transfers from prepaid expenses to property and equipment	0	3,313	0
Balance transfer from term loan to revolving credit facility	$ 0	$ 80,000	$ 0