Unaudited Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Cash flows from operating activities
Net income	$ 91,930	$ 64,616
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	21,655	14,916
Accretion of discount on available-for-sale securities	(303)	(77)
Non-cash marketing expense	437
Loss on disposition of property and equipment		132
Amortization of debt issuance costs	9	9
Stock-based compensation expense	22,055	23,581
Cash paid for derivative settlement	(174)	(232)
(Gain)/loss on derivative	(1,089)	(424)
Deferred income taxes, net	(10,332)	2,738
Changes in operating assets and liabilities:
Accounts receivable	(8,455)	(10,662)
Prepaid expenses	(4,859)	(6,255)
Inventory	124	(125)
Other assets	(2,970)	559
Deferred contract costs	(36,261)	(26,575)
Accounts payable	5,406	803
Income taxes, net	39,593	23,424
Accrued commissions and bonuses	(10,309)	(6,922)
Accrued payroll and vacation	8,579	8,105
Deferred revenue	3,390	2,167
Accrued expenses and other current liabilities	(1,195)	(321)
Net cash provided by operating activities	117,231	89,457
Cash flows from investing activities
Purchases of investments from funds held for clients	(169,152)	(47,215)
Proceeds from investments from funds held for clients	136,000	80,000
Purchases of property and equipment	(34,474)	(25,330)
Net cash provided by (used in) investing activities	(67,626)	7,455
Cash flows from financing activities
Withholding taxes paid related to net share settlements	(218)	(377)
Payments on long-term debt	(444)	(444)
Net change in client funds obligation	2,099,530	686,190
Net cash provided by (used in) financing activities	2,098,868	685,369
Increase (decrease) in cash, cash equivalents, restricted cash and restricted cash equivalents	2,148,473	782,281
Cash, cash equivalents, restricted cash and restricted cash equivalents
Cash, cash equivalents, restricted cash and restricted cash equivalents, beginning of period	1,812,691	1,585,275
Cash, cash equivalents, restricted cash and restricted cash equivalents, end of period	3,961,164	2,367,556
Cash and cash equivalents	360,594	215,093
Restricted cash included in funds held for clients	3,600,570	2,152,463
Non-cash investing and financing activities:
Purchases of property and equipment, accrued but not paid	5,394	6,217
Stock-based compensation for capitalized software	1,891	1,456
Right of use assets obtained in exchange for operating lease liabilities	$ 4,146	$ 541