Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities
Net income	$ 340,788	$ 281,389	$ 195,960
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	113,948	92,699	67,222
Accretion of discount on available-for-sale securities	(520)	(1,020)	(452)
Non-cash marketing expense	1,658	1,734	1,051
Loss (Gain) on disposition of property and equipment	23	(150)	146
Amortization of debt issuance costs	1,225	847	36
Stock-based compensation expense	129,806	94,898	97,506
Loss on extinguishment of debt	1,222
Cash paid for derivative settlement		205	(741)
Gain on derivative		(1,559)	(662)
Deferred income taxes, net	2,557	(3,210)	32,906
Other	122	(206)
Changes in operating assets and liabilities:
Accounts receivable	6,401	(13,353)	(360)
Prepaid expenses	(6,617)	(6,497)	(5,875)
Inventory	224	(224)	481
Other assets	(43,431)	(13,907)	(7,862)
Deferred contract costs	(127,657)	(122,440)	(103,356)
Accounts payable	(5,155)	11,676	(660)
Income taxes, net	(12,808)	10,830	(5,966)
Accrued commissions and bonuses	2,053	6,082	8,654
Accrued payroll and vacation	11,063	10,764	9,730
Deferred revenue	13,053	15,990	14,600
Accrued expenses and other current liabilities	57,082	555	17,004
Net cash provided by operating activities	485,037	365,103	319,362
Cash flows from investing activities
Purchases of investments from funds held for clients	(25,000)	(268,718)	(398,819)
Proceeds from investments from funds held for clients	25,000	382,230	267,341
Purchases of intangible assets	(4,244)	(4,120)	(5,500)
Purchases of property and equipment	(192,587)	(132,678)	(120,692)
Proceeds from sale of property and equipment	119
Net cash used in investing activities	(196,712)	(23,286)	(257,670)
Cash flows from financing activities
Proceeds from the issuance of debt		29,000
Repurchases of common stock	(286,618)	(94,652)
Withholding taxes paid related to net share settlements	(13,927)	(5,171)	(65,580)
Payments on long-term debt	(29,000)	(29,287)	(1,775)
Dividends paid	(64,838)
Net change in client funds obligation	120,370	361,133	233,079
Payment of debt issuance costs	(647)	(6,436)
Net cash (used in) provided by financing activities	(274,660)	254,587	165,724
Increase in cash, cash equivalents, restricted cash and restricted cash equivalents	13,665	596,404	227,416
Cash, cash equivalents, restricted cash and restricted cash equivalents
Cash, cash equivalents, restricted cash and restricted cash equivalents, beginning of period	2,409,095	1,812,691	1,585,275
Cash, cash equivalents, restricted cash and restricted cash equivalents, end of period	2,422,760	2,409,095	1,812,691
Cash and cash equivalents	294,025	400,730	277,978
Restricted cash included in funds held for clients	2,128,735	2,008,365	1,534,713
Total cash, cash equivalents, restricted cash and restricted cash equivalents, end of period	2,422,760	2,409,095	1,812,691
Supplemental disclosures of cash flow information:
Cash paid for interest, net of amounts capitalized	985	507	2
Cash paid for income taxes	139,914	100,578	33,068
Non-cash investing and financing activities:
Purchases of property and equipment, accrued but not paid	9,025	5,899	7,581
Stock-based compensation for capitalized software	14,657	8,965	7,141
Right of use assets obtained in exchange for operating lease liabilities	$ 50,315	$ 21,467	$ 14,141