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	$ 120,968	$ 105,354	$ 70,887
Adjustments to reconcile net income to net cash provided by operating activities:
Gain on sale of operations, net of tax	(176)	(413)	(5,995)
Depreciation and amortization expense	36,269	32,895	27,078
Bad debt expense, net of recoveries	1,551	1,173	3,054
Adjustment to contingent earnout liability, net	2,743	2,435	2,367
Deferred income taxes	11,273	13,877	9,234
Stock-based compensation expense	12,286	14,689	11,407
Other, net	(2,365)	(1,835)	(150)
Changes in assets and liabilities, net of acquisitions and divestitures:
Accounts receivable, net	(36,093)	(61,106)	(17,040)
Other assets	(6,626)	(11,855)	3,474
Accounts payable	2,210	14,363	3,312
Income taxes payable	(5,918)	(5,578)	(4,108)
Accrued personnel costs	2,711	24,009	24,525
Other liabilities	14,674	(1,876)	3,109
Net cash provided by operating activities	153,507	126,132	131,154
Cash flows from investing activities:
Business acquisitions and purchases of client lists, net of cash acquired	(53,110)	(79,141)	(66,734)
Purchases of client fund investments	(14,122)	(19,771)	(26,980)
Proceeds from the sales and maturities of client fund investments	18,465	12,400	14,877
Proceeds from sales of assets and divested operations	3,059	3,022	9,710
Additions to property and equipment	(23,052)	(8,641)	(8,984)
Other, net	(10,633)	(6,987)	(3,899)
Net cash used in investing activities	(79,393)	(99,118)	(82,010)
Cash flows from financing activities:
Proceeds from bank debt	1,224,000	824,900	852,100
Payment of bank debt	(1,177,300)	(714,500)	(804,800)
Payment for acquisition of treasury stock	(65,378)	(122,538)	(97,450)
Indirect repurchase of shares for minimum tax withholding	(8,448)	(7,289)	(3,037)
Changes in client funds obligations	(13,574)	15,352	(8,874)
Payment of contingent consideration of acquisitions and client lists	(45,175)	(21,231)	(14,084)
Proceeds from exercise of stock options	8,764	10,035	7,311
Other, net	0	(2,072)	(171)
Net cash used in financing activities	(77,111)	(17,343)	(69,005)
Net (decrease) increase in cash, cash equivalents and restricted cash	(2,997)	9,671	(19,861)
Cash, cash equivalents and restricted cash at beginning of year	160,145	150,474	170,335
Cash, cash equivalents and restricted cash at end of year	157,148	160,145	150,474
Reconciliation of cash, cash equivalents and restricted cash to the Consolidated Balance Sheets:
Cash and cash equivalents	8,090	4,697	1,997
Restricted cash	30,362	28,487	30,383
Cash equivalents included in funds held for clients	118,696	126,961	118,094
Cash, cash equivalents and restricted cash at end of year	157,148	160,145	150,474
Supplemental disclosures of cash flow information:
Cash paid for interest	19,127	7,421	3,350
Cash paid for income taxes, net of income tax refunds	$ 39,976	$ 27,815	$ 16,998