Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Cash flows from operating activities:
Net income	$ 80,507	$ 78,393
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization expense	19,921	17,277
Gain (loss) on sale of operations, net	(6,385)	(78)
Bad debt expense, net of recoveries	562	3,166
Adjustment to contingent earnout liability	1,599	(80)
Stock-based compensation expense	8,359	6,765
Excess tax benefits from share based payment arrangements	(4,114)	(1,674)
Deferred income taxes	7,141	(1,809)
Other, net	(373)	388
Changes in assets and liabilities, net of acquisitions and divestitures:
Accounts receivable, net	(66,017)	(27,913)
Other assets	53	1,823
Accounts payable	12,126	(18,404)
Income taxes payable	9,359	12,048
Accrued personnel costs	15,329	(4,862)
Other liabilities	2,897	16,822
Operating cash flows provided by continuing operations	80,964	81,862
Operating cash flows used in discontinued operations	(18)	(66)
Net cash provided by operating activities	80,946	81,796
Cash flows from investing activities:
Business acquisitions and purchases of client lists, net of cash acquired	(66,155)	(33,782)
Purchases of client fund investments	(13,050)	(3,447)
Proceeds from the sales and maturities of client fund investments	10,800	32,967
Proceeds from sales of divested operations	9,785	651
Change in funds held for clients	(5,708)	3,250
Additions to property and equipment	(6,451)	(9,486)
Other, net	51	356
Net cash used in investing activities	(70,728)	(9,491)
Cash flows from financing activities:
Proceeds from bank debt	680,400	550,454
Payment of bank debt	(598,200)	(545,954)
Payment for acquisition of treasury stock	(84,950)	(32,083)
Indirect repurchase of shares for minimum tax withholding	(3,037)	(2,040)
Changes in client funds obligations	8,375	(57,517)
Proceeds from exercise of stock options	7,143	4,719
Payment of contingent consideration for acquisitions	(7,883)	(11,242)
Other, net	(170)	(395)
Net cash provided by (used in) financing activities	1,678	(94,058)
Net increase (decrease) in cash, cash equivalents and restricted cash	11,896	(21,753)
Cash, cash equivalents and restricted cash at beginning of year	170,335	146,505
Cash, cash equivalents and restricted cash at end of period	182,231	124,752
Reconciliation of cash, cash equivalents and restricted cash to the   Condensed Consolidated Balance Sheets:
Cash and cash equivalents	2,749	6,113
Restricted cash	37,320	25,275
Cash equivalents included in funds held for clients	142,162	93,364
Total cash, cash equivalents and restricted cash	$ 182,231	$ 124,752