CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Cash Flows from Operating Activities:
Net income	$ 268.1	$ 409.9	$ 200.3
Adjustments to reconcile net income to net cash provided by operating activities:
Gain on sale of discontinued operations	0.0	(216.9)	0.0
Depreciation and amortization	91.4	89.6	89.7
Stock-based compensation	49.3	52.7	32.3
Deferred income taxes	31.5	(19.7)	1.3
Other	8.2	6.3	5.9
Changes in operating assets and liabilities, net of effects of acquisitions:
Accounts receivable	(116.3)	(111.1)	(12.9)
Prepaid expenses and income taxes	2.0	(18.2)	6.5
Accounts payable	7.6	(23.6)	0.8
Accrued payroll	11.3	67.4	12.6
Payroll tax deferral and other	(45.3)	(42.7)	88.3
Net cash provided by operating activities	307.8	193.7	424.8
Cash Flows from Investing Activities
Cash paid for property and equipment	(37.5)	(34.7)	(32.6)
Cash paid for acquisitions, net of cash acquired	(484.6)	(222.8)	(186.2)
Proceeds from Divestiture of Businesses	9.8	503.8	0.0
Other	2.3	0.2	(0.2)
Net cash provided by (used in) investing activities	(510.0)	246.5	(219.0)
Cash Flows from Financing Activities
Proceeds from long-term debt	94.0	0.0	65.5
Principal payments of long-term debt	(62.5)	0.0	(65.5)
Proceeds from employee stock purchase plan	18.9	14.3	12.1
Repurchase of common stock	(281.4)	(181.3)	(27.9)
Payment of employment taxes related to release of restricted stock awards	(16.6)	(16.0)	(12.0)
Payment of contingent consideration	(8.1)	0.0	0.0
Debt issuance or amendment costs	(0.8)	(1.4)	(1.2)
Net cash used in financing activities	(256.5)	(184.4)	(29.0)
Effect of exchange rate changes on cash and cash equivalents	(0.6)	(0.6)	2.4
Net Increase in Cash and Cash Equivalents	(459.3)	255.2	179.2
Cash and Cash Equivalents at Beginning of Year	529.6	274.4	95.2
Cash and Cash Equivalents at End of Year	70.3	529.6	274.4
Supplemental Disclosure of Cash Flow Information
Income taxes	54.5	170.3	64.2
Interest	$ 43.7	$ 35.2	$ 37.6