Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
NET INCOME	$ 673.9	$ 637.7	$ 570.4
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	278.5	202.9	157.1
Provision for uncollectible receivables	10.1	6.5	9.5
Amortization of restricted stock and other non-cash compensation	80.2	82.2	82.0
Net amortization of bond discounts and deferred financing costs	9.3	6.5	5.8
Deferred income tax provision	9.7	14.1	(9.5)
Net losses on sales of businesses	43.4	61.9	24.1
Other	9.9	1.2	12.7
Changes in assets and liabilities, net of acquisitions and divestitures, providing (using) cash:
Accounts receivable	(111.2)	(603.8)	37.6
Accounts receivable, billable to clients	(38.7)	(209.5)	(165.5)
Other current assets	(27.2)	(67.2)	50.1
Accounts payable	546.0	428.7	336.4
Accrued liabilities	27.4	(24.2)	(241.3)
Contract liabilities	46.5	44.9	(12.0)
Change in operating lease right-of-use asset and lease liabilities	0.7	(0.0)	(0.0)
Other non-current assets and liabilities	(29.3)	(16.8)	24.4
Net cash provided by operating activities	1,529.2	565.1	881.8
CASH FLOWS FROM INVESTING ACTIVITIES:
Acquisitions, net of cash acquired	0.6	2,309.8	30.6
Capital expenditures	198.5	177.1	155.9
Other investing activities	37.4	(4.6)	(9.7)
Net cash used in investing activities	(161.7)	(2,491.5)	(196.2)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from Issuance of Long-term Debt	0.0	2,494.2	0.0
Exercise of stock options	4.3	15.5	13.1
Common stock dividends	(363.1)	(322.1)	(280.3)
Repurchases of common stock	(0.0)	(117.1)	(300.1)
Repayments of long-term debt	(403.3)	(104.8)	(324.6)
Acquisition-related payments	(15.8)	(33.7)	(53.7)
Tax payments for employee shares withheld	(22.4)	(29.2)	(38.8)
Net (decrease) increase in short-term borrowings	(19.8)	(17.5)	3.0
Distributions to noncontrolling interests	(21.6)	(16.9)	(20.4)
Other financing activities	(1.3)	(15.2)	(3.1)
Net cash (used in) provided by financing activities	(843.0)	1,853.2	(1,004.9)
Effect of foreign exchange rate changes on cash, cash equivalents and restricted cash	(6.0)	(47.3)	16.8
Net increase (decrease) in cash, cash equivalents and restricted cash	518.5	(120.5)	(302.5)
Cash, cash equivalents and restricted cash at beginning of period	677.2	797.7	1,100.2
Cash, cash equivalents and restricted cash at end of period	$ 1,195.7	$ 677.2	$ 797.7