Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
CASH FLOWS FROM OPERATING ACTIVITIES:
NET INCOME	$ 354.2	$ 673.9	$ 637.7
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	290.6	278.5	202.9
Non-cash restructuring charges	265.6	11.7	0.0
Amortization of restricted stock and other non-cash compensation	67.0	80.2	82.2
Net losses on sales of businesses	67.0	43.4	61.9
Provision for uncollectible receivables	59.5	10.1	6.5
Net amortization of bond discounts and deferred financing costs	11.4	9.3	6.5
Deferred income tax provision	(46.4)	9.7	14.1
Other	20.0	6.8	1.2
Changes in assets and liabilities, net of acquisitions and divestitures, providing (using) cash:
Accounts receivable	551.4	(111.2)	(603.8)
Accounts receivable, billable to clients	122.5	(38.7)	(209.5)
Other current assets	11.9	(27.2)	(67.2)
Accounts payable	(27.0)	546.0	428.7
Accrued liabilities	179.3	27.4	(24.2)
Contract liabilities	62.0	46.5	44.9
Change in operating lease right-of-use asset and lease liabilities	(192.6)	(9.4)
Other non-current assets and liabilities	(141.8)	(37.2)	(16.8)
Net cash provided by operating activities	1,847.2	1,529.2	565.1
CASH FLOWS FROM INVESTING ACTIVITIES:
Acquisitions, net of cash acquired	4.9	0.6	2,309.8
Capital expenditures	167.5	198.5	177.1
Other investing activities	(43.8)	37.4	(4.6)
Net cash used in investing activities	(216.2)	(161.7)	(2,491.5)
CASH FLOWS FROM FINANCING ACTIVITIES:
Repayments of long-term debt	(503.7)	(403.3)	(104.8)
Common stock dividends	(398.1)	(363.1)	(322.1)
Acquisition-related payments	(46.6)	(15.8)	(33.7)
Tax payments for employee shares withheld	(22.3)	(22.4)	(29.2)
Distributions to noncontrolling interests	(19.5)	(21.6)	(16.9)
Proceeds from Long-term Debt	646.2	0.0	2,494.2
Exercise of stock options	6.5	4.3	15.5
Net increase (decrease) in short-term borrowings	1.5	(19.8)	(17.5)
Repurchases of common stock	0.0	0.0	(117.1)
Other financing activities	(10.2)	(1.3)	(15.2)
Net cash (used in) provided by financing activities	(346.2)	(843.0)	1,853.2
Effect of foreign exchange rate changes on cash, cash equivalents and restricted cash	31.0	(6.0)	(47.3)
Net increase (decrease) in cash, cash equivalents and restricted cash	1,315.8	518.5	(120.5)
Cash, cash equivalents and restricted cash at beginning of period	1,195.7	677.2	797.7
Cash, cash equivalents and restricted cash at end of period	$ 2,511.5	$ 1,195.7	$ 677.2