Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
CASH FLOWS FROM OPERATING ACTIVITIES:
NET INCOME	$ 637.7	$ 570.4	$ 629.0
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	202.9	157.1	160.2
Provision for uncollectible receivables	6.5	9.5	16.7
Amortization of restricted stock and other non-cash compensation	82.2	82.0	85.6
Net amortization of bond discounts and deferred financing costs	6.5	5.8	5.6
Deferred income tax provision	14.1	(9.5)	44.6
Net losses on sales of businesses	61.9	24.1	41.4
Other	1.2	12.7	35.5
Changes in assets and liabilities, net of acquisitions and divestitures, providing (using) cash:
Accounts receivable	(603.8)	37.6	(220.7)
Accounts receivable, billable to clients	(209.5)	(165.5)	(2.2)
Other current assets	(67.2)	50.1	0.5
Accounts payable	428.7	336.4	(147.4)
Accrued liabilities	(24.2)	(241.3)	(61.1)
Contract liabilities	44.9	(12.0)	20.6
Other non-current assets and liabilities	(16.8)	24.4	(95.5)
Net cash provided by operating activities	565.1	881.8	512.8
CASH FLOWS FROM INVESTING ACTIVITIES:
Acquisitions, net of cash acquired	2,309.8	30.6	52.0
Capital expenditures	177.1	155.9	200.7
Other investing activities	(4.6)	(9.7)	(11.2)
Net cash used in investing activities	(2,491.5)	(196.2)	(263.9)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from Issuance of Long-term Debt	2,494.2	0.0	0.0
Exercise of stock options	15.5	13.1	10.2
Common stock dividends	(322.1)	(280.3)	(238.4)
Repurchases of common stock	(117.1)	(300.1)	(303.3)
Repayments of long-term debt	(104.8)	(324.6)	(1.8)
Acquisition-related payments	(33.7)	(53.7)	(40.8)
Tax payments for employee shares withheld	(29.2)	(38.8)	(23.1)
Net (decrease) increase in short-term borrowings	(17.5)	3.0	(56.2)
Distributions to noncontrolling interests	(16.9)	(20.4)	(13.7)
Other financing activities	(15.2)	(3.1)	0.7
Net cash provided by (used in) financing activities	1,853.2	(1,004.9)	(666.4)
Effect of foreign exchange rate changes on cash, cash equivalents and restricted cash	(47.3)	16.8	11.6
Net decrease in cash, cash equivalents and restricted cash	(120.5)	(302.5)	(405.9)
Cash, cash equivalents and restricted cash at beginning of period	797.7	1,100.2	1,506.1
Cash, cash equivalents and restricted cash at end of period	$ 677.2	$ 797.7	$ 1,100.2