Consolidated Statement of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net earnings	$ 499.2	$ 445.0	$ 389.1
Adjustments to reconcile net earnings to net cash provided by operating activities:
Net gain on investments and other	(0.1)	(6.5)	(6.6)
Depreciation and amortization	385.8	350.8	334.2
Change in estimated acquisition earnout payables	30.9	32.1	40.6
Amortization of deferred compensation and restricted stock	33.5	28.5	22.7
Stock-based and other noncash compensation expense	17.3	14.7	11.2
Payments on acquisition earnouts in excess of original estimates	(57.9)	(22.8)	(12.1)
Effect of changes in foreign exchange rate	2.8	(3.0)	(0.2)
Net change in premiums receivable	(220.3)	(242.8)	(209.3)
Net change in premiums payable	334.3	240.2	252.2
Net change in other current assets	(48.5)	(55.2)	(34.7)
Net change in accrued compensation and other accrued liabilities	69.3	69.1	217.8
Net change in fees receivable/unearned fees	0.4	2.8	(49.6)
Net change in income taxes payable	2.0	(10.8)	(18.5)
Net change in deferred income taxes	(183.4)	(158.0)	(161.2)
Net change in other noncurrent assets and liabilities	(11.1)	(34.5)	(89.5)
Net cash provided by operating activities	854.2	649.6	686.1
Cash flows from investing activities:
Capital expenditures	(129.2)	(217.8)	(99.0)
Cash paid for acquisitions, net of cash and restricted cash acquired	(376.1)	(243.4)	(249.6)
Net proceeds from sales of operations/books of business	3.2	7.8	9.2
Net funding of investment transactions	(8.9)	(31.9)	(29.5)
Net cash used by investing activities	(511.0)	(485.3)	(368.9)
Cash flows from financing activities:
Payments on acquisition earnouts	(41.7)	(45.5)	(21.8)
Proceeds from issuance of common stock	60.4	45.6	203.3
Tax impact from issuance of common stock		6.5	5.3
Repurchases of common stock	(17.6)	(101.0)
Payments to noncontrolling interests	(35.1)	(41.8)	(39.9)
Dividends paid	(282.7)	(272.2)	(257.5)
Net borrowings on premium financing debt facility	0.6	(12.2)	23.9
Borrowings on line of credit facilities	3,643.0	2,740.0	849.0
Repayments on line of credit facilities	(3,731.0)	(2,657.0)	(794.0)
Borrowings of corporate related long-term debt	648.0	376.0
Repayments of corporate related long-term debt	(300.0)	(50.0)
Settlements on terminated interest rate swaps	8.3
Net cash used by financing activities	(47.8)	(11.6)	(31.7)
Effect of changes in foreign exchange rates on cash, cash equivalents and restricted cash	72.0	(107.6)	(75.0)
Net increase in cash, cash equivalents and restricted cash	367.4	45.1	210.5
Cash, cash equivalents and restricted cash at beginning of year	1,937.6	1,892.5	1,682.0
Cash, cash equivalents and restricted cash at end of year	2,305.0	1,937.6	1,892.5
Supplemental disclosures of cash flow information:
Interest paid	124.8	112.8	103.9
Income taxes paid	$ 55.8	$ 66.1	$ 78.3