Consolidated Statement of Cash Flows - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017		Dec. 31, 2016
Cash flows from operating activities:
Net earnings		$ 675.9	$ 516.9	[1]	$ 430.3	[1]
Adjustments to reconcile net earnings to net cash provided by operating activities:
Net gain on investments and other		(8.4)	(0.1)	[1]	(6.5)	[1]
Depreciation and amortization		419.0	385.8	[1]	350.8	[1]
Change in estimated acquisition earnout payables		9.6	30.9	[1]	32.1	[1]
Amortization of deferred compensation and restricted stock		41.6	33.5	[1]	28.5	[1]
Stock-based and other noncash compensation expense		13.7	17.3	[1]	14.7	[1]
Payments on acquisition earnouts in excess of original estimates		(64.6)	(57.9)	[1]	(22.8)	[1]
Effect of changes in foreign exchange rate		(2.9)	3.9	[1]	(5.3)	[1]
Net change in premium and fees receivable		(783.1)	(47.7)	[1]	(777.2)	[1]
Net change in deferred revenue		18.4	0.9	[1]	15.1	[1]
Net change in premiums payable to underwriting enterprises		819.7	166.9	[1]	770.0	[1]
Net change in other current assets		(134.7)	(35.3)	[1]	(45.5)	[1]
Net change in accrued compensation and other accrued liabilities		44.9	69.6	[1]	69.8	[1]
Net change in income taxes payable		(46.0)	2.0	[1]	(10.8)	[1]
Net change in deferred income taxes		(216.0)	(219.3)	[1]	(166.1)	[1]
Net change in other noncurrent assets and liabilities		(22.0)	(13.2)	[1]	(27.5)	[1]
Net cash provided by operating activities		765.1	854.2	[1]	649.6	[1]
Cash flows from investing activities:
Capital expenditures		(124.4)	(129.2)	[1]	(217.8)	[1]
Cash paid for acquisitions, net of cash and restricted cash acquired		(784.8)	(376.1)	[1]	(243.4)	[1]
Net proceeds from sales of operations/books of business		14.5	3.2	[1]	7.8	[1]
Net funding of investment transactions		(15.6)	(8.9)	[1]	(31.9)	[1]
Net cash used by investing activities		(910.3)	(511.0)	[1]	(485.3)	[1]
Cash flows from financing activities:
Payments on acquisition earnouts		(62.1)	(41.7)	[1]	(45.5)	[1]
Proceeds from issuance of common stock		81.9	60.4	[1]	45.6	[1]
Tax impact from issuance of common stock	[1]				6.5
Repurchases of common stock		(11.3)	(17.7)	[1]	(101.0)	[1]
Payments to noncontrolling interests		(54.2)	(35.0)	[1]	(41.8)	[1]
Dividends paid		(301.8)	(282.7)	[1]	(272.2)	[1]
Net borrowings on premium financing debt facility		32.9	0.6	[1]	(12.2)	[1]
Borrowings on line of credit facility		3,075.0	3,643.0	[1]	2,740.0	[1]
Repayments on line of credit facility		(3,000.0)	(3,731.0)	[1]	(2,657.0)	[1]
Net borrowings of corporate related long-term debt		400.0	348.0	[1]	326.0	[1]
Debt acquisition costs		(1.3)
Settlements on terminated interest rate swaps		2.9	8.3	[1]
Net cash provided (used) by financing activities		162.0	(47.8)	[1]	(11.6)	[1]
Effect of changes in foreign exchange rates on cash, cash equivalents and restricted cash		(85.0)	72.0	[1]	(107.6)	[1]
Net (decrease) increase in cash, cash equivalents and restricted cash		(68.2)	367.4	[1]	45.1	[1]
Cash, cash equivalents and restricted cash at beginning of year	[1]	2,305.0	1,937.6		1,892.5
Cash, cash equivalents and restricted cash at end of year		2,236.8	2,305.0	[1]	1,937.6	[1]
Supplemental disclosures of cash flow information:
Interest paid		139.2	124.8	[1]	112.8	[1]
Income taxes paid		$ 68.1	$ 55.8	[1]	$ 66.1	[1]

[1] See Note 3 - Revenues from Contracts with Customers for additional information about the restatements related to Topic 606.