Consolidated Statement of Earnings - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenues before reimbursements	$ 9,926.5	$ 8,420.1	$ 8,076.4
Reimbursements	145.4	130.5	133.0
Total revenues	10,071.9	8,550.6	8,209.4
Compensation	5,681.2	4,799.8	3,927.5
Operating	1,689.7	1,330.9	1,072.4
Reimbursements	145.4	130.5	133.0
Cost of revenues from clean coal activities		22.9	1,173.2
Interest	296.7	256.9	226.1
Loss on extinguishment of debt			16.2
Depreciation	165.2	144.7	151.2
Amortization	531.3	454.9	415.1
Change in estimated acquisition earnout payables	377.3	83.0	119.6
Total expenses	8,886.8	7,223.6	7,234.3
Earnings before income taxes	1,185.1	1,327.0	975.1
Provision for income taxes	219.1	211.0	20.1
Net earnings	966.0	1,116.0	955.0
Net earnings (loss) attributable to noncontrolling interests	(3.5)	1.8	48.2
Net earnings attributable to controlling interests	$ 969.5	$ 1,114.2	$ 906.8
Basic net earnings per share	$ 4.51	$ 5.3	$ 4.47
Diluted net earnings per share	4.42	5.19	4.37
Dividends declared per common share	$ 2.2	$ 2.04	$ 1.92
Commissions [Member]
Revenues before reimbursements	$ 5,865.0	$ 5,187.4	$ 4,132.3
Broker Fees [Member]
Revenues before reimbursements	3,144.7	2,567.7	2,264.1
Supplemental Revenue [Member]
Revenues before reimbursements	314.2	284.7	248.7
Contingent Revenue [Member]
Revenues before reimbursements	235.3	207.3	188.0
Interest Income, Premium Finance Revenues and Other Income [Member]
Revenues before reimbursements	$ 367.3	150.0	102.5
Clean Coal Activities [Member]
Revenues before reimbursements		$ 23.0	$ 1,140.8