Note 3 - Revenues - Disaggregated Revenues (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Revenues	$ 677.6	$ 610.1	$ 2,004.2	$ 1,866.5
UNITED STATES
Revenues	564.9	520.5	1,680.1	1,585.1
UNITED KINGDOM
Revenues	48.5	41.1	140.4	127.9
Other Countries [Member]
Revenues	64.2	48.5	183.7	153.5
Insurance [Member]
Revenues	677.6	610.1	2,004.2	1,806.5
Insurance [Member] | Underwriting [Member]
Revenues	475.2	436.2	1,413.7	1,290.0
Insurance [Member] | Claims [Member]
Revenues	202.4	173.9	590.5	516.5
Energy and Specialized Markets [Member]
Revenues	0.0	0.0	0.0	22.4
Financial Services [Member]
Revenues	$ 0.0	$ 0.0	$ 0.0	$ 37.6