Note 3 - Revenues - Disaggregated Revenues (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Revenues	$ 675.0	$ 612.8	$ 1,326.6	$ 1,256.4
UNITED STATES
Revenues	563.4	529.9	1,115.2	1,064.6
UNITED KINGDOM
Revenues	45.0	41.7	91.9	86.8
Other Countries [Member]
Revenues	66.6	41.2	119.5	105.0
Insurance [Member]
Revenues	675.0	610.0	1,326.6	1,196.4
Insurance [Member] | Underwriting [Member]
Revenues	478.1	437.8	938.6	853.8
Insurance [Member] | Claims [Member]
Revenues	196.9	172.2	388.0	342.6
Energy and Specialized Markets [Member]
Revenues	0.0	0.0	0.0	22.4
Financial Services [Member]
Revenues	$ 0.0	$ 2.8	$ 0.0	$ 37.6