Goodwill and Other Intangible Assets - Summary of Goodwill and Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Goodwill [Line Items]
Goodwill, fair value	$ 675.7	$ 525.5
Goodwill, impairment loss	30.2	0.0
Goodwill	645.5	525.5
Other intangible assets, fair value	1,196.1	843.3
Other intangible assets, accumulated amortization	93.8	54.7
Other intangible assets, net	244.7
Goodwill and intangible asset impairment	36.4	6.2
Ark
Goodwill [Line Items]
Goodwill, fair value	116.8	0.0
Goodwill, impairment loss	0.0	0.0
Goodwill	116.8	0.0
NSM
Goodwill [Line Items]
Goodwill, fair value	533.4	506.4
Goodwill, impairment loss	30.2	0.0
Goodwill	503.2	506.4
Other intangible assets, fair value	315.2	288.9
Other intangible assets, accumulated amortization	86.8	52.3
Impairments and Amounts Allocated to Held for Sale	6.2	6.2
Other intangible assets, net	222.2	230.4
Kudu
Goodwill [Line Items]
Goodwill, fair value	7.6	7.6
Goodwill, impairment loss	0.0	0.0
Goodwill	7.6	7.6
Other
Goodwill [Line Items]
Goodwill, fair value	17.9	11.5
Goodwill, impairment loss	0.0	0.0
Goodwill	17.9	11.5
Other intangible assets, fair value	27.3	26.7
Other intangible assets, accumulated amortization	6.1	1.8
Impairments and Amounts Allocated to Held for Sale	0.0
Other intangible assets, net	21.2	24.9
Trade names | Ark
Goodwill [Line Items]
Other intangible assets, fair value	175.7	0.0
Other intangible assets, accumulated amortization	0.0	0.0
Impairments and Amounts Allocated to Held for Sale	0.0	0.0
Other intangible assets, net	$ 175.7	0.0
Trade names | NSM
Goodwill [Line Items]
Acquired other intangible assets, weighted average useful life (in years)	18 years
Other intangible assets, fair value	$ 68.6	65.4
Other intangible assets, accumulated amortization	11.9	8.3
Impairments and Amounts Allocated to Held for Sale	1.0	1.0
Other intangible assets, net	$ 55.7	56.1
Trade names | Kudu
Goodwill [Line Items]
Acquired other intangible assets, weighted average useful life (in years)	7 years
Other intangible assets, fair value	$ 2.2	2.2
Other intangible assets, accumulated amortization	0.9	0.6
Impairments and Amounts Allocated to Held for Sale	0.0	0.0
Other intangible assets, net	$ 1.3	1.6
Trade names | Other
Goodwill [Line Items]
Acquired other intangible assets, weighted average useful life (in years)	17 years 6 months
Other intangible assets, fair value	$ 8.2	3.6
Other intangible assets, accumulated amortization	1.5	0.3
Impairments and Amounts Allocated to Held for Sale	0.0	0.0
Other intangible assets, net	$ 6.7	3.3
Customer relationships | NSM
Goodwill [Line Items]
Acquired other intangible assets, weighted average useful life (in years)	9 years
Other intangible assets, fair value	$ 159.9	136.2
Other intangible assets, accumulated amortization	57.0	36.7
Impairments and Amounts Allocated to Held for Sale	3.5	3.5
Other intangible assets, net	$ 99.4	96.0
Customer relationships | Other
Goodwill [Line Items]
Acquired other intangible assets, weighted average useful life (in years)	13 years
Other intangible assets, fair value	$ 18.8	14.2
Other intangible assets, accumulated amortization	4.5	1.4
Impairments and Amounts Allocated to Held for Sale	0.0	0.0
Other intangible assets, net	$ 14.3	12.8
Information technology platform | NSM
Goodwill [Line Items]
Acquired other intangible assets, weighted average useful life (in years)	0 years
Other intangible assets, fair value	$ 3.1	3.1
Other intangible assets, accumulated amortization	1.4	1.4
Impairments and Amounts Allocated to Held for Sale	1.7	1.7
Other intangible assets, net	$ 0.0	0.0
Renewal rights | NSM
Goodwill [Line Items]
Acquired other intangible assets, weighted average useful life (in years)	12 years
Other intangible assets, fair value	$ 82.5	82.5
Other intangible assets, accumulated amortization	15.8	4.9
Impairments and Amounts Allocated to Held for Sale	0.0	0.0
Other intangible assets, net	66.7	77.6
Insurance licenses (2) | Other
Goodwill [Line Items]
Other intangible assets, fair value	0.0	8.6
Other intangible assets, accumulated amortization	0.0	0.0
Impairments and Amounts Allocated to Held for Sale	0.0	0.0
Other intangible assets, net	0.0	8.6
Insurance licenses (2) | Other | Disposal Group, Held-for-sale, Not Discontinued Operations
Goodwill [Line Items]
Other intangible assets, net	$ 8.6
Other | NSM
Goodwill [Line Items]
Acquired other intangible assets, weighted average useful life (in years)	3 years 3 months 18 days
Other intangible assets, fair value	$ 1.1	1.7
Other intangible assets, accumulated amortization	0.7	1.0
Impairments and Amounts Allocated to Held for Sale	0.0	0.0
Other intangible assets, net	$ 0.4	0.7
Other | Other
Goodwill [Line Items]
Acquired other intangible assets, weighted average useful life (in years)	5 years 3 months 18 days
Other intangible assets, fair value	$ 0.3	0.3
Other intangible assets, accumulated amortization	0.1	0.1
Impairments and Amounts Allocated to Held for Sale	0.0	0.0
Other intangible assets, net	0.2	0.2
Total other intangible assets
Goodwill [Line Items]
Other intangible assets, fair value	520.4	317.8
Other intangible assets, accumulated amortization	93.8	54.7
Impairments and Amounts Allocated to Held for Sale	6.2	6.2
Other intangible assets, net	420.4	256.9
Total Equity
Goodwill [Line Items]
Goodwill and other intangible assets	1,065.9	782.4
Non-controlling Interests
Goodwill [Line Items]
Goodwill and other intangible assets	(117.6)	(28.1)
Total
Goodwill [Line Items]
Goodwill and other intangible assets	948.3	754.3
Goodwill
Goodwill [Line Items]
Goodwill, impairment loss	0.0	0.0
Goodwill	645.5	525.5	$ 394.7
Goodwill, foreign currency translation gain	(1.5)	13.4
Goodwill | NSM
Goodwill [Line Items]
Goodwill, foreign currency translation gain	(1.5)	13.4
Total other intangible assets
Goodwill [Line Items]
Goodwill, impairment loss	0.0	6.2
Total other intangible assets | NSM
Goodwill [Line Items]
Goodwill, foreign currency translation gain	$ (0.3)	$ 1.6