Goodwill and Other Intangible Assets - Fair Value of Goodwill and Other Intangible Assets (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Apr. 07, 2020	Mar. 31, 2020	Jun. 28, 2019	Apr. 04, 2019	Apr. 01, 2019	Mar. 31, 2019	Mar. 12, 2019	Dec. 31, 2018
Goodwill [Line Items]
Goodwill, acquisition date fair value	$ 518.2		$ 518.2		$ 402.3
Goodwill, Impairment Loss					7.6
Goodwill and other intangible assets	759.9		759.9		654.7
Goodwill	518.2		518.2		394.7
Impairment of Intangible Assets, Finite-lived					10.4
Renewal Rights
Goodwill [Line Items]
Goodwill and intangible assets acquired								$ 82.5
Kingsbridge [Member]
Goodwill [Line Items]
Goodwill and intangible assets acquired						$ 125.1
NSM Holding Co LLC
Goodwill [Line Items]
Goodwill, acquisition date fair value	504.9		504.9		381.6
Goodwill and intangible assets acquired	275.2		275.2
Goodwill	504.9		504.9		381.6
Impairment of Intangible Assets, Finite-lived					2.4
NSM Holding Co LLC | Renewal Rights
Goodwill [Line Items]
Impairment of Intangible Assets, Finite-lived					0.0
Kudu investments
Goodwill [Line Items]
Goodwill, acquisition date fair value	7.6		7.6		7.6
Goodwill	7.6		7.6		7.6
Other [Member]
Goodwill [Line Items]
Goodwill, acquisition date fair value	5.7		5.7		13.1
Goodwill, Impairment Loss					7.6
Goodwill	5.7		5.7		5.5
Impairment of Intangible Assets, Finite-lived					0.4
Embrace Pet Insurance
Goodwill [Line Items]
Capitalized Computer Software, Additions		$ 3.4
Goodwill and intangible assets acquired										$ 67.6
Goodwill										$ 52.2
Kudu
Goodwill [Line Items]
Goodwill and intangible assets acquired									$ 9.8
Other Operations
Goodwill [Line Items]
Goodwill and intangible assets acquired												$ 22.6
Goodwill
Goodwill [Line Items]
Goodwill, Foreign Currency Translation Gain (Loss)	0.7	(1.2)	(1.8)	$ 0.0
Goodwill	518.2	$ 428.6	518.2	$ 428.6	394.7		$ 392.4				$ 349.7		$ 379.9
Other Intangible Assets | NSM Holding Co LLC
Goodwill [Line Items]
Finite Lived Intangible Assets, Foreign Currency Translation Gain (Loss)			(0.4)		0.7
Fresh Insurance Services Group Limited
Goodwill [Line Items]
Impairment of Intangible Assets, Finite-lived			6.2
Fresh Insurance Services Group Limited | NSM Holding Co LLC
Goodwill [Line Items]
Impairment of Intangible Assets, Finite-lived			6.2
Fresh Insurance Services Group Limited | NSM Holding Co LLC | Renewal Rights
Goodwill [Line Items]
Impairment of Intangible Assets, Finite-lived			0.0
NSM Holding Co LLC
Goodwill [Line Items]
Goodwill and other intangible assets	$ 728.6		728.6		623.0
NSM Holding Co LLC | Goodwill
Goodwill [Line Items]
Goodwill, Foreign Currency Translation Gain (Loss)			$ (1.8)		$ 1.4