Goodwill and Other Intangible Assets - Schedule of Goodwill and Other Intangible Assets Rollforward (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Goodwill [Line Items]
Goodwill, acquisition date fair value	$ 392.4		$ 402.3
Goodwill, Impairment Loss			7.6
Goodwill	392.4		394.7
Other intangible assets, acquisition date fair value	680.2		694.4
Other intangible assets, accumulated amortization	33.4		29.3
Impairment of Intangible Assets, Finite-lived			10.4
Goodwill and intangible assets, net carrying value	646.8		654.7
NSM Holding Co LLC
Goodwill [Line Items]
Goodwill, acquisition date fair value	379.1		381.6
Goodwill	379.1		381.6
Other intangible assets, acquisition date fair value	268.6		271.7
Other intangible assets, accumulated amortization	32.5		27.9
Impairment of Intangible Assets, Finite-lived			2.4
Other intangible assets, net carrying value	236.1		241.4
Amortization of Intangible Assets	(4.8)	$ (5.0)
Kudu investments
Goodwill [Line Items]
Goodwill, acquisition date fair value	7.6		7.6
Goodwill	7.6		7.6
Amortization of Intangible Assets	(0.1)	0.0
MediaAlpha
Goodwill [Line Items]
Other intangible assets, acquisition date fair value	17.0		18.2
Other intangible assets, accumulated amortization	0.6		1.2
Impairment of Intangible Assets, Finite-lived			0.4
Other intangible assets, net carrying value	16.4
Goodwill and intangible assets, net carrying value			16.6
Amortization of Intangible Assets	0.0	(1.6)
Other
Goodwill [Line Items]
Goodwill, acquisition date fair value	5.7		13.1
Goodwill, Impairment Loss			7.6
Goodwill	5.7		5.5
Customer relationships | NSM Holding Co LLC
Goodwill [Line Items]
Other intangible assets, acquisition date fair value	120.1		121.7
Other intangible assets, accumulated amortization	23.5		19.8
Impairment of Intangible Assets, Finite-lived			1.4
Other intangible assets, net carrying value	$ 96.6		100.5
Acquired finite-lived intangible assets, weighted average useful life	9 years
Customer relationships | MediaAlpha
Goodwill [Line Items]
Other intangible assets, acquisition date fair value	$ 7.2		7.2
Other intangible assets, accumulated amortization	0.5		0.4
Impairment of Intangible Assets, Finite-lived			0.0
Other intangible assets, net carrying value	$ 6.7
Goodwill and intangible assets, net carrying value			6.8
Customer relationships | Other
Goodwill [Line Items]
Acquired finite-lived intangible assets, weighted average useful life	11 years
Trade names | NSM Holding Co LLC
Goodwill [Line Items]
Other intangible assets, acquisition date fair value	$ 61.2		61.9
Other intangible assets, accumulated amortization	5.8		5.3
Impairment of Intangible Assets, Finite-lived			0.4
Other intangible assets, net carrying value	$ 55.4		56.2
Acquired finite-lived intangible assets, weighted average useful life	19 years
Trade names | Kudu investments
Goodwill [Line Items]
Other intangible assets, acquisition date fair value	$ 2.2		2.2
Other intangible assets, accumulated amortization	0.3		0.2
Impairment of Intangible Assets, Finite-lived			0.0
Other intangible assets, net carrying value	$ 1.9		2.0
Acquired finite-lived intangible assets, weighted average useful life	7 years
Trade names | MediaAlpha
Goodwill [Line Items]
Other intangible assets, acquisition date fair value			1.7
Other intangible assets, accumulated amortization			0.5
Impairment of Intangible Assets, Finite-lived			0.2
Goodwill and intangible assets, net carrying value			1.0
Trade names | Other
Goodwill [Line Items]
Other intangible assets, acquisition date fair value	$ 1.0
Other intangible assets, accumulated amortization	0.1
Other intangible assets, net carrying value	$ 0.9
Acquired finite-lived intangible assets, weighted average useful life	10 years
Information technology | NSM Holding Co LLC
Goodwill [Line Items]
Other intangible assets, acquisition date fair value	$ 3.1		3.9
Other intangible assets, accumulated amortization	1.3		1.4
Impairment of Intangible Assets, Finite-lived			0.6
Other intangible assets, net carrying value	$ 1.8		1.9
Acquired finite-lived intangible assets, weighted average useful life	5 years
Information technology | MediaAlpha
Goodwill [Line Items]
Other intangible assets, acquisition date fair value	$ 0.0		0.5
Other intangible assets, accumulated amortization	0.0		0.3
Impairment of Intangible Assets, Finite-lived			0.2
Other intangible assets, net carrying value	$ 0.0
Goodwill and intangible assets, net carrying value			0.0
Information technology | Other
Goodwill [Line Items]
Acquired finite-lived intangible assets, weighted average useful life	5 years
Other | NSM Holding Co LLC
Goodwill [Line Items]
Other intangible assets, acquisition date fair value	$ 1.7		1.7
Other intangible assets, accumulated amortization	0.9		0.7
Impairment of Intangible Assets, Finite-lived			0.0
Other intangible assets, net carrying value	$ 0.8		1.0
Acquired finite-lived intangible assets, weighted average useful life	3 years
Other | MediaAlpha
Goodwill [Line Items]
Other intangible assets, acquisition date fair value	$ 0.2		0.2
Other intangible assets, accumulated amortization	0.0		0.0
Impairment of Intangible Assets, Finite-lived			0.0
Other intangible assets, net carrying value	$ 0.2
Goodwill and intangible assets, net carrying value			0.2
Other | Other
Goodwill [Line Items]
Acquired finite-lived intangible assets, weighted average useful life	5 years
Renewal Rights | NSM Holding Co LLC
Goodwill [Line Items]
Other intangible assets, acquisition date fair value	$ 82.5		82.5
Other intangible assets, accumulated amortization	1.0		0.7
Impairment of Intangible Assets, Finite-lived			0.0
Other intangible assets, net carrying value	$ 81.5		81.8
Acquired finite-lived intangible assets, weighted average useful life	12 years
Other Intangible Assets
Goodwill [Line Items]
Foreign currency translation	$ (0.5)	0.3
Measurement Period Adjustments	0.0	5.9
Intangible Assets, Net (Excluding Goodwill)	254.4	160.5	260.0	$ 157.6
Other intangible assets, acquisition date fair value	287.8		292.1
Other intangible assets, accumulated amortization	33.4		29.3
Impairment of Intangible Assets, Finite-lived			2.8
Other intangible assets, net carrying value	254.4
Goodwill and intangible assets, net carrying value			260.0
Deconsolidation of Business	0.0	(23.5)
Adjustments to reflect acquisition date fair value	0.0	26.8
Amortization of Intangible Assets	(5.1)	(6.6)
Acquisitions of businesses	0.0	0.0
Licensing Agreements [Member] | MediaAlpha
Goodwill [Line Items]
Other intangible assets, acquisition date fair value	8.6		8.6
Other intangible assets, accumulated amortization	0.0		0.0
Impairment of Intangible Assets, Finite-lived			0.0
Other intangible assets, net carrying value	8.6
Goodwill and intangible assets, net carrying value			8.6
Non-controlling interest
Goodwill [Line Items]
Goodwill and intangible assets, net carrying value	(23.5)		(23.4)
Total
Goodwill [Line Items]
Goodwill and intangible assets, net carrying value	623.3		631.3
Goodwill
Goodwill [Line Items]
Measurement Period Adjustments	0.2	0.3
Goodwill	392.4	349.7	394.7	379.9
Deconsolidation of Business	0.0	(18.3)
Adjustments to reflect acquisition date fair value	0.0	(26.8)
Goodwill, Acquired During Period	0.0	13.4
Foreign currency translation	(2.5)	1.2
Intangible Asset and Goodwill
Goodwill [Line Items]
Foreign currency translation	(3.0)	1.5
Measurement Period Adjustments	0.2	6.2
Goodwill and intangible assets, acquisition date fair value	646.8	510.2	654.7	$ 537.5
Deconsolidation of Business	0.0	(41.8)
Amortization of Intangible Assets	(5.1)	(6.6)
Acquisitions of businesses	0.0	$ 13.4
Other Intangible Assets | NSM Holding Co LLC
Goodwill [Line Items]
Foreign currency translation			0.7
NSM Holding Co LLC
Goodwill [Line Items]
Goodwill and intangible assets, net carrying value	615.2		623.0
NSM Holding Co LLC | Goodwill
Goodwill [Line Items]
Foreign currency translation	$ (2.5)		$ 1.4