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Investment Securities (Significant Unobservable Inputs) (Details) - Standard Poors NR Rating $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Measurement Input, Discount Rate | MediaAlpha
Quantitative information for Level 3 Fair Value Measurements Assets
Fair Value, Discount Rate	15.00%
Measurement Input, Discount Rate | DavidShield & PassportCard
Quantitative information for Level 3 Fair Value Measurements Assets
Fair Value, Discount Rate	22.00%	18.00%
Measurement Input, Discount Rate | Elementum Holdings, L.P.
Quantitative information for Level 3 Fair Value Measurements Assets
Fair Value, Discount Rate	20.00%
Terminal Revenue Growth Rate	4.00%
Measurement Input, Discount Rate | Private debt instrument
Quantitative information for Level 3 Fair Value Measurements Assets
Fair Value, Discount Rate		9.00%
Measurement Input, Discount Rate | Other
Quantitative information for Level 3 Fair Value Measurements Assets
Fair Value, Discount Rate		23.00%
Terminal Revenue Growth Rate	4.00%
Measurement Input, Discount Rate | Compare.com
Quantitative information for Level 3 Fair Value Measurements Assets
Fair Value, Discount Rate		22.00%
Measurement Input, Revenue Multiple | DavidShield & PassportCard
Quantitative information for Level 3 Fair Value Measurements Assets
Terminal Revenue Growth Rate	4.00%
Equity Securities, FV-NI, Measurement Input		1
Measurement Input, Revenue Multiple | Compare.com
Quantitative information for Level 3 Fair Value Measurements Assets
Equity Securities, FV-NI, Measurement Input		3
Measurement Input, Long-term Revenue Growth Rate | MediaAlpha
Quantitative information for Level 3 Fair Value Measurements Assets
Terminal Revenue Growth Rate	4.00%
Estimated Net Realizable Value | Compare.com
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value	$ 2.5
Minimum | Measurement Input, Discount Rate | Kudu Investments
Quantitative information for Level 3 Fair Value Measurements Assets
Fair Value, Discount Rate	15.00%
Minimum | Measurement Input, Discount Rate | Private debt instrument
Quantitative information for Level 3 Fair Value Measurements Assets
Fair Value, Discount Rate	4.00%
Minimum | Measurement Input, Discount Rate | Other
Quantitative information for Level 3 Fair Value Measurements Assets
Fair Value, Discount Rate	25.00%
Minimum | Measurement Input, Revenue Multiple | Other
Quantitative information for Level 3 Fair Value Measurements Assets
Equity Securities, FV-NI, Measurement Input		2
Maximum | Measurement Input, Discount Rate | Kudu Investments
Quantitative information for Level 3 Fair Value Measurements Assets
Fair Value, Discount Rate	22.00%
Maximum | Measurement Input, Discount Rate | Private debt instrument
Quantitative information for Level 3 Fair Value Measurements Assets
Fair Value, Discount Rate	9.00%
Maximum | Measurement Input, Discount Rate | Other
Quantitative information for Level 3 Fair Value Measurements Assets
Fair Value, Discount Rate	32.00%
Maximum | Measurement Input, Revenue Multiple | Other
Quantitative information for Level 3 Fair Value Measurements Assets
Equity Securities, FV-NI, Measurement Input		4
Estimated Net Realizable Value | Compare.com
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value	$ 2.5
Discounted Cash Flow Valuation Technique | Kudu Investments
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value	266.5
Discounted Cash Flow Valuation Technique | MediaAlpha
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value	180.0
Discounted Cash Flow Valuation Technique | DavidShield & PassportCard
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value	90.0	$ 75.0
Discounted Cash Flow Valuation Technique | Elementum Holdings, L.P.
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value	55.1
Discounted Cash Flow Valuation Technique | Private debt instrument
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value	23.7	10.0
Discounted Cash Flow Valuation Technique | Other
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value	$ 23.7	30.0
Discounted Cash Flow Valuation Technique | Compare.com
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value		16.9
Multiple of EBITDA | Galvanic
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value		$ 3.1
Equity Securities, FV-NI, Measurement Input		6

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