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Debt (Debt Outstanding) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	May 18, 2018	May 11, 2018
Debt Instrument
Debt	$ 283.5	$ 192.7
Other Debt
Debt Instrument
Debt instrument at face value	11.1	0.0
NSM Holding Co LLC
Debt Instrument
Debt instrument at face value				$ 100.0
Debt	219.2	178.5
Kudu | Kudu Debt
Debt Instrument
Debt	53.6
MediaAlpha
Debt Instrument
Debt	0.0	14.2
MediaAlpha | MediaAlpha Bank Facility
Debt Instrument
Debt instrument at face value	0.0	14.3
Unamortized Debt Issuance Expense	0.0	(0.1)
Debt	$ 0.0	$ 14.2
Effective yield (as a percent)		7.10%
Other Operations | Other Debt
Debt Instrument
Debt	$ 10.7
Term Loan | NSM Holding Co LLC | NSM Bank Facility
Debt Instrument
Debt instrument at face value	221.3	$ 180.4	$ 51.0
Unamortized Debt Issuance Expense	(3.9)	(3.8)
Debt	$ 217.4	$ 176.6
Effective yield (as a percent)	7.50%	7.40%
Term Loan | NSM Holding Co LLC | Other NSM
Debt Instrument
Debt instrument at face value	$ 1.8
Debt	$ 1.8	$ 1.9
Effective yield (as a percent)	3.00%	2.20%
Term Loan | Kudu | Kudu Debt
Debt Instrument
Unamortized Debt Issuance Expense	$ (3.4)
Effective yield (as a percent)	8.30%
Term Loan | MediaAlpha | MediaAlpha Bank Facility
Debt Instrument
Debt instrument at face value		$ 14.3
Term Loan | Other Operations | Other Debt
Debt Instrument
Unamortized Debt Issuance Expense	$ (0.4)
Effective yield (as a percent)	8.30%

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Face (par) amount of debt instrument at time of issuance.

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Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

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