Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	$ 192.7	$ 23.8
NSM Holding Co LLC
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	178.5	0.0
NSM Holding Co LLC | Fair value | NSM Bank Facility
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	176.1	0.0
MediaAlpha
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	14.2	23.8
MediaAlpha | MediaAlpha Bank Facility
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	14.2	23.8
MediaAlpha | Fair value | MediaAlpha Bank Facility
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	14.6	23.9
MediaAlpha | Carrying Value | MediaAlpha Bank Facility
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	14.2	23.8
Term Loan | NSM Holding Co LLC | NSM Bank Facility
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt		0.0
Term Loan | NSM Holding Co LLC | Carrying Value | NSM Bank Facility
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	$ 176.6	$ 0.0