Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	$ 442.4	$ 343.1
Tranzact [Member] | Tranzact Bank Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt		67.4
Tranzact [Member] | Fair value | Tranzact Bank Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Fair Value Disclosure	102.8	68.7
Tranzact [Member] | Carrying Value | Tranzact Bank Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	102.9	67.4
OneBeacon | 2012 OBH Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	274.8	274.7
OneBeacon | Fair value | 2012 OBH Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Fair Value Disclosure	276.4	286.0
OneBeacon | Carrying Value | 2012 OBH Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	274.8	$ 274.7
MediaAlpha [Member] | Fair value | MediaAlpha Bank Facility [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Fair Value Disclosure	15.0
MediaAlpha [Member] | Carrying Value | MediaAlpha Bank Facility [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	$ 14.7