Discontinued Operations - Surplus Note (Details) - OneBeacon - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Assets, fair value adjustment	$ (30.5)	$ (29.1)
Seller Priority Surplus Note
Assets, fair value adjustment	(9.0)
Pari Passu Surplus Note
Assets, fair value adjustment	(21.5)
Par Value
Surplus notes	101.0	$ 101.0
Par Value | Seller Priority Surplus Note
Surplus notes	57.9
Par Value | Pari Passu Surplus Note
Surplus notes	$ 43.1
Fair Value
Basis points	4.00%	2.50%
Surplus notes	$ 70.5	$ 71.9
Fair Value | Seller Priority Surplus Note
Surplus notes	48.9
Fair Value | Pari Passu Surplus Note
Surplus notes	21.6
Current market rates on repayments
Assets, fair value adjustment	10.0	5.1
Current market rates on repayments | Seller Priority Surplus Note
Assets, fair value adjustment	$ 7.9
RBC Score	250.00%
Current market rates on repayments | Pari Passu Surplus Note
Assets, fair value adjustment	$ 2.1
Regulatory Approval
Assets, fair value adjustment	(11.0)	(15.6)
Regulatory Approval | Seller Priority Surplus Note
Assets, fair value adjustment	2.7
Regulatory Approval | Pari Passu Surplus Note
Assets, fair value adjustment	(13.7)
Liquidity Adjustment
Assets, fair value adjustment	(29.5)	$ (18.6)
Liquidity Adjustment | Seller Priority Surplus Note
Assets, fair value adjustment	(19.6)
Liquidity Adjustment | Pari Passu Surplus Note
Assets, fair value adjustment	$ (9.9)