SCHEDULE IV REINSURANCE (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Premiums earned
Gross amount	$ 1,322.0	$ 1,233.5	$ 1,043.8
Ceded to other companies	(179.7)	(119.4)	(71.4)
Assumed from other companies	45.9	70.9	148.5
Net earned premiums	1,188.2	1,185.0	1,120.9
OneBeacon
Premiums earned
Gross amount	1,298.0	1,209.1	1,043.3
Ceded to other companies	(167.7)	(102.9)	(71.4)
Assumed from other companies	45.9	70.9	148.5
Net earned premiums	$ 1,176.2	$ 1,177.1	$ 1,120.4
Percentage of amount assumed to net	3.90%	6.00%	13.30%
HG/BAM
Premiums earned
Gross amount	$ 3.3	$ 1.8	$ 0.5
Ceded to other companies	0.0	0.0	0.0
Assumed from other companies	0.0	0.0	0.0
Net earned premiums	$ 3.3	$ 1.8	0.5
Percentage of amount assumed to net	0.00%	0.00%
Other Segments
Premiums earned
Gross amount	$ 20.7	$ 22.6
Ceded to other companies	(12.0)	(16.5)
Assumed from other companies	0.0	0.0
Net earned premiums	$ 8.7	$ 6.1	$ 0.0
Percentage of amount assumed to net	0.00%	0.00%