Variable Interest Entities (Details) (Variable Interest Entity, Primary Beneficiary, USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
New Ocean Capital Management Ltd
Variable Interest Entity [Line Items]
Non-controlling interest in consolidated subsidiaries	$ 0.2	$ 0.3
New Ocean Focus Cat Fund
Variable Interest Entity [Line Items]
Total assets of consolidated entity	93.9	46.5
Non-controlling interest in consolidated subsidiaries	57.4	6.9
New Ocean Market Value Cat Fund [Member]
Variable Interest Entity [Line Items]
Total assets of consolidated entity	46.1
Non-controlling interest in consolidated subsidiaries	$ 1.0