Acquisitions and Disposals - Sale of subsidiaries narrative (Details) - USD ($) $ in Millions	Oct. 11, 2016	Sep. 30, 2016	Dec. 31, 2016
New Ocean Capital Management Ltd
Business Acquisition [Line Items]
Disposal Group, Including Discontinued Operation, Consideration	$ 3.9
Sale of Subsidiary Stock, Percentage	7.80%
Sale of Subsidiary Preferred Stock, Percentage	6.40%
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal	$ 3.5
XL Life Insurance and Annuity Company
Business Acquisition [Line Items]
Disposal Group, Including Discontinued Operation, Consideration			$ 20.9
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal		$ 3.7