Investments (Details 15) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Financial Asset Offsetting
Gross amount of recognized assets subject to netting agreements	$ 609.5	$ 716.7
Amount of liabilities that offset the gross amount of assets subject to netting agreements not offset in statement of financial position	(451.0)	(581.5)
Collateral received, financial assets	(140.6)	(133.9)
Net amount of assets subject to netting agreements	17.9	1.3
Derivative assets
Financial Asset Offsetting
Gross amount of recognized assets subject to netting agreements	558.7	664.9
Amount of liabilities that offset the gross amount of assets subject to netting agreements not offset in statement of financial position	(451.0)	(581.5)
Collateral received, financial assets	(89.8)	(82.1)
Net amount of assets subject to netting agreements	17.9	1.3
Gross amount of assets not subject to netting agreements	0	0.2
Reverse repurchase agreements
Financial Asset Offsetting
Gross amount of recognized assets subject to netting agreements	50.8	51.8
Collateral received, financial assets	$ (50.8)	$ (51.8)