Investments Repurchase Agreement, Securities Lending, VIEs (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	5 Months Ended
	Jun. 30, 2012	Oct. 29, 2012 tranche	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013 Collateralized loan obligations Not a primary beneficiary of the VIE	Dec. 31, 2012 Collateralized loan obligations Not a primary beneficiary of the VIE	Dec. 31, 2013 Securities pledged as collateral	Dec. 31, 2012 Securities pledged as collateral	Dec. 31, 2013 Payables under securities loan agreement, including collateral held	Dec. 31, 2012 Payables under securities loan agreement, including collateral held	Mar. 31, 2012 Variable Interest Entity, Sold Not a primary beneficiary of the VIE	Dec. 31, 2013 Notes Receivable
Available-for-sale Securities Including Securities Pledged [Line Items]
Fair value of loaned securities			$ 97.6	$ 180.2			$ 97.6	$ 180.2
Securities received as collateral			102.7	186.1
Payables under securities loan agreement, including collateral held			264.4	353.2					102.7	186.1
Variable Interest Entity, Not Primary Beneficiary, Disclosures [Abstract]
Carrying value of VIE					1.0	1.3					331.9
Gain (loss) on sale of investments	38.7
Sale transaction, number of tranches		2
Promissory note included in consideration received												$ 23.0