Investing Activities - Narrative (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014 security counterparty	Dec. 31, 2013
Concentration Risk [Line Items]
Unrealized losses on below-investment-grade debt securities depressed of amortized cost, percentage	20.00%
Unrealized losses on below-investment-grade debt securities depressed of amortized cost, amount	$ 0.9
Unrealized losses on below-investment-grade debt securities depressed of amortized cost for more than 12 month, amount	0.7
Unrealized losses on below-investment-grade debt securities depressed of amortized cost for more than 12 month, percentage	20.00%
Number of debt securities	94
Private equity investments	8.1	7.9
Direct equity investments	2.6	2.6
Carrying value of investments in non-consolidated VIEs	15.0	15.6
Fixed maturities below-investment-grade assets	163.3	137.7
Derivative assets, net of liabilities	83.0
Number of Counterparties	11
Debt securities, fair value	51.9
Maximum amount of loss due to credit risk	$ 134.9
Stockholders' Equity, Total
Concentration Risk [Line Items]
Concentration risk (percent)	10.00%