Investment Securities (Significant Unobservable Inputs) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011
Quantitative information for Level 3 Fair Value Measurements Assets
Number of Investments with Significant Unobseravble Inputs	1
Moody's, A2 Rating | Agency CMBS | Broker Pricing
Quantitative information for Level 3 Fair Value Measurements Assets
Fair value Assets	$ 22.1	[1]
Standard Poors NR Rating | Redeemable preferred stocks | Discounted cash flows
Quantitative information for Level 3 Fair Value Measurements Assets
Fair value Assets	70.8	[1]
Standard Poors NR Rating | Redeemable preferred stocks | Discount Yield
Quantitative information for Level 3 Fair Value Measurements Assets
Discount Yield (as a percent)	7.60%
Standard Poors NR Rating | Redeemable preferred stocks | Multiple of GAAP book value
Quantitative information for Level 3 Fair Value Measurements Assets
Book Value Multiple to Calculate Fair Value	100.00%
Standard Poors NR Rating | Private equity securities | Multiple of GAAP book value
Quantitative information for Level 3 Fair Value Measurements Assets
Fair value Assets	36.9
Fixed maturity investments | Level 3 Inputs
Quantitative information for Level 3 Fair Value Measurements Assets
Transfers in	$ 22.1		$ 18.2

[1] As of December 31, 2012 each asset type consists of one security.