Investment Securities (Significant Unobservable Inputs) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013
Standard Poors NR Rating | Preferred Stock | Discounted cash flows
Quantitative information for Level 3 Fair Value Measurements Assets
Fair value Assets	$ 70.9	[1]
Discount Yield (as a percent)	7.40%	[1]
Standard Poors NR Rating | Security Owned Not Readily Marketable, Name [Domain] | Multiple of GAAP book value
Quantitative information for Level 3 Fair Value Measurements Assets
Fair value Assets	36.8
Book value multiple (as a percent)	100.00%
Standard & Poor's, BBB- Rating | Agency CMBS | Broker Pricing
Quantitative information for Level 3 Fair Value Measurements Assets
Fair value Assets	8.0
Standard & Poor's, AA Plus Rating | Agency CMBS | Broker Pricing
Quantitative information for Level 3 Fair Value Measurements Assets
Fair value Assets	$ 22.1

[1] As of March 31, 2013 asset type consists of one security