Investment Securities (Significant Unobservable Inputs) (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 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)	7.50%	[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	37.6
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	24.0
AAA | Agency CMBS | Discounted cash flows
Quantitative information for Level 3 Fair Value Measurements Assets
Fair Value Inputs Constant Prepayment Rate	15.00%
Fair value input, swap spread rate	3.05%
Standard & Poor's, AA Plus Rating | Agency CMBS | Broker Pricing
Quantitative information for Level 3 Fair Value Measurements Assets
Fair value Assets	$ 22.0

[1] As of June 30, 2013, asset type consists of one security