Investment Securities (Significant Unobservable Inputs) (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Quantitative information for Level 3 Fair Value Measurements Assets
Number of Investments with Significant Unobseravble Inputs	1
Conditional Prepayment Rate	12.00%
loss severity [Member]
Quantitative information for Level 3 Fair Value Measurements Assets
Fair Value Inputs, Discount Rate	50.00%
Discount Yield [Member]
Quantitative information for Level 3 Fair Value Measurements Assets
Fair Value Inputs, Discount Rate	11.30%	11.00%
NR | Preferred Stock | Discounted cash flows
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, Fair Value Disclosure	71,400,000	71,100,000
NR | Preferred Stock | Discount Yield [Member]
Quantitative information for Level 3 Fair Value Measurements Assets
Fair Value Inputs, Discount Rate	7.10%	7.10%
NR | Private equity funds | Multiple of GAAP book value [Member]
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, Fair Value Disclosure	32,600,000	40,200,000
Book Value Multiple to Calculate Fair Value	110.00%	110.00%
NR | Private equity funds | Recent transaction [Member]
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, Fair Value Disclosure	20,100,000	20,100,000
NR | Private equity funds | Average Share Price [Member]
Quantitative information for Level 3 Fair Value Measurements Assets
Average Share Price Used As Unobservable Input	1.06	1.06
NR | Convertible Preferred Stock [Member] | Multiple of EBITA [Member]
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, Fair Value Disclosure	3,900,000	3,800,000
Average Share Price Used As Unobservable Input	6.00	6.00
Unobservable Inputs	0
NR | Convertible Preferred Stock [Member] | Recent transaction [Member]
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, Fair Value Disclosure		4,500,000
Average Share Price Used As Unobservable Input		0.71
NR | Seller Priority Surplus Note [Member] | Discounted cash flows
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, Fair Value Disclosure	46,500,000	44,000,000
Fair Value Inputs, Discount Rate	9.40%	9.30%
Timing of interest payments	5 years	5 years
Timing of principal payments	10 years	10 years
NR | Pari Passu Surplus Note [Member] | Discounted cash flows
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, Fair Value Disclosure	21,600,000	21,100,000
Fair Value Inputs, Discount Rate	14.40%	13.50%
Timing of interest payments	5 years	5 years
Timing of principal payments	15 years	10 years
Standard & Poor's, A- Rating | Non-Agency Commercial Mortgage Backed Securities [Member] [Member] | Broker Pricing [Member]
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, Fair Value Disclosure	20,600,000
Standard & Poor's, A- Rating | Non-Agency Residential Mortgage [Member] | Discounted cash flows
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, Fair Value Disclosure	47,100,000
durchblicker.at [Member] | NR | Private equity funds | Recent Transaction Two [Member]
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, Fair Value Disclosure	9,200,000	10,400,000
Average Share Price Used As Unobservable Input	290.96	290.96
BE Reinsurance [Member] | NR | Private equity funds | Recent Transaction Three [Member]
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, Fair Value Disclosure	14,200,000	15,800,000
Average Share Price Used As Unobservable Input	0.13	0.13
Centrus [Member] | NR | Debt securities issued by corporations | Discounted cash flows
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, Fair Value Disclosure		5,600,000
Unobservable Inputs		0.10
Minimum | discount spread [Member]
Quantitative information for Level 3 Fair Value Measurements Assets
Basis points	0.45%
Minimum | Default Rate [Member]
Quantitative information for Level 3 Fair Value Measurements Assets
Constant Default Rate	2.50%
Maximum | discount spread [Member]
Quantitative information for Level 3 Fair Value Measurements Assets
Basis points	1.80%
Maximum | Default Rate [Member]
Quantitative information for Level 3 Fair Value Measurements Assets
Constant Default Rate	8.75%
Standard & Poor's, B Rating [Member]
Quantitative information for Level 3 Fair Value Measurements Assets
Basis points	2.50%
Standard & Poor's, CCC Rating [Member]
Quantitative information for Level 3 Fair Value Measurements Assets
Basis points	2.50%