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Investment Securities (Significant Unobservable Inputs) (Details) | 9 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Sep. 30, 2015 USD ($) Investment | Dec. 31, 2014 USD ($) | Jun. 30, 2015 input
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Number of Investments with Significant Unobseravble Inputs | Investment | 1 |  |
Conditional Prepayment Rate | 12.00% |  |
Discount Yield [Member] |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Fair Value Inputs, Discount Rate |  |  |
NR | Preferred Stock | Discounted cash flows |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Assets, Fair Value Disclosure | $ 70,300,000 | $ 71,100,000 |
NR | Preferred Stock | Discount Yield [Member] |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Fair Value Inputs, Discount Rate | 8.40% | 7.10% |
NR | Convertible Preferred Stock [Member] | Multiple of EBITA [Member] |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Unobservable Inputs | input |  |  | 0
Assets, Fair Value Disclosure | $ 5,600,000 | $ 3,800,000 |
Share Price of Most Recent Transaction | 6.00 | 6.00 |
NR | Convertible Preferred Stock [Member] | Recent transaction [Member] |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Assets, Fair Value Disclosure |  | 4,500,000 |
Share Price of Most Recent Transaction |  | 0.71 |
NR | Seller Priority Surplus Note [Member] | Discounted cash flows |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Assets, Fair Value Disclosure | $ 41,000,000 | $ 44,000,000 |
Fair Value Inputs, Discount Rate | 11.60% | 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 | $ 17,000,000 | $ 21,100,000 |
Fair Value Inputs, Discount Rate | 18.30% | 13.50% |
Timing of interest payments | 5 years | 5 years |
Timing of principal payments | 15 years | 10 years |
CompareNow [Member] | NR | Private equity funds | Average Share Price |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Share Price of Most Recent Transaction | $ 1.06 |  |
Ironshore [Member] | NR | Private equity funds | Recent transaction [Member] |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Assets, Fair Value Disclosure | 34,200,000 | $ 39,500,000 |
Ironshore [Member] | NR | Private equity funds | Multiple of GAAP book value [Member] |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Share Price of Most Recent Transaction |  | 1.10 |
Ironshore [Member] | NR | Private equity funds | Average Share Price |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Share Price of Most Recent Transaction | 17.16 |  |
durchblicker.at [Member] | NR | Private equity funds | Recent transaction [Member] |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Assets, Fair Value Disclosure | 9,600,000 | 10,400,000 |
Share Price of Most Recent Transaction | 290.96 | 290.96 |
Centrus [Member] | NR | Debt securities issued by corporations | Discounted cash flows |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Assets, Fair Value Disclosure |  | $ 5,300,000 |
Fair Value Inputs, Discount Rate |  | 10.00% |
PassportCard [Member] | NR | Private equity funds | Average Share Price |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Share Price of Most Recent Transaction | $ 1.00 |  |
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% |  |
PassportCard [Member] | NR | Private equity funds | Recent transaction [Member] |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Assets, Fair Value Disclosure | $ 21,000,000 |  |
CompareNow [Member] | 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 |
CompareNow [Member] | NR | Private equity funds | Average Share Price |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Share Price of Most Recent Transaction |  | $ 1.06 |

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- Definition Interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value. For example, but not limited to, weighted average cost of capital (WACC), cost of capital, cost of equity and cost of debt. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (bbb) -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258 + Details
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