Financial Derivatives (Credit Default Swaps) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Financial derivatives–assets, at fair value-	$ 16,788	$ 20,001
Financial derivatives–liabilities, at fair value-	(27,621)	$ (20,806)
Fair Value	10,833
Credit default swaps on asset-backed indices
Derivative [Line Items]
Financial derivatives–assets, at fair value-	3,319
Financial derivatives–liabilities, at fair value-	(250)
Credit default swaps on asset-backed indices | Financial Derivatives - Assets | Long
Derivative [Line Items]
Notional Amount	695
Financial derivatives–assets, at fair value-	10
Credit default swaps on asset-backed indices | Financial Derivatives - Assets | Short
Derivative [Line Items]
Notional Amount	63,515
Financial derivatives–assets, at fair value-	3,309
Credit default swaps on asset-backed indices | Financial Derivatives - Liabilities | Long
Derivative [Line Items]
Notional Amount	344
Financial derivatives–liabilities, at fair value-	(145)
Credit default swaps on asset-backed indices | Financial Derivatives - Liabilities | Short
Derivative [Line Items]
Notional Amount	4,501
Financial derivatives–liabilities, at fair value-	(105)
Credit default swaps on asset-backed securities
Derivative [Line Items]
Financial derivatives–assets, at fair value-	993
Credit default swaps on asset-backed securities | Financial Derivatives - Assets | Short
Derivative [Line Items]
Notional Amount	2,640
Financial derivatives–assets, at fair value-	993
Credit default swaps on corporate bonds
Derivative [Line Items]
Financial derivatives–assets, at fair value-	2
Financial derivatives–liabilities, at fair value-	(1,693)
Credit default swaps on corporate bonds | Financial Derivatives - Assets | Long
Derivative [Line Items]
Notional Amount	430
Financial derivatives–assets, at fair value-	2
Credit default swaps on corporate bonds | Financial Derivatives - Liabilities | Short
Derivative [Line Items]
Notional Amount	10,800
Financial derivatives–liabilities, at fair value-	(1,693)
Credit default swaps on corporate bond indices
Derivative [Line Items]
Financial derivatives–assets, at fair value-	5,599
Financial derivatives–liabilities, at fair value-	(14,524)
Credit default swaps on corporate bond indices | Financial Derivatives - Assets | Long
Derivative [Line Items]
Notional Amount	130,707
Financial derivatives–assets, at fair value-	5,547
Credit default swaps on corporate bond indices | Financial Derivatives - Assets | Short
Derivative [Line Items]
Notional Amount	1,997
Financial derivatives–assets, at fair value-	52
Credit default swaps on corporate bond indices | Financial Derivatives - Liabilities | Short
Derivative [Line Items]
Notional Amount	250,088
Financial derivatives–liabilities, at fair value-	(14,524)
Credit default swaps
Derivative [Line Items]
Notional Amount	201,365
Fair Value	$ 6,554
Weighted Average | Credit default swaps on asset-backed indices | Financial Derivatives - Assets | Long
Derivative [Line Items]
Remaining Years to Maturity	23 years 9 months 18 days
Weighted Average | Credit default swaps on asset-backed indices | Financial Derivatives - Assets | Short
Derivative [Line Items]
Remaining Years to Maturity	38 years 4 months 24 days
Weighted Average | Credit default swaps on asset-backed indices | Financial Derivatives - Liabilities | Long
Derivative [Line Items]
Remaining Years to Maturity	29 years 4 months 6 days
Weighted Average | Credit default swaps on asset-backed indices | Financial Derivatives - Liabilities | Short
Derivative [Line Items]
Remaining Years to Maturity	40 years 3 months 21 days
Weighted Average | Credit default swaps on asset-backed securities | Financial Derivatives - Assets | Short
Derivative [Line Items]
Remaining Years to Maturity	15 years 7 months 17 days
Weighted Average | Credit default swaps on corporate bonds | Financial Derivatives - Assets | Long
Derivative [Line Items]
Remaining Years to Maturity	11 hours
Weighted Average | Credit default swaps on corporate bonds | Financial Derivatives - Liabilities | Short
Derivative [Line Items]
Remaining Years to Maturity	3 years 11 months 1 day
Weighted Average | Credit default swaps on corporate bond indices | Financial Derivatives - Assets | Long
Derivative [Line Items]
Remaining Years to Maturity	2 years 5 months 1 day
Weighted Average | Credit default swaps on corporate bond indices | Financial Derivatives - Assets | Short
Derivative [Line Items]
Remaining Years to Maturity	3 years 11 months 19 days
Weighted Average | Credit default swaps on corporate bond indices | Financial Derivatives - Liabilities | Short
Derivative [Line Items]
Remaining Years to Maturity	2 years 6 months 3 days
Weighted Average | Credit default swaps
Derivative [Line Items]
Remaining Years to Maturity	14 years 10 months 17 days