Financial Derivatives (Credit Default Swaps) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Financial derivatives–assets, at fair value-	[1]	$ 15,356	$ 20,001
Financial derivatives–liabilities, at fair value-	[1]	(26,904)	$ (20,806)
Fair Value		(11,548)
Credit default swaps on asset-backed indices
Derivative [Line Items]
Financial derivatives–assets, at fair value-		3,276
Credit default swaps on asset-backed indices | Long
Derivative [Line Items]
Notional amount, assets		837
Notional amount, liabilities		(5,439)
Financial derivatives–assets, at fair value-		9
Financial derivatives–liabilities, at fair value-		$ 819
Remaining Maturity, Assets		23 years 208 days
Remaining Maturity, Liability		40 years 266 days
Credit default swaps on asset-backed indices | Short
Derivative [Line Items]
Notional amount, assets		$ 32,326
Notional amount, liabilities		(2,500)
Financial derivatives–assets, at fair value-		3,267
Financial derivatives–liabilities, at fair value-		$ (3)
Remaining Maturity, Assets		37 years 219 days
Remaining Maturity, Liability		38 years 212 days
Credit default swaps on asset-backed securities
Derivative [Line Items]
Financial derivatives–assets, at fair value-		$ 1,233
Financial derivatives–liabilities, at fair value-		(822)
Credit default swaps on asset-backed securities | Short
Derivative [Line Items]
Notional amount, assets		2,909
Financial derivatives–assets, at fair value-		$ 1,233
Remaining Maturity, Assets		16 years 150 days
Credit default swaps on corporate bonds
Derivative [Line Items]
Financial derivatives–assets, at fair value-		$ 715
Financial derivatives–liabilities, at fair value-		(945)
Credit default swaps on corporate bonds | Long
Derivative [Line Items]
Notional amount, assets		3,070
Notional amount, liabilities		(2,980)
Financial derivatives–assets, at fair value-		296
Financial derivatives–liabilities, at fair value-		$ 407
Remaining Maturity, Assets		2 years 354 days
Remaining Maturity, Liability		1 year 354 days
Credit default swaps on corporate bonds | Short
Derivative [Line Items]
Notional amount, assets		$ 3,033
Notional amount, liabilities		(16,955)
Financial derivatives–assets, at fair value-		419
Financial derivatives–liabilities, at fair value-		$ (538)
Remaining Maturity, Assets		1 year 358 days
Remaining Maturity, Liability		1 year 51 days
Credit default swaps on corporate bond indices
Derivative [Line Items]
Financial derivatives–assets, at fair value-		$ 3,519
Financial derivatives–liabilities, at fair value-		(11,907)
Credit default swaps on corporate bond indices | Long
Derivative [Line Items]
Notional amount, assets		76,904
Financial derivatives–assets, at fair value-		$ 3,519
Remaining Maturity, Assets		4 years 33 days
Credit default swaps on corporate bond indices | Short
Derivative [Line Items]
Notional amount, liabilities		$ (223,080)
Financial derivatives–liabilities, at fair value-		$ (11,907)
Remaining Maturity, Liability		2 years 172 days
Recovery swaps
Derivative [Line Items]
Financial derivatives–liabilities, at fair value-		$ (8)
Recovery swaps | Short
Derivative [Line Items]
Notional amount, liabilities		(2,600)
Financial derivatives–liabilities, at fair value-		$ (8)
Remaining Maturity, Liability		80 days
Credit default swaps
Derivative [Line Items]
Notional Amount		$ (194,173)
Fair Value		$ (4,939)
Remaining Years to Maturity		7 years 15 days

[1] In the Company's Consolidated Statement of Assets, Liabilities, and Equity, all balances associated with repurchase agreements, reverse repurchase agreements, and financial derivatives are presented on a gross basis.