Consolidated Condensed Schedule of Investments (Repurchase Agreements) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)
Schedule of Investments [Line Items]
Repurchase agreements, at fair value	$ 61,274
Repurchase agreements, cost	61,274
Securities Purchased under Agreements to Resell [Member]
Schedule of Investments [Line Items]
Repurchase agreements, at fair value	$ 61,274
Investment owned as a percentage of equity	10.30%	[1],[2],[3]
Repurchase agreements, cost	$ 61,274	[2],[3]
Securities Purchased under Agreements to Resell [Member] | JP Morgan Securities LLC Collateralized by Par Value $13,600 U.S. Treasury Note, Coupon 2.88%, Maturity Date 2021 11 [Member]
Schedule of Investments [Line Items]
Current Principal/Notional Amount	$ 13,854
Rate	(3.25%)
Securities collateralized by par value	$ 13,600	[2],[3]
Coupon rate on underlying collateral	2.88%	[2],[3]
Maturity date of securities	2021-11	[2],[3]
Repurchase agreements, at fair value	$ 13,854
Investments maturity date	2019-01	[2],[3]
Securities Purchased under Agreements to Resell [Member] | JP Morgan Securities LLC Collateralized by Par Value $10,451 U.S. Treasury Note, Coupon 2.88%, Maturity Date 2023 10 [Member]
Schedule of Investments [Line Items]
Current Principal/Notional Amount	$ 10,712
Rate	(3.15%)
Securities collateralized by par value	$ 10,451	[2],[3]
Coupon rate on underlying collateral	2.88%	[2],[3]
Maturity date of securities	2023-10	[2],[3]
Repurchase agreements, at fair value	$ 10,712
Investments maturity date	2019-01	[2],[3]
Securities Purchased under Agreements to Resell [Member] | JP Morgan Securities LLC Collateralized by Par Value $10,102 Sovereign Government Bond, Coupon 0.75% Maturity Date 2021 07 [Member]
Schedule of Investments [Line Items]
Current Principal/Notional Amount	$ 10,365
Rate	(0.75%)
Securities collateralized by par value	$ 10,102	[2],[3]
Coupon rate on underlying collateral	0.75%	[2],[3]
Maturity date of securities	2021-07	[2],[3]
Repurchase agreements, at fair value	$ 10,365
Investments maturity date	2019-01	[2],[3]
Securities Purchased under Agreements to Resell [Member] | JP Morgan Securities LLC Collateralized by Par Value $9,161 Sovereign Government Bond, Coupon 2.75%, Maturity Date 2019 04 [Member]
Schedule of Investments [Line Items]
Current Principal/Notional Amount	$ 9,379
Rate	(0.65%)
Securities collateralized by par value	$ 9,161	[2],[3]
Coupon rate on underlying collateral	2.75%	[2],[3]
Maturity date of securities	2019-04	[2],[3]
Repurchase agreements, at fair value	$ 9,379
Investments maturity date	2019-01	[2],[3]
Securities Purchased under Agreements to Resell [Member] | JP Morgan Securities LLC Collateralized by Par Value $3,400 U.S. Treasury Note, Coupon 3.13%, Maturity Date 2028 11 [Member]
Schedule of Investments [Line Items]
Current Principal/Notional Amount	$ 3,562
Rate	(3.05%)
Securities collateralized by par value	$ 3,400	[2],[3]
Coupon rate on underlying collateral	3.13%	[2],[3]
Maturity date of securities	2028-11	[2],[3]
Repurchase agreements, at fair value	$ 3,562
Investments maturity date	2019-01	[2],[3]
Securities Purchased under Agreements to Resell [Member] | JP Morgan Securities LLC Collateralized by Par Value $2,800 U.S. Treasury Note, Coupon 2.88%, Maturity Date 2028 08 [Member]
Schedule of Investments [Line Items]
Current Principal/Notional Amount	$ 2,884
Rate	(2.95%)
Securities collateralized by par value	$ 2,800	[2],[3]
Coupon rate on underlying collateral	2.88%	[2],[3]
Maturity date of securities	2028-08	[2],[3]
Repurchase agreements, at fair value	$ 2,884
Investments maturity date	2019-01	[2],[3]
Securities Purchased under Agreements to Resell [Member] | Bank of America Securities Collateralized by Par Value $2,062 U.S. Treasury Note, Coupon 2.88%, Maturity Date 2023 11 [Member]
Schedule of Investments [Line Items]
Current Principal/Notional Amount	$ 2,098
Rate	(2.90%)
Securities collateralized by par value	$ 2,062	[2],[3]
Coupon rate on underlying collateral	2.88%	[2],[3]
Maturity date of securities	2023-11	[2],[3]
Repurchase agreements, at fair value	$ 2,098
Investments maturity date	2019-01	[2],[3]
Securities Purchased under Agreements to Resell [Member] | Bank of America Securities Collateralized by Par Value $1,939 U.S. Treasury Note, Coupon 2.75%, Maturity Date 2023 08 [Member]
Schedule of Investments [Line Items]
Current Principal/Notional Amount	$ 1,975
Rate	(2.90%)
Securities collateralized by par value	$ 1,939	[2],[3]
Coupon rate on underlying collateral	2.75%	[2],[3]
Maturity date of securities	2023-08	[2],[3]
Repurchase agreements, at fair value	$ 1,975
Investments maturity date	2019-01	[2],[3]
Securities Purchased under Agreements to Resell [Member] | Barclays Capital Inc Collateralized by Par Value $1,900 Exchange-Traded Corporate Debt, Coupon 5.95%, Maturity Date 2026 12 [Member]
Schedule of Investments [Line Items]
Current Principal/Notional Amount	$ 1,710
Rate	(1.65%)
Securities collateralized by par value	$ 1,900	[2],[3]
Coupon rate on underlying collateral	5.95%	[2],[3]
Maturity date of securities	2026-12	[2],[3]
Repurchase agreements, at fair value	$ 1,710
Investments maturity date	2019-01	[2],[3]
Securities Purchased under Agreements to Resell [Member] | Bank of America Securities Collateralized by Par Value $1,355 U.S. Treasury Note, Coupon 2.75%, Maturity Date 2023 04 [Member]
Schedule of Investments [Line Items]
Current Principal/Notional Amount	$ 1,369
Rate	(3.05%)
Securities collateralized by par value	$ 1,355	[2],[3]
Coupon rate on underlying collateral	2.75%	[2],[3]
Maturity date of securities	2023-04	[2],[3]
Repurchase agreements, at fair value	$ 1,369
Investments maturity date	2019-01	[2],[3]
Securities Purchased under Agreements to Resell [Member] | Morgan Stanley Collateralized by Par Value $1,000 Exchange-Traded Corporate Debt, Coupon 5.95%, Maturity Date 2026 12 [Member]
Schedule of Investments [Line Items]
Current Principal/Notional Amount	$ 957
Rate	(2.15%)
Securities collateralized by par value	$ 1,000	[2],[3]
Coupon rate on underlying collateral	5.95%	[2],[3]
Maturity date of securities	2026-12	[2],[3]
Repurchase agreements, at fair value	$ 957
Investments maturity date	2019-01	[2],[3]
Securities Purchased under Agreements to Resell [Member] | Barclays Capital Inc Collateralized by Par Value $1,200 Exchange-Traded Corporate Debt, Coupon 9.88%, Maturity Date 2024 02 [Member]
Schedule of Investments [Line Items]
Current Principal/Notional Amount	$ 797
Rate	(0.75%)
Securities collateralized by par value	$ 1,200	[2],[3]
Coupon rate on underlying collateral	9.88%	[2],[3]
Maturity date of securities	2024-02	[2],[3]
Repurchase agreements, at fair value	$ 797
Investments maturity date	2019-01	[2],[3]
Securities Purchased under Agreements to Resell [Member] | Barclays Capital Inc Collateralized by Par Value $800 Exchange-Traded Corporate Debt, Coupon 9.88%, Maturity Date 2024 02 [Member]
Schedule of Investments [Line Items]
Current Principal/Notional Amount	$ 531
Rate	(1.25%)
Securities collateralized by par value	$ 800	[2],[3]
Coupon rate on underlying collateral	9.88%	[2],[3]
Maturity date of securities	2024-02	[2],[3]
Repurchase agreements, at fair value	$ 531
Investments maturity date	2019-01	[2],[3]
Securities Purchased under Agreements to Resell [Member] | RBC Capital Markets LLC Collateralized by Par Value $500 Exchange-Traded Corporate Debt, Coupon 5.75%, Maturity Date 2022 10 [Member]
Schedule of Investments [Line Items]
Current Principal/Notional Amount	$ 525
Rate	(2.05%)
Securities collateralized by par value	$ 500	[2],[3]
Coupon rate on underlying collateral	5.75%	[2],[3]
Maturity date of securities	2022-10	[2],[3]
Repurchase agreements, at fair value	$ 525
Investments maturity date	2019-01	[2],[3]
Securities Purchased under Agreements to Resell [Member] | Bank of America Securities Collateralized by Par Value $463 U.S. Treasury Note, Coupon 2.63%, Maturity Date 2023 06 [Member]
Schedule of Investments [Line Items]
Current Principal/Notional Amount	$ 469
Rate	(3.05%)
Securities collateralized by par value	$ 463	[2],[3]
Coupon rate on underlying collateral	2.63%	[2],[3]
Maturity date of securities	2023-06	[2],[3]
Repurchase agreements, at fair value	$ 469
Investments maturity date	2019-01	[2],[3]
Securities Purchased under Agreements to Resell [Member] | Societe Generale Collateralized by Par Value $100 Exchange-Traded Corporate Debt, Coupon 5.95%, Maturity Date 2026 12 [Member]
Schedule of Investments [Line Items]
Current Principal/Notional Amount	$ 87
Rate	(1.85%)
Securities collateralized by par value	$ 100	[2],[3]
Coupon rate on underlying collateral	5.95%	[2],[3]
Maturity date of securities	2026-12	[2],[3]
Repurchase agreements, at fair value	$ 87
Investments maturity date	2019-01	[2],[3]

[1] Classification percentages are based on Total Equity.

[2] In general, securities received pursuant to repurchase agreements were delivered to counterparties in short sale transactions.

[3] See Note 2 and Note 3 in Notes to Consolidated Financial Statements.