Consolidated Condensed Schedule Of Investments (Investments Sold Short) - USD ($) shares in Thousands, $ in Thousands		3 Months Ended		12 Months Ended
		Mar. 31, 2018		Dec. 31, 2017
Investments Sold, Not yet Purchased [Line Items]
Investments sold short, at fair value-		$ (691,962)		$ (642,240)
Proceeds from investments sold short		$ (687,783)		$ (640,202)
TBA - Fixed Rate Agency Securities Sold Short [Member]
Investments Sold, Not yet Purchased [Line Items]
Investment Sold, Not yet Purchased, Percent of Equity		(81.91%)	[1],[2],[3]	(74.11%)	[4],[5],[6]
Current Principal/Notional Amount		$ (488,078)		$ (442,197)
Investments sold short, at fair value-		(499,620)	[1],[3]	(460,189)	[4],[6]
Proceeds from investments sold short		(497,379)	[1],[3]	(459,953)	[4],[6]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal Home Loan Mortgage Corporation (30 Year) 4 Point 00 Percent [Member] | Mortgage-related Residential [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount		$ (99,307)	[1],[3]	$ (27,547)	[4],[6]
Rate		4.00%	[1],[3]	4.00%	[4],[6]
Investments maturity date		2018-05	[1],[3]	2018-01	[4],[6]
Investments sold short, at fair value-		$ (101,759)	[1],[3]	$ (28,815)	[4],[6]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Government National Mortgage Association (30 Year) 3 Point 50 Percent [Member] | Mortgage-related Residential [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount		$ (65,010)	[1],[3]	$ (24,410)	[4],[6]
Rate		3.50%	[1],[3]	3.50%	[4],[6]
Investments maturity date		2018-04	[1],[3]	2018-01	[4],[6]
Investments sold short, at fair value-		$ (65,635)	[1],[3]	$ (25,249)	[4],[6]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 3.50% [Member] | Mortgage-related Residential [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount		$ (63,302)	[1],[3]	$ (69,372)	[4],[6]
Rate		3.50%	[1],[3]	3.50%	[4],[6]
Investments maturity date		2018-04	[1],[3]	2018-01	[4],[6]
Investments sold short, at fair value-		$ (63,435)	[1],[3]	$ (71,247)	[4],[6]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 4.50% [Member] | Mortgage-related Residential [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount		$ (50,210)	[1],[3]	$ (21,710)	[4],[6]
Rate		4.50%	[1],[3]	4.50%	[4],[6]
Investments maturity date		2018-04	[1],[3]	2018-01	[4],[6]
Investments sold short, at fair value-		$ (52,571)	[1],[3]	$ (23,097)	[4],[6]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Government National Mortgage Association (30 Year) 4 Point 00 Percent [Member] | Mortgage-related Residential [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount		$ (42,594)	[1],[3]	$ (35,000)	[4],[6]
Rate		4.00%	[1],[3]	4.00%	[4],[6]
Investments maturity date		2018-05	[1],[3]	2018-02	[4],[6]
Investments sold short, at fair value-		$ (43,719)	[1],[3]	$ (36,485)	[4],[6]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Corporation (30 Year) 4 Point 50 Percent 201805 [Member] | Mortgage-related Residential [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	[1],[3]	$ (39,000)
Rate	[1],[3]	4.50%
Investments maturity date	[1],[3]	2018-05
Investments sold short, at fair value-	[1],[3]	$ (40,766)
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal Home Loan Mortgage Corporation (30 Year) 4 Point 50 Percent [Member] | Mortgage-related Residential [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount		$ (33,451)	[1],[3]	$ (12,351)	[4],[6]
Rate		4.50%	[1],[3]	4.50%	[4],[6]
Investments maturity date		2018-05	[1],[3]	2018-01	[4],[6]
Investments sold short, at fair value-		$ (34,961)	[1],[3]	$ (13,134)	[4],[6]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (15 Year) 3 Point 50 Percent [Member] | Mortgage-related Residential [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount		$ (28,320)	[1],[3]	$ (43,220)	[4],[6]
Rate		3.50%	[1],[3]	3.50%	[4],[6]
Investments maturity date		2018-04	[1],[3]	2018-01	[4],[6]
Investments sold short, at fair value-		$ (28,868)	[1],[3]	$ (44,618)	[4],[6]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 4.00% [Member] | Mortgage-related Residential [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount		$ (23,257)	[1],[3]	$ (55,000)	[4],[6]
Rate		4.00%	[1],[3]	4.00%	[4],[6]
Investments maturity date		2018-04	[1],[3]	2018-02	[4],[6]
Investments sold short, at fair value-		$ (23,864)	[1],[3]	$ (57,447)	[4],[6]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (15 Year) 3 Point 00 Percent [Member] | Mortgage-related Residential [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount		$ (13,590)	[1],[3]	$ (21,520)	[4],[6]
Rate		3.00%	[1],[3]	3.00%	[4],[6]
Investments maturity date		2018-04	[1],[3]	2018-01	[4],[6]
Investments sold short, at fair value-		$ (13,572)	[1],[3]	$ (21,923)	[4],[6]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 3 Point 00 Percent [Member] | Mortgage-related Residential [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount		$ (12,112)	[1],[3]	$ (12,112)	[4],[6]
Rate		3.00%	[1],[3]	3.00%	[4],[6]
Investments maturity date		2018-04	[1],[3]	2018-01	[4],[6]
Investments sold short, at fair value-		$ (11,813)	[1],[3]	$ (12,113)	[4],[6]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 5 Point 50 Percent [Member] | Mortgage-related Residential [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount		$ (6,860)	[1],[3]	$ (6,860)	[4],[6]
Rate		5.50%	[1],[3]	5.50%	[4],[6]
Investments maturity date		2018-05	[1],[3]	2018-01	[4],[6]
Investments sold short, at fair value-		$ (7,448)	[1],[3]	$ (7,520)	[4],[6]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal Home Loan Mortgage Corporation (30 Year) 3 Point 00 Percent [Member] | Mortgage-related Residential [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount		$ (5,515)	[1],[3]	$ (5,515)	[4],[6]
Rate		3.00%	[1],[3]	3.00%	[4],[6]
Investments maturity date		2018-04	[1],[3]	2018-01	[4],[6]
Investments sold short, at fair value-		$ (5,378)	[1],[3]	$ (5,517)	[4],[6]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 5 Point 00 Percent [Member] | Mortgage-related Residential [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount		$ (4,500)	[1],[3]	$ (5,680)	[4],[6]
Rate		5.00%	[1],[3]	5.00%	[4],[6]
Investments maturity date		2018-05	[1],[3]	2018-01	[4],[6]
Investments sold short, at fair value-		$ (4,798)	[1],[3]	$ (6,104)	[4],[6]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Government National Mortgage Association (30 Year) 3.00% [Member] | Mortgage-related Residential [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount		$ (1,050)	[1],[3]	$ (1,800)	[4],[6]
Rate		3.00%	[1],[3]	3.00%	[4],[6]
Investments maturity date		2018-04	[1],[3]	2018-01	[4],[6]
Investments sold short, at fair value-		$ (1,033)	[1],[3]	$ (1,813)	[4],[6]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal Home Loan Mortgage Corporation (15 Year) 3 Point 50 Percent [Member] | Mortgage-related Residential [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	[4],[6]			$ (1,100)
Rate	[4],[6]			3.50%
Investments maturity date	[4],[6]			2018-01
Investments sold short, at fair value-	[4],[6]			$ (1,137)
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal Home Loan Mortgage Corporation (30 Year) 4 Point 00 Percent 201802 [Member] | Mortgage-related Residential [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	[4],[6]			$ (68,000)
Rate	[4],[6]			4.00%
Investments maturity date	[4],[6]			2018-02
Investments sold short, at fair value-	[4],[6]			$ (71,028)
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 4 Point 50 Percent 201802 [Member] | Mortgage-related Residential [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	[4],[6]			$ (31,000)
Rate	[4],[6]			4.50%
Investments maturity date	[4],[6]			2018-02
Investments sold short, at fair value-	[4],[6]			$ (32,942)
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association [Member]
Investments Sold, Not yet Purchased [Line Items]
Investment Sold, Not yet Purchased, Percent of Equity		(40.52%)		(44.61%)
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal Home Loan Mortgage Corporation [Member]
Investments Sold, Not yet Purchased [Line Items]
Investment Sold, Not yet Purchased, Percent of Equity		(23.29%)		(19.27%)
TBA - Fixed Rate Agency Securities Sold Short [Member] | Government National Mortgage Association [Member]
Investments Sold, Not yet Purchased [Line Items]
Investment Sold, Not yet Purchased, Percent of Equity		(18.10%)		(10.23%)
US Government Debt Securities [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Investment Sold, Not yet Purchased, Percent of Equity		(11.34%)	[2],[3]	(8.54%)	[5],[6]
Investments sold short, at fair value-		$ (69,156)	[3]	$ (53,021)	[6]
Proceeds from investments sold short		(68,716)	[3]	(53,322)	[6]
US Government Debt Securities [Member] | U.S. Treasury Note, 2.50 Percent, Maturity Date 2025 01 [Member] | Government [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	[3]	$ (33,320)
Rate	[3]	2.50%
Investments maturity date	[3]	2025-01
Investments sold short, at fair value-	[3]	$ (32,942)
US Government Debt Securities [Member] | U.S. Treasury Note, 2.75 Percent, Maturity Date 2028 02 [Member] | Government [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	[3]	$ (17,167)
Rate	[3]	2.75%
Investments maturity date	[3]	2028-02
Investments sold short, at fair value-	[3]	$ (17,174)
US Government Debt Securities [Member] | U.S. Treasury Note, 2.38 Percent, Maturity Date 2023 01 [Member] | Government [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	[3]	$ (13,727)
Rate	[3]	2.38%
Investments maturity date	[3]	2023-01
Investments sold short, at fair value-	[3]	$ (13,614)
US Government Debt Securities [Member] | U.S. Treasury Note, 2.63 Percent, Maturity Date 2023 02 [Member] | Government [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	[3]	$ (2,689)
Rate	[3]	2.63%
Investments maturity date	[3]	2023-02
Investments sold short, at fair value-	[3]	$ (2,697)
US Government Debt Securities [Member] | U.S. Treasury Bond, 3.00 Percent, Maturity Date 2048 02 [Member] | Government [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	[3]	$ (1,050)
Rate	[3]	3.00%
Investments maturity date	[3]	2048-02
Investments sold short, at fair value-	[3]	$ (1,055)
US Government Debt Securities [Member] | U.S. Treasury Note, 1.88 Percent, Maturity Date 2019 12 [Member] | Government [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	[3]	$ (968)
Rate	[3]	1.88%
Investments maturity date	[3]	2019-12
Investments sold short, at fair value-	[3]	$ (961)
US Government Debt Securities [Member] | U.S. Treasury Note, 2.75 Percent, Maturity Date 2025 02 [Member] | Government [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	[3]	$ (448)
Rate	[3]	2.75%
Investments maturity date	[3]	2025-02
Investments sold short, at fair value-	[3]	$ (450)
US Government Debt Securities [Member] | U.S. Treasury Bond, 2.75 Percent, Maturity Date 2047 08 [Member] | Government [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	[3]	$ (275)
Rate	[3]	2.75%
Investments maturity date	[3]	2047-08
Investments sold short, at fair value-	[3]	$ (263)
US Government Debt Securities [Member] | U.S. Treasury Note, 2.25 Percent, Maturity Date 2027 02 [Member] | Government [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	[6]			$ (30,501)
Rate	[6]			2.25%
Investments maturity date	[6]			2027-02
Investments sold short, at fair value-	[6]			$ (30,108)
US Government Debt Securities [Member] | US Treasury Note, 1.88 Percent, Maturity Date 2020 12 [Member] | Government [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	[6]			$ (14,000)
Rate	[6]			1.88%
Investments maturity date	[6]			2020-12
Investments sold short, at fair value-	[6]			$ (13,961)
US Government Debt Securities [Member] | U.S. Treasury Note, 1.75 Percent, Maturity Date 2022 05 [Member] | Government [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	[6]			$ (6,000)
Rate	[6]			1.75%
Investments maturity date	[6]			2022-05
Investments sold short, at fair value-	[6]			$ (5,896)
US Government Debt Securities [Member] | U.S. Treasury Note, 2.25 Percent, Maturity Date 2027 11 [Member] | Government [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	[6]			$ (2,223)
Rate	[6]			2.25%
Investments maturity date	[6]			2027-11
Investments sold short, at fair value-	[6]			$ (2,192)
US Government Debt Securities [Member] | US Treasury Note, 2.00 Percent, Maturity Date 2022 11 [Member] | Government [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	[6]			$ (615)
Rate	[6]			2.00%
Investments maturity date	[6]			2022-11
Investments sold short, at fair value-	[6]			$ (610)
US Government Debt Securities [Member] | U.S. Treasury Bond, 2.25 Percent, Maturity Date 2046 08 [Member] | Government [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	[6]			$ (281)
Rate	[6]			2.25%
Investments maturity date	[6]			2046-08
Investments sold short, at fair value-	[6]			$ (254)
Foreign Government Debt Securities [Member] | Europe [Member]
Investments Sold, Not yet Purchased [Line Items]
Investment Sold, Not yet Purchased, Percent of Equity		(6.23%)	[2],[3]	(5.98%)	[5],[6]
Investments sold short, at fair value-		$ (38,000)	[3]	$ (37,128)	[6]
Proceeds from investments sold short		(35,101)	[3]	(35,149)	[6]
Foreign Government Debt Securities [Member] | Spanish Sovereign Bond, 0.25 Percent [Member] | Government [Member] | Europe [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount		$ (16,915)	[3]	$ (16,516)	[6]
Rate		0.25%	[3]	0.25%	[6]
Investments maturity date		2018-04	[3]	2018-04	[6]
Investments sold short, at fair value-		$ (16,926)	[3]	$ (16,556)	[6]
Foreign Government Debt Securities [Member] | Spanish Sovereign Bond, 0.75 Percent [Member] | Government [Member] | Europe [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount		$ (10,700)	[3]	$ (10,447)	[6]
Rate		0.75%	[3]	0.75%	[6]
Investments maturity date		2021-07	[3]	2021-07	[6]
Investments sold short, at fair value-		$ (11,041)	[3]	$ (10,704)	[6]
Foreign Government Debt Securities [Member] | Spanish Sovereign Bond, 2.75 Percent [Member] | Government [Member] | Europe [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount		$ (9,704)	[3]	$ (9,474)	[6]
Rate		2.75%	[3]	2.75%	[6]
Investments maturity date		2019-04	[3]	2019-04	[6]
Investments sold short, at fair value-		$ (10,033)	[3]	$ (9,868)	[6]
Government debt [Member]
Investments Sold, Not yet Purchased [Line Items]
Investment Sold, Not yet Purchased, Percent of Equity		(17.57%)	[2],[3]	(14.52%)	[5],[6]
Investments sold short, at fair value-		$ (107,156)	[3]	$ (90,149)	[6]
Proceeds from investments sold short		$ (103,817)	[3]	$ (88,471)	[6]
Common Stock Sold Short [Member]
Investments Sold, Not yet Purchased [Line Items]
Investment Sold, Not yet Purchased, Percent of Equity		(6.27%)	[2],[3]	(5.91%)	[5],[6]
Investments sold short, at fair value-		$ (38,242)	[3]	$ (36,691)	[6]
Proceeds from investments sold short		(39,111)	[3]	(36,666)	[6]
Common Stock Sold Short [Member] | Exchange Traded Equity [Member] | Energy [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Investments sold short, at fair value-	[6]			$ (68)
Investment Sold, Not yet Purchased, Balance, Shares	[6]			(1)
Common Stock Sold Short [Member] | Exchange Traded Equity [Member] | Financial [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Investments sold short, at fair value-		$ (38,242)	[3]	$ (36,623)	[6]
Investment Sold, Not yet Purchased, Balance, Shares		(824)	[3]	(671)	[6]
Corporate Debt Sold Short [Member]
Investments Sold, Not yet Purchased [Line Items]
Investment Sold, Not yet Purchased, Percent of Equity		(7.70%)	[2],[3]	(8.89%)	[5],[6]
Investments sold short, at fair value-		$ (46,944)	[3]	$ (55,211)	[6]
Proceeds from investments sold short		(47,476)	[3]	(55,112)	[6]
Corporate Debt Sold Short [Member] | Various Issuer [Member] | Basic Materials [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	[3]	(1,746)
Investments sold short, at fair value-	[3]	$ (1,719)
Corporate Debt Sold Short [Member] | Various Issuer [Member] | Basic Materials [Member] | North America [Member] | Minimum [Member]
Investments Sold, Not yet Purchased [Line Items]
Rate	[3]	4.55%
Investments maturity date	[3]	2024-11
Corporate Debt Sold Short [Member] | Various Issuer [Member] | Basic Materials [Member] | North America [Member] | Maximum [Member]
Investments Sold, Not yet Purchased [Line Items]
Rate	[3]	7.00%
Investments maturity date	[3]	2027-03
Corporate Debt Sold Short [Member] | Various Issuer [Member] | Communications [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount		$ (21,548)	[3]	(18,590)	[6]
Investments sold short, at fair value-		$ (20,427)	[3]	$ (17,196)	[6]
Corporate Debt Sold Short [Member] | Various Issuer [Member] | Communications [Member] | North America [Member] | Minimum [Member]
Investments Sold, Not yet Purchased [Line Items]
Rate		3.40%	[3]	4.13%	[6]
Investments maturity date		2022-09	[3]	2022-07	[6]
Corporate Debt Sold Short [Member] | Various Issuer [Member] | Communications [Member] | North America [Member] | Maximum [Member]
Investments Sold, Not yet Purchased [Line Items]
Rate		10.50%	[3]	10.50%	[6]
Investments maturity date		2027-03	[3]	2027-03	[6]
Corporate Debt Sold Short [Member] | Various Issuer [Member] | Consumer [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount		$ (9,085)	[3]	$ (23,805)	[6]
Investments sold short, at fair value-		$ (8,935)	[3]	$ (23,854)	[6]
Corporate Debt Sold Short [Member] | Various Issuer [Member] | Consumer [Member] | North America [Member] | Minimum [Member]
Investments Sold, Not yet Purchased [Line Items]
Rate		3.50%	[3]	2.88%	[6]
Investments maturity date		2020-10	[3]	2020-10	[6]
Corporate Debt Sold Short [Member] | Various Issuer [Member] | Consumer [Member] | North America [Member] | Maximum [Member]
Investments Sold, Not yet Purchased [Line Items]
Rate		5.88%	[3]	6.75%	[6]
Investments maturity date		2026-12	[3]	2026-05	[6]
Corporate Debt Sold Short [Member] | Various Issuer [Member] | Energy [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount		$ (10,960)	[3]	$ (13,311)	[6]
Investments sold short, at fair value-		$ (10,026)	[3]	$ (12,834)	[6]
Corporate Debt Sold Short [Member] | Various Issuer [Member] | Energy [Member] | North America [Member] | Minimum [Member]
Investments Sold, Not yet Purchased [Line Items]
Rate		4.30%	[3]	3.25%	[6]
Investments maturity date		2022-04	[3]	2022-04	[6]
Corporate Debt Sold Short [Member] | Various Issuer [Member] | Energy [Member] | North America [Member] | Maximum [Member]
Investments Sold, Not yet Purchased [Line Items]
Rate		8.25%	[3]	8.25%	[6]
Investments maturity date		2027-06	[3]	2027-06	[6]
Corporate Debt Sold Short [Member] | Various Issuer [Member] | Financial [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	[6]			$ (960)
Investments sold short, at fair value-	[6]			$ (1,019)
Corporate Debt Sold Short [Member] | Various Issuer [Member] | Financial [Member] | North America [Member] | Minimum [Member]
Investments Sold, Not yet Purchased [Line Items]
Rate	[6]			5.13%
Investments maturity date	[6]			2022-03
Corporate Debt Sold Short [Member] | Various Issuer [Member] | Financial [Member] | North America [Member] | Maximum [Member]
Investments Sold, Not yet Purchased [Line Items]
Rate	[6]			5.25%
Investments maturity date	[6]			2024-09
Corporate Debt Sold Short [Member] | Various Issuer [Member] | Industrial Sector [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	[3]	$ (4,110)
Rate	[3]	5.13%
Investments maturity date	[3]	2024-10
Investments sold short, at fair value-	[3]	$ (4,194)
Corporate Debt Sold Short [Member] | Various Issuer [Member] | Technology Sector [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	[6]			$ (330)
Rate	[6]			3.63%
Investments maturity date	[6]			2021-10
Investments sold short, at fair value-	[6]			$ (308)
Corporate Debt Sold Short [Member] | Various Issuer [Member] | Utilities [Member] | North America [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	[3]	(1,575)
Investments sold short, at fair value-	[3]	$ (1,643)
Corporate Debt Sold Short [Member] | Various Issuer [Member] | Utilities [Member] | North America [Member] | Minimum [Member]
Investments Sold, Not yet Purchased [Line Items]
Rate	[3]	5.13%
Investments maturity date	[3]	2026-05
Corporate Debt Sold Short [Member] | Various Issuer [Member] | Utilities [Member] | North America [Member] | Maximum [Member]
Investments Sold, Not yet Purchased [Line Items]
Rate	[3]	7.25%
Investments maturity date	[3]	2027-09
Investments Sold Short [Member]
Investments Sold, Not yet Purchased [Line Items]
Investment Sold, Not yet Purchased, Percent of Equity		(113.45%)	[2],[3]	(103.43%)	[5],[6]
Investments sold short, at fair value-		$ (691,962)	[3]	$ (642,240)	[6]
Proceeds from investments sold short		$ (687,783)	[3]	$ (640,202)	[6]

[1] At March 31, 2018, the Company's short investments guaranteed by the Federal National Mortgage Association, the Federal Home Loan Mortgage Corporation, and the Government National Mortgage Association, represented 40.52%, 23.29%, and 18.10% of Total Equity, respectively.

[2] Classification percentages are based on Total Equity.

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

[4] At December 31, 2017, the Company's short investments guaranteed by the Federal National Mortgage Association, the Federal Home Loan Mortgage Corporation, and the Government National Mortgage Association, represented 44.61%, 19.27%, and 10.23% of Total Equity, respectively.

[5] Classification percentages are based on Total Equity.

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