Consolidated Condensed Schedule Of Investments (Investments Sold Short) - USD ($) shares in Thousands, $ in Thousands		3 Months Ended		12 Months Ended
		Mar. 31, 2016		Dec. 31, 2015
Investments Sold, Not yet Purchased [Line Items]
Investments sold short, at fair value-		$ (712,128)		$ (728,747)
Proceeds from investments sold short		$ (708,403)		$ (731,048)
TBA - Fixed Rate Agency Securities Sold Short [Member]
Investments Sold, Not yet Purchased [Line Items]
Investment Sold, Not yet Purchased, Percent of Equity		(82.18%)	[1],[2],[3]	(82.93%)	[4],[5],[6]
Current Principal/Notional Amount		$ (535,080)		$ (580,992)
Investments sold short, at fair value-		(571,063)	[1],[3]	(612,777)	[4],[6]
Proceeds from investments sold short		$ (569,273)	[1],[3]	$ (612,749)	[4],[6]
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		(57.42%)		(57.51%)
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		(18.46%)		(23.25%)
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		(6.30%)		(2.17%)
Government debt sold short [Member]
Investments Sold, Not yet Purchased [Line Items]
Investment Sold, Not yet Purchased, Percent of Equity		(18.68%)	[2],[3]	(15.43%)	[5],[6]
Investments sold short, at fair value-		$ (129,798)	[3]	$ (114,051)	[6]
Proceeds from investments sold short		$ (128,295)	[3]	$ (115,745)	[6]
Common Stock Sold Short [Member]
Investments Sold, Not yet Purchased [Line Items]
Investment Sold, Not yet Purchased, Percent of Equity		(1.19%)	[2],[3]	(0.20%)	[5],[6]
Investments sold short, at fair value-		$ (8,238)	[3]	$ (1,471)	[6]
Proceeds from investments sold short		$ (7,827)	[3]	$ (1,878)	[6]
Corporate Debt Sold Short [Member]
Investments Sold, Not yet Purchased [Line Items]
Investment Sold, Not yet Purchased, Percent of Equity		(0.43%)	[2],[3]	(0.06%)	[5],[6]
Investments sold short, at fair value-		$ (3,029)	[3]	$ (448)	[6]
Proceeds from investments sold short		$ (3,008)	[3]	$ (676)	[6]
Securities Sold Short - Securities Sold, Not Yet Purchased [Member]
Investments Sold, Not yet Purchased [Line Items]
Investment Sold, Not yet Purchased, Percent of Equity		(102.48%)	[2],[3]	(98.62%)	[5],[6]
Investments sold short, at fair value-		$ (712,128)	[3]	$ (728,747)	[6]
Proceeds from investments sold short		$ (708,403)	[3]	$ (731,048)	[6]
North America [Member] | Government debt sold short [Member]
Investments Sold, Not yet Purchased [Line Items]
Investment Sold, Not yet Purchased, Percent of Equity		(10.37%)	[2],[3]	(12.11%)	[5],[6]
Investments sold short, at fair value-		$ (72,071)	[3]	$ (89,489)	[6]
Proceeds from investments sold short		$ (70,785)	[3]	$ (89,735)	[6]
Europe [Member] | Government debt sold short [Member]
Investments Sold, Not yet Purchased [Line Items]
Investment Sold, Not yet Purchased, Percent of Equity		(8.31%)	[2],[3]	(3.32%)	[5],[6]
Investments sold short, at fair value-		$ (57,727)	[3]	$ (24,562)	[6]
Proceeds from investments sold short		(57,510)	[3]	(26,010)	[6]
Mortgage-related Residential [Member] | North America [Member] | TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 4.50% [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount		$ (94,600)	[1],[3]	$ (79,210)	[4],[6]
Rate		4.50%	[1],[3]	4.50%	[4],[6]
Investments maturity date		2016-04	[1],[3]	2016-01	[4],[6]
Investments sold short, at fair value-		$ (102,940)	[1],[3]	$ (85,553)	[4],[6]
Mortgage-related Residential [Member] | North America [Member] | TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal Home Loan Mortgage Corporation (30 Year) 4.00% [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount		$ (76,917)	[1],[3]	$ (110,327)	[4],[6]
Rate		4.00%	[1],[3]	4.00%	[4],[6]
Investments maturity date		2016-04	[1],[3]	2016-01	[4],[6]
Investments sold short, at fair value-		$ (82,109)	[1],[3]	$ (116,593)	[4],[6]
Mortgage-related Residential [Member] | North America [Member] | TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (15 year) 3.50% [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount		$ (71,400)	[1],[3]	$ (69,760)	[4],[6]
Rate		3.50%	[1],[3]	3.50%	[4],[6]
Investments maturity date		2016-04	[1],[3]	2016-01	[4],[6]
Investments sold short, at fair value-		$ (75,408)	[1],[3]	$ (73,054)	[4],[6]
Mortgage-related Residential [Member] | North America [Member] | TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 4.00% [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount		$ (54,218)	[1],[3]	$ (48,200)	[4],[6]
Rate		4.00%	[1],[3]	4.00%	[4],[6]
Investments maturity date		2016-04	[1],[3]	2016-02	[4],[6]
Investments sold short, at fair value-		$ (57,935)	[1],[3]	$ (50,911)	[4],[6]
Mortgage-related Residential [Member] | North America [Member] | TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 5.00% [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount		$ (50,620)	[1],[3]	$ (51,970)	[4],[6]
Rate		5.00%	[1],[3]	5.00%	[4],[6]
Investments maturity date		2016-04	[1],[3]	2016-01	[4],[6]
Investments sold short, at fair value-		$ (56,002)	[1],[3]	$ (57,214)	[4],[6]
Mortgage-related Residential [Member] | North America [Member] | TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 3.00% [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount		$ (42,962)	[1],[3]	$ (23,600)	[4],[6]
Rate		3.00%	[1],[3]	3.00%	[4],[6]
Investments maturity date		2016-04	[1],[3]	2016-02	[4],[6]
Investments sold short, at fair value-		$ (44,071)	[1],[3]	$ (23,555)	[4],[6]
Mortgage-related Residential [Member] | North America [Member] | TBA - Fixed Rate Agency Securities Sold Short [Member] | Government National Mortgage Association (30 Year) 3.50% [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount		$ (41,400)	[1],[3]	$ (5,050)	[4],[6]
Rate		3.50%	[1],[3]	3.50%	[4],[6]
Investments maturity date		2016-04	[1],[3]	2016-01	[4],[6]
Investments sold short, at fair value-		$ (43,763)	[1],[3]	$ (5,267)	[4],[6]
Mortgage-related Residential [Member] | North America [Member] | TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 3.50% [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount		$ (25,042)	[1],[3]	$ (43,842)	[4],[6]
Rate		3.50%	[1],[3]	3.50%	[4],[6]
Investments maturity date		2016-04	[1],[3]	2016-01	[4],[6]
Investments sold short, at fair value-		$ (26,256)	[1],[3]	$ (45,233)	[4],[6]
Mortgage-related Residential [Member] | North America [Member] | TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal Home Loan Mortgage Corporation (30 Year) 4.50% [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount		$ (20,951)	[1],[3]	$ (21,881)	[4],[6]
Rate		4.50%	[1],[3]	4.50%	[4],[6]
Investments maturity date		2016-04	[1],[3]	2016-01	[4],[6]
Investments sold short, at fair value-		$ (22,761)	[1],[3]	$ (23,577)	[4],[6]
Mortgage-related Residential [Member] | North America [Member] | TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (15 Year) 2.50% [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	[1],[3]	$ (16,600)
Rate	[1],[3]	2.50%
Investments maturity date	[1],[3]	2016-04
Investments sold short, at fair value-	[1],[3]	$ (17,042)
Mortgage-related Residential [Member] | North America [Member] | TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal Home Loan Mortgage Corporation (15 Year) 3.00% [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount		$ (13,510)	[1],[3]	$ (16,510)	[4],[6]
Rate		3.00%	[1],[3]	3.00%	[4],[6]
Investments maturity date		2016-04	[1],[3]	2016-01	[4],[6]
Investments sold short, at fair value-		$ (14,126)	[1],[3]	$ (17,018)	[4],[6]
Mortgage-related Residential [Member] | North America [Member] | TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (15 Year) 4.00% [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount		$ (11,170)	[1],[3]	$ (11,170)	[4],[6]
Rate		4.00%	[1],[3]	4.00%	[4],[6]
Investments maturity date		2016-04	[1],[3]	2016-01	[4],[6]
Investments sold short, at fair value-		$ (11,637)	[1],[3]	$ (11,629)	[4],[6]
Mortgage-related Residential [Member] | North America [Member] | TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal Home Loan Mortgage Corporation (15 Year) 3.50% [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount		$ (8,790)	[1],[3]	$ (13,980)	[4],[6]
Rate		3.50%	[1],[3]	3.50%	[4],[6]
Investments maturity date		2016-04	[1],[3]	2016-01	[4],[6]
Investments sold short, at fair value-		$ (9,279)	[1],[3]	$ (14,618)	[4],[6]
Mortgage-related Residential [Member] | North America [Member] | TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 5.50% [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		2016-04	[1],[3]	2016-01	[4],[6]
Investments sold short, at fair value-		$ (7,692)	[1],[3]	$ (7,646)	[4],[6]
Mortgage-related Residential [Member] | North America [Member] | TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (15 Year) 3.00% [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount		$ (40)	[1],[3]	$ (37,140)	[4],[6]
Rate		3.00%	[1],[3]	3.00%	[4],[6]
Investments maturity date		2016-04	[1],[3]	2016-01	[4],[6]
Investments sold short, at fair value-		$ (42)	[1],[3]	$ (38,264)	[4],[6]
Mortgage-related Residential [Member] | North America [Member] | TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 3.50% 201602 [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	[4],[6]			$ (17,600)
Rate	[4],[6]			3.50%
Investments maturity date	[4],[6]			2016-02
Investments sold short, at fair value-	[4],[6]			$ (18,120)
Mortgage-related Residential [Member] | North America [Member] | TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 3.00% 2016-01 [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	[4],[6]			$ (13,742)
Rate	[4],[6]			3.00%
Investments maturity date	[4],[6]			2016-01
Investments sold short, at fair value-	[4],[6]			$ (13,743)
Mortgage-related Residential [Member] | North America [Member] | TBA - Fixed Rate Agency Securities Sold Short [Member] | Government National Mortgage Association (30 year) 4.00% [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	[4],[6]			$ (10,150)
Rate	[4],[6]			4.00%
Investments maturity date	[4],[6]			2016-01
Investments sold short, at fair value-	[4],[6]			$ (10,782)
Government [Member] | North America [Member] | Government debt sold short [Member] | US Treasury Notes Securities [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount		(59,007)	[3]	(90,120)	[6]
Investments sold short, at fair value-		(60,053)	[3]	$ (89,489)	[6]
Government [Member] | North America [Member] | Government debt sold short [Member] | US Treasury Bond Securities [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	[3]	$ (12,320)
Rate	[3]	2.50%
Investments maturity date	[3]	2046-02
Investments sold short, at fair value-	[3]	$ (12,018)
Government [Member] | North America [Member] | Government debt sold short [Member] | Minimum [Member] | US Treasury Notes Securities [Member]
Investments Sold, Not yet Purchased [Line Items]
Rate		1.13%	[3]	1.25%	[6]
Investments maturity date		2018-10	[3]	2018-10	[6]
Government [Member] | North America [Member] | Government debt sold short [Member] | Maximum [Member] | US Treasury Notes Securities [Member]
Investments Sold, Not yet Purchased [Line Items]
Rate		2.25%	[3]	2.25%	[6]
Investments maturity date		2026-02	[3]	2025-08	[6]
Government [Member] | Europe [Member] | Government debt sold short [Member] | Sovereign Debt Securities [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount		$ (56,281)	[3]	$ (23,907)	[6]
Investments sold short, at fair value-		$ (57,727)	[3]	$ (24,562)	[6]
Government [Member] | Europe [Member] | Government debt sold short [Member] | Minimum [Member] | Sovereign Debt Securities [Member]
Investments Sold, Not yet Purchased [Line Items]
Rate		0.25%	[3]	0.25%	[6]
Investments maturity date		2016-09	[3]	2016-09	[6]
Government [Member] | Europe [Member] | Government debt sold short [Member] | Maximum [Member] | Sovereign Debt Securities [Member]
Investments Sold, Not yet Purchased [Line Items]
Rate		4.00%	[3]	4.00%	[6]
Investments maturity date		2020-11	[3]	2019-04	[6]
Energy [Member] | North America [Member] | Common Stock Sold Short [Member] | Exchange Traded Equity [Member]
Investments Sold, Not yet Purchased [Line Items]
Investments sold short, at fair value-		$ (3,799)	[3]	$ (1,471)	[6]
Investment Sold, Not yet Purchased, Balance, Shares		(386)	[3]	(306)	[6]
Energy [Member] | North America [Member] | Corporate Debt Sold Short [Member] | Various Issuer [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	[6]			$ (1,120)
Investments sold short, at fair value-	[6]			$ (448)
Energy [Member] | North America [Member] | Corporate Debt Sold Short [Member] | Minimum [Member] | Various Issuer [Member]
Investments Sold, Not yet Purchased [Line Items]
Rate	[6]			10.00%
Investments maturity date	[6]			2020-03
Energy [Member] | North America [Member] | Corporate Debt Sold Short [Member] | Maximum [Member] | Various Issuer [Member]
Investments Sold, Not yet Purchased [Line Items]
Rate	[6]			11.00%
Investments maturity date	[6]			2020-06
Financial [Member] | North America [Member] | Common Stock Sold Short [Member] | Publicly Traded Real Estate Investment Trusts [Member]
Investments Sold, Not yet Purchased [Line Items]
Investments sold short, at fair value-	[3]	$ (4,439)
Investment Sold, Not yet Purchased, Balance, Shares	[3]	(300)
Basic Materials [Member] | North America [Member] | Corporate Debt Sold Short [Member] | Various Issuer [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	[3]	$ (571)
Rate	[3]	3.55%
Investments maturity date	[3]	2022-03
Investments sold short, at fair value-	[3]	$ (397)
Consumer [Member] | North America [Member] | Corporate Debt Sold Short [Member] | Various Issuer [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	[3]	(1,998)
Investments sold short, at fair value-	[3]	$ (2,005)
Consumer [Member] | North America [Member] | Corporate Debt Sold Short [Member] | Minimum [Member] | Various Issuer [Member]
Investments Sold, Not yet Purchased [Line Items]
Rate	[3]	5.13%
Investments maturity date	[3]	2021-08
Consumer [Member] | North America [Member] | Corporate Debt Sold Short [Member] | Maximum [Member] | Various Issuer [Member]
Investments Sold, Not yet Purchased [Line Items]
Rate	[3]	5.88%
Investments maturity date	[3]	2022-06
Industrial [Member] | North America [Member] | Corporate Debt Sold Short [Member] | Various Issuer [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	[3]	$ (572)
Rate	[3]	3.90%
Investments maturity date	[3]	2021-05
Investments sold short, at fair value-	[3]	$ (627)

[1] At March 31, 2016, 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 57.42%, 18.46%, and 6.30% of 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, 2015, 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 57.51%, 23.25%, and 2.17% of equity, respectively.

[5] Classification percentages are based on Total Equity.

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