v3.8.0.1
Consolidated Condensed Schedule Of Investments (Investments Sold Short) - USD ($)
shares in Thousands, $ in Thousands
 9 Months Ended 12 Months Ended
Sep. 30, 2017
Dec. 31, 2016
Investments Sold, Not yet Purchased [Line Items]    
Investments sold short, at fair value- $ (675,650) $ (584,896)
Proceeds from investments sold short $ 672,506 $ 589,429
TBA - Fixed Rate Agency Securities Sold Short [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Investment Sold, Not yet Purchased, Percent of Equity (74.71%) [1],[2],[3] (62.77%) [4],[5],[6]
Current Principal/Notional Amount $ (447,590) $ (384,155)
Investments sold short, at fair value- (470,487) [1],[3] (404,728) [4],[6]
Proceeds from investments sold short (471,204) [1],[3] (404,967) [4],[6]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (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 $ (65,000) [1],[3] $ (50,930) [4],[6]
Rate 4.50% [1],[3] 4.50% [4],[6]
Investments maturity date 2017-11 [1],[3] 2017-01 [4],[6]
Investments sold short, at fair value- $ (69,695) [1],[3] $ (54,748) [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 $ (64,000) [1],[3] $ (87,767) [4],[6]
Rate 4.00% [1],[3] 4.00% [4],[6]
Investments maturity date 2017-11 [1],[3] 2017-01 [4],[6]
Investments sold short, at fair value- $ (67,280) [1],[3] $ (92,210) [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 $ (60,000) [1],[3] $ (26,000) [4],[6]
Rate 4.00% [1],[3] 4.00% [4],[6]
Investments maturity date 2017-11 [1],[3] 2017-02 [4],[6]
Investments sold short, at fair value- $ (63,077) [1],[3] $ (27,295) [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 $ (45,188) [1],[3] $ (24,352) [4],[6]
Rate 3.50% [1],[3] 3.50% [4],[6]
Investments maturity date 2017-10 [1],[3] 2017-01 [4],[6]
Investments sold short, at fair value- $ (46,588) [1],[3] $ (24,960) [4],[6]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 4 Point 00 Percent 201710 [Member] | Mortgage-related Residential [Member] | North America [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount [1],[3] $ (43,187)  
Rate [1],[3] 4.00%  
Investments maturity date [1],[3] 2017-10  
Investments sold short, at fair value- [1],[3] $ (45,469)  
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 4 Point 50 Percent 201710 [Member] | Mortgage-related Residential [Member] | North America [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount [1],[3] $ (35,730)  
Rate [1],[3] 4.50%  
Investments maturity date [1],[3] 2017-10  
Investments sold short, at fair value- [1],[3] $ (38,352)  
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 3 Point 50 Percent 201711 [Member] | Mortgage-related Residential [Member] | North America [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount [1],[3] $ (36,000)  
Rate [1],[3] 3.50%  
Investments maturity date [1],[3] 2017-11  
Investments sold short, at fair value- [1],[3] $ (37,049)  
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal Home Loan Mortgage Corporation (30 Year) 4 Point 00 Percent 201710 [Member] | Mortgage-related Residential [Member] | North America [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount [1],[3] $ (23,467)  
Rate [1],[3] 4.00%  
Investments maturity date [1],[3] 2017-10  
Investments sold short, at fair value- [1],[3] $ (24,705)  
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (15 Year) 3.00% [Member] | Mortgage-related Residential [Member] | North America [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount $ (21,520) [1],[3] $ (20,740) [4],[6]
Rate 3.00% [1],[3] 3.00% [4],[6]
Investments maturity date 2017-10 [1],[3] 2017-01 [4],[6]
Investments sold short, at fair value- $ (22,113) [1],[3] $ (21,285) [4],[6]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Government National Mortgage Association (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 [4],[6]   $ (15,770)
Rate [4],[6]   4.50%
Investments maturity date [4],[6]   2017-01
Investments sold short, at fair value- [4],[6]   $ (17,058)
TBA - Fixed Rate Agency Securities Sold Short [Member] | Government National Mortgage Association (30 Year) 3 Point 50 Percent 201710 [Member] | Mortgage-related Residential [Member] | North America [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount [1],[3] $ (12,810)  
Rate [1],[3] 3.50%  
Investments maturity date [1],[3] 2017-10  
Investments sold short, at fair value- [1],[3] $ (13,317)  
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 2017-10 [1],[3] 2017-01 [4],[6]
Investments sold short, at fair value- $ (7,591) [1],[3] $ (7,622) [4],[6]
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 $ (6,951) [1],[3] $ (23,151) [4],[6]
Rate 4.50% [1],[3] 4.50% [4],[6]
Investments maturity date 2017-10 [1],[3] 2017-01 [4],[6]
Investments sold short, at fair value- $ (7,453) [1],[3] $ (24,840) [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 $ (7,112) [1],[3] $ (4,612) [4],[6]
Rate 3.00% [1],[3] 3.00% [4],[6]
Investments maturity date 2017-10 [1],[3] 2017-01 [4],[6]
Investments sold short, at fair value- $ (7,135) [1],[3] $ (4,584) [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 [1],[3] $ (6,700)  
Rate [1],[3] 3.50%  
Investments maturity date [1],[3] 2017-10  
Investments sold short, at fair value- [1],[3] $ (6,978)  
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 $ (5,680) [1],[3] $ (31,620) [4],[6]
Rate 5.00% [1],[3] 5.00% [4],[6]
Investments maturity date 2017-10 [1],[3] 2017-01 [4],[6]
Investments sold short, at fair value- $ (6,199) [1],[3] $ (34,426) [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] $ (3,155) [4],[6]
Rate 3.00% [1],[3] 3.00% [4],[6]
Investments maturity date 2017-10 [1],[3] 2017-01 [4],[6]
Investments sold short, at fair value- $ (5,532) [1],[3] $ (3,134) [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 $ (1,870) [1],[3] $ (8,790) [4],[6]
Rate 3.50% [1],[3] 3.50% [4],[6]
Investments maturity date 2017-10 [1],[3] 2017-01 [4],[6]
Investments sold short, at fair value- $ (1,954) [1],[3] $ (9,169) [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 [4],[6]   $ (21,940)
Rate [4],[6]   3.50%
Investments maturity date [4],[6]   2017-01
Investments sold short, at fair value- [4],[6]   $ (22,819)
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 [4],[6]   $ (1,700)
Rate [4],[6]   4.00%
Investments maturity date [4],[6]   2017-01
Investments sold short, at fair value- [4],[6]   $ (1,806)
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal Home Loan Mortgage Corporation (15 Year) 3 Percent [Member] | Mortgage-related Residential [Member] | North America [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount [4],[6]   $ (13,510)
Rate [4],[6]   3.00%
Investments maturity date [4],[6]   2017-01
Investments sold short, at fair value- [4],[6]   $ (13,869)
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (15 Year) 4 Percent [Member] | Mortgage-related Residential [Member] | North America [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount [4],[6]   $ (11,170)
Rate [4],[6]   4.00%
Investments maturity date [4],[6]   2017-01
Investments sold short, at fair value- [4],[6]   $ (11,494)
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 4.00% 2017 01 [Member] | Mortgage-related Residential [Member] | North America [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount [4],[6]   $ (20,558)
Rate [4],[6]   4.00%
Investments maturity date [4],[6]   2017-01
Investments sold short, at fair value- [4],[6]   $ (21,611)
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 [4],[6]   $ (6,500)
Rate [4],[6]   3.00%
Investments maturity date [4],[6]   2017-01
Investments sold short, at fair value- [4],[6]   $ (6,568)
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (15 Year) 3.50% [Member] | Mortgage-related Residential [Member] | North America [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount [4],[6]   $ (2,530)
Rate [4],[6]   3.50%
Investments maturity date [4],[6]   2017-02
Investments sold short, at fair value- [4],[6]   $ (2,633)
TBA - Fixed Rate Agency Securities Sold Short [Member] | Government National Mortgage Association (30 Year) 3.50% 2017 02 [Member] | Mortgage-related Residential [Member] | North America [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount [4],[6]   $ (2,500)
Rate [4],[6]   3.50%
Investments maturity date [4],[6]   2017-02
Investments sold short, at fair value- [4],[6]   $ (2,597)
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 (55.62%) (32.67%)
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 (16.98%) (22.21%)
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 (2.11%) (7.89%)
US Government Debt Securities [Member] | North America [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Investment Sold, Not yet Purchased, Percent of Equity (8.01%) [2],[3] (10.82%) [5],[6]
Investments sold short, at fair value- $ (50,467) [3] $ (69,762) [6]
Proceeds from investments sold short (50,523) [3] (69,946) [6]
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 [3] $ (30,501)  
Rate [3] 2.25%  
Investments maturity date [3] 2027-02  
Investments sold short, at fair value- [3] $ (30,320)  
US Government Debt Securities [Member] | US 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 [3] $ (6,560)  
Rate [3] 1.75%  
Investments maturity date [3] 2022-05  
Investments sold short, at fair value- [3] $ (6,517)  
US Government Debt Securities [Member] | U.S. Treasury Note, 2.00 Percent, Maturity Date 2026 11 [Member] | Government [Member] | North America [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount $ (5,633) [3] $ (48,133) [6]
Rate 2.00% [3] 2.00% [6]
Investments maturity date 2026-11 [3] 2026-11 [6]
Investments sold short, at fair value- $ (5,490) [3] $ (46,287) [6]
US Government Debt Securities [Member] | U.S. Treasury Note, 2.25 Percent, Maturity Date 2027 08 [Member] | Government [Member] | North America [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount [3] $ (4,715)  
Rate [3] 2.25%  
Investments maturity date [3] 2027-08  
Investments sold short, at fair value- [3] $ (4,684)  
US Government Debt Securities [Member] | US Treasury Note, 2.38 Percent, Maturity Date 2027 02 [Member] | Government [Member] | North America [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount [3] $ (1,869)  
Rate [3] 2.38%  
Investments maturity date [3] 2027-02  
Investments sold short, at fair value- [3] $ (1,877)  
US Government Debt Securities [Member] | US Treasury Note, 1.63 Percent, Maturity Date 2022 08 [Member] | Government [Member] | North America [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount [3] $ (1,350)  
Rate [3] 1.63%  
Investments maturity date [3] 2022-08  
Investments sold short, at fair value- [3] $ (1,332)  
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 [3] $ (281)  
Rate [3] 2.25%  
Investments maturity date [3] 2046-08  
Investments sold short, at fair value- [3] $ (247)  
US Government Debt Securities [Member] | US Treasury Note, 1.38 Percent, Maturity Date 2021 04 [Member] | Government [Member] | North America [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount [6]   $ (1,305)
Rate [6]   1.38%
Investments maturity date [6]   2021-04
Investments sold short, at fair value- [6]   $ (1,280)
US Government Debt Securities [Member] | US Treasury Note, 1.25 Percent, Maturity Date 2021 10 [Member] | Government [Member] | North America [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount [6]   $ (800)
Rate [6]   1.25%
Investments maturity date [6]   2021-10
Investments sold short, at fair value- [6]   $ (776)
US Government Debt Securities [Member] | US Treasury Note, 1.13 Percent, Maturity Date 2021 07 [Member] | Government [Member] | North America [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount [6]   $ (549)
Rate [6]   1.13%
Investments maturity date [6]   2021-07
Investments sold short, at fair value- [6]   $ (531)
US Government Debt Securities [Member] | US Treasury Note, 1.13 Percent, Maturity Date 2021 09 [Member] | Government [Member] | North America [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount [6]   $ (1,968)
Rate [6]   1.13%
Investments maturity date [6]   2021-09
Investments sold short, at fair value- [6]   $ (1,898)
US Government Debt Securities [Member] | US Treasury Note, 1.50 Percent, Maturity Date 2026 08 [Member] | Government [Member] | North America [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount [6]   $ (12,160)
Rate [6]   1.50%
Investments maturity date [6]   2026-08
Investments sold short, at fair value- [6]   $ (11,179)
US Government Debt Securities [Member] | US Treasury Note, 1.75 Percent, Maturity Date 2021 11 [Member] | Government [Member] | North America [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount [6]   $ (4,726)
Rate [6]   1.75%
Investments maturity date [6]   2021-11
Investments sold short, at fair value- [6]   $ (4,690)
US Government Debt Securities [Member] | US Treasury Note, 1.13 Percent, Maturity Date 2021 08 [Member] | Government [Member] | North America [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount [6]   $ (3,230)
Rate [6]   1.13%
Investments maturity date [6]   2021-08
Investments sold short, at fair value- [6]   $ (3,121)
Foreign Government Debt Securities [Member] | Europe [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Investment Sold, Not yet Purchased, Percent of Equity (11.11%) [2],[3] (9.72%) [5],[6]
Investments sold short, at fair value- $ (69,940) [3] $ (62,680) [6]
Proceeds from investments sold short (66,592) [3] (66,800) [6]
Foreign Government Debt Securities [Member] | Sovereign Debt Securities [Member] | Government [Member] | Europe [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount $ (23,262) [3] $ (20,754) [6]
Investments maturity date 2020-11 [3] 2020-11 [6]
Investments sold short, at fair value- $ (23,691) [3] $ (21,219) [6]
Foreign Government Debt Securities [Member] | Sovereign Debt Securities [Member] | Government [Member] | Europe [Member] | Minimum [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Rate 0.25% [3] 0.25% [6]
Foreign Government Debt Securities [Member] | Sovereign Debt Securities [Member] | Government [Member] | Europe [Member] | Maximum [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Rate 0.65% [3] 0.65% [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 $ (16,260) [3] $ (14,507) [6]
Rate 0.25% [3] 0.25% [6]
Investments maturity date 2018-04 [3] 2018-04 [6]
Investments sold short, at fair value- $ (16,318) [3] $ (14,614) [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 $ (10,285) [3] $ (9,176) [6]
Rate 0.75% [3] 0.75% [6]
Investments maturity date 2021-07 [3] 2021-07 [6]
Investments sold short, at fair value- $ (10,560) [3] $ (9,379) [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 $ (9,328) [3] $ (8,322) [6]
Rate 2.75% [3] 2.75% [6]
Investments maturity date 2019-04 [3] 2019-04 [6]
Investments sold short, at fair value- $ (9,783) [3] $ (8,888) [6]
Foreign Government Debt Securities [Member] | Spanish Sovereign Bond, 1.15 Percent [Member] | Government [Member] | Europe [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount $ (9,254) [3] $ (8,257) [6]
Rate 1.15% [3] 1.15% [6]
Investments maturity date 2020-07 [3] 2020-07 [6]
Investments sold short, at fair value- $ (9,588) [3] $ (8,580) [6]
Government debt [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Investment Sold, Not yet Purchased, Percent of Equity (19.12%) [2],[3] (20.54%) [5],[6]
Investments sold short, at fair value- $ (120,407) [3] $ (132,442) [6]
Proceeds from investments sold short $ (117,115) [3] $ (136,746) [6]
Common Stock Sold Short [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Investment Sold, Not yet Purchased, Percent of Equity (2.25%) [2],[3] (1.26%) [5],[6]
Investments sold short, at fair value- $ (14,189) [3] $ (8,154) [6]
Proceeds from investments sold short (14,105) [3] (8,052) [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- [3] $ (313)  
Investment Sold, Not yet Purchased, Balance, Shares [3] (13)  
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- $ (13,876) [3] $ (8,154) [6]
Investment Sold, Not yet Purchased, Balance, Shares (379) [3] (207) [6]
Corporate Debt Sold Short [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Investment Sold, Not yet Purchased, Percent of Equity (11.21%) [2],[3] (6.14%) [5],[6]
Investments sold short, at fair value- $ (70,567) [3] $ (39,572) [6]
Proceeds from investments sold short (70,082) [3] (39,664) [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 $ (3,310) [3] (8,970) [6]
Rate [3] 3.75%  
Investments maturity date [3] 2023-02  
Investments sold short, at fair value- $ (3,365) [3] $ (8,717) [6]
Corporate Debt Sold Short [Member] | Various Issuer [Member] | Basic Materials [Member] | North America [Member] | Minimum [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Rate [6]   3.88%
Investments maturity date [6]   2021-10
Corporate Debt Sold Short [Member] | Various Issuer [Member] | Basic Materials [Member] | North America [Member] | Maximum [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Rate [6]   5.13%
Investments maturity date [6]   2023-03
Corporate Debt Sold Short [Member] | Various Issuer [Member] | Communications [Member] | North America [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount (17,690) [3] $ (8,750) [6]
Investments sold short, at fair value- $ (17,529) [3] $ (8,551) [6]
Corporate Debt Sold Short [Member] | Various Issuer [Member] | Communications [Member] | North America [Member] | Minimum [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Rate 4.25% [3] 5.25% [6]
Investments maturity date 2021-09 [3] 2021-07 [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] 9.25% [6]
Investments maturity date 2024-11 [3] 2022-09 [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 $ (23,600) [3] $ (8,930) [6]
Investments sold short, at fair value- $ (23,758) [3] $ (8,695) [6]
Corporate Debt Sold Short [Member] | Various Issuer [Member] | Consumer [Member] | North America [Member] | Minimum [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Rate 2.90% [3] 3.88% [6]
Investments maturity date 2019-04 [3] 2022-01 [6]
Corporate Debt Sold Short [Member] | Various Issuer [Member] | Consumer [Member] | North America [Member] | Maximum [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Rate 7.38% [3] 6.88% [6]
Investments maturity date 2026-05 [3] 2026-04 [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 $ (21,490) [3] $ (10,597) [6]
Investments sold short, at fair value- $ (21,138) [3] $ (10,041) [6]
Corporate Debt Sold Short [Member] | Various Issuer [Member] | Energy [Member] | North America [Member] | Minimum [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Rate 3.25% [3] 2.40% [6]
Investments maturity date 2022-04 [3] 2021-06 [6]
Corporate Debt Sold Short [Member] | Various Issuer [Member] | Energy [Member] | North America [Member] | Maximum [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Rate 8.00% [3] 8.00% [6]
Investments maturity date 2027-06 [3] 2025-01 [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 $ (3,440) [3] $ (1,130) [6]
Rate [6]   4.13%
Investments maturity date [6]   2022-02
Investments sold short, at fair value- $ (3,653) [3] $ (1,121) [6]
Corporate Debt Sold Short [Member] | Various Issuer [Member] | Financial [Member] | North America [Member] | Minimum [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Rate [3] 5.13%  
Investments maturity date [3] 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 [3] 5.25%  
Investments maturity date [3] 2024-09  
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 [3] $ (1,050)  
Rate [3] 6.38%  
Investments maturity date [3] 2023-12  
Investments sold short, at fair value- [3] $ (1,124)  
Corporate Debt Sold Short [Member] | Various Issuer [Member] | Utilities [Member] | North America [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount [6]   $ (2,430)
Rate [6]   6.25%
Investments maturity date [6]   2022-07
Investments sold short, at fair value- [6]   $ (2,447)
Investments Sold Short [Member]    
Investments Sold, Not yet Purchased [Line Items]    
Investment Sold, Not yet Purchased, Percent of Equity (107.29%) [2],[3] (90.71%) [5],[6]
Investments sold short, at fair value- $ (675,650) [3] $ (584,896) [6]
Proceeds from investments sold short $ (672,506) [3] $ (589,429) [6]
[1] At September 30, 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 55.62%, 16.98%, and 2.11% 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, 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 32.67%, 22.21%, and 7.89% 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.