Securities Owned and Securities Sold, But Not Yet Purchased - Classifications (Details) - USD ($) $ in Thousands | Mar. 31, 2016 | Dec. 31, 2015 |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | $ 3,780 | $ 4,079 |
Securities sold, but not yet purchased, at fair value | (311) | (238) |
Level 1 | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | | 1,286 |
Securities sold, but not yet purchased, at fair value | (22) | (8) |
Level 2 | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | | 2,793 |
Securities sold, but not yet purchased, at fair value | (289) | (230) |
Level 3 | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | | 0 |
Securities sold, but not yet purchased, at fair value | 0 | 0 |
Certificates of deposit | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | 339 | 359 |
Securities sold, but not yet purchased, at fair value | 0 | 0 |
Certificates of deposit | Level 1 | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | | 359 |
Certificates of deposit | Level 2 | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | | 0 |
Certificates of deposit | Level 3 | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | | 0 |
Debt securities | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | 1,586 | 1,125 |
Securities sold, but not yet purchased, at fair value | (42) | (30) |
Debt securities | Level 1 | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | | 0 |
Securities sold, but not yet purchased, at fair value | 0 | 0 |
Debt securities | Level 2 | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | | 1,125 |
Securities sold, but not yet purchased, at fair value | (42) | (30) |
Debt securities | Level 3 | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | | 0 |
Securities sold, but not yet purchased, at fair value | 0 | 0 |
U.S. Treasury notes | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | 102 | 101 |
Securities sold, but not yet purchased, at fair value | (247) | (200) |
U.S. Treasury notes | Level 1 | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | | 0 |
Securities sold, but not yet purchased, at fair value | 0 | 0 |
U.S. Treasury notes | Level 2 | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | | 101 |
Securities sold, but not yet purchased, at fair value | (247) | (200) |
U.S. Treasury notes | Level 3 | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | | 0 |
Securities sold, but not yet purchased, at fair value | 0 | 0 |
Common stock and warrants | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | | 1,885 |
Securities sold, but not yet purchased, at fair value | (22) | (8) |
Common stock and warrants | Level 1 | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | | 927 |
Securities sold, but not yet purchased, at fair value | (22) | (8) |
Common stock and warrants | Level 2 | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | | 958 |
Securities sold, but not yet purchased, at fair value | 0 | 0 |
Common stock and warrants | Level 3 | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | | 0 |
Securities sold, but not yet purchased, at fair value | 0 | 0 |
Other investments | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | 605 | 609 |
Securities sold, but not yet purchased, at fair value | 0 | 0 |
Other investments | Level 1 | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | | 0 |
Other investments | Level 2 | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | | 609 |
Other investments | Level 3 | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | | $ 0 |
Fair value | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | 3,780 | |
Fair value | Level 1 | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | 712 | |
Fair value | Level 2 | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | 3,068 | |
Fair value | Level 3 | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | 0 | |
Fair value | Certificates of deposit | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | 339 | |
Fair value | Certificates of deposit | Level 1 | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | 339 | |
Fair value | Certificates of deposit | Level 2 | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | 0 | |
Fair value | Certificates of deposit | Level 3 | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | 0 | |
Fair value | Debt securities | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | 1,586 | |
Fair value | Debt securities | Level 1 | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | 0 | |
Fair value | Debt securities | Level 2 | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | 1,586 | |
Fair value | Debt securities | Level 3 | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | 0 | |
Fair value | U.S. Treasury notes | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | 102 | |
Fair value | U.S. Treasury notes | Level 1 | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | 0 | |
Fair value | U.S. Treasury notes | Level 2 | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | 102 | |
Fair value | U.S. Treasury notes | Level 3 | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | 0 | |
Fair value | Common stock and warrants | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | 1,148 | |
Fair value | Common stock and warrants | Level 1 | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | 373 | |
Fair value | Common stock and warrants | Level 2 | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | 775 | |
Fair value | Common stock and warrants | Level 3 | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | 0 | |
Fair value | Other investments | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | 605 | |
Fair value | Other investments | Level 1 | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | 0 | |
Fair value | Other investments | Level 2 | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | 605 | |
Fair value | Other investments | Level 3 | | |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] | | |
Securities owned, at fair value | $ 0 | |