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Investments and Fair Value Measurements - Additional Information (Detail) - USD ($) | 3 Months Ended |
--- | --- | ---
Mar. 31, 2016 | Mar. 31, 2015 | Dec. 31, 2015
Schedule of Held-to-maturity Securities [Line Items] |  |  |
Acquisition payable | $ 4,687,000 |  | $ 3,942,000
Acquisition contingent payment | 745,000 | $ 257,000 |
Boost Shareholders [Member] |  |  |
Schedule of Held-to-maturity Securities [Line Items] |  |  |
Acquisition contingent payment | 745,000 | $ 257,000 |
Level 3 [Member] |  |  |
Schedule of Held-to-maturity Securities [Line Items] |  |  |
Acquisition payable | 4,687,000 |  |
Estimated fair value of acquisition payable | $ 9,900,000 |  |
Discounted cash flows, discount rate | 27.50% |  |
Level 3 [Member] | ETP [Member] | Europe [Member] | Minimum [Member] |  |  |
Schedule of Held-to-maturity Securities [Line Items] |  |  |
Projected AUM | $ 1,000,000,000 |  |
Level 3 [Member] | ETP [Member] | Europe [Member] | Maximum [Member] |  |  |
Schedule of Held-to-maturity Securities [Line Items] |  |  |
Projected AUM | $ 6,000,000,000 |  |

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- Definition Amount of other liabilities due after one year or the normal operating cycle, if longer, assumed at the acquisition date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=56956791&loc=d3e4845-128472 + Details
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