Investments and Fair Value Measurements - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Schedule of Held-to-maturity Securities [Line Items]
Acquisition payable	$ 3,942,000	$ 1,757,000
Acquisition contingent payment	2,185,000
Boost Shareholders [Member]
Schedule of Held-to-maturity Securities [Line Items]
Acquisition contingent payment	2,185,000
Level 3 [Member]
Schedule of Held-to-maturity Securities [Line Items]
Acquisition payable	3,942,000
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