Organization and Nature of Operations - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Collaboration Arrangement Disclosure [Abstract]
Investment banking revenue	59.00%	63.00%	76.00%
Percentage of investment banking revenues derived from major transactions	56.00%	70.00%	68.00%