Management Contracts Purchased - Additional Information (Detail) (USD $)	0 Months Ended	9 Months Ended	12 Months Ended				0 Months Ended		9 Months Ended	12 Months Ended
	Oct. 28, 2012	Jun. 30, 2014	Sep. 30, 2013	Oct. 26, 2012 Funds	Sep. 30, 2012	Jun. 06, 2012	Nov. 05, 2013 FBR Funds [Member]	Oct. 28, 2012 FBR Funds [Member]	Jun. 30, 2014 FBR Funds [Member]	Sep. 30, 2013 FBR Funds [Member]	Oct. 28, 2013 FBR Funds [Member]
Contracts In Progress Costs And Earnings [Line Items]
Number of mutual funds		Thirteen
Number of funds acquired				10
Acquisition of FBR & Co. (FBRC)				$ 2,200,000,000
Additional loan borrowed	16,300,000									13,286,666
Payments to acquire management contract rights through available cash	3,400,000
Additional capitalized transaction cost			1,000,000		200,000	1,200,000
Initial payment based upon the net asset value of the FBR Funds								19,692,137
Contingent payment based upon the net asset value of the FBR Funds			19,193,595				19,193,595
Contingent payment due under the Asset Purchase Agreement											19,193,595
Long term liability			11,625,883							11,625,883
Capitalized transaction costs in current quarter		$ 58,232							$ 58,232